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Original Research: CRITICAL CARE MEDICINE |

Outcomes of Patients Ventilated With Synchronized Intermittent Mandatory Ventilation With Pressure Support: A Comparative Propensity Score Study FREE TO VIEW

Guillermo Ortiz, MD; Fernando Frutos-Vivar, MD; Niall D. Ferguson, MD, MSc; Andres Esteban, MD, PhD; Konstantinos Raymondos, MD; Carlos Apezteguía, MD; Javier Hurtado, MD; Marco González, MD; Vinko Tomicic, MD; José Elizalde, MD; Fekri Abroug, MD; Yaseen Arabi, MD, FCCP; Paolo Pelosi, MD; Antonio Anzueto, MD; for the Ventila Group*
Author and Funding Information

From the Hospital de Santa Clara (Dr Ortiz), Bogotá, Colombia; Hospital Universitario de Getafe, and CIBER Enfermedades Respiratorias (Drs Frutos-Vivar and Esteban), Madrid, Spain; Interdepartmental Division of Critical Care Medicine and Department of Medicine (Dr Ferguson), Division of Respirology, University Health Network and Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada; Medizinische Hochschule (Dr Raymondos), Hannover, Germany; Hospital Profesor A. Posadas (Dr Apezteguía), El Palomar, Buenos Aires, Argentina; Hospital de Clínicas (Dr Hurtado), Montevideo, Uruguay; Clínica Medellín y Universidad Pontificia Bolivariana (Dr González), Medellín, Colombia; Clínica Alemana de Santiago (Dr Tomicic), Santiago, Chile; Hospital ABC (Dr Elizalde), México DF, México; Fattouma Bourguiba Monastir (Dr Abroug), Monastir, Tunisia; King Saud Bin Abdulaziz University for Health Sciences (Dr Arabi), Riyadh, Saudi Arabia; Ospedale di Circolo, Università degli Studi dell’Insubria (Dr Pelosi), Varese, Italy; and the South Texas Veterans Health Care System and University of Texas Health Science Center (Dr Anzueto), San Antonio, TX.

Correspondence to: Andrés Esteban, MD, PhD, Intensive Care Unit, Hospital Universitario de Getafe, Carretera de Toledo km, 12,500, 28905-Madrid, Spain; e-mail: aesteban@ucigetafe.com


A complete list of study participants is located in the Appendix.

Funding/Support: This study was funded by CIBER Enfermedades Respiratorias from Instituto de Salud Carlos III, Spain. Dr Ferguson is supported by a Canadian Institutes of Health Research New Investigator Award (Ottawa, ON, Canada).

For editorial comment see page 1256

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestpubs.org/site/misc/reprints.xhtml).


© 2010 American College of Chest Physicians


Chest. 2010;137(6):1265-1277. doi:10.1378/chest.09-2131
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Background:  Few data are available regarding the benefits of one mode over another for ventilatory support. We set out to compare clinical outcomes of patients receiving synchronized intermittent mandatory ventilation with pressure support (SIMV-PS) compared with assist-control (A/C) ventilation as their primary mode of ventilatory support.

Methods:  This was a secondary analysis of an observational study conducted in 349 ICUs from 23 countries. A propensity score stratified analysis was used to compare 350 patients ventilated with SIMV-PS with 1,228 patients ventilated with A/C ventilation. The primary outcome was in-hospital mortality.

Results:  In a logistic regression model, patients were more likely to receive SIMV-PS if they were from North America, had lower severity of illness, or were ventilated postoperatively or for trauma. SIMV-PS was less likely to be selected if patients were ventilated because of asthma or coma, or if they developed complications such as sepsis or cardiovascular failure during mechanical ventilation. In the stratified analysis according to propensity score, we did not find significant differences in the in-hospital mortality. After adjustment for propensity score, overall effect of SIMV-PS on in-hospital mortality was not significant (odds ratio, 1.04; 95% CI, 0.77-1.42; P = .78).

Conclusions:  In our cohort of ventilated patients, ventilation with SIMV-PS compared with A/C did not offer any advantage in terms of clinical outcomes, despite treatment-allocation bias that would have favored SIMV-PS.

Figures in this Article

Synchronized intermittent mandatory ventilation (SIMV) is a mode of mechanical ventilation that allows patients to breathe spontaneously between mandatory machine-cycled breaths.1 Respiratory efforts in excess of the mandatory set rate are spontaneous breaths on continuous positive airway pressure (CPAP) with or without pressure support (PS). SIMV, originally designed as a mode for weaning from mechanical ventilation,2 has also been proposed as a primary mode of ventilatory support.3,4 Compared with controlled mechanical ventilation (CMV) or assist-control (A/C) ventilation, proponents have claimed that SIMV has clinical advantages based on its allowance for spontaneous breathing.1 However, some studies5,6 that have evaluated physiologic variables comparing SIMV with other modes of ventilation did not find advantages of this mode of ventilation in terms of work of breathing. To unload inspiratory muscle work during the spontaneous breathing cycles the addition of PS has been proposed.7

SIMV was first used in adult patients as method for discontinuing mechanical ventilation.2 Two randomized controlled trials8,9 showed that SIMV was associated with significant increases in weaning duration compared with daily T-piece trials or gradual reductions in PS. Additionally, Jounieaux et al10 found no difference in weaning success when comparing weaning with SIMV alone with SIMV with PS (SIMV-PS) in patients with COPD.

However, despite these negative studies, investigators have documented that SIMV (with or without PS) continues to be used frequently as a mode of ventilation and for weaning.11-15 To our knowledge, there are no published studies that have evaluated the use of SIMV-PS (vs A/C) on clinical outcomes, including mortality. Using the data of an international prospective cohort study of mechanical ventilation,14 we set out to compare clinical outcomes (duration of ventilatory support, ICU mortality, in-hospital mortality) of patients receiving SIMV-PS vs A/C ventilation as their primary mode of ventilatory support.

Patients

We analyzed data from a cohort of 4,968 mechanically ventilated adult patients in 349 ICUs from 23 countries14 (see the list of the investigators in Appendix 1). The study protocol was approved by the Institutional Review Board at each of the participating centers with a waiver for consent. For the purpose of this study we selected patients who were ventilated only with SIMV-PS or only with A/C during their total time of ventilatory support. We excluded patients ventilated with SIMV-PS who received neuromuscular blockers (n = 17).

Full details of the methodology are shown in Appendix 2. Briefly, for each patient enrolled we collected baseline data on demographics, severity of illness, and reason for initiation of ventilation. Daily we collected data related to ventilatory parameters, organ failures (cardiovascular, respiratory, renal, hepatic, hematologic) defined as a Sequential Organ Failure Assessment score > 2 points for at least 2 consecutive days, and complications (barotrauma, ventilator-associated pneumonia, sepsis, ARDS) arising during ventilation. The onset of weaning was the time that the physician in charge considered the patient likely to resume and sustain spontaneous breathing after a patient met standard criteria for weaning readiness. Weaning was classified as simple weaning (extubation on the first attempt of spontaneous breathing); difficult weaning (patients who required up to 7 days from the first spontaneous breathing trial to achieve successful weaning); or prolonged weaning (patients who required > 7 days of weaning after the first spontaneous breathing trial).15 Patients were prospectively followed to hospital discharge.

Statistical Analysis

Data are expressed as mean (standard deviation), median (interquartile range), or proportions as appropriate. We used Student t test and the Mann-Whitney U test to compare continuous variables, and used a χ2 test or Fisher exact test to compare proportions as appropriate.

Propensity Score Development:

Because the use of SIMV-PS was not randomly assigned, we attempted to deal with treatment-indication bias by developing a propensity score for the use of SIMV-PS. For this purpose, we performed a multivariate analysis using a backward stepwise logistic regression model. Based on a univariate association with a P value < .10, we entered the following variables in the analysis: Simplified Acute Physiology Score II, geographical area, reason for initiation of ventilation (chronic obstructive pulmonary disease, asthma, coma, neuromuscular disease, postoperative acute respiratory failure, sepsis, trauma, or congestive heart failure), and complications arising during ventilation (barotrauma, ARDS, sepsis, ventilator-associated pneumonia, renal failure, hematologic failure, cardiovascular failure). We assessed goodness-of-fit of the model using the Hosmer-Lemeshow test and model discrimination by evaluating the area under the receiver operator curve.

Estimation of the Effect of the Mode of Ventilation:

Patients were stratified into quintiles according to their predicted probability of ventilation with SIMV-PS. Patients in quintile 1 were least likely to receive ventilation with SIMV-PS (4% of SIMV-PS patients were located in this quintile), whereas those in quintile 5 were most likely to receive ventilation with SIMV-PS (48% of SIMV-PS patients were located in this quintile). Within each quintile, the absolute and relative effects on mortality in the hospital were determined. In addition, the overall effectiveness of mode of ventilation on mortality in the hospital was assessed by logistic regression to adjust by propensity score strata. Within each quintile, a univariate analysis was used to compare the secondary outcomes: use of sedatives, days of ventilatory support, length of stay in the ICU, and mortality in the ICU.

