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Original Research: Critical Care |

Noninvasive Positive Pressure Ventilation Following EsophagectomyEsophagectomy Anastomosis Pressure Tolerance: Safety Demonstrated in a Pig Model FREE TO VIEW

Vignesh Raman, BS; Caitlyn E. MacGlaflin, MS; Cherie P. Erkmen, MD
Author and Funding Information

From the Division of Thoracic Surgery, Department of Surgery, Dartmouth-Hitchcock Medical Center Lebanon, NH.

CORRESPONDENCE TO: Cherie P. Erkmen, MD, Temple University Health System, Thoracic Surgery, Parkinson Pavilion, Ste C-100, Philadelphia, PA 19140; e-mail: Cherie.P.Erkmen@tuhs.temple.edu


Dr Erkmen is currently at Temple University Health System (Philadelphia, PA).

FUNDING/SUPPORT: Funding was obtained from a Dartmouth SYNERGY grant [Grant 30.169.287104.594503.1025].

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2015;147(2):356-361. doi:10.1378/chest.14-0886
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Published online

BACKGROUND:  Respiratory complications occur in 20% to 65% of patients who have undergone esophagectomy. While noninvasive positive pressure ventilation (NPPV) is associated with fewer complications than endotracheal intubation (ET), it is relatively contraindicated after esophagectomy due to potential injury to the anastomosis. We created ex vivo and in vivo pig models to determine the pressure tolerance of an esophagectomy anastomosis and compare it to esophageal pressure during NPPV.

METHODS:  We created a stapled side-to-side, functional end-to-end esophagogastric anastomosis. With continuous intraluminal pressure monitoring, we progressively insufflated the anastomosis with a syringe until we detected an anastomotic leak, and recorded the maximum pressure before leakage. We performed this experiment in 10 esophageal specimens and 10 live pigs. We then applied a laryngeal mask airway (LMA) to five live pigs and measured the pressure in the proximal esophagus with increasing ventilatory pressures.

RESULTS:  The perforation was always at the anastomosis. The ex vivo and in vivo anastomoses tolerated a mean of 101 ± 44 cm H2O and 84 ± 38 cm H2O before leak, respectively. There was no significant difference between the pressure thresholds of ex vivo and in vivo anastomoses (P = .51). When 20, 30, and 40 cm H2O of positive pressure via LMA were delivered, the esophagus sensed 5 ± 4 cm H2O (25%), 11 ± 11 cm H2O (37%), and 15 ± 9 cm H2O (38%), respectively.

CONCLUSIONS:  Our pig model suggests that an esophagectomy anastomosis can tolerate a considerably higher pressure than is transmitted to the esophagus during NPPV. NPPV may be a safe alternative to ET after esophagectomy.

Figures in this Article

Esophagectomy for esophageal cancer is a complex operation with a 20% to 60% morbidity rate.13 Respiratory complications, commonly including acute respiratory failure (ARF), pneumonia, pleural effusions, and atelectasis, occur frequently and can account for about one-half the total morbidity and mortality of the operation.4,5 For the management of ARF, noninvasive positive pressure ventilation (NPPV) has achieved increasing popularity over endotracheal intubation, as it reduces the need for intubation, number of complications, length of stay in the ICU, short-term mortality, and cost.616 Further, in patients with postoperative respiratory insufficiency short of ARF, NPPV has resulted in lower intubation rates, better gas exchange, and shortened length of stay.1719

However, in patients who have undergone esophagectomy, clinicians have hesitated to use NPPV because of concerns that positive pressure would translate into stress on the esophagogastric anastomosis.6,10,15,17,19,20 Two European studies have demonstrated safety of NPPV in empirical use in esophagectomy patients.6,19 Our aim was to quantify the maximum, safe intraluminal pressures that can be administered to an anastomosis. We then looked to quantify the esophageal pressures experienced with NPPV, thereby establishing a safe range of positive pressure tolerance. This information could be used as a basis for a trial of NPPV in patients who have undergone esophagectomy.

