Low carbon dioxide production linked to central sleep apnea in men with heart failure

Key takeaways:

• Researchers found a link between low BMI and central sleep apnea in men with heart failure.
• Decreased carbon dioxide production was also related to central sleep apnea.

Reduced carbon dioxide production is linked to central sleep apnea in men with heart failure with reduced ejection fraction, according to data published in Annals of the American Thoracic Society.

Researchers also found a link between low BMI and central sleep apnea (CSA) in this population.

“Our finding may have potential clinical implications for poor prognosis in some patients with heart failure with low BMI/cachexia, in whom there is a complex interplay among mortality, body composition and metabolism,” Shahrokh Javaheri, MD, professor emeritus of medicine at University of Cincinnati College of Medicine and medical director at Sleepcare Diagnostics, and Loretta A. Simbartl, BS, MS, statistician at the Veterans Affairs Medical Center in Ohio, wrote.

Javaheri and Simbartl evaluated 28 veterans (mean age, 65 years; 100% men) with heart failure with reduced ejection fraction (HFrEF) to determine if metabolic rate, shown through carbon dioxide production, is linked to CSA development in regression models.

This study took place in a sleep laboratory, and researchers collected several variables from each veteran during their second night in the lab: polysomnography, left ventricular ejection fraction, pulmonary function test data, carbon dioxide production and arterial blood samples.

Of the total cohort, researchers found that BMI ranged from 20 kg/m² to 40 kg/m², with a mean BMI of 26.9 kg/m². A larger range was observed in carbon dioxide production (167 mL/min-434 mL/min).

Central sleep apnea was evident in this population through a central apnea index of 16 events per hour. Further, central sleep apnea-hypopnea was deemed to be moderate based on a mean apnea-hypopnea index (AHI) of 25 events per hour.

When assessing associations, researchers found a relationship between reduced BMI and CSA.

Although BMI was related to both steady-state carbon dioxide production (P < .001) and oxygen consumption (P = .002), only carbon dioxide production was linked to CSA (AHI, central AHI) in the analysis.

“This is an important physiological finding because it is the fluctuation in P_CO2 [carbon dioxide tension/partial pressure] and its reduction below the apneic threshold for P_CO2 that causes cessation of breathing (a central apnea),” Javaheri and Simbartl wrote. “The results of this study in humans confirm the theoretical basis for the association of low [metabolic rate] and V_CO2 [carbon dioxide production] with CSA.”