Validation of the Propensity Score:

We explored graphically, using box-plots, the within-quintile residual imbalance in the estimated propensity score. Comparison of propensity score in each quintile was performed with nonparametric Kolmogorov-Smirnov test. We used SPSS 17.0 (SPSS Inc.; Chicago, IL) to conduct analyses and considered a P value < .05 to indicate statistical significance.

Among the 4,968 patients included in the original cohort, we identified 350 patients who were ventilated only with SIMV-PS and compared them with 1,228 patients ventilated continually with A/C (Fig 1). Baseline characteristics for both groups are shown in Table 1.

Figure Jump LinkFigure 1. Crude mortality of patients according to mode of ventilation. The group of patients ventilated only with SIMV-PS includes the 17 patients excluded from analysis because they received neuromuscular blockers. A/C = assist-control; SIMV = synchronized intermittent mandatory ventilation; SIMV-PS = synchronized intermittent mandatory ventilation with pressure support.Grahic Jump Location
Table Graphic Jump Location
Table 1 —Baseline Characteristics of Patients Included in the Analysis

A/C = assist-control; SIMV-PS = synchronized intermittent mandatory ventilation with pressure support.

Factors Associated With SIMV-PS Use

Table 2 shows univariate and multivariate analyses of the factors associated with SIMV-PS use. Patients receiving SIMV-PS were less likely to be from Latin America or Europe, had lower severity of illness, and were more frequently ventilated postoperatively or for trauma; they were less likely to be ventilated because of asthma or coma or to have developed complications, such as sepsis or cardiovascular failure, during mechanical ventilation. The model obtained (right-hand column of Table 2) showed an adequate goodness-of-fit (χ2 = 12.04; P = .15) and moderate discrimination (area under receiver operator curve = 0.76; 95% CI, 0.73-0.79; P < .001).

Table Graphic Jump Location
Table 2 —Factors Associated With Ventilation Using SIMV-PS: Univariate and Multivariate Logistic-Regression Analysis

See Table 1 for expansion of abbreviation.

Estimation of Treatment Effect: Stratifying on the Quintiles of the Propensity Score

There were no significant differences for in-hospital mortality across propensity strata (Table 3). After adjustment for propensity score, overall effect of SIMV-PS on mortality was also not significant (odds ratio 1.04; 95% CI, 0.77-1.42; P = .78).

Table Graphic Jump Location
Table 3 —Univariate Analysis of Effect of SIMV-PS on In-Hospital Mortality Across the Propensity Score Strata

See Table 1 for expansion of abbreviations.

In Table 4 we show secondary outcomes according to propensity score quintiles. There was a trend toward a lower sedation (statistically significant in the third quintile) in patients ventilated with SIMV-PS.

Table Graphic Jump Location
Table 4 —Comparison of Secondary Outcomes According to Stratification by the Propensity Score

See Table 1 for expansion of abbreviations.

a 

P = .002.

b 

P = .04.

Box plots of the estimated propensity score for both groups are depicted in Figure 2. The distribution of the propensity score was similar within each quintile of the propensity score excepting the fifth quintile. The Kolmogorov-Smirnov test indicated that distributions were comparable between two groups in each quintile (P = .41; P = .59; P = .68; P = .23; respectively) excepting in the fifth quintile (P < .001). Thus, there is some evidence of residual imbalance in observed characteristics between patients ventilated with SIMV-PS and with A/C within the last quintile.

Figure Jump LinkFigure 2. Comparison of propensity score in each quintile. Gray box plots correspond to the A/C group and white box plots correspond to the SIMV-PS group. The black vertical line at the center of each box denotes the median value. The lower and upper limits of the box denote the 25th and 75th percentile, respectively. The vertical lines indicate the extremes values. See Figure 1 for expansion of abbreviations.Grahic Jump Location
Weaning

In the A/C group, 638 patients (52%) were weaned successfully compared with 245 patients (70%) in the SIMV-PS group (P < .001). We compared weaning modes in the overall cohort without stratification (Table 5). In both groups, 60% of patients had a simple weaning. In the subgroups of both difficult and prolonged weaning, there were no differences in the duration of weaning between patients receiving SIMV-PS vs A/C. In these subgroups the most common method of weaning was a gradual reduction of ventilatory support. In the SIMV-PS group, the method most common was SIMV with or without PS (55 of 109 patients; 55%), whereas in the A/C group, PS was used most frequently (109 of 242 patients; 45%). There were no differences in the rate of reintubation (9% in SIMV-PS group vs 9% in A/C group; P = .78) or tracheostomy (9% in SIMV-PS group vs 9% in A/C group; P = .84).

Table Graphic Jump Location
Table 5 —Methods Used for Weaning From Mechanical Ventilation

CPAP = continuous positive airway pressure; PS = pressure support; SIMV = synchronized intermittent mandatory ventilation. See Table 1 for expansion of other abbreviations.

Our main finding is that ventilation with SIMV-PS did not have any significant advantage or disadvantage over ventilation with A/C. For a similar probability of ventilation with SIMV-PS, patients ventilated with A/C had a similar duration of mechanical ventilation and mortality.

SIMV has been evaluated in small studies with physiologic variables as outcomes in most of the studies. More than 20 years ago, Marini et al5 published a study whose purpose was to measure the work of breathing done by 12 patients during spontaneous and SIMV-assisted breaths. There was very little difference between the muscular force generated during spontaneous and assisted breaths, regardless of the level of assistance. Measurement of muscular force output was done through registration of the development of respiratory work per liter of ventilation or through the pressure-time product. These investigators demonstrated that the ventilatory pump remained active during both types of ventilatory support, and there was an increased work of breathing that occurred almost immediately after patients were switched from A/C to SIMV. Their conclusion was that SIMV resulted in significantly less respiratory muscle rest than A/C. This finding was corroborated by Imsand et al6 in a study including five patients during acute exacerbations of COPD. These authors evaluated assisted and spontaneous breaths at different levels of assistance offered by the ventilator. This was done by measuring intrapleural pressure with an esophageal balloon and assessing muscular activity through electromyograms of the diaphragm and the sternomastoid muscles. A slight reduction of the esophageal pressure-time index was found in pressure-control SIMV-assisted breaths. During conventional volume-control SIMV, patients responded to increases in the level of assistance with reductions in the amplitude of the neural inspiratory impulse, although its duration remained stable. It was found that the degree of inspiratory muscle rest offered by SIMV is not proportional to the level of assistance given by the ventilator. In addition, Leung et al7 undertook a comparison, in 11 ventilator-dependent patients, of patient-ventilator interactions with four ventilator modes: A/C, IMV, PS, and a combination of IMV and PS. Progressive increases in IMV rate and PS level each decreased inspiratory pressure-time product. When a pressure support of 10 cm H2O was added to a given level of IMV, greater reductions in pressure-time product were achieved not only during intervening breaths but also during mandatory breaths; this additional unloading during mandatory breaths was proportional to the decrease in respiratory drive observed during intervening spontaneous breaths. These studies provide a physiologic demonstration of potential detrimental effects of SIMV on respiratory muscles and central drive.

Despite these data, SIMV (with or without PS) continues to be used as a mode of ventilation and as a weaning mode. In a survey by Venus et al,11 72% of the responders indicated that IMV was their primary mode of ventilatory support. In contrast, more recent epidemiologic studies12-14 have reported a decrease in the use of SIMV, especially alone without PS. However, although use of SIMV as a weaning mode may be decreasing, it remains the second most commonly used mode for ongoing ventilatory support in our cohort studies.13,14 Moreover, a recent survey carried out in 55 ICUs in Australia and New Zealand16 revealed that SIMV, with or without PS, is the mode preferred by specialists in that region.

We observed that physicians were more likely use SIMV-PS as a preferred mode in patients with a lower baseline illness severity, whereas A/C was preferred for those who were more severely ill and likely to develop complications over the course of mechanical ventilation. This is consistent with the observed raw mortality rates, wherein patients ventilated continually with SIMV-PS had a lower mortality than patients initially ventilated with SIMV-PS and later switched to A/C, or those ventilated continually with A/C (Fig 1).

One of the most important advantages of SIMV-PS could be the reduction in the need for sedation.17 We only found significant differences in the proportion of patients with sedatives in the third quintile. However, in practice this difference did not translate into any significant differences in outcomes (duration of mechanical ventilation, weaning, stay in the ICU).