Ex Vivo Pig Model for Esophagectomy

An ex vivo model for esophagectomy was developed with porcine, nonpreserved pharyngoesophagogastric specimens (n = 10). The esophagus was transected at a midesophageal location, the stomach was transected near the cardia, and a linear stapler (ETHICON ENDO-SURGERY Linear Cutter 75; Ethicon Endosurgery Inc) was used to create a side-to-side, functional end-to-end esophagogastric anastomosis. To create a closed system, the esophagus was ligated with 2-0 silk ties at its most proximal end and and the stomach at its most distal end. An 18-gauge angiocatheter was introduced into the esophageal lumen close to the anastomosis, and a pressure probe (FISO FOP 62.5 microns; FISO Technologies Inc) was inserted into the lumen of the esophagus via the angiocatheter. Another 18-gauge angiocatheter was inserted into the esophagus, and a 60-mL syringe was attached to it. With concurrent pressure monitoring, the syringe was used to progressively insufflate the anastomosis until a leak was identified by (1) the failure of the anastomosis to hold pressure, (2) a hissing sound from the anastomosis, or (3) the discharge of air bubbles from the anastomosis when submerged in a water bath. The anastomotic leak was confirmed by the injection into the esophageal lumen and subsequent extravasation of methylene blue from the anastomotic staple lines. The intraluminal pressure at which first evidence of anastomotic leak appeared was recorded. The baseline intraluminal pressure was measured as atmospheric in every experiment and was subtracted from the final maximum esophageal pressure resulting in the applied pressure in cm H2O.

In Vivo Pig Model for Esophagectomy

The ex vivo model was then applied to live, nonsurvival pigs to determine any difference in pressure tolerance between both types of tissue. A pig weighing 30 to 40 kg (n = 10) was anesthetized, prepared, and draped in the usual sterile fashion. A xipho-umbilical incision was performed for the creation of the gastric conduit. The stomach with is gastroepiploic blood supply was passed through the diaphragmatic hiatus. The pig was then placed in the right lateral decubitus position, prepared, and draped in sterile fashion and a thoracotomy was performed to visualize the thoracic esophagus (Fig 1A). The stomach conduit was then delivered into the thorax via the diaphragmatic hiatus. We proceeded with removal of the distal esophagus and performed a side-to-side, functional end-to-end stapled anastomosis identical to the ex vivo model. Once again, 18-gauge angiocatheters were used to introduce pressure probes and insufflate the anastomosis with a syringe (Fig 1B) until an anastomotic leak was identified and confirmed with methylene blue (Fig 1C). The intraluminal pressure at which an anastomotic leak occurred was recorded.

Figure Jump LinkFigure 1 –  Intraoperative photographs. A, Thoracotomy being performed. B, The angiocatheter apparatus used to introduce pressure probes and insufflation to the anastomosis. C, Methylene blue extravasation confirming staple line leakage of the anastomosis beyond maximum tolerated pressure.Grahic Jump Location
Application of NPPV in Live Pigs

To measure the amount of pressure transmitted to the esophagus in NPPV, pressure probes were inserted via an angiocatheter into the normal, proximal esophagus in five live, anesthetized pigs that had undergone a thoracotomy and had a patent GI tract. Because NPPV via a face mask was not feasible with the size and shape of the pig’s mouth and nose, we opted for a size 4 laryngeal mask airway (LMA) device placed proximal to the glottis above the esophageal and laryngeal inlets.21,22 The LMA placed in this location exerted a positive pressure to both the airway and the esophagus. Positive pressure, at 20, 30, and 40 cm H2O, was delivered in a pressure-controlled manner as the esophageal pressures were measured. Consistent pressures > 40 cm H2O could not be applied due to extensive leakage around the LMA into the proximal pharynx and mouth. The baseline intraluminal pressure was measured as atmospheric in every experiment and was subtracted from the pressure transmitted to esophagus from NPPV, resulting in the net exerted pressure in cm H2O. Our project was approved by the Institutional Animal Care and Use Committee of Dartmouth College (protocol erkm.cp.1).

