Inspiratory neural drive response to hypoxia adequately estimates peripheral chemosensitivity in OSAHS patients

The aim of the present study was to examine the relationships between the responses to progressive isocapnic hypoxia and hypoxic withdrawal test in patients with obstructive sleep apnoea-hypopnoea syndrome (OSAHS) and to analyse the determinants of carotid body sensitivity in OSAHS. Nineteen consecutive OSAHS patients and 13 healthy subjects were selected. Ventilatory (delta V'I/Sa,O2/BSA) and inspiratory neural drive (delta P0.1/Sa,O2) responses to progressive isocapnic hypoxia were determined. Peripheral chemosensitivity was evaluated by the hypoxic withdrawal test, which measures the decrease in ventilation caused by two breaths of 100% oxygen (%delta V'I). Withdrawal response and ventilatory and inspiratory neural drive responses to hypoxia were lower in OSAHS patients than in control subjects. In patients with OSAHS, %delta V'I correlated significantly with delta V'I/Sa,O2/BSA and with delta P0.1/Sa,O2. On stepwise multiple linear regression analysis, a strong correlation between %delta V'I and delta P0.1/Sa,O2 was found. Moreover, %delta V'I, delta V'I/Sa,O2/BSA and delta P0.1/Sa,O2 were significantly correlated with minimum arterial oxygen saturation and with arousal index. Obstructive sleep apnoea-hypopnoea syndrome patients have a strong relationship between peripheral chemosensitivity and respiratory response to hypoxia, suggesting that hypoxic stimulation of central chemoreceptors is minimally relevant in obstructive sleep apnoea-hypopnoea syndrome. Moreover, sensitivity of the carotid body in patients with obstructive sleep apnoea-hypopnoea syndrome is related to sleep disruption and to nocturnal hypoxia.