The efficacy of IMV as a weaning technique was initially evaluated in three small studies18-20 with methodological limitations. In the mid-1990s two large randomized controlled trials8,9 compared the most popular methods of weaning and found that the use of SIMV prolonged the time of weaning vs pressure support8 or vs trials with T-piece.9 These results have influenced how clinicians treat difficult-to-wean patients, and there has been a decrease in the use of SIMV as a method of weaning in recent years.13,14 In the current study, it is relevant to note that more than half of the patients who were ventilated with SIMV-PS during the acute phase of their illness were still undergoing weaning with SIMV-PS, a mode that has not been shown to be more effective.10

Our study has several limitations. First, this is an observational study, the assignment of ventilatory mode was not random, and the regression analysis model for developing the propensity score showed only moderate discrimination and calibration. It is probable that some confounder variables, which could influence the decision of choosing SIMV-PS as the mode of ventilation, were not taken into account in our model. In these cases it is important to consider the direction in which this residual confounding would potentially bias results. Patients in the A/C group were clearly significantly sicker than those receiving SIMV-PS; thus we would expect residual confounding to lead to results favoring SIMV-PS. Therefore, the fact that we did not find any significant advantages to the use of SIMV-PS, which is in the opposite direction of this potential bias, is likely to be robust. Second, we included patients from many countries. Although this is clearly adds to the generalizability of our results, different local practices may have influenced our results. We tried to minimize this issue by including the geographical area in the model, considering similar practices in areas with cultural and economic similarities. Third, we only collected data on total respiratory rate and we did not know the proportion of mandatory vs spontaneous breaths in the SIMV-PS group, or the proportion of assisted vs controlled breaths in the A/C group. It is therefore possible that some patients assigned as SIMV-PS could have received full-support ventilation without any differences from A/C. However, the differences observed between the baseline characteristics of groups clearly suggest clinicians were targeting distinctly different patients for SIMV-PS vs A/C and we believe it is likely they would have selected SIMV-PS when patients were making at least some spontaneous efforts.

Regarding our chosen methodology for developing the propensity scores in this study, we considered the patient on mechanical ventilation to be a patient undergoing a dynamic and changing process. We therefore decided to take variables that were available before and after initiating respiratory support into consideration in the model; we believe that the evolution of the patient could influence the decision either to remain on SIMV-PS or switch away from it. We based this decision partly on recommendations proposed by several studies using the propensity score method,21 which suggest including both baseline variables at admission and variables related to the outcome.

In conclusion, in a large cohort of mechanically ventilated patients, ventilation with SIMV-PSV compared with A/C was more likely to be used in less severely ill patients, either because of trauma or postoperatively. However, when baseline differences between groups were accounted for using a propensity score analysis, no differences were observed in clinically relevant outcomes, such as duration of mechanical ventilation or mortality, despite biases that would have favored SIMV-PS.

Appendix 1: Ventila Group Member Collaborators

Argentina: Coordinators: Carlos Apezteguia (Hospital Prof. A. Posadas, El Palomar, Buenos Aires) and Pablo Desmery (Sanatorio Mitre, Buenos Aires).

A. Sarasino and D. Ceraso (Hospital Dr Juan A. Fernández, Buenos Aires), D. Pezzola and F. Villarejo (Hospital Prof. A. Posadas, El Palomar), C. Cozzani and M. Torres Boden (Hospital Dr C. Argerich, Buenos Aires), C. Santos and E. Capparelli (Hospital Eva Perón, San Martín), M. Tavella and C. Irrazábal (Hospital de Clínicas José de San Martín, Buenos Aires), L. Cardonnet and A. Diez (Hospital Provincial del Centenario, Rosario), A. Giannelli and L. Vargas (Policlínico de Neuquén), M. Bustamante (Hospital Héroes de Malvinas, Merlo), E. Turchetto (Hospital Privado de la Comunidad, Mar del Plata), J. Teves and O. Elefante (Hospital Oscar Alende, Mar del Plata), C. Sola and J. Mele (Hospital Dr José Penna, Bahía Blanca), V. Sciuto and P. Grana (Hospital Provincial de Neuquén), G. Jannello and R. Valentini (CEMIC, Buenos Aires), S. Ilutovich (Sanatorio Mitre, Buenos Aires), L. Huespe Gardel (Hospital Escuela José F. de San Martín, Corrientes), J. Scapellato and E. Orsini (Hospital F. Santojanni, Buenos Aires), G. Agüero and Á. Sánchez (Policlínico Regional J. Perón, Mercedes), R. Fernández and L. Villalobos Castañeda (Hospital Italiano, Buenos Aires), F. González and E. Estenssoro (Hospital General San Martín, La Plata), S. Lasdica (Hospital Privado del Sur, Bahía Blanca), A. Gómez and J. Scapellato (Clínica de la Esperanza, Buenos Aires), P. Pratesi (Hospital Universitario Austral, Pilar), M. Blasco and F. Villarejo (Clínica Olivos, Olivos), G. Olarte and C. Bevilacqua (Clínica Modelo de Morón/Hospital San Juan de Dios, R. Mejía), M. Quinteros (Sanatorio San Lucas, San Isidro), P. Ripoll (Clínica La Sagrada Familia, Buenos Aires), S. Filippus (Clínica del Valle, Comodoro Rivadavia), F. Guzman Díaz and M. Deheza (Hospital B. Rivadavia, Buenos Aires), E. García and J. Arrieta (Hospital Regional de Comodoro Rivadavia), P. Pardo and J. Neira (Sanatorio de la Trinidad de Palermo, Buenos Aires), J. Núñez and F. Pálizas (Clínica Bazterrica, Buenos Aires), A. Ciccolini and G. Murias (Sanatorio Santa Isabel, Buenos Aires), W. Vázquez and M. Grilli (Hospital Español de Mendoza, Godoy Cruz), F. Chertcoff and E. Soloaga (Hospital Británico, Buenos Aires), D. Vargas and J. Berón (Hospital Pablo Soria, San Salvador de Jujuy), A. Maceira and P. Schoon (Hospital Prof. Luis Güemes, Haedo), D. Pina (Sanatorio Franchín, Buenos Aires), E. Sobrino and A. Raimondi (Sanatorio Mater Dei, Buenos Aires), E. De Vito (IIM Alfredo Lanari, Buenos Aires).

Belgium: M. Malbrain (Ziekenhuis Netwerk, Antwerpen).

Bolivia: Coordinator: Freddy Sandi Lora (Hospital Obrero N° 1, La Paz).

A. Lavandez and C. Alfaro (Complejo Hospitalario Viedma, La Paz), J. Guerra (Instituto Gastroenterológico Boliviano Japonés, Santa Cruz).

Canada: Coordinators: Niall D. Ferguson (Toronto Hospital Western Division, Toronto, ON) and Maureen O. Meade (McMaster University, Hamilton, ON).

J. T. Granton (Toronto General Hospital, Toronto, ON), S. E. Lapinsky (Mount Sinai, Toronto, ON), J. Meyer (St. Joseph´s Hospital, Toronto, ON), D. C. Scales (St. Michael’s Hospital, Toronto, ON), R. A. Fowler (Sunnybrook Health Sciences Centre, Toronto, ON), B. Kashin (William Osler Health Centre, Brampton, ON), D. J. Cook (St. Joseph’s Healthcare, Hamilton, ON).

Colombia: Coordinator: Marco A. González (Clínica Medellín y Universidad Pontificia Bolivariana, Medellín).

A. Guerra (Hospital General de Medellín and Clínica SOMA, Medellín), C. Cadavid (Hospital Pablo Tobón Uribe, Medellín), R. Panesso (Clínica Las Américas, Medellín), M. Granados (Clínica Valle del Lilli, Cali), C. Dueñas (Hospital Bocagrande, Cartagena), F. Molina (Clínica Bolivariana, Medellín), R. Camargo (Clínica General del Norte de Barranquilla), G. Ortiz (Hospital de Santa Clara, Bogotá), M. Gómez (Hospital de San José).

Chile: Coordinator: Vinko Tomicic (Clínica Alemana de Santiago).

L. Soto (Instituto Nacional del Tórax, Santiago), C. Romero (Hospital Clínico Pontificia Universidad Católica, Santiago), M. Teresa Caballero and L. Chiang (Hospital naval almirante NEF), E. Poch (Instituto de Neurocirugía), J. Canteros Gatica (Hospital Curico), H. Ugarte (Hospital de Coquimbo), M. Calvo, C. Vargas, and M. Yacsich (Hospital Regional de Valdivia), E. Tobar (Hospital Clínico de la Universidad de Chile, Santiago), J. G. Urra (Clínica Alemana de Temuco).

England: Coordinator: Peter Nightingale (Wythenshawe Hospital, Manchester)

J. Hunter (Macclesfield District General Hospital, Macclesfield), J. Hunter (Rotherdam District General Hospital, Rotherdam), S. Mousdale (Blackburn Royal Infimary, Blackburn), J. Harper (Royal Liverpool University Hospital, Liverpool), A. Conn (Wansbeck General Hospital, Ashington), D. Higgins (Southend Hospital, Westcliffe-on-Sea), D. Jayson (Southport & Formby District General Hospital, Southport), D. Hawkins (North Staffordshire Hospital, Stoke on Trent).