Statistical Analysis

All data are reported as a mean with 95% CI and error bars as SEM, unless otherwise stated. Continuous data comparison between the in vivo and ex vivo groups was performed with the two-tailed Student t test. We obtained 95% CIs with nine degrees of freedom and a t value of 2.262 for anastomotic pressure tolerance (n = 10) and four degrees of freedom and a t value of 2.776 for pressure transmitted to the esophagus in NPPV (n = 5). Statistical analysis was performed with GraphPad Prism version 6.00 (GraphPad Software Inc).

Pressure Tolerance of Esophagectomy Anastomosis

Ex vivo anastomoses tolerated a mean of 101 ± 44 cm H2O of pressure (95% CI, 57-145), while in vivo anastomoses withstood 84 ± 38 cm H2O of pressure (95% CI, 46-122) before leakage was demonstrated (Fig 2A). The range of pressures tolerated by ex vivo and in vivo anastomoses before leakage was 21 to 232 cm H2O (median, 92 cm H2O) and 54 to 225 cm H2O (median, 57 cm H2O), respectively. There was no significant difference in maximum tolerated pressure between ex vivo and in vivo groups (P = .51). Leaks occurred everywhere on the staple lines with no discernible predilection for any region. Notably, leaks only occurred at the staple lines and never in surrounding tissue upon insufflation.

Figure Jump LinkFigure 2 –  A, The maximum pressure tolerated by in vivo and ex vivo anastomoses before leakage. B, Pressure transmitted to the esophagus during noninvasive positive pressure ventilation via laryngeal mask airway (all error bars represent SEM).Grahic Jump Location
Pressure Received in Esophagus During NPPV via LMA

The proximal, cervical esophagus recorded a mean of 5 ± 4 cm H2O (25% of applied pressure; 95% CI, 1-9) when 20 cm H2O was delivered via LM (Fig 2B). A mean of 11 ± 11 cm H2O (37%; 95% CI, 0-22) and 15 ± 9 cm H2O (38%; 95% CI, 6-24) of pressure were received in the esophagus when 30 and 40 cm H2O of pressure were applied, respectively (Fig 2B). The ranges of received pressures at 20, 30, and 40 cm H2O of applied pressure were 2 to 7 cm H2O (median, 6 cm H2O), 7 to 25 cm H2O (median, 7 cm H2O), and 3 to 21 cm H2O (median, 15 cm H2O), respectively. In two animals, progressive gastric insufflation was observed with sustained positive pressure of 30 to 40 cm H2O. The occurrence of gastric insufflation appeared to correlate to the amount of leakage around the LMA, with increased insufflation observed in animals where the LMA did not seal the laryngeal inlet perfectly, which was noticeable from the difficulty reaching desired ventilatory pressures.

Our pig model suggests that an esophagogastric anastomosis can tolerate manifold higher pressures than are delivered to the esophagus with NPPV. Specifically, an esophagogastric anastomosis can tolerate, on average, about 15, seven, and five times as much pressure as is transmitted to the esophagus with 20, 30, and 40 cm H2O of positive pressure, respectively, indicating the potential safety of NPPV after esophagectomy. Additionally, the similar data obtained in our ex vivo and in vivo studies suggest the ex vivo model can be used in place of in vivo pressure studies in the future, given its technical equivalence, increased cost effectiveness, and humaneness.

The risks of NPPV after esophagectomy must be weighed against its benefits. A case-control study has demonstrated several benefits with up to 25 cm H2O of NPPV in ARF following esophagectomy, including lower reintubation rates, lower frequency of ARDS, reduced ICU stay, and improved gas exchange without increasing the risk of anastomotic leak.6 A prospective, randomized trial also reported reduced reintubation rates when continuous positive airway pressure was administered to patients recovering normally after esophagectomy.19 Given the high respiratory morbidity after esophagectomy, NPPV could have an important role both as prophylaxis and as first-line therapy for ARF. The safe use of positive pressure in these European studies in conjunction with our pig model results suggest that the benefits may outweigh the risks of applying NPPV to patients after esophagectomy.

