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Cherie P. Erkmen, MD; Vignesh Raman, BS
Author and Funding Information

FINANCIAL/NONFINANCIAL DISCLOSURES: None declared.

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

CORRESPONDENCE TO: Cherie P. Erkmen, MD, Temple University Health System, Thoracic Surgery, Parkinson Pavilion, 3401 N Broad St, Ste C-100m, Philadelphia, PA 19140.


Copyright 2016, American College of Chest Physicians. All Rights Reserved.


Chest. 2016;149(2):602-603. doi:10.1016/j.chest.2015.11.006
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We thank Drs Giani and Beretta for their interest in our work recently published in CHEST.

They assert that our esophageal pressure measurements do not reflect transmural pressure. We performed our experiments on pigs that had undergone a thoracotomy, and therefore the extraesophageal pressure was atmospheric. As mentioned in our Methods section, we subtracted atmospheric pressure from our intraesophageal measurements to arrive at pressure measurements that were transmural and not merely transmitted pressures. In a patient with a closed chest, positive pressure ventilation would result in higher pleural pressures, reducing transesophageal pressure.,, Our experimental environment generated much higher transmural pressures than would be expected in the clinical scenario of a closed chest. Given our findings, increased transesophageal pressures during noninvasive positive pressure ventilation (NPPV) are not likely to threaten an anastomosis. However, our data are from an animal model and we hope they will provide the basis for future clinical trials.

Drs Giani and Beretta also point out our use of a laryngeal mask airway rather than a face mask for delivery of NPPV. As we describe in our Methods section, we were unable to fit a traditional face mask in our pigs and consequently simulated face mask ventilation by placing the laryngeal mask airway device proximal to the glottis. This experimental modification probably exerted increased intraluminal esophageal pressures higher than would be measured in a patient with a face mask. Again, our experimental environment was more stressful than what we would expect in the clinical setting.

We acknowledge in our article the observation of significant but variable gastric distension with NPPV. We agree with Drs Giani and Beretta that this is a potential threat to the anastomosis. We are currently examining the effect of gastric distension on esophageal anastomoses in a separate study.

We reiterate our findings that an esophageal anastomosis can tolerate manifold higher pressures than are transmitted to the esophagus during NPPV. We suggest that this experimental model provides the necessary safety data for future studies in humans. We hope to examine NPPV in patients after esophagectomy. We appreciate the input from Drs Giani and Beretta as we will certainly assess transmural pressures and gastric distension along with anastomosis viability in future studies.

References

Raman V. .MacGlaflin C.E. .Erkmen C.P. . Noninvasive positive pressure ventilation following esophagectomy: safety demonstrated in a pig model. Chest. 2015;147:356-361 [PubMed]journal. [CrossRef] [PubMed]
 
Shekerdemian L. .Bohn D. . Cardiovascular effects of mechanical ventilation. Arch Dis Child. 1999;80:475-480 [PubMed]journal. [CrossRef] [PubMed]
 
Auler J.O. Jr..Zin W.A. .Caldeira M.P. .Cardoso W.V. .Saldiva P.H. . Pre- and postoperative inspiratory mechanics in ischemic and valvular heart disease. Chest. 1987;92:984-990 [PubMed]journal. [CrossRef] [PubMed]
 
Neto P.P.R. .Auler J.O.C. . Respiratory mechanical properties during fentanyl and alfentanil anaesthesia. Can J Anaesth. 1992;39:458-465 [PubMed]journal. [CrossRef] [PubMed]
 

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References

Raman V. .MacGlaflin C.E. .Erkmen C.P. . Noninvasive positive pressure ventilation following esophagectomy: safety demonstrated in a pig model. Chest. 2015;147:356-361 [PubMed]journal. [CrossRef] [PubMed]
 
Shekerdemian L. .Bohn D. . Cardiovascular effects of mechanical ventilation. Arch Dis Child. 1999;80:475-480 [PubMed]journal. [CrossRef] [PubMed]
 
Auler J.O. Jr..Zin W.A. .Caldeira M.P. .Cardoso W.V. .Saldiva P.H. . Pre- and postoperative inspiratory mechanics in ischemic and valvular heart disease. Chest. 1987;92:984-990 [PubMed]journal. [CrossRef] [PubMed]
 
Neto P.P.R. .Auler J.O.C. . Respiratory mechanical properties during fentanyl and alfentanil anaesthesia. Can J Anaesth. 1992;39:458-465 [PubMed]journal. [CrossRef] [PubMed]
 
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