Hypoxic burden to guide CPAP treatment allocation in patients with obstructive sleep apnoea: aPost-hocstudy of the ISAACC trial

Hypoxic burden (HB) has emerged as a strong predictor of cardiovascular risk in obstructive sleep apnoea (OSA). We aimed to assess the potential of HB to predict the cardiovascular benefit of treating OSA with continuous positive airway pressure (CPAP). Post-hoc analysis of the ISAACC trial ( NCT01335087 ), including non-sleepy patients with acute coronary syndrome (ACS) diagnosed with OSA (apnoea-hypopnoea index ≥15 events·h −1 ) by respiratory polygraphy. Patients were randomised to CPAP or Usual Care and followed for a minimum of 1 year. HB was calculated as the total area under all automatically-identified desaturations divided by total sleep time. Patients were categorised as having high or low baseline HB according to the median value (73.1%min·h −1 ). Multivariable Cox regression models were used to assess whether the effect of CPAP on the incidence of cardiovascular outcomes was dependent on the baseline HB level. The population (362 patients assigned to CPAP and 365 to Usual Care) was middle-aged, overweight/obese, and mostly males. A significant interaction was found between the treatment arm and the HB categories. In the high HB group, CPAP treatment was associated with a significant reduction in the incidence of cardiovascular events [HR (95% CI)=0.57 (0.34 to 0.96)]. In the low HB group, CPAP-treated patients exhibited a trend toward a higher risk of cardiovascular outcomes than those receiving Usual Care [HR (95% CI)=1.33 (0.79 to 2.25)]. The differential effect of the treatment depending on the baseline HB level followed a dose-response relationship. In non-sleepy ACS patients with OSA, high HB levels were associated with a long-term protective effect of CPAP on cardiovascular prognosis.