While NPPV appears safe after esophagectomy, there are reasons for caution. First, we observed a significant variability in pressure tolerance between animals. One ex vivo anastomosis tolerated a dangerously low pressure of 21 cm H2O, while another tolerated 46 cm H2O. The remaining ex vivo and all in vivo anastomoses tolerated pressures higher than 50 cm H2O. The two anastomoses that tolerated a low pressure were examined and found to have no gross technical error. While the low pressure tolerance measured in these two experiments could be attributed to human error, it is likely that a few patients will also be intolerant to high positive pressures, due to intrinsic differences in compliance or trauma to the tissue intra- or postoperatively. Indeed, a singular case report describes esophageal perforation soon after induction of 15 cm H2O of NPPV. This patient had a nephrectomy for renal adenocarcinoma. Perhaps this is an example of increased susceptibility to perforation due to underlying disease or inherently poor tensile strength.20 Importantly, our pig model does not account for perioperative changes to the tissue including potential scarring from neoadjuvant radiation therapy and inflammation, hypoxia, and frank necrosis after surgery, which may all compromise the anastomosis. This study is a springboard for future investigation into the pressure tolerance of diseased tissue.

Second, there was significant gastric insufflation with and leakage around the LMA with increasing pressures. Surprisingly, proximal esophageal pressures were not especially raised with high pressures. Pressure exerted by an LMA was more likely to result in an air leak around the LMA or in stomach distension than elevated esophageal pressure. Although proximal esophageal pressures did not increase during the few minutes of our measurements, there is a risk of eventual damage to the gastric conduit with sustained NPPV even at lower pressures, especially with reduced motility in the immediate postoperative period when ARF would also occur. Distension of a gastric conduit could cause increased wall tension, decreased venous outflow, and vascular congestion within a gastric conduit, thus posing a threat to the anastomosis. One of the important limitations of our study is that we did not examine the risk of prolonged variable pressurization of the anastomosis, where it is possible that submaximal but sustained pressures may eventually compromise the tissue at the staple line and result in perforation. Third, LMA has been associated with a higher leak fraction but lower incidence of gastric insufflation when compared with NPPV with a face mask, which indicates that conduit insufflation and the risk of anastomotic compromise may be worse with a face mask.2325

Fourth, we only used a linear stapled anastomosis in all our experiments, and our results, therefore, are not generalizable to other anastomotic techniques. Mechanical, or stapled, anastomoses are now more common than hand-sewn anastomoses, but the choice of stapling technique, circular or linear, depends on the surgeon’s preference.26 A large, single-institution, retrospective study showed that hand-sewn anastomoses had the highest leak rate, while the linear stapled technique had the lowest stricture rate.26 We can reasonably surmise, therefore, that the pressure tolerance of a hand-sewn anastomosis might be lower than that of a stapled one, but cannot speculate on the differences between stapling techniques.

Fifth, a pig model may also not accurately reflect the pressure dynamics in human beings. However, the similar esophageal histology in both species and identical surgical technique and materials used minimized the variables.27 The absolute pressure measurements may vary between the two species due to an inherent difference in tissue tensile strength, but we can reasonably expect that the fractional relationships in our experiments, especially the manifold higher pressure tolerance of the anastomosis than the pressure transmitted to the esophagus with NPPV, will hold true in humans, as well.

