Objective: To investigate the change of exercise cardiopulmonary function in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS).
Methods: Thirty OSAHS patients and 18 normal healthy adults (control group) were studied by cardiopulmonary exercise test (CPET). The results including maximal oxygen uptake percent predicted (Vo(2)max% predicted), oxygen uptake to work rate (Vo(2)/WR), oxygen pulse percent predicted (Vo(2)/HRmax% predicted), anaerobic threshold to maximal oxygen uptake (AT/Vo(2)max), breathing reserve (V(E)max/MVV) and ventilatory equivalents for carbon dioxide (V(E)/V(CO2)) were compared between two groups.
Results: The levels of Vo(2)max% predicted, AT/Vo(2)max, Vo(2)/HRmax% predicted, Vo(2)/WR, and V(E)max/MVV in the OSAHS group [(83 +/- 5)%, (44 +/- 6)%, (79 +/- 5)%, (9.3 +/- 0.6) ml.min(-1).W(-1), (73 +/- 8)%] were lower than those in the control group [(88 +/- 5)%, (49 +/- 6)%, (83 +/- 4)%, (10.9 +/- 2.3) ml.min(-1).W(-1), (79 +/- 9)%, all P < 0.05]. The levels of V(E)/V(CO2) in the OSAHS group (29 +/- 3) was higher than the control group (26 +/- 3, P < 0.05). In the OSAHS group Vo(2)max% predicted, Vo(2)/HRmax% predicted, Vo(2)/WR AT/Vo(2)max and V(E)max/MVV correlated negatively with apnea-hypopnea index (AHI, r = -0.52, -0.62, -0.59, -0.37, -0.66, P < 0.05). Vo(2)max% predicted, Vo(2)/HRmax% predicted, Vo(2)/WR, AT/Vo(2)max and V(E)max/MVV correlated with lowest oxygen saturation (LSaO(2), r = 0.60, 0.63, 0.64, 0.40, 0.59, P < 0.05). V(E)/V(CO2) correlated with AHI (r = 0.57, P < 0.01) and correlated negatively with LSaO(2) (r = -0.62, P < 0.01).
Conclusions: The cardiac output of patients with OSAHS can not meet the demand of hard exercise. At the same time, there is more significant ventilation-perfusion disturbance in OSAHS patients than normal subjects. The patients' exercise cardiopulmonary function has been compromised although there are no symptoms.