Ecuador: Coordinator: Manuel Jibaja (Hospital Militar de Quito)

G. Paredes and E. Bazantes (Hospital Enrique Garcés, Quito), P. Jiménez (Hospital Carlos Andrade Martín, Quito), J. Vergara and L. González (Hospital Luis Vernaza Valdez, Guayaquil).

France: Coordinators: Laurent Brochard (Hôpital Henri Mondor, Créteil) and Arnaud Thille (Hôpital Henri Mondor, Créteil).

L. Mallet (Centre Hospitalier D’Auch), P. Andrivet (Centre Médico-Chirurgical de Bligny, Bris-sous-Forges), O. Peyrouset (Hôpital Ambroise Paré, Boulogne Billancourt), I. Mohammedi (Hôpital Edouard Herriot, Lyon), E. Guerot (Hôpital Européen Georges Pompidou, Paris), N. Deye (Hôpital Lariboisière, Paris), S. Monsel and F. Bouvet (Hôpital Pitié Salpétrière, Paris), M. Darmon (Hôpital Saint Louis, Paris), M. Fartoukh and A. Harb (Hôpital Tenon, Paris), N. Anguel (Hôpital de Bicêtre, Kremlin-Bicêtre).

Germany: Coordinator: Konstantinos Raymondos (Medizinische Hochschule Hannover).

A. Nowak, T. Pahlitzsch, and K. F. Rothe (Krankenhaus Dresden-Friedrichstadt), M. Ragaller and T. Koch (Universitaetsklinikum Carl Gustav Carus Dresden), G. Sterzel (Kreiskrankenhaus Loebau, Ebersbach), R. Wittich (Carl-Thiem-Klinikum Cottbus gGmbH), K. Rudolph and J. Raumanns (St. Elisabeth gGmbH Leipzig), U. Grueneisen and F. Stupacher (Bundeswehrkrankenhaus Leipzig), H. Bromber, G. Leonhardt, and J. Soukup (Universitaetsklinikum der Martin-Luther-Universitaet Halle-Wittenberg), C. Wuttke (Krankenhaus St. Elisabeth und St. Barbara Halle, Saale), M. Holler (Staedtisches Krankenhaus Martha-Maria Halle-Doelau gGmbH), J. Haberkorn (Georgius-Agricola-Klinikum Zeitz), P. Jehle (Paul-Gerhard-Stiftung, Lutherstadt Wittenberg), B. Albrecht (Zeisigwaldkliniken Bethanien Chemnitz), D. M. Klut (Kreiskrankenhaus Rochlitz), H. J. Hartung (Vivantes Krankenhaus am Urban, Berlin-Kreuzberg), H. Gerlach (Vivantes-Klinikum Neukoelln, Berlin), T. Henneberg, S. Weber-Carstens, K. Haid, C. Melzer-Gartzke, and M. Oppert (Charité Universitaetsklinikum, Campus Virchow, Berlin), M. Reffenberg (Lungenklinik Heckeshorn, Berlin), Ch. Werel and A. Kopietz (Klinikum Barnim GmbH, Werner Forßmann Krankenhaus, Eberswalde), T. Nippraschk and D. Hoffmeister (Ruppiner Klinikum GmbH, Neuruppin), M. Schneider (Dietrich-Bonhoeffer-Klinikum-Neubrandenburg), D. A. Vagts and G. Noeldge-Schomburg (Medizinische Fakultaet der Universitaet Rostock), G. Savinski and T. Kloess (Allgemeines Krankenhaus Harburg, Hamburg), C. Frenkel, D. Yakisan, H. Schroeder, and C. Daniels (Staedtisches Klinikum Lueneburg), B. Sedemund-Adib (Universitaetsklinikum Schleswig Holstein - Campus Luebeck), S. Krueper (Klinikum Hannover Nordstadt), J. Ahrens, U. Molitoris, and K. Johanning (Medizinische Hochschule Hannover), D. Korth and W. Seitz (Kreiskrankenhaus Hameln), J. Kleideiter and P. Palomino (Staedtische Kliniken Bielefeld gGmbH), A. Lunkeit and J. Schlechtweg (Klinikum Bad Salzungen gGmbH), M. Quintel (Universitaetsklinikum der Georg-August-Universitaet Goettingen), E. Schild and C. P. Criée (Evangelisches Krankenhaus Goettingen-Weende e.V., Bovenden-Lenglern), M. Bund (Albert-Schweitzer-Krankenhaus Northeim), M. Hundt, U. Schulze, and J. Kolle (Kreiskrankenhaus Charlottenstift, Stadtoldendorf), J. Offensand, S. Youssef, and J. P. Juvana (Klinikum Salzgitter GMBH), W. Seyde (Staedtisches Klinikum Wolfenbuettel), T. Luecke and A. Gruener (Universitaetsklinikum Mannheim), E. Calzia (Universitaetsklinikum fur Anasthesiologie, Ulm), J. Heine, M. Borth, U. von Leitner, and M. Hoffmann (Dr. Herbert-Nieper-Krankenhaus-Goslar), W. Brandt (Universitaetsklinikum Magdeburg), A. Keller and S. Scieszka (Krankenhaus Neuwerk, Moenchengladbach), E. Schroeder and F. L. Deres (Kreiskrankenhaus Dormagen), M. Burrichter, T. Bernhardt and W. Wilhelm (St.-Marien-Hospital, Luenen), M. Beiderlinden (Universitaetklinikum Essen), H. Steiniger and V. Weißkopf (Ruhrlandklinik, Essen), H. Militzer (Evangelisches und Johanniter Klinikum, Dinslaken), K. Eicker and F. Hinder (Universitaetsklinikum Muenster), C. Weilbach and M. Raab (St. Josefs-Stift Cloppenburg), F. Ragalmuto (Kliniken der Stadt Koeln Krankenhaus Holweide), T. Moellhoff and K. Tsompanidis (Katholische Stiftung Marienhospital Aachen), D. Henzler and R. Kuhlen (Universitaetsklinikum Aachen), H. Wrigge, C. Putensen and F. L. Dumoulin (Universitaetsklinikum Bonn), M. Foedisch and J. Busch (Evangelisches Waldkrankenhaus Bad Godesberg gGmbH, Bonn), W. Theelen (St. Johannes-Krankenhaus Troisdorf), A. Deller (Krankenhaus der Barmherzigen Brueder, Trier), W. Baier (St. Nikolaus-Stiftshospital GmbH, Andernach), B. Eller (Staedt. Hellmig-Krankenhaus, Kamen), K. Schwarke (Evang. Krankenhaus Schwerte GmbH), J. Büttner (Evangelisches Krankenhaus Elisabethenstift gGmbH, Darmstadt), K. P. Wresch and K. Steidel (St.-Vincentius-Krankenhaus Speyer), J. F. Meyer (Universitaetsklinikum der Ruprecht-Karls-Universitaet Heidelberg), M. Layer (Thoraxklinik Heidelberg gGmbH), G. Meinhardt (Robert-Bosch-Krankenhaus, Stuttgart), J. Fritschi and P. Zaar (Ermstalklinik Staedtisches Krankenhaus Sindelfingen), H. P. Stegbauer (Kreiskrankenhaus Leonberg), V. Tumbass and S. Hahn (Ermstalklinik Bad Urach), H. Mende, M. Fischer, J. Martin, and A. Assmann (Klinik am Eichert Goeppingen), V. Schoeffel, K. van Deyk, and S. Seyboth (Stadtklinik Baden-Baden), H. Kerger and J. Ernst (Evangelisches Diakoniekrankenhaus, Freiburg), H. F. Ginz (Kreiskrankenhaus Loerrach), F. Brettner (Krankenhaus der Barmherzigen Brueder, Muenchen), O. Karg (ASKLEPIOS Fachkliniken Muenchen-Gauting), M. Glaser, and T. P. Zucker (Klinikum Traunstein), J. Jahn and A. Schneider (Fachkliniken Wangen), M. Burkert (Bundeswehrkrankenhaus Ulm), H. Kuenzig and T. Bein (Klinikum der Universitaet Regensburg), A. Speicher (Krankenhaus der Barmherzigen Brueder, Regensburg), J. Brederlau, E. Kaufmann, F. Schuster, and C. Soellmann (Universitaetsklinik Wuerzburg), S. Frenzel and L. Pfeiffer (Unstrut-Hainich Kreiskrankenhaus Muehlhausen), S. Weber-Carstens, K. Haid, C. Melzer-Gartzke, C. von Heymann, and B. Temmesfeld (Charité Universitaetsklinikum, Campus Mitte, Berlin).