There are several potential sources of error in our experiments. First, our pressure measurements were all performed in pigs that had undergone a thoracotomy, thereby subjecting the pleura and mediastinum to atmospheric pressure during measurements. However, no significant restrictive effect was observed, since the intraluminal esophageal pressure was atmospheric at baseline in every experiment in both ex vivo and in vivo studies. Second, all our in vivo studies were performed in anesthetized pigs, and anesthetic agents can affect the esophageal muscle tone, with prior experiments demonstrating a lowering of lower esophageal sphincter threshold pressure by anesthetic agents.28 The similarity of maximum esophageal pressures in ex vivo studies, which were not subject to anesthetics, and in vivo experiments suggests that anesthesia played a minimal role in determining the pressure tolerance of the anastomosis. Third, our LMA pig model may not accurately reflect pressures of NPPV. However, the error would be on the side of exerting more pressure to the esophagus than NPPV exerted by a well-sealed face mask. Additionally, there was significant oscillation in LMA pressures below 7 to 8 cm H2O. Again, to err on the side of caution, we measured the peak pressures during our LMA experiments.

NPPV has several advantages over endotracheal intubation in patients with postoperative respiratory insufficiency. However, the positive pressure exerted to the airway can be translated to the esophagus. Thus, NPPV has been relatively contraindicated in patients after esophagectomy. We successfully created ex vivo and in vivo pig models quantifying the pressure threshold of an esophagogastric anastomosis and the pressures transmitted to the esophagus with NPPV. Our models demonstrate that an anastomosis can tolerate manifold higher pressures than are transmitted to the esophagus during NPPV. Further, our models establish safe ranges of airway pressure that can be exerted on a porcine esophagogastric anastomosis. Our work can provide a basis for future clinical trials.

Author contributions: C. P. E. served as principal author, had full access to all of the data in the study, and takes responsibility for the integrity of the data and the accuracy of the data analysis. C. P. E. conceived the project; V. R., C. E. M., and C. P. E. contributed to performing the experiments; V. R. contributed to writing the manuscript; and V. R., C. E. M., and C. P. E. contributed to critical review 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.

Role of sponsors: The sponsor had no role in the design of the study, the collection and analysis of the data, or the preparation of the manuscript.

Other contributions: We are grateful to Susan Kane, CVT, and Karen Moodie, DVM, for their assistance in pig surgery, and to Athos Rassias, MD, for materials support.

ARF

acute respiratory failure

LMA

laryngeal mask airway

NPPV

noninvasive positive pressure ventilation

Enzinger PC, Mayer RJ. Esophageal cancer. N Engl J Med. 2003;349(23):2241-2252. [CrossRef] [PubMed]
 
Finks JF, Osborne NH, Birkmeyer JD. Trends in hospital volume and operative mortality for high-risk surgery. N Engl J Med. 2011;364(22):2128-2137. [CrossRef] [PubMed]
 
Whooley BP, Law S, Murthy SC, Alexandrou A, Wong J. Analysis of reduced death and complication rates after esophageal resection. Ann Surg. 2001;233(3):338-344. [CrossRef] [PubMed]
 
Crozier TA, Sydow M, Siewert JR, Braun U. Postoperative pulmonary complication rate and long-term changes in respiratory function following esophagectomy with esophagogastrostomy. Acta Anaesthesiol Scand. 1992;36(1):10-15. [CrossRef] [PubMed]
 
Dumont P, Wihlm JM, Hentz JG, Roeslin N, Lion R, Morand G. Respiratory complications after surgical treatment of esophageal cancer. A study of 309 patients according to the type of resection. Eur J Cardiothorac Surg. 1995;9(10):539-543. [CrossRef] [PubMed]
 
Michelet P, D’Journo XB, Seinaye F, Forel JM, Papazian L, Thomas P. Non-invasive ventilation for treatment of postoperative respiratory failure after oesophagectomy. Br J Surg. 2009;96(1):54-60. [CrossRef] [PubMed]
 
Auriant I, Jallot A, Hervé P, et al. Noninvasive ventilation reduces mortality in acute respiratory failure following lung resection. Am J Respir Crit Care Med. 2001;164(7):1231-1235. [CrossRef] [PubMed]
 
Brochard L, Isabey D, Piquet J, et al. Reversal of acute exacerbations of chronic obstructive lung disease by inspiratory assistance with a face mask. N Engl J Med. 1990;323(22):1523-1530. [CrossRef] [PubMed]
 
