Letters to the Editor: Letter to the Editor
To the Editor
Lam et al1 point out that when a person lies supine at night, a “rostral fluid shift” from the legs to the neck and upper airway occurs and that the increased neck and upper airway fluid causes increased airway collapsibility and, in patients with obstructive sleep apnea (OSA), an increase in the apnea–hypopnea index. In addition, they suggest in Figure 1 that the application of positive airway pressure could reverse the supine position-induced increase in upper airway collapsibility and apnea–hypopnea index.
During sleep in the supine position, the lungs of some patients with OSA, in addition to the upper airways, may also gain some edema fluid. Fletcher et al2 showed that pulmonary edema may develop in some supine spontaneously ventilating supine dogs subjected to recurrent (every 30 seconds) obstructive apneas (produced by clamping the endotracheal tube at end-expiration for 45 seconds). The increase in lung fluid in these supine spontaneously breathing dogs was correctly partially attributed to the development of negative-pressure pulmonary edema. In addition, I reported that in a series of 12 closed medical malpractice cases of patients with OSA being found dead in bed that I reviewed as a medical expert, 4 of these patients had pulmonary edema.3 I concluded based on the totality of the evidence contained in the medical records, depositions, and autopsies that the only explanation for the lung edema in these 4 patients was negative-pressure pulmonary edema. Thus, sleep in the supine position for patients with OSA may pose an additional newly understood double jeopardy, namely, a nightly increase in the severity of OSA because of wet airways and a nightly deterioration in lung function because of wet lungs.
Jonathan L. Benumof, MDDepartment of AnesthesiologyUCSD Medical CenterSan Diego, Californiajbenumof@ucsd.edu
1. Lam T, Singh M, Yadollahi A, Chung F. Is perioperative fluid and salt balance a contributing factor in postoperative worsening of obstructive sleep apnea? Anesth Analg. 2016;122:13351339.
2. Fletcher EC, Proctor M, Yu J, et al. Pulmonary edema develops after recurrent obstructive apneas. Am J Respir Crit Care Med. 1999;160:16881696.
3. Benumof JL. Mismanagement of obstructive sleep apnea may result in finding these patients dead in bed. Can J Anaesth. 2016;63:37.