Hypoxic burden (HB) is defined as the sum of individual area under oxygen saturation curves related to every respiratory event during the total sleep (or recording) time. It integrates information about duration, frequency and depth of oxygen desaturations. HB seems one of the most promising metrics as a parameter to estimate the severity and consequences of Obstructive Sleep Apnoea (OSA).

Objective:To analyze the correlation between HB and sleepiness, cardiovascular (CV) risk factors, previous CV events and traditional polygraphic parameters (apnoea-hypopnoea index (AHI), oxygen desaturation index (ODI) and Tsat90% in patients with OSA

Methods Descriptive, cross-sectional study in consecutive OSA patients (AHI>5 events/hour). Polygraphic parameters were assessed using Sleepware G3 software 10(v4.0.1.0). Correlation between variables were assessed using Pearson's or Spearman correlation tests.

Results 681 patients, mean age (±SD) of 56.5 years(±13.6), 64% men were included. 47% had hypertension, 16% diabetes, 5% CV events. Mean Epworth Sleepiness Scale (ESS) was 9.4(±3.8), 37% with an ESS > 10 points. The mean AHI was 29.6/h(±20.7), ODI3% 31.2/h(±23.6) and Tsat90% 11.3%(±19). The mean HB was 77.9(±82.8) %min/hour. The correlation between HB and AHI was 0.81(p=0.001), ODI 0.82(p=0.001) and Tsat90% 0.41(p=0.001), however, HB correlated better than AHI, ODI and Tsat90% with the EES, EES>10 and CV risk factors. Correlation with age, sex and other comorbidities were not statistically different.

Conclusion HB presented higher correlation than traditional polygraphic parameters with the presence of hypersomnia and CV risk factors in OSA patients.