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Communications to the Editor |

Noninvasive Positive Pressure Ventilation in the Emergency DepartmentResponse FREE TO VIEW

Thierry M. Sottiaux, MD
Author and Funding Information

Affiliations: Intensive Care Unit Clinique Notre-Dame de Grâce Gosselies, Belgium ,  Washington School of Medicine St. Louis, MO



Chest. 1999;115(1):301-303. doi:10.1378/chest.115.1.301-a
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Published online

I read with interest the clinical trial recently published by Wood and colleagues.1 The authors evaluated the efficacy of noninvasive positive pressure ventilation (NPPV) in the emergency department (ED) in avoiding the need for endotracheal intubation (ETI) and mechanical ventilation (MV) and in improving outcome of patients admitted for acute respiratory failure (ARF). The study was prospective and randomized. Inclusion criteria were a respiratory rate greater than 25 breaths/min and one of the following data: pH < 7.35, Paco2 > 45 mm Hg, Pao2 < 55 mm Hg (room air), arterial oxygen saturation < 90% (room air) or alveolar-arterial oxygen pressure gradient > 100 mm Hg (with supplemental oxygen). NPPV was applied with a nasal mask; “keeping mouth closed with chin strap if needed.” The authors reported a “possible detrimental outcome” associated with early use of NIPPV in ED (no difference in the need for ETI and MV, as in the ICU stay and the duration of MV, but a trend towards increased hospital mortality).,1

This study raises up many questions about the indiscriminate use of NIPPV in ARF patients. In this clinical trial, inclusion criteria did not take into account the admission diagnosis. Wysocki2showed that NPPV failed in more than 50% of consecutive nonselected patients with ARF and that NPPV failed in the majority of patients suffering from acute pneumonia. In patients with an acute exacerbation of COPD, NPPV can significantly decrease the incidence of ETI and MV.3,,4 In the work of Wysocki, NPPV was associated with a reduction in the rate of ETI only in patients with Paco2 above 45 mm Hg.

NPPV is more suitable for hypercapnic respiratory failure than for hypoxemic respiratory failure.

Accurate inclusion criteria must be respected. In this clinical trial,1 admission diagnosis were different between the two groups. Seven of 43 patients (8%) of the NPPV group suffered from acute pneumonia vs only 2 of 18 patients (2%) in the control group. Furthermore, Pao2 was lower in the NPPV group than in the control group (59.8 ± 20.7 vs 71.3 ± 22.7, p = NS). Acute exacerbation of COPD was most common in the control group than in the NPPV group (36.4% vs 12.5%, respectively). The probability for success of NPPV was thus basically reduced in the studied group. The control group did appear more in accordance with criteria for NPPV than the NPPV group itself.

Using a nasal mask to treat ARF patients is also questionable. Acute ARF patients are frequently mouth breathers, and mouth breathing bypasses the resistances of the nasal passage. Respiratory comfort is essential for the acceptance of NPPV. Keeping the mouth closed by using a chin strap probably increases the risk of discomfort and poor collaboration.

Thirty-seven and a half percent (NPPV group) and 36.4% (control group) of the patients were admitted for acute cardiogenic pulmonary edema. Using NPPV for acute pulmonary edema is still questioned. Mehta and colleagues5 reported a higher incidence of acute myocardial infarction in a group of patients suffering from acute pulmonary edema and receiving NPPV than in a group of patients receiving continuous positive airway pressure ventilation at the same mean airway pressure.

Efficacy of NPPV must be assessed within 1 or 2 h after starting treatment, on the basis of clinical and gasometric criteria. Delaying ETI and MV remains one of the major hazards of NPPV and can probably increase morbidity (length of stay, duration of MV) and mortality.6 In this publication,1 ETI was performed with a mean time interval of 26 ± 27 h. This delay is disconcerting and some ETI have probably been performed in critical conditions (not specified in the study).

In this study, several items of information were lacking: the mean levels of inspiratory positive airway pressure and expiratory positive airway pressure after readjustments during treatment (initial inspiratory positive airway pressure and expiratory positive airway pressure appear relatively low); the modality of NPPV application (continuous vs sequential); the characteristics of the patients who failed to successfully respond to NPPV; the precise cause leading to the decision to intubate the patient; the mean duration of ventilator assistance in patient with favorable outcome. Furthermore, the authors give no information about the cooperation of the patients. In an editorial, Di Benedetto and Van Nguyen7 wrote:“ Let us not indiscriminately utilize this modality.” We must identify patients in whom NPPV is not likely to be effective, so avoiding a dangerous delay before effective therapy is applied. We must dissuade physicians from the indiscriminate use of NPPV in ARF patients.

