Response to hypoxic provocation in patients with chronic heart failure and its predictive value for central sleep apnea

Abstract

Introduction Central apneas are usually clustered in periodic sequences in patients with chronic heart failure (CHF) and central sleep apnea (CSA), triggered by destabilizing events. We hypothesized that a provocation with exogenous hypoxic hypoxia may destabilize a system with abnormal gain (controller and plant) enough to trigger visually recognizable central events during wakefulness in those patients. The aim of the study is to investigate the response to hypoxic provocation in patients with CHF and its capability to predict the presence of CSA. Materials and methods Nineteen patients with CHF (age=65.5±7.3, EF=51.9±6.6) have been recruited and subjected to polysomnography and hypoxic provocation. Central apnea-hypopnea index (cAHI)>5 determined the presence of CSA, dividing the patients in 2 groups – with CSA ( n =13, cAHI=29.2±16.2) and CHF without CSA ( n =6, cAHI=4.0±1.6, p 3% were scored for each period and respective indices for apneas and hypopneas (hAHI) and oxygen desaturations (hODI) have been calculated in the classical manner (count per 1h). Results No differences were present between the 2 groups in the prehypoxic period (hAHIpre=27.6±26.7 vs. 16.3±27.3, NS; hODIpre=18.6±23.5 vs. 12.9±17.6, NS; average desaturation (hAvDespre)=2.5±2.4 vs. 2.3±1.9, NS in patients and controls, respectively). Significantly higher values for these parameters were found after the hypoxic provocation in the CHF+CSA group, compared to CHF controls (hAHIpost=54.5±28.8 vs. 18.8±28.8, p =0.022; hODIpost=37.0±23.2 vs. 2.4±4.5, p p =0.007). Exogenous hypoxia provoked significantly more events in the posthypoxic period, compared to baseline values only in CHF+CSA patients (hAHIpre/hAHIpost, p =0.002; hODIpre/hODIpost, p =0.002; hAvDespre/hAvDespost, p =0.008). Strong significant correlation was found between cAHI and hAHI3 (rho=0.553, p =0.05) and hODI3 (rho=0.564, p =0.05). Patients presenting with positive hypoxic provocation test (empirically chosen if hAHIpost>30) had 11.8 times higher odds (95% CI=1.34–105, p =0.026) to have CSA. Conclusion Hypoxic provocation triggers central events during wakefulness in the majority of CHF+CSA patients and may be used as a predictor of the presence and magnitude of CSA in CHF. Acknowledgement The study was financed by the Bulgarian Ministry of Youth and Science.