Temporal shifts in fluid in pulmonary hypertension with and without sleep apnea

Overnight extracellular rostral fluid shifts have been shown to be of importance in patients with fluid-retaining states and are associated with a higher prevalence of sleep apnea. Pulmonary hypertension is frequently associated with right ventricular dysfunction and progressive right ventricular failure, and an increased prevalence of sleep apnea has been described. In light of the importance of fluid shifts in the pathophysiology of sleep apnea, we aimed to explore temporal fluid shifts in patients with pulmonary hypertension with and without sleep apnea. Patients with pulmonary hypertension (WHO Group 1 or 4) had overnight extracellular rostral fluid shift assessment before and a minimum of 3 months after initiation of pulmonary hypertension-specific therapy. Fluid shift measurements of extracellular leg, abdominal, thoracic and neck fluid volumes were performed simultaneously. Twenty-nine patients with pulmonary hypertension (age 55 ± 16 years, 69% female) participated. Sleep apnea was diagnosed in 15 subjects (apnea-hypopnea index 14 [8-27] per hr). There were no significant differences in baseline or overnight leg extracellular rostral fluid, abdominal extracellular rostral fluid, thoracic extracellular rostral fluid or neck extracellular rostral fluid between those with and without sleep apnea. There was a significant inverse correlation between the sleep apnea severity and the overnight change in leg extracellular rostral fluid (r = -0.375, p = 0.049). There were no significant differences detected in overnight extracellular rostral fluid shifts from baseline to follow-up. Treatment-naïve patients with pulmonary hypertension both with and without sleep apnea demonstrate overnight extracellular rostral fluid shifts from the legs into the thorax and neck. Pulmonary hypertension-specific treatment, while significantly improving cardiac haemodynamics, had little impact on nocturnal extracellular rostral fluid shifts or the presence of sleep apnea.