Celikel T, Sungur M, Ceyhan B, Karakurt S. Comparison of noninvasive positive pressure ventilation with standard medical therapy in hypercapnic acute respiratory failure. Chest. 1998;114(6):1636-1642. [CrossRef] [PubMed]
 
Jaber S, Delay J-M, Chanques G, et al. Outcomes of patients with acute respiratory failure after abdominal surgery treated with noninvasive positive pressure ventilation. Chest. 2005;128(4):2688-2695. [CrossRef] [PubMed]
 
Girault C, Briel A, Hellot M-F, et al. Noninvasive mechanical ventilation in clinical practice: a 2-year experience in a medical intensive care unit. Crit Care Med. 2003;31(2):552-559. [CrossRef] [PubMed]
 
Esteban A, Frutos-Vivar F, Ferguson ND, et al. Noninvasive positive-pressure ventilation for respiratory failure after extubation. N Engl J Med. 2004;350(24):2452-2460. [CrossRef] [PubMed]
 
Antonelli M, Conti G, Rocco M, et al. A comparison of noninvasive positive-pressure ventilation and conventional mechanical ventilation in patients with acute respiratory failure. N Engl J Med. 1998;339(7):429-435. [CrossRef] [PubMed]
 
Kramer N, Meyer TJ, Meharg J, Cece RD, Hill NS. Randomized, prospective trial of noninvasive positive pressure ventilation in acute respiratory failure. Am J Respir Crit Care Med. 1995;151(6):1799-1806. [CrossRef] [PubMed]
 
Squadrone V, Coha M, Cerutti E, et al; Piedmont Intensive Care Units Network (PICUN). Continuous positive airway pressure for treatment of postoperative hypoxemia: a randomized controlled trial. JAMA. 2005;293(5):589-595. [CrossRef] [PubMed]
 
Varon J, Walsh GL, Fromm RE Jr. Feasibility of noninvasive mechanical ventilation in the treatment of acute respiratory failure in postoperative cancer patients. J Crit Care. 1998;13(2):55-57. [CrossRef] [PubMed]
 
Chiumello D, Chevallard G, Gregoretti C. Non-invasive ventilation in postoperative patients: a systematic review. Intensive Care Med. 2011;37(6):918-929. [CrossRef] [PubMed]
 
Aguiló R, Togores B, Pons S, Rubí M, Barbé F, Agustí AG. Noninvasive ventilatory support after lung resectional surgery. Chest. 1997;112(1):117-121. [CrossRef] [PubMed]
 
Fagevik Olsén M, Wennberg E, Johnsson E, Josefson K, Lönroth H, Lundell L. Randomized clinical study of the prevention of pulmonary complications after thoracoabdominal resection by two different breathing techniques. Br J Surg. 2002;89(10):1228-1234. [CrossRef] [PubMed]
 
Van de Louw A, Brocas E, Boiteau R, Perrin-Gachadoat D, Tenaillon A. Esophageal perforation associated with noninvasive ventilation: a case report. Chest. 2002;122(5):1857-1858. [CrossRef] [PubMed]
 
Fulkerson PJ, Gustafson SB. Use of laryngeal mask airway compared to endotracheal tube with positive-pressure ventilation in anesthetized swine. Vet Anaesth Analg. 2007;34(4):284-288. [CrossRef] [PubMed]
 
Wemyss-Holden SA, Porter KJ, Baxter P, Rudkin GE, Maddern GJ. The laryngeal mask airway in experimental pig anaesthesia. Lab Anim. 1999;33(1):30-34. [CrossRef] [PubMed]
 
Ho-Tai LM, Devitt JH, Noel AG, O’Donnell MP. Gas leak and gastric insufflation during controlled ventilation: face mask versus laryngeal mask airway. Can J Anaesth. 1998;45(3):206-211. [CrossRef] [PubMed]
 