Wood, KA, Lewis, L, Von Harz, B, et al (1998) The use of noninvasive positive pressure ventilation in the emergency department: results of a randomized clinical trial.Chest113,1339-1346
 
Wysocki, M, Tric, L, Wolff, MA, et al Noninvasive pressure support ventilation in patients with acute respiratory failure: a randomized comparison with conventional therapy.Chest1995;107,761-768
 
Brochard, L, Mancebo, J, Wysocki, M, et al Noninvasive ventilation for acute exacerbations of chronic obstructive pulmonary disease.N Engl J Med1995;333,817-822
 
Hilbert, G, Gruson, D, Gbikpi-Benissan, G, et al Sequential use of noninvasive pressure support ventilation for acute exacerbations of COPD.Intensive Care Med1997;23,955-961
 
Mehta, S, Jay, GD, Woolard, RH, et al Randomized, prospective trial of bilevel versus continuous positive airway pressure in acute pulmonary edema.Crit Care Med1997;25,620-628
 
Guérin, C, Girard, R, Chemorin, C, et al Facial mask noninvasive mechanical ventilation reduces the incidence of nosocomial pneumonia: a prospective epidemiological survey from a single ICU.Intensive Care Med1997;23,1024-1032
 
DiBenedetto, RJ, Van Nguyen, A Noninvasive ventilation: a welcome resurgence and a plea for caution [editorial].Chest1997;111,1482-1483
 
To the Editor:

The evaluation of respiratory failure can be difficult in the emergency department setting, especially within busy emergency departments caring for critically ill patients. The exact etiology of respiratory failure may not be determined for many of these patients until they reach the ICU and further diagnostic evaluation is performed. Under these circumstances, we performed our clinical study to evaluate the usefulness of noninvasive positive pressure ventilation (NPPV) in the emergency department. Our study results support those of Wysocki and colleagues1-1 which demonstrated that NPPV should not be used indiscriminately for all patients with acute respiratory failure. However, it is difficult to find specific validated criteria for the application of NPPV in the emergency department setting. We also agree that patients with hypercapnia (Paco2 > 45 cm H2O) are more likely to respond to NPPV compared to patients with hypoxic respiratory failure.

Our use of nasal masks for the administration of NPPV may not have been optimal for all patients. We acknowledge this in our article. We also agree with other authors that additional investigations to evaluate the optimal application of NPPV are required. It is not clear that nasal mask ventilation is inferior to full-face mask ventilation. In our study, we purposely attempted to minimize mouth breathing despite the use of a nasal mask, by using a chin strap. We also agree that endotracheal intubation should not be unnecessarily delayed when patients are not responding to NPPV. We specifically required that arterial blood gases be performed at 1 h following the start of NPPV to assist in the evaluation of the need for endotracheal intubation. However, the decision to intubate is often based on a clinician’s impression of the patient’s overall medical condition. As we state in our article, the use of NPPV may have contributed to a delay in the clinical recognition of the need for intubation in some patients. Among our seven patients receiving NPPV who required mechanical ventilation, two had evidence of aspiration and inability to control airway secretions while the remaining five were intubated for progressive respiratory insufficiency. The mean level of inspiratory positive airway pressure administered to our study patients was 13.5 cm of water and the mean level of expiratory positive airway pressure was 3.0 cm of water during NPPV.

In summary we agree with Dr. Sottiaux that the administration of NPPV should not be indiscriminate as has been suggested by other authors.1-2 However, additional clinical studies are needed to best define the optional application of this technology in the emergency department as well as other clinical settings. The optimal use of NPPV may be different in the emergency department compared with the intensive care unit. Only after such investigations are performed can we better hope to improve our understanding of how to best use this technology.

References
Wysocki, M, Tric, L, Wolff, MA, et al Noninvasive pressure support ventilation in patients with acute respiratory failure: a randomized comparison with conventional therapy.CHEST1995;107,761-768
 
DiBenedetto, RJ, Van Nguyen, A Noninvasive ventilation. A welcome resurgence and a plea for caution.CHEST1997;111,1482-1483
 

Figures

Tables

References

Wood, KA, Lewis, L, Von Harz, B, et al (1998) The use of noninvasive positive pressure ventilation in the emergency department: results of a randomized clinical trial.Chest113,1339-1346
 
Wysocki, M, Tric, L, Wolff, MA, et al Noninvasive pressure support ventilation in patients with acute respiratory failure: a randomized comparison with conventional therapy.Chest1995;107,761-768
 
Brochard, L, Mancebo, J, Wysocki, M, et al Noninvasive ventilation for acute exacerbations of chronic obstructive pulmonary disease.N Engl J Med1995;333,817-822
 
Hilbert, G, Gruson, D, Gbikpi-Benissan, G, et al Sequential use of noninvasive pressure support ventilation for acute exacerbations of COPD.Intensive Care Med1997;23,955-961
 
Mehta, S, Jay, GD, Woolard, RH, et al Randomized, prospective trial of bilevel versus continuous positive airway pressure in acute pulmonary edema.Crit Care Med1997;25,620-628
 
Guérin, C, Girard, R, Chemorin, C, et al Facial mask noninvasive mechanical ventilation reduces the incidence of nosocomial pneumonia: a prospective epidemiological survey from a single ICU.Intensive Care Med1997;23,1024-1032
 
DiBenedetto, RJ, Van Nguyen, A Noninvasive ventilation: a welcome resurgence and a plea for caution [editorial].Chest1997;111,1482-1483
 
Wysocki, M, Tric, L, Wolff, MA, et al Noninvasive pressure support ventilation in patients with acute respiratory failure: a randomized comparison with conventional therapy.CHEST1995;107,761-768
 
DiBenedetto, RJ, Van Nguyen, A Noninvasive ventilation. A welcome resurgence and a plea for caution.CHEST1997;111,1482-1483
 
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