Greece: Coordinator: Dimitrios Matamis (Papageorgiou General Hospital, Thessaloniki).

H. Mouloudi (Ippokration General Hospital, Athens).

Italy: Coordinator: Paolo Pelosi (Ospedale di Circolo di Varese).

A. Pesenti and N. Rossi (Ospedale San Gerardo, Monza), D. Chiumello and L. Gattinoni (Ospedale Maggiore Policlinico, Milano), P. Severgnini (Ospedale di Circolo di Varese), R. Fumagalli and A. Nikiforov (Ospedali Riuniti di Bergamo), S. Grasso (Ospedale di Venere, Bari).

Mexico: Coordinator: José Elizalde (Hospital ABC, México DF).

P. Cerda (Centro Médico de las Américas, Mérida), R. Mercado (Hospital Universitario de Monterrey), J.Albe Castañón (Instituto mexicano del seguro social HECMNS XXI, México DF).

Netherlands: Michael Kuiper, P. H. M. Egbers, and M. Koopmans (Medical Center Leeuwarden)

Peru: Coordinator: Ana María Montañez

M. Contardo, J. Cerna and R. Roldán (Hospital Edgardo Rebagliati Martins, Jesús María), J. Zevallos and S. Alcabes (Hospital Guillermo Almenara Irigoyen, La Victoria), C. Salcedo and D. Bruzone (Hospital Nacional Daniel Alcides Carrión, Callao), J. Quiñones (Hospital de Emergencias Grau, Lima), M. Suárez Lazo (Hospital Nacional Hipólito Unanue, El Agustino), A. Cifuentes (Hospital de Emergencias José Casimiro Ulloa, Miraflores), M. Mayorga (Clínica San Pablo, Lima).

Portugal: Coordinator: Rui Moreno (Hospital de Santo António dos Capuchos, Lisboa).

P. Casanova (Hospitais da Universidade de Coimbra), R. Matos and A. L. Jardim (Hospital de Santo António dos Capuchos, UCIP, Lisboa), A. Godinho (Hospital dos SAMS, UCI, Lisboa), P. Póvoa (Hospital São Francisco Xavier, UCIM, Lisboa), P. Coutinho (Centro Hospitalar de Coimbra), L. Reis (Hospital de São José, Unidade de Urgência Médica, Lisboa).

Saudi Arabia: Coordinator: Yaseen Arabi (King Fahad National Guard Hospital).

N. Abouchala (King Faisal Hospital), F. Hameed (King Khalid National Guard Hospital).

Spain: Coordinators: Nicolas Nin and Eva Tejerina (Hospital Universitario de Getafe).

F. Gordo (Fundación Hospital de Alcorcón), R. Fernandez (Complejo Hospitalario Parc Taulí, Sabadell), R. de Pablo (Hospital Universitario Príncipe de Asturias, Alcalá de Henares), J. Ibañez (Hospital Son Dureta, Palma de Mallorca), E. Fernández Mondejar (Hospital Virgen de las Nieves, Granada), F. del Nogal (Hospital Severo Ochoa, Leganés), F. Taboada (Hospital Central de Asturias, Oviedo), A. García Jiménez (Hospital Arquitecto Marcide, El Ferrol), Ll. Cabré and J. Morillas (Hospital de Barcelona-SCIAS), S. Macias (Hospital General de Segovia), R. de Celis (Hospital de Galdakao), J. M. Añón (Hospital Virgen de la Luz, Cuenca), P. Ugarte (Hospital Marqués de Valdecilla, Santander), T. Mut (Hospital de la Plana, Vila-Real), J. Diarte (Complejo Hospitalario de Ciudad Real), V. Sagredo (Hospital Clínico de Salamanca), M. Valledor (Hospital San Agustín, Avilés), G. González and L. Rodríguez (Hospital Morales Meseguer, Murcia), V. Parra and E. Gómez (Hospital de Sagunto), F. Jara (Hospital Mutua de Terrassa), J. M. Quiroga (Hospital de Cabueñes, Gijón), L. Arnaiz (Hospital Clínico Universitario de San Carlos, Madrid), Á. Ayensa (Hospital Virgen de la Salud, Toledo), F. Suárez Sippman (Fundación Jiménez Díaz), F. Charizosa (Hospital General de Jerez de la Frontera), J. A. Rodríguez Sarría (Hospital de Elda), C. Homs (Hospital San Jorge, Huesca), A. Díaz Lamas (Hospital Cristal πñor, Ourense), M. León (Hospital Arnau de Vilanova, Lleida), J. Allegue (Hospital Nuestra Señora del Rosell, Cartagena), M. Ruano (Hospital La Fe, Valencia).

Tunicia: Coordinator: Fekri Abroug (Fattouma Bourguiba Monastir).

M. Besbes, J. Ben Khelil, K. Belkhouja and K. BenRomdhane (Hospital Abderrahmane Mami, Ariana), S. Ben Lakhal, S. Abdellatif, and K. Bousselmi (La Rabta Tunis), M. Amamou and H. Thabet (CAMUR), L. Besbes and N. Nciri (Fattouma Bourguiba Monastir), M. Bouaziz, H. Kallel and M. Bahloul (Habib Bourguiba Sfax), S. ElAtrous, S. Merghli, and M. Feki Hassen (Tahar Sfar Mahdia).

Turkey: Coordinator: Nahit Cakar (Istanbul Medical Faculty, Istanbul).

R. Iscimen (Uludag University School of Medicine, Bursa), M. Kyzylkaya (College of Medicine, Ataturk University, Erzurum), B. Yelken (Osmangazi University, Eskisemir), I. Kati (Medical Faculty of Yuzuncu Yil University, Van), T. Guldem (Haydarpasa Numune Teaching and Research Hospital, Istanbul), U. Koca (Dokuz Eylun University, Istanbul), M.Cicek (Inonu University of Medical Faculty, Malatya), H. Sungurtekin (Pamukkale University Medical Faculty)

United States: Coordinator: Antonio Anzueto (University of Texas Health Science Center, San Antonio, TX).

A. C. Arroliga (Cleveland Clinic, Cleveland, OH), O. Gajic and M. Ali (Mayo Clinic, Rochester, MN), D. Ost, A. Fein, A. Kyprianou, L. Shulman, and S. Chang (North Shore University Hospital, New York, NY), J. S. Steingrub, M. A. Tidswell and K. Kozikowski (Baystate Medical Center, Springfield, MA), C. A. Piquette and L. Morrow (Creighton University Medical Center, Omaha, NE), P. Scheinberg and J. Green (Saint Joseph’s Hospital, Atlanta, GA), L. Penogreen and K. Kannady (Georgia State University, Kennestone, GA), M. Moss, M. Mealer, and R. D. Restrepo (Grady Hospital Georgia, Atlanta, GA), H. E. Fessler, R. Brower, D. Hager, and A. Scully (John Hopkins University Hospital, Baltimore, MD), J. Beamis, D. E. Craven and W. Miner (Lahey Clinic Medical Center, Burlington, MA), S. Blosser, K. Miller, L. Cornman and J. Breidinger (Penn State Hershey Medical Center, Hershey, PA), J. T. Huggins and Ch. Strange (Medical University of South Carolina, Charleston, SC), N. S. Hill and L. Lawler (Tufts-New England Medical Center, Boston, MA), M. Rembert (Newark Beth Israel Medical Center, Newark, NJ), H. K. Donnelly, J. D. D’Amico, R. G. Wunderink, N. Queseda, and J. Topin (Northwestern Memorial Home Health University, Chicago, IL), G. T. Kinasewitz and G. L. Lee (University of Oklahoma Health Sciences Center, Oklahoma City, OK), J. Walls and V. Zimmer (Presbyterian Healthcare, Charlotte, NC), A. X. Freire (Regional Medical Center, Memphis, TN), C. Steven and L. Caskey (Louisiana State University Health Sciences Center, Shreveport, LA), R. Dhand and L. A. Despins (University Hospital and Clinics MU Healthcare, Columbia, MO), R. Hyzy, R. E. Dechert, C. Haas and D. Fickle (University of Michigan Medical Center, Ann Arbor, MI), Ch. Burger and L. Gambino (Mayo Clinic, Jacksonville, FL), D. Marks and S. Benslimane (University of Texas Health Science Center, San Antonio, TX), V. J. Cardenas Jr (University of Texas Medical Branch Galveston , TX), M. J. Wing and P. Krumpe (VA Sierra Nevada Health Care System, Reno, NV), J. Truwit and M. Marshall (University of Virginia Health System, Charlottesville, VA), D. L. Herr (Washington Hospital Center, Washington, DC), R. D. Hite (Wake Forest Baptist Hospital Medical Center, Winston Salem, NC), P. J. McShane and K. N. Olivier (Wilford Hall Medical Center, San Antonio, TX), K. W. Presberg (Froedtert & Medical College, Milwaukee, WI).

