Nocturnal hypoxia and arterial lactate levels in sleep-related breathing disorders.

Background: Lactate may be useful in pointing out the higher risk subgroups in sleep-related breathing disorders (SRBD) with various patterns of hypoxemia. We aimed to search whether morning and night lactate levels are related to apnea-hypopnea, hypoventilation, and hypoxemia in patients with SRBD and to compare it with patients without SRBD (No-SRBD).

Methods: Eighty patients with suspected SRBD underwent polysomnography (PSG) testing. SRBD patients had obstructive sleep apnea syndrome with or without sleep-related hypoventilation/hypoxemic conditions. Patients without SRBD were in the control group. Measurements included pulmonary function testing, PSG, analysis of arterial blood gases, and arterial lactate before and after PSG. Arterial lactate was compared with SRBD and No-SRBD patients.

Results: Morning lactate was significantly higher in the SRBD group than the No-SRBD group (1.65 +/- 0.48 and 1.35 +/- 0.57 mmol/L, respectively) (P = 0.003). Lactate levels at night and the change overnight in lactate levels were not significantly different between groups. After an adjustment for age, gender, and body mass index, lactate levels before PSG were related to the apnea-hypopnea index (beta: 0.004, 95% CI: 0.000-0.008) and the rate of sleep-time spent under 90% oxygen saturation (T90%). The following morning lactate level was correlated with the T90% (beta: 0.005, 95% CI: 0.000-0.010). After an adjustment for lactate levels before PSG, lactate in the morning was correlated with T90% (beta: 0.004, 95% CI: 0.000-0.008).

Conclusion: As a marker of tissue hypoxia, arterial lactate may be used to assess the severity of SRBD.