Body Fluid Shift in Obstructive Sleep Apnea

TORONTO, Dec. 18 -- For patients with fluid-retaining conditions the simple act of lying down in bed at night may cause a fluid shift to the upper body that results in obstructive sleep apnea, a small study here suggested.

In healthy participants whose body fluid was shifted to mimic the effects of fluid redistribution in edematous patients when lying down, airflow resistance in the pharynx increased by 102% after five minutes, reported T. Douglas Bradley, M.D., of the Toronto General Hospital here.

Fluid accumulation in the neck and around the pharynx from conditions such as such as heart or kidney failure "may cause pharyngeal narrowing and increase the likelihood of pharyngeal occlusion in patients predisposed to obstructive sleep apnea," Dr. Bradley and colleagues said in the Dec. 15 issue of the American Journal of Respiratory and Critical Care Medicine.

The crossover study included 11 healthy, non-obese adult volunteers with no history of snoring or daytime sleepiness. Their average age was 36, and their average BMI was 22.9.

Neck circumference and airflow resistance in the pharynx were measured while volunteers were awake and lying down. The volunteers were then randomized to either a control period of simply continuing to recline or to five minutes in anti-shock pants. The pants put pressure on the legs and displaced fluid into the upper body.

After one minute in the pants, neck circumference increased by 0.3% from baseline (P

Edematous patients, including those with heart failure, kidney failure, and idiopathic peripheral edema, are particularly prone to obstructive sleep apnea, which suggests that fluid overload might contribute to the condition in some patients, the authors said.