Targeting volume overload and overnight rostral fluid shift: A new perspective to treat sleep apnea

Sleep apnea is a common condition associated with increased morbidity and mortality. Continuous positive airway pressure and oral appliances are efficient for treating sleep apnea; however, they are often poorly tolerated. Therefore, alternative therapies are needed. Overnight rostral fluid shift has been implicated in the pathogenesis of sleep apnea, particularly in conditions associated with fluid overload. Fluid shift predisposes to both obstructive and central sleep apnea, with the type of sleep apnea being related to whether the fluid shifts from the legs into the neck or chest, respectively. The amount of fluid that shifts from the legs to the upper part of the body at night is correlated with the severity of sleep apnea. As a result of this observation, it has been suggested that the prevention of overnight fluid shift may reduce sleep apnea severity. It has recently been shown that interventions targeting fluid overload and daytime fluid accumulation in the legs consistently attenuate nocturnal fluid shift and sleep apnea, as greater reductions in fluid shift are correlated with greater reductions in sleep apnea severity. This review will focus on interventions that counteract fluid shift, such as diuretics, ultrafiltration/dialysis, physical activity, compression stockings and salt/fluid restriction, which have been shown to have efficacy in reducing sleep apnea severity.