Sleeping ventilatory patterns in patients with severe chronic airflow obstruction causing respiratory failure.

During sleep some patients with airways obstruction and hypoxaemia developed tachypnoea. This could not be explained by the severity of their abnormality of lung function, their CO2 responsiveness, the nature of their lung disease or their personality. This nocturnal tachypnoea correlated best with a raised resting arterial blood PCO2, and was not seen hypoxaemic patients with a normal PCO2 who showed the usual fall in respiratory rate when asleep. We suggest that in patients with both hypoxaemia and hypercapnia sleep removes a cortical inhibitory mechanism which slows breathing durigng waking hours, and is linked to the arterial blood PCO2.