The use of cardiopulmonary exercise testing in identifying the presence of obstructive sleep apnea syndrome in patients with compatible symptomatology.

The aim of this study was to investigate the relationship between cardiopulmonary exercise testing (CPET) and the presence of obstructive sleep apnea syndrome (OSAS) in order to provide an innovative tool to identify patients with OSAS. A prospective nested case control design was adopted. A consecutive population of male volunteers referred to a Sleep Unit was subjected to nocturnal polysomnography, full lung function testing and maximal CPET. A stepwise linear discriminant function analysis (DFA) was applied to construct a model which could identify individuals with moderate-to-severe OSAS from healthy controls. The total of 30 volunteers formed the OSAS and 24 the non-OSAS groups. Demographic and somatometric parameters were similar between groups. Patients presented with lower Expiratory Reserve Volume (ERV: 106.7 ± 28.3 vs. 123.9 ± 22.1, p < 0.001), Leg FatigueBorg scale (3.9 ± 1.1 vs. 6.1 ± 1.4, p < 0.001), VO2peak(25.0 ± 5.9 vs. 32.9 ± 7.2 ml/kg-1/min-1, p < 0.001), peak breathing frequency (31.0 ± 5.8 vs. 35.5 ± 7.3 1/min-1, p < 0.001) and peak heart rate (151.1 ± 17.7 vs. 171.2 ± 12.6 beats/min-1, p < 0.001) compared to controls, but higher peak end-tidal CO2 (PETCO2peak:38.6 ± 4.2 vs. 35.0 ± 4.9 mmHg, p = 0.043) and peak systolic (SBP:188.3 ± 21.9 vs. 173.1 ± 17.9 mmHg, p = 0.009) and diastolic (DBP: 91.3 ± 8.2 vs. 85.4 ± 8.2 mmHg, p = 0.011) blood pressure. Stepwise DFA indicated that ERV% of predicted (0.372), PETCO2peak (-0.376), SpO2resting (0.0667), Leg Fatigue Borg scale (0.564), HRpeak (0.530) and DBPpeak (-0.543) could separate the two groups, with an overall predictive accuracy of 96.3%. Selected CPET parameters (ERV% of predicted, PETCO2peak, SpO2resting, HRpeak, DBPpeak and Leg FatigueBorg Scale) are independently associated with OSAS presence and could discriminate patients with and without this disorder.