Letters to the Editor: Letters & Announcements
We disagree with the interpretation of our conclusion by Overdyk and Ahmed1 that the findings of our study2 suggest that patients with obstructive sleep apnea (OSA) require no closer postoperative surveillance than obese patients without OSA. However, we believe that our study indicates that morbidly obese non-OSA patients are equally at risk for postoperative hypoxemia and should receive the same monitoring as those with OSA.
We do agree that there have been differences among pulse oximeters in detection of the Oxygen Desaturation Index and that the detection difference is greatest when comparing signal averaging times between 3 and 12 s.3,4 In our study, two dedicated pulse oximeters from the same manufacturer were used for collection of postoperative data, and there was no difference in the numbers of subjects in either group monitored by either of the monitors. In addition, both groups demonstrated a significant number of desaturations, and the potential for underestimation was similar for both groups. We also agree that a limitation of our findings was the routine use of oxygen in the postoperative period; however, we are unaware of any study that demonstrates that supplemental oxygen could reduce the incidence of obstructive episodes in morbidly obese subjects with OSA more than morbidly obese subjects without OSA.
Shireen Ahmad, MD
Robert J. McCarthy, PharmD
Department of Anesthesiology
Northwestern University Feinberg School of Medicine
1.Overdyk FJ, Ahmed Q. Postoperative monitoring of Obese Patients with Obstructive Sleep Apnea. Anesth Analg 2009;108:1044–5
2.Ahmad S, Nagle A, McCarthy RJ, Fitzgerald PC, Sullivan JT, Prystowsky J. Postoperative hypoxemia in morbidly obese patients with and without obstructive sleep apnea undergoing laparoscopic bariatric surgery. Anesth Analg 2008;107:138–43
3.Davila DG, Richards KC, Marshall BL, O’Sullivan PS, Osbahr LA, Huddleston RB, Jordan JC. Oximeter’s acquisition parameter influences the profile of respiratory disturbances. Sleep 2003;26:91–5
4.Farré R, Montserrat JM, Ballester E, Hernández L, Rotger M, Navajas D. Importance of the pulse oximeter averaging time when measuring oxygen desaturation in sleep apnea. Sleep 1998;21:386–90