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Contrasting Effects of Lower Body Positive Pressure on Upper Airways: Resistance and Partial Pressure of Carbon Dioxide in Men With Heart Failure and Obstructive or Central Sleep Apnea
Study Questions:
What are the effects of rostral fluid displacement from the legs on transpharyngeal resistance (Rph), minute volume of ventilation (Vmin), and partial pressure of carbon dioxide (PCO2) in men with heart failure (HF) and either obstructive (OSA) or central sleep apnea (CSA)?
Methods:
Men with HF were divided into those with mainly OSA (obstructive-dominant, n =18) and those with mainly CSA (central-dominant, n = 10). While patients were supine, antishock trousers were deflated (control) or inflated for 15 minutes (lower body positive pressure [LBPP]) in random order. Within each group, two-way repeated-measures analysis of variance, followed by a post hoc analysis with Bonferroni correction for multiple comparisons, was used to compare values obtained during the baseline and either LBPP or control periods.
Results:
LBPP reduced leg fluid volume and increased neck circumference in both obstructive- and central-dominant groups. However, in contrast to the obstructive-dominant group in whom LBPP induced an increase in Rph, a decrease in Vmin, and an increase in PCO2, in the central-dominant group, LBPP induced a reduction in Rph, an increase in Vmin, and a reduction in PCO2.
Conclusions:
The authors concluded that rostral fluid shifts contribute to the pathogenesis of OSA and CSA in men with HF.
Perspective:
The current study provides mechanistic evidence to suggest that nocturnal rostral fluid shift can contribute to the pathogenesis of both OSA and CSA in men with HF. The data suggest that in those in whom rostral fluid shift induces an increase in transpharyngeal resistance, susceptibility to OSA will increase, whereas in those in whom it induces an increase in respiratory drive with reductions in transpharyngeal resistance and PCO2, susceptibility to CSA will increase. The study raises the possibility that prevention of fluid accumulation in the legs during the daytime or rostral fluid shift at night may alleviate OSA or CSA in some men with HF. Further research is needed to examine these possibilities.
Keywords: Fluid Shifts, Pyrrolidinones, Partial Pressure, Carbon Dioxide, Polysomnography, Heart Failure, Cardiovascular Diseases, Blood Pressure, Lower Extremity, Respiration, Sleep Apnea Syndromes
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