The article by Krodel et al1 in an issue of CHEST (November 2011) reported a case of negative pressure pulmonary edema following bronchospasm, highlighting the potential contribution of lower airway obstruction. The phenomenon is commonly seen in cases of upper airway obstruction, including obstructive sleep apnea (OSA). In my experience, I have noted this several times in patients with untreated OSA who were mechanically ventilated; unsurprisingly, all had a high BMI. In these cases, sleep studies have gone on to demonstrate OSA after the initial event in the recovery phase. In the quoted case, the patient may have been on systemic steroids for some time (given her systemic lupus erythematosus), and it would be interesting to know her BMI and whether undiagnosed OSA could have been a contributory factor. It is important to consider occult OSA in unexplained postoperative pulmonary edema in ventilated patients, even in patients with lower airway obstruction.