Weiler N, Latorre F, Eberle B, Goedecke R, Heinrichs W. Respiratory mechanics, gastric insufflation pressure, and air leakage of the laryngeal mask airway. Anesth Analg. 1997;84(5):1025-1028. [PubMed]
 
Brimacombe J. The advantages of the LMA over the tracheal tube or facemask: a meta-analysis. Can J Anaesth. 1995;42(11):1017-1023. [CrossRef] [PubMed]
 
Price TN, Nichols FC, Harmsen WS, et al. A comprehensive review of anastomotic technique in 432 esophagectomies. Ann Thorac Surg. 2013;95(4):1154-1160. [CrossRef] [PubMed]
 
Christie KN, Thomson C, Hopwood D. A comparison of membrane enzymes of human and pig oesophagus; the pig oesophagus is a good model for studies of the gullet in man. Histochem J. 1995;27(3):231-239. [CrossRef] [PubMed]
 
Rabey PG, Murphy PJ, Langton JA, Barker P, Rowbotham DJ. Effect of the laryngeal mask airway on lower oesophageal sphincter pressure in patients during general anaesthesia. Br J Anaesth. 1992;69(4):346-348. [CrossRef] [PubMed]
 

Figures

Figure Jump LinkFigure 1 –  Intraoperative photographs. A, Thoracotomy being performed. B, The angiocatheter apparatus used to introduce pressure probes and insufflation to the anastomosis. C, Methylene blue extravasation confirming staple line leakage of the anastomosis beyond maximum tolerated pressure.Grahic Jump Location
Figure Jump LinkFigure 2 –  A, The maximum pressure tolerated by in vivo and ex vivo anastomoses before leakage. B, Pressure transmitted to the esophagus during noninvasive positive pressure ventilation via laryngeal mask airway (all error bars represent SEM).Grahic Jump Location

Tables

References

Enzinger PC, Mayer RJ. Esophageal cancer. N Engl J Med. 2003;349(23):2241-2252. [CrossRef] [PubMed]
 
Finks JF, Osborne NH, Birkmeyer JD. Trends in hospital volume and operative mortality for high-risk surgery. N Engl J Med. 2011;364(22):2128-2137. [CrossRef] [PubMed]
 
Whooley BP, Law S, Murthy SC, Alexandrou A, Wong J. Analysis of reduced death and complication rates after esophageal resection. Ann Surg. 2001;233(3):338-344. [CrossRef] [PubMed]
 
Crozier TA, Sydow M, Siewert JR, Braun U. Postoperative pulmonary complication rate and long-term changes in respiratory function following esophagectomy with esophagogastrostomy. Acta Anaesthesiol Scand. 1992;36(1):10-15. [CrossRef] [PubMed]
 
Dumont P, Wihlm JM, Hentz JG, Roeslin N, Lion R, Morand G. Respiratory complications after surgical treatment of esophageal cancer. A study of 309 patients according to the type of resection. Eur J Cardiothorac Surg. 1995;9(10):539-543. [CrossRef] [PubMed]
 
Michelet P, D’Journo XB, Seinaye F, Forel JM, Papazian L, Thomas P. Non-invasive ventilation for treatment of postoperative respiratory failure after oesophagectomy. Br J Surg. 2009;96(1):54-60. [CrossRef] [PubMed]
 
Auriant I, Jallot A, Hervé P, et al. Noninvasive ventilation reduces mortality in acute respiratory failure following lung resection. Am J Respir Crit Care Med. 2001;164(7):1231-1235. [CrossRef] [PubMed]
 
Brochard L, Isabey D, Piquet J, et al. Reversal of acute exacerbations of chronic obstructive lung disease by inspiratory assistance with a face mask. N Engl J Med. 1990;323(22):1523-1530. [CrossRef] [PubMed]
 
Celikel T, Sungur M, Ceyhan B, Karakurt S. Comparison of noninvasive positive pressure ventilation with standard medical therapy in hypercapnic acute respiratory failure. Chest. 1998;114(6):1636-1642. [CrossRef] [PubMed]
 