Uruguay: Coordinator: Javier Hurtado (Cudam Sanatorio Colón, Sanatorio IMPASA and Hospital de Clínicas, Montevideo).

M. Borde, E. Echavarría, S. Gómez, and M. Berón (Hospital Maciel, Montevideo), F. Villalba (Sanatorio Casa de Galicia, Montevideo), I. Porras (Sanatorio CASMU 2, Montevideo), P. Cardinal, C. Surraco, and V. Navarrete (Sanatorio CASMU 4, Montevideo), F. Rodríguez and J. C. Bagattini (Hospital Británico, Montevideo), R. Garrido (Hospital Evangélico and Sanatorio IMPASA, Montevideo), S. Infanzón and J. Caraballo (Hospital Militar and CTI-SMI, Montevideo), C. Santos and A. García (Hospital de Clínicas, Montevideo), R. Cal (CTI-SMI, Montevideo), G. Pittini and J. Cabrera (Centro Nacional de Quemados, Montevideo), F. Bazzano and F. Domínguez (Hospital Pasteur, Colonia), P. Alzugaray, D. González and M. Machado (Sanatorio CAMOC, Carmelo), F. Torres (Sanatorio Mautone and Asistencial Medica de Maldonado, Maldonado), S. Mareque, M. Korintan, F. Mora, E. Altieri, E. Gianoni, C. Fregosi, A. Crossi, and G. Larrarte (Sanatorio CAAMS, Soriano), O. Pereira (Sanatorio COMTA, Tacuarembó), J. Baraibar (Hospital Regional de Tacuarembó), A. Soler (Sanatorio COMEPA, Paysandú), M. Rodríguez Verde (Hospital Paysandú), M. Díaz (Hospital de Salto and Sanatorio Uruguay, Salto), J. Martínez Ramos (Sanatorio Uruguay, Salto), I. Iturralde, W. González and E. Cubas (Sanatorio CAMDEL, Minas), A. Cataldo (Sanatorio CAMEDUR, Durazno), O. Rocha (Sanatorio GREMEDA, Artigas), A. Deicas (Sanatorio CASMU 2 and Sanatorio CASMU 4).

Venezuela: Coordinator: Gabriel D’Empaire (Hospital de Clínicas, Caracas).

R. Zerpa (Hospital Militar de Caracas), M. Narvez (Hospital Domingo Luciani, Caracas), F. Pérez (Hospital de Clínicas, Caracas), J. España (Hospital Universitario de Caracas).

Appendix 2: Protocol of the Second International Study on Mechanical Ventilation
Objectives of Study

The main objective of this study was to obtain a better understanding of the spectrum of use of mechanical ventilation in ICUs.

  • 1. To know the current status of mechanical ventilation in the ICU. Determine the number and percentage of patients who are admitted to an ICU and require mechanical ventilation. This protocol excluded patients admitted after elective surgery and who required mechanical ventilation for < 12 h (excepting patients who receive noninvasive ventilation).

  • 2. To analyze the results obtained in this study in following aspects:

  •  a. Patient characteristics

  •  b. Modes of ventilation and setting

  •  c. Outcome of overall population

  •  d. Characteristics and outcome of patients with:

  •   i. Stroke or brain trauma

  •   ii. Asthma

  •   iii. COPD

  •  e. Epidemiology and outcome of noninvasive ventilation

  •  f. Outcome of weaning

Overview

This was a multicenter, international study that collected data of all patients who were admitted to the study ICUs and who met the inclusion/exclusion criteria between April 1, 2004, at 12:00 am and the finish date of April 30, 2004, at 11:59 pm. Patients who were already mechanically ventilated prior to April 1 at 12:00 am were not included in the study.

Study Population

  • 1. Inclusion Criteria

  •  a. Patients who were admitted to the ICU and required invasive mechanical ventilation (endotracheal tube or tracheostomy) for > 12 h

  •  b. Patients who were admitted to the ICU and required noninvasive mechanical ventilation (bilevel pressure ventilation or CPAP with nasal or facial mask) for > 1 h

  •  c. Patients in whom mechanical ventilation was started outside the study ICU at the same institution and/or a different institution, including emergency room or operating room, and were then transferred to the ICU

  •  d. This study was conducted in ICUs that met the following criteria:

  •   i. Units that had six or more beds and/or average (during prior 12 months) > 30% of the patients admitted required mechanical ventilation

  •   ii. Units that had staff or visiting physicians with intensive care training and/or physicians who had > 5 years of intensive care experience

  • 2. Exclusion Criteria

  •  a. Patient < 18 y of age

  •  b. Patients who were admitted to an ICU after elective surgery and required mechanical ventilation for < 12 h

  •  c. The following ICUs were excluded:

  •   i. Pediatric ICU

  •   ii. Postoperative anesthesia recovery room

Study Protocol

Data from patients who met the inclusion criteria and who were enrolled in the study were followed according to the following situations, whichever occurred first: for 28 days after enrollment in the study or until discharge from the hospital and/or death within 28 days after inclusion in the study. The data were collected by the Investigator or Research Coordinator in each ICU. The Study Coordinator for each country was consulted regarding any protocol-related questions.

Data Collection:

  • 1. Demographic data: age, sex, weight expressed in kilograms, height expressed in centimeters, Simplified Acute Physiology Score was calculated at admission to ICU, date of hospital admission, date of admission to the study ICU

  • 2. Type of problem: medical or surgical (including scheduled and nonscheduled surgery)

  • 3. Primary reason to start the mechanical ventilation:

  •  a. Acute-on-chronic respiratory disease:

  •   i. Acute exacerbation of COPD: Patient had the diagnosis of COPD and had an exacerbation that required mechanical ventilation

  •   ii. Asthma: Mechanical ventilation started because of status asthmaticus and/or acute exacerbation in a patient with prior history of reactive airway disease

  •   iii. Other chronic respiratory disease: Patient with diagnosis of chronic respiratory disease other than COPD or asthma (eg, pulmonary fibrosis)

  •  b. Acute respiratory failure: Any patient who required mechanical ventilation and had one of the following conditions:

  •   i. ARDS: Based on the criteria established by the American-European Consensus Conference of ARDS (acute onset, Pao2/Fio2 < 200, bilateral infiltrate on chest radiograph, absence of heart failure)

  •   ii. Postoperative: patients who underwent surgery and were not weaned from mechanical ventilation because of obesity, abdominal or thoracic surgery, advanced age, and so forth. Prior to surgery patients had not been on mechanical ventilation.

  •   iii. Acute pulmonary edema and/or congestive heart failure: patients with (1) acute cardiogenic pulmonary edema, (2) congestive heart failure with severe dyspnea with or without radiologic infiltrate, (3) cardiogenic shock

  •   iv. Aspiration: patients who had gastric contents in their airway or tracheal aspirate

  •   v. Pneumonia: patients with a new radiographic alveolar infiltrate or worsening of previous alveolar infiltrate associated with fever/hypothermia and leukocytosis/leukopenia

  •   vi. Sepsis: based on the criteria established by Consensus Conference on Sepsis by American College of Chest Physicians/Society of Critical Care Medicine22: systemic inflammatory response syndrome (hyperthermia/hypothermia, tachycardia, tachypnea, leukocytosis/leukopenia) secondary to infection

  •   vii. Trauma: mechanical ventilation because of chest, abdominal, or multiple trauma (this category did not include patients with only brain trauma)

  •   viii. Cardiac arrest: mechanical ventilation because of sudden and unexpected cessation of cardiopulmonary functions

  •   ix. Other: etiology of acute respiratory failure not mentioned above

  •  c. Coma

  •   i. Metabolic: due to primary metabolic event (eg, hepatic encephalopathy)

  •   ii. Overdose/intoxication: secondary to accidental or voluntary ingestion of drugs or illegal substances

  •   iii. Stroke: acute cerebrovascular accident of ischemic or hemorrhagic cause

  •   iv. Brain trauma

  •   v. Neuromuscular disease: respiratory failure due to primary impairment of peripheral neurologic system, muscle mass, and/or motor plaque

  • 4. Monitoring

  •  a. Arterial blood gases: Arterial blood gases immediately before mechanical ventilation (invasive or noninvasive) started and within the first hour after starting mechanical ventilation, if available, were documented. Arterial blood gases, if available, were documented daily (for a maximum of 28 days) while the patient continued receiving mechanical ventilation.

  •  b. Mode of ventilator and settings: Ventilatory mode, settings (tidal volume, total respiratory rate, inspiratory fraction of oxygen, applied positive end-expiratory pressure) and ventilatory parameters (peak pressure and plateau pressure) were documented within the first hour after intubation and daily (for a maximum of 28 days) while patient continued receiving mechanical ventilation. Mode and ventilator settings at the time the arterial blood gases were obtained.

