Heart rate recovery and oxygen kinetics after exercise in obstructive sleep apnea syndrome.
BACKGROUND
Patients who suffer from obstructive sleep apnea (OSA) have a decreased exercise capacity and abnormal autonomic nervous function. However, the kinetics of early oxygen (O2) and heart rate recovery (HRR) have not been described.


METHODS
We evaluated 21 men with moderate to severe OSA (mean age: 48 +/- 11 yrs, mean apnea-hypopnea index [AHI]: 55 +/- 13) and without known heart disease and 10 healthy men matched for age and body mass index (BMI; controls). Men with OSA underwent overnight polysomnography, and both groups underwent symptom-limited incremental cardiopulmonary exercise testing (CPET). We recorded the CPET parameters including peak O2 uptake (VO2p), kinetics of early O2 recovery by the first degree slope of VO2 during the first minute (VO2/t slope), the time required for a 50% decline of VO2p during recovery (T(1/2)), and early heart rate recovery (HRR = HR at maximal exercise - HR at 1 min of recovery), as well as the chronotropic reserve to exercise ([CR] = [peak HR - resting HR/220 - age - resting HR] x 100). Patients with OSA had a lower VO2p (28.7 +/- 4.0 vs 34.7 +/- 6.2 mL/kg/min), VO2/t slope (1.04 +/- 0.3 vs 1.4 +/- 0.17 mL/kg/min2), and T(1/2) (74 +/- 10 vs 56 +/- 6 sec) compared to controls (all P < 0.001). In addition, both HRR and CR were lower in the OSA group (22.0 +/- 7.0 vs 31.0 +/- 6.0 bpm, P:0.003, and 79.0% +/- 15% vs 99.0% +/- 13.0%, P:0.01, respectively).


CONCLUSIONS
Patients with OSA demonstrate reduced exercise capacity, delayed oxygen kinetics, and reduced HRR. These data point to abnormal oxygen delivery and/or oxidative function of the peripheral muscles and impaired autonomic nervous activity in OSA patients.
Nanas
Serafim
S
Pulmonary and Critical Care Medicine Department, Cardiopulmonary Exercise Testing and Rehabilitation and Sleep Laboratories, National and Kapodestrian University of Athens, Athens, Greece.
Sakellariou
Dimitrios
D
Kapsimalakou
Smaragda
S
Dimopoulos
Stavros
S
Tassiou
Antonia
A
Tasoulis
Athanasios
A
Anastasiou-Nana
Maria
M
Vagiakis
Emmanouil
E
Roussos
Charalampos
C
D000222:Adaptation, Physiological; D000328:Adult; D001341:Autonomic Nervous System; D015992:Body Mass Index; D016022:Case-Control Studies; D015444:Exercise; D005080:Exercise Test; D017079:Exercise Tolerance; D006305:Health Status Indicators; D006339:Heart Rate; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D017286:Polysomnography; D012129:Respiratory Function Tests; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*; D013223:Statistics as Topic
D010100:Oxygen