Variabilidade ventilatória durante exercício dinâmico em indivíduos saudáveis e com insuficiência cardíaca

Abstract

Exercise periodic breathing confers a bad prognosis in patients with heart failure. There is no agreement among proposed criteria to diagnose exercise periodic breathing. The dichotomic interpretation (presence or absence) when diagnosing this phenomenon impairs a more detailed risk stratification in heart failure. Thus, this thesis evaluates the use of established signal variability techniques to quantify ventilatory oscillations during cardiopulmonary exercise test, in healthy individuals, athletes and patients with heart failure. A short protocol used to perform cardiopulmonary exercise test in arm crank was proposes and validated. This protocol was used in the next study, which found that, although timing of breathing was not altered by exercise type, ventilatory variability was greater during arm dynamic exercise when compared to leg exercise. Aerobic capacity of healthy individuals also influences ventilatory variability during cardiopulmonary exercise test. This was proven by the lower time-domain ventilatory variability in athletes when compared to sedentary individuals. The evaluation of these individuals with principal components analysis showed that tidal volume variability is the principal component o minute-ventilation variability in athletes, whilst in sedentary men, respiratory frequency variability is the responsible for minute-ventilation variability. In a randomized controlled study we have found that even healthy individuals reduce their exercise ventilatory variability after 12 weeks exercise training. We have shown that cardiac rehabilitation reverted exercise periodical breathing in a patient with heart failure and, finally, found that exercise ventilatory variability inversely correlates to left ventricle ejection fraction in patients with heart failure. Future studies should evaluate the prognostic value of ventilatory variability in these patients.