Jaber S, Delay J-M, Chanques G, et al. Outcomes of patients with acute respiratory failure after abdominal surgery treated with noninvasive positive pressure ventilation. Chest. 2005;128(4):2688-2695. [CrossRef] [PubMed]
 
Girault C, Briel A, Hellot M-F, et al. Noninvasive mechanical ventilation in clinical practice: a 2-year experience in a medical intensive care unit. Crit Care Med. 2003;31(2):552-559. [CrossRef] [PubMed]
 
Esteban A, Frutos-Vivar F, Ferguson ND, et al. Noninvasive positive-pressure ventilation for respiratory failure after extubation. N Engl J Med. 2004;350(24):2452-2460. [CrossRef] [PubMed]
 
Antonelli M, Conti G, Rocco M, et al. A comparison of noninvasive positive-pressure ventilation and conventional mechanical ventilation in patients with acute respiratory failure. N Engl J Med. 1998;339(7):429-435. [CrossRef] [PubMed]
 
Kramer N, Meyer TJ, Meharg J, Cece RD, Hill NS. Randomized, prospective trial of noninvasive positive pressure ventilation in acute respiratory failure. Am J Respir Crit Care Med. 1995;151(6):1799-1806. [CrossRef] [PubMed]
 
Squadrone V, Coha M, Cerutti E, et al; Piedmont Intensive Care Units Network (PICUN). Continuous positive airway pressure for treatment of postoperative hypoxemia: a randomized controlled trial. JAMA. 2005;293(5):589-595. [CrossRef] [PubMed]
 
Varon J, Walsh GL, Fromm RE Jr. Feasibility of noninvasive mechanical ventilation in the treatment of acute respiratory failure in postoperative cancer patients. J Crit Care. 1998;13(2):55-57. [CrossRef] [PubMed]
 
Chiumello D, Chevallard G, Gregoretti C. Non-invasive ventilation in postoperative patients: a systematic review. Intensive Care Med. 2011;37(6):918-929. [CrossRef] [PubMed]
 
Aguiló R, Togores B, Pons S, Rubí M, Barbé F, Agustí AG. Noninvasive ventilatory support after lung resectional surgery. Chest. 1997;112(1):117-121. [CrossRef] [PubMed]
 
Fagevik Olsén M, Wennberg E, Johnsson E, Josefson K, Lönroth H, Lundell L. Randomized clinical study of the prevention of pulmonary complications after thoracoabdominal resection by two different breathing techniques. Br J Surg. 2002;89(10):1228-1234. [CrossRef] [PubMed]
 
Van de Louw A, Brocas E, Boiteau R, Perrin-Gachadoat D, Tenaillon A. Esophageal perforation associated with noninvasive ventilation: a case report. Chest. 2002;122(5):1857-1858. [CrossRef] [PubMed]
 
Fulkerson PJ, Gustafson SB. Use of laryngeal mask airway compared to endotracheal tube with positive-pressure ventilation in anesthetized swine. Vet Anaesth Analg. 2007;34(4):284-288. [CrossRef] [PubMed]
 
Wemyss-Holden SA, Porter KJ, Baxter P, Rudkin GE, Maddern GJ. The laryngeal mask airway in experimental pig anaesthesia. Lab Anim. 1999;33(1):30-34. [CrossRef] [PubMed]
 
Ho-Tai LM, Devitt JH, Noel AG, O’Donnell MP. Gas leak and gastric insufflation during controlled ventilation: face mask versus laryngeal mask airway. Can J Anaesth. 1998;45(3):206-211. [CrossRef] [PubMed]
 
Weiler N, Latorre F, Eberle B, Goedecke R, Heinrichs W. Respiratory mechanics, gastric insufflation pressure, and air leakage of the laryngeal mask airway. Anesth Analg. 1997;84(5):1025-1028. [PubMed]
 
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    Print ISSN: 0012-3692
    Online ISSN: 1931-3543