  •  c. Prone position and noninvasive ventilation, when these techniques were used, were registered.

  • 5. Complications: refers to conditions that developed after the patient was started on mechanical ventilation:

  •  a. Barotrauma: if the patient had any air leaks (pneumothorax, subcutaneous emphysema, pneumomediastinum, pneumopericardium) considered secondary to ventilatory management. Barotrauma secondary to chest trauma or to insertion of central lines was not included in this category.

  •  b. ARDS: based on the criteria established by the American-European Consensus Conference of ARDS (acute onset, Pao2/Fio2 < 200, bilateral infiltrate on chest radiograph, absence of heart failure): pulmonary origin when the initial injury was pneumonia, aspiration, chest trauma or inhalation. Extrapulmonary origin when the initial injury was sepsis, shock, multiple trauma, pancreatitis, blood product transfusions.

  •  c. Sepsis: based on the criteria established by Consensus Conference on sepsis by American College of Chest Physicians/Society of Critical Care Medicine22: systemic inflammatory response syndrome (hyperthermia/hypothermia, tachycardia, tachypnea, leukocytosis/leukopenia) secondary to infection.

  •  d. Ventilator-associated pneumonia: Values corresponding to diagnosis criteria were collected: (1) temperature > 38.5°C or < 36°C, (2) white cell count > 12,000 cells/μL or < 4,000 cells/μL, (3) purulent bronchial secretions, (4) alveolar infiltrate.

  •  e. Organ failure: Organ dysfunctions developed after the patient was started on mechanical ventilation. To estimate the influence of the grade of dysfunction associated with the outcome we have registered the absolute value of any of the variables related to organ failure.

  •   i. Cardiovascular failure: if mean arterial pressure is < 70 mm Hg during 2 consecutive h and if patient is receiving vasoactive drugs.

  •   ii. Renal failure: value of creatinine in mg/dL

  •   iii. Hepatic failure: value of bilirubin in mg/dL

  •   iv. Hematologic failure: platelet count

  •   v. Neurologic failure: Best Glasgow Coma Scale. If patients had received any sedative drugs or neuromuscular blockers for at least 3 h in the previous 24 h, the drug was indicated and the previous Glasgow Coma Scale to sedation and/or neuromuscular blocking was registered.

  • 6. Weaning: The following data were collected:

  •  a. Date when the patient met the following criteria: improvement of the cause of respiratory failure, Pao2/Fio2 > 200, positive end-expiratory pressure < 5 cm H2O and stable cardiovascular function (no vasoactive drugs)

  •  b. Date of the first spontaneous breathing trial and the method (T-piece, CPAP, PS ≤ 7 cm H2O) used for its performance

  •  c. Date when started a gradual reduction of ventilatory support and the mode (SIMV with or without PS, gradual reduction of PS, other method) used for it

  •  d. Date the patient is extubated. Type of extubation: scheduled or accidental

  •  e. Reintubation: any reintubation that occurred within 48 h after extubation. The time elapsed from extubation to reintubation also was documented as 0 to 12 h, 12 to 24 h, or 24 to 48 h.

  •  f. Tracheostomy: date the tracheostomy was performed and the method: percutaneous or surgical

  • 7. Outcome:

  •  a. Date of discharge from ICU and status: alive/dead

  •  b. Date of hospital discharge and status: alive/dead

Author contributions:Dr Ortiz: contributed to study concept and design, analysis and interpretation of data, and drafting of the manuscript.

Dr Frutos-Vivar: contributed to study concept and design, coordination for the acquisition of data, analysis and interpretation of data, statistical expertise, and drafting of the manuscript.

Dr Ferguson: contributed to study concept and design, analysis and interpretation of data, statistical expertise, and critical revision of the manuscript.

Dr Esteban: contributed to study concept and design, analysis and interpretation of data, and critical revision of the manuscript.

Dr Raymondos: contributed to coordination for the acquisition of data and critical revision of the manuscript.

DrApezteguía: contributed to coordination for the acquisition of data, analysis and interpretation of data, and critical revision of the manuscript.

Dr Hurtado: contributed to coordination for the acquisition of data and critical revision of the manuscript.

Dr González: contributed to coordination for the acquisition of data and critical revision of the manuscript.

Dr Tomicic: contributed to coordination for the acquisition of data, analysis and interpretation of data, and critical revision of the manuscript.

Dr Elizalde: contributed to coordination for the acquisition of data and critical revision of the manuscript.

Dr Abroug: contributed to coordination for the acquisition of data and critical revision of the manuscript.

Dr Aribi: contributed to coordination for the acquisition of data, analysis and interpretation of data, and critical revision of the manuscript.

Dr Pelosi: contributed to coordination for the acquisition of data and critical revision of the manuscript.

Dr Anzueto: contributed to study concept and design, coordination for the acquisition of data, analysis and interpretation of data, and critical revision of the manuscript.

Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

A/C

assist-control ventilation

CMV

controlled mechanical ventilation

CPAP

continuous positive airway pressure

IMV

intermittent mandatory ventilation

PS

pressure support

SIMV

synchronized intermittent mandatory ventilation

SIMV-PS

synchronized intermittent mandatory ventilation with pressure support

Sasoon CSH.Tobin MJ. Intermittent mandatory ventilation. Principles and Practice of Mechanical Ventilation. 2006; New York, NY McGraw-Hill:201-220
 
Downs JB, Klein EF Jr, Desautels D, Modell JH, Kirby RR. Intermittent mandatory ventilation: a new approach to weaning patients from mechanical ventilators. Chest. 1973;643:331-335. [CrossRef] [PubMed]
 
Downs JB, Perkins HM, Modell JH. Intermittent mandatory ventilation. An evaluation. Arch Surg. 1974;1094:519-523. [CrossRef] [PubMed]
 
Downs JB, Block AJ, Vennum KB. Intermittent mandatory ventilation in the treatment of patients with chronic obstructive pulmonary disease. Anesth Analg. 1974;533:437-443. [CrossRef] [PubMed]
 
Marini JJ, Smith TC, Lamb VJ. External work output and force generation during synchronized intermittent mechanical ventilation. Effect of machine assistance on breathing effort. Am Rev Respir Dis. 1988;1385:1169-1179. [PubMed]
 
Imsand C, Feihl F, Perret C, Fitting JW. Regulation of inspiratory neuromuscular output during synchronized intermittent mechanical ventilation. Anesthesiology. 1994;801:13-22. [CrossRef] [PubMed]
 
Leung P, Jubran A, Tobin MJ. Comparison of assisted ventilator modes on triggering, patient effort, and dyspnea. Am J Respir Crit Care Med. 1997;1556:1940-1948. [PubMed]
 
Brochard L, Rauss A, Benito S, et al. Comparison of three methods of gradual withdrawal from ventilatory support during weaning from mechanical ventilation. Am J Respir Crit Care Med. 1994;1504:896-903. [PubMed]
 
Esteban A, Frutos F, Tobin MJ, et al; Spanish Lung Failure Collaborative Group Spanish Lung Failure Collaborative Group A comparison of four methods of weaning patients from mechanical ventilation. N Engl J Med. 1995;3326:345-350. [CrossRef] [PubMed]
 
Jounieaux V, Duran A, Levi-Valensi P. Synchronized intermittent mandatory ventilation with and without pressure support ventilation in weaning patients with COPD from mechanical ventilation. Chest. 1994;1054:1204-1210. [CrossRef] [PubMed]
 
Venus B, Smith RA, Mathru M. National survey of methods and criteria used for weaning from mechanical ventilation. Crit Care Med. 1987;155:530-533. [CrossRef] [PubMed]
 
Esteban A, Anzueto A, Alía I, et al. How is mechanical ventilation employed in the intensive care unit? An international utilization review. Am J Respir Crit Care Med. 2000;1615:1450-1458. [PubMed]
 
Esteban A, Anzueto A, Frutos F, et al; Mechanical Ventilation International Study Group Mechanical Ventilation International Study Group Characteristics and outcomes in adult patients receiving mechanical ventilation: a 28-day international study. JAMA. 2002;2873:345-355. [CrossRef] [PubMed]
 
Esteban A, Ferguson ND, Meade MO, et al; VENTILA Group VENTILA Group Evolution of mechanical ventilation in response to clinical research. Am J Respir Crit Care Med. 2008;1772:170-177. [CrossRef] [PubMed]
 
Boles JM, Bion J, Connors A, et al. Weaning from mechanical ventilation. Eur Respir J. 2007;295:1033-1056. [CrossRef] [PubMed]
 
Rose L, Presneill JJ, Johnston L, Nelson S, Cade JF. Ventilation and weaning practices in Australia and New Zealand. Anaesth Intensive Care. 2009;371:99-107. [PubMed]
 
