The effect of CPAP treatment on venous lactate and arterial blood gas among obstructive sleep apnea syndrome patients.

PURPOSE: The aim of this observational study was to investigate the influence of continuous positive airway pressure (CPAP) on arterial blood gas and venous lactate, markers of tissue hypoxia, among obstructive sleep apnea syndrome (OSAS) patients, and determine the risk factor of serum lactate and hydrogen ion concentration (PH) in OSAS patients.

MATERIALS AND METHODS: One-hundred and nine patients with newly diagnosed OSAS were enrolled in the study. All individuals were treated with CPAP for one night. Venous lactate and arterial blood gas were gathered from all subjects in the morning at the end of polysomnography and the next morning after CPAP treatment.

RESULTS: Of the 109 selected subjects, the average lactate level was 2.23 ± 0.59 mmol/L, and the mean PH, PaO2 , and PaCO2 were 7.380 ± 0.23, 88.14 ± 17.83 mmHg, and 38.70 ± 4.28 mmHg, respectively. Compared to baseline, lactic acid significantly decreased (2.10 ± 0.50 mmol/L, p = 0.03), while PH increased (7.388 ± 0.27, p < 0.05) after CPAP treatment. In addition, neck circumference and the polysomnographic parameters, including apnea-hypopnea index, oxygen desaturation index (ODI), mean oxygen saturation (SpO2 ), and the percentage of sleep time with SpO2 <90 % (TS90 %), positively correlated with lactate, while age correlated negatively with lactate (all p < 0.05). Significantly positive associations were found between age, neck circumference, and PH; furthermore, a negative correlation was found between ODI and PH. Finally, after adjusting for confounding factors, TS90 % was the major contributing predictor for elevated lactate (p < 0.05), and age was a predictor for an increase in PH (p < 0.05).

CONCLUSIONS: The results indicated that CPAP treatment could reduce serum lactate and increase PH in OSAS patients and might alleviate acid-base balance disorders in OSAS. Furthermore, TS90 % was a risk factor for elevated lactate, and age was independently associated with PH.