European Heart Journal Advance Access originally published online on May 25, 2006
European Heart Journal 2006 27(13):1632-1633; doi:10.1093/eurheartj/ehl054
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Obstructive sleep apnoea: hypoapnoea syndrome reversibly depresses cardiac response to exercise
UF de Recherche sur l'exercice musculaire du CHU de Grenoble
Laboratoire HP2
Université Joseph Fourier
Grenoble
Service d'Exploration Fonctionnelle Cardio-Respiratoire
du CHU de Grenoble
France
UF de recherche Clinique sur l'Exercice musculaire
Hôpital Sud
BP185
38042 Grenoble Cedex 09
France
Tel: +33 4 76 76 58 48
Fax: +33 4 76 76 89 21
E-mail address: pflore{at}chu-grenoble.fr
UF de Recherche sur l'exercice musculaire du CHU de Grenoble
Laboratoire HP2
Université Joseph Fourier
Grenoble
Service d'Exploration Fonctionnelle Cardio-Respiratoire
du CHU de Grenoble
France
Laboratoire du Sommeil du CHU de Grenoble
Laboratoire HP2
Université Joseph Fourier
Grenoble
Service d'Exploration Fonctionnelle Cardio-Respiratoire
du CHU de Grenoble
France
Laboratoire du Sommeil du CHU de Grenoble
Laboratoire HP2
Université Joseph Fourier
Grenoble
Service d'Exploration Fonctionnelle Cardio-Respiratoire
du CHU de Grenoble
France
UF de Recherche sur l'exercice musculaire du CHU de Grenoble
Laboratoire HP2
Université Joseph Fourier
Grenoble
Service d'Exploration Fonctionnelle Cardio-Respiratoire
du CHU de Grenoble
France
As a research team interested in both obstructive sleep apnoea syndrome (OSAS) and exercise physiology, we read with great interest the recent publication of Alonso-Fernandez et al.1 regarding the cardiac response of OSAS patients during exercise and its modification by continuous positive airway pressure (CPAP). We greatly appreciate the design of this study dealing with such a relevant subject. Indeed, metabolic and cardiovascular abnormalities encountered in OSAS may account for exercise intolerance and fatigability reported in these patients.2 Hence, physiological adaptations in OSAS patients at exercise deserve attention. However, we are greatly concerned with the stroke volume (SV) and cardiac output (Qc) values reported in this study. According to Figure 2, at 60% maximal workload, SV reached 200 mL and Qc reached 30 L min–1 in the control group. Such values are surprising and in the same range as that measured in high-level endurance cyclists.3 Taking into account a Qc of 30 L min–1 and assuming a mean oxygen extraction of 0.12 L min–1 at 60% VO2peak4 (direct Fick method) in healthy subjects, oxygen consumption recalculation leads to 41 mL min–1 kg–1 (3.6 L min–1, average body weight of 88 kg), a value greater than VO2peak measured in the control group i.e. an average of 25 mL min–1 kg–1. An extrapolation to maximal exercise intensity would lead to a VO2peak of 60 mL min–1 kg–1. A part of the Qc and SV values determined in this study is not valid and may weaken the conclusions of this well-designed paper. At first, owing to the apparent overestimation of Qc in controls [but normal in OSAS as Qc=VO2/(0.0572+(0.001*%VO2max))5], the first conclusion stating OSAS is associated with a lower Qc and SV response during exercise may be disputed. Secondly, although the reproducibility of cardiac indexes between baseline and sham-CPAP is very reassuring, the Qc of at least nine subjects treated with CPAP seemed to be greatly overestimated (Figure 3). We cannot assert whether these overestimations would challenge the positive effect of CPAP on cardiac indexes. However, abnormally high Qc values obtained with CO2 re-breathing method should be taken as indicative rather than definitive evidence that CPAP improved Qc in OSAS patients.
References
- Alonso-Fernandez A, Garcia-Rio F, Arias MA, Mediano O, Pino JM, Martinez I, Villamor J. (2006) Obstructive sleep apnoea-hypoapnoea syndrome reversibly depresses cardiac response to exercise. Eur Heart J 27:207–215.
[Abstract/Free Full Text] - Aguillard RN, Riedel BW, Lichstein KL, Grieve FG, Johnson CT, Noe SL. (1998) Daytime functioning in obstructive sleep apnea patients: exercise tolerance, subjective fatigue, and sleepiness. Appl Psychophysiol Biofeedback 23:207–217.[CrossRef][Web of Science][Medline]
- Rice AJ, Thornton AT, Gore CJ, Scroop GC, Greville HW, Wagner H, Wagner PD, Hopkins SR. (1999) Pulmonary gas exchange during exercise in highly trained cyclists with arterial hypoxemia. J Appl Physiol 87:1802–1812.
[Abstract/Free Full Text] - Saltin B, Blomqvist G, Mitchell JH, Johnson RL Jr, Wildenthal K, Chapman CB. (1968) Response to exercise after bed rest and after training. Circulation 38:Suppl. 5, V1–V78.
- Cooper CB and Storer TW. (2001) Exercise Testing and Interpretation. A Practical Approach (University Press, Cambridge).
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