Rathgeber J, Schorn B, Falk V, Kazmaier S, Spiegel T, Burchardi H. The influence of controlled mandatory ventilation (CMV), intermittent mandatory ventilation (IMV) and biphasic intermittent positive airway pressure (BIPAP) on duration of intubation and consumption of analgesics and sedatives. A prospective analysis in 596 patients following adult cardiac surgery. Eur J Anaesthesiol. 1997;146:576-582. [CrossRef] [PubMed]
 
Schachter EN, Tucker D, Beck GJ. Does intermittent mandatory ventilation accelerate weaning? JAMA. 1981;24611:1210-1214. [CrossRef] [PubMed]
 
Hastings PR, Bushnell LS, Skillman JJ, Weintraub RM, Hedley-Whyte J. Cardiorespiratory dynamics during weaning with IMV versus spontaneous ventilation in good-risk cardiac-surgery patients. Anesthesiology. 1980;535:429-431. [PubMed]
 
Tomlinson JR, Miller KS, Lorch DG, Smith L, Reines HD, Sahn SA. A prospective comparison of IMV and T-piece weaning from mechanical ventilation. Chest. 1989;962:348-352. [CrossRef] [PubMed]
 
Weitzen S, Lapane KL, Toledano AY, Hume AL, Mor V. Principles for modeling propensity scores in medical research: a systematic literature review. Pharmacoepidemiol Drug Saf. 2004;1312:841-853. [CrossRef] [PubMed]
 
Bone RC, Balk RA, Cerra FB, et al. The ACCP/SCCM Consensus Conference Committee. American College of Chest Physicians/Society of Critical Care Medicine. Definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. Chest. 1992;1016:1644-1655. [CrossRef] [PubMed]
 

Figures

Figure Jump LinkFigure 1. Crude mortality of patients according to mode of ventilation. The group of patients ventilated only with SIMV-PS includes the 17 patients excluded from analysis because they received neuromuscular blockers. A/C = assist-control; SIMV = synchronized intermittent mandatory ventilation; SIMV-PS = synchronized intermittent mandatory ventilation with pressure support.Grahic Jump Location
Figure Jump LinkFigure 2. Comparison of propensity score in each quintile. Gray box plots correspond to the A/C group and white box plots correspond to the SIMV-PS group. The black vertical line at the center of each box denotes the median value. The lower and upper limits of the box denote the 25th and 75th percentile, respectively. The vertical lines indicate the extremes values. See Figure 1 for expansion of abbreviations.Grahic Jump Location

Tables

Table Graphic Jump Location
Table 1 —Baseline Characteristics of Patients Included in the Analysis

A/C = assist-control; SIMV-PS = synchronized intermittent mandatory ventilation with pressure support.

Table Graphic Jump Location
Table 2 —Factors Associated With Ventilation Using SIMV-PS: Univariate and Multivariate Logistic-Regression Analysis

See Table 1 for expansion of abbreviation.

Table Graphic Jump Location
Table 3 —Univariate Analysis of Effect of SIMV-PS on In-Hospital Mortality Across the Propensity Score Strata

See Table 1 for expansion of abbreviations.

Table Graphic Jump Location
Table 4 —Comparison of Secondary Outcomes According to Stratification by the Propensity Score

See Table 1 for expansion of abbreviations.

a 

P = .002.

b 

P = .04.

Table Graphic Jump Location
Table 5 —Methods Used for Weaning From Mechanical Ventilation

CPAP = continuous positive airway pressure; PS = pressure support; SIMV = synchronized intermittent mandatory ventilation. See Table 1 for expansion of other abbreviations.

References

Sasoon CSH.Tobin MJ. Intermittent mandatory ventilation. Principles and Practice of Mechanical Ventilation. 2006; New York, NY McGraw-Hill:201-220
 
Downs JB, Klein EF Jr, Desautels D, Modell JH, Kirby RR. Intermittent mandatory ventilation: a new approach to weaning patients from mechanical ventilators. Chest. 1973;643:331-335. [CrossRef] [PubMed]
 
Downs JB, Perkins HM, Modell JH. Intermittent mandatory ventilation. An evaluation. Arch Surg. 1974;1094:519-523. [CrossRef] [PubMed]
 
Downs JB, Block AJ, Vennum KB. Intermittent mandatory ventilation in the treatment of patients with chronic obstructive pulmonary disease. Anesth Analg. 1974;533:437-443. [CrossRef] [PubMed]
 
Marini JJ, Smith TC, Lamb VJ. External work output and force generation during synchronized intermittent mechanical ventilation. Effect of machine assistance on breathing effort. Am Rev Respir Dis. 1988;1385:1169-1179. [PubMed]
 
Imsand C, Feihl F, Perret C, Fitting JW. Regulation of inspiratory neuromuscular output during synchronized intermittent mechanical ventilation. Anesthesiology. 1994;801:13-22. [CrossRef] [PubMed]
 
Leung P, Jubran A, Tobin MJ. Comparison of assisted ventilator modes on triggering, patient effort, and dyspnea. Am J Respir Crit Care Med. 1997;1556:1940-1948. [PubMed]
 
Brochard L, Rauss A, Benito S, et al. Comparison of three methods of gradual withdrawal from ventilatory support during weaning from mechanical ventilation. Am J Respir Crit Care Med. 1994;1504:896-903. [PubMed]
 
Esteban A, Frutos F, Tobin MJ, et al; Spanish Lung Failure Collaborative Group Spanish Lung Failure Collaborative Group A comparison of four methods of weaning patients from mechanical ventilation. N Engl J Med. 1995;3326:345-350. [CrossRef] [PubMed]
 
Jounieaux V, Duran A, Levi-Valensi P. Synchronized intermittent mandatory ventilation with and without pressure support ventilation in weaning patients with COPD from mechanical ventilation. Chest. 1994;1054:1204-1210. [CrossRef] [PubMed]
 
Venus B, Smith RA, Mathru M. National survey of methods and criteria used for weaning from mechanical ventilation. Crit Care Med. 1987;155:530-533. [CrossRef] [PubMed]
 
Esteban A, Anzueto A, Alía I, et al. How is mechanical ventilation employed in the intensive care unit? An international utilization review. Am J Respir Crit Care Med. 2000;1615:1450-1458. [PubMed]
 
Esteban A, Anzueto A, Frutos F, et al; Mechanical Ventilation International Study Group Mechanical Ventilation International Study Group Characteristics and outcomes in adult patients receiving mechanical ventilation: a 28-day international study. JAMA. 2002;2873:345-355. [CrossRef] [PubMed]
 
Esteban A, Ferguson ND, Meade MO, et al; VENTILA Group VENTILA Group Evolution of mechanical ventilation in response to clinical research. Am J Respir Crit Care Med. 2008;1772:170-177. [CrossRef] [PubMed]
 
Boles JM, Bion J, Connors A, et al. Weaning from mechanical ventilation. Eur Respir J. 2007;295:1033-1056. [CrossRef] [PubMed]
 
Rose L, Presneill JJ, Johnston L, Nelson S, Cade JF. Ventilation and weaning practices in Australia and New Zealand. Anaesth Intensive Care. 2009;371:99-107. [PubMed]
 
Rathgeber J, Schorn B, Falk V, Kazmaier S, Spiegel T, Burchardi H. The influence of controlled mandatory ventilation (CMV), intermittent mandatory ventilation (IMV) and biphasic intermittent positive airway pressure (BIPAP) on duration of intubation and consumption of analgesics and sedatives. A prospective analysis in 596 patients following adult cardiac surgery. Eur J Anaesthesiol. 1997;146:576-582. [CrossRef] [PubMed]
 
Schachter EN, Tucker D, Beck GJ. Does intermittent mandatory ventilation accelerate weaning? JAMA. 1981;24611:1210-1214. [CrossRef] [PubMed]
 
Hastings PR, Bushnell LS, Skillman JJ, Weintraub RM, Hedley-Whyte J. Cardiorespiratory dynamics during weaning with IMV versus spontaneous ventilation in good-risk cardiac-surgery patients. Anesthesiology. 1980;535:429-431. [PubMed]
 
Tomlinson JR, Miller KS, Lorch DG, Smith L, Reines HD, Sahn SA. A prospective comparison of IMV and T-piece weaning from mechanical ventilation. Chest. 1989;962:348-352. [CrossRef] [PubMed]
 
Weitzen S, Lapane KL, Toledano AY, Hume AL, Mor V. Principles for modeling propensity scores in medical research: a systematic literature review. Pharmacoepidemiol Drug Saf. 2004;1312:841-853. [CrossRef] [PubMed]
 
Bone RC, Balk RA, Cerra FB, et al. The ACCP/SCCM Consensus Conference Committee. American College of Chest Physicians/Society of Critical Care Medicine. Definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. Chest. 1992;1016:1644-1655. [CrossRef] [PubMed]
 
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