Anesth Analg 2007;104:455-456
© 2007 International Anesthesia Research Society
doi: 10.1213/01.ane.0000253565.98827.e0
LETTER TO THE EDITOR
Section Editor:
Lawrence Saidman
Alveolar Recruitment and Positive End-Expiratory Pressure in Obesity: Another Merry Chase?
Francis Whalen, MD,
Ogjen Gajic, MD,
Juraj Sprung, MD, PhD,
David O. Warner, MD, and
Rolf Hubmayr, MD
Department of Anesthesiology; Division of Pulmonary and Critical Care Medicine; Mayo Clinic College of Medicine; Mayo Clinic, Rochester, Minnesota; whalen.francis{at}mayo.edu
In Response:
We are grateful for Dr. Satya Krishna Ramachandran for his remarks which show that he has carefully read our article. Despite the fact that we did not directly measure the degree of atelectasis it is known that obese patients develop atelectasis, and the recruitment maneuver reverses this. Lung volume is a prime factor that determines lung compliance; with recruitment dynamic compliance increased reflecting a reduction in atelectasis. The mechanism is speculative, but consistent with improved compliance.
We did observe preserved oxygenation despite "derecruitment" (reflected by the gradual decrease in dynamic compliance). We clearly acknowledge that there may be some uncoupling between the redevelopment of atelectasis and oxygenation. It is unclear whether high intraperitoneal pressure plays a role in preserving oxygenation.
We specifically state that recruitment did not affect the efficiency of ventilation. We did observe only a transient improvement in respiratory compliance. The beneficial effect of RM and PEEP may in part be explained by improved ventilation-perfusion matching.
We disagree with the notion that noninvasive ventilation is "absolutely contraindicated" in patients undergoing upper gastrointestinal surgery. Indeed, 6% of patients enrolled in the landmark study by Squadrone et al. had upper gastrointestinal surgery (gastrectomy) (1).
Presently and at the time of this study all patients at Mayo prescribed CPAP or BiPAP preoperatively receive this immediately postoperatively. This is a standard of care in these patients (2); the ASA task force that developed this guideline included a bariatric surgeon. There is no clear evidence that this is in any way contraindicated.
Our study was not powered to determine the incidence of postoperative pulmonary complications. We did not observe any case of postoperative pneumonia. In the study by Dresel et al., (3) the incidence of atelectasis and the need for intubation for more than 24 h was not reported. Therefore the incidence of complications could not be compared between these two studies.
REFERENCES
- Squadrone V, Coha M, Cerutti E, et al. Continuous positive airway pressure for treatment of postoperative hypoxemia: a randomized controlled trial. JAMA 2005; 293:589–95.[Abstract/Free Full Text]
- Practice guidelines for the perioperative management of patients with obstructive sleep apnea. A report by the American Society of Anesthesiologists Task Force on perioperative management of patients with obstructive sleep apnea. Approved by the House of Delegates on October 25, 2005.
- Dresel A, Kuhn JA, McCarty TM. Laparoscopic Roux-en-Y gastric bypass in morbidly obese and super morbidly obese patients. Am J Surg 2004;187:230–2.[Web of Science][Medline]
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