Respiratory Muscles Performance Is Related to Oxygen Kinetics During Maximal Exercise and Early Recovery in Patients With Congestive Heart Failure

Abstract

Background-Dyspnea and fatigue are the main causes of exercise limitation in chronic heart failure (CHF) patients, whose peak inspiratory (Pi max ) and expiratory pressures (Pe max ) are often reduced. The aim of this study was to examine the relationship between respiratory muscle performance and oxygen kinetics. Methods and Results-A total of 55 patients (NYHA class I to III) and 11 healthy subjects underwent cardiopulmonary exercise tests (CPET) on a treadmill. In 45 of the 55 patients (group I) and in healthy subjects (group II), pulmonary function tests, Pi max , and Pe max were measured before and 10 minutes after exercise, and oxygen kinetics were monitored throughout and during early recovery from CPET. The first degree slope of oxygen consumption (V O 2 ) decline during early recovery (V O 2 /t-slope) and V O 2 half-time (T 1/2 ) were calculated. In 10 of the 55 CHF patients (group III), the measurements of Pi max were repeated 2, 5, and 10 minutes after CPET. A Ͼ10% reduction in Pi max after CPET (subgroup IA) was measured in 11 of 45 patients. In contrast, 34 of 45 CHF patients (subgroup IB) and all control subjects (group II) had Pi max Ͼ90% of baseline value after CPET. Subgroup IA patients had significantly lower peak V O 2 (13.5Ϯ2.1 versus 17.8Ϯ5.6 mL ⅐ kg Ϫ1 ⅐ min Ϫ1 ; PϽ0.001), lower anaerobic thresholds (10.1Ϯ2.4 versus 13.6Ϯ4.6 mL ⅐ kg Ϫ1 ⅐ min

Heart Rate Recovery and Oxygen Kinetics After Exercise in Obstructive Sleep Apnea Syndrome

“…34 A delayed recovery of O 2 kinetics has also been observed in patients presenting with heart failure, compared with healthy subjects. 27 The prolonged recovery of total body O 2 uptake, reflecting a higher O 2 debt, might be attributed to a slower recovery of muscle energy stores after exercise, probably due to the impaired delivery of O 2 to the peripheral muscles, or to histological and biochemical skeletal muscles alterations, or both. 26 Other noteworthy observations made in our study were the delayed kinetics of HRR and weaker CR in patients with OSA than in controls.…”

“…22 Furthermore, the severity of OSA, as expressed by AHI, correlated with O 2 kinetics, and with HRR indicating that the severity of OSA is associated with both parasympathetic dysfunction and O 2 debt. Both of these indices have been shown to contain significant prognostic information for patients with heart failure 21,26,27 ; however, whether these indices are potent prognostic markers in patients with OSA must be confirmed by larger prospective studies. Future studies aiming to evaluate treatment strategies such as β-blockers or exercise training programs in patients with OSA might also be an interesting field of research.…”

“…In order to evaluate VO 2 kinetics during early recovery, the first-degree slope of VO 2 decline during the first minute of recovery (VO 2 /t slope) was calculated as described in previous studies 26,27 by a linear regression model, assuming that the decline in VO 2 during early recovery is linear. In addition HRR was measured as the difference between heart rate at peak exercise minus heart rate at the first minute of recovery (heart rate peak − heart rate first min of recovery), respectively.…”

“…24,25 Evaluation of the early phase of recovery after exercise is of special interest to physicians, as parameters of recovery entail important information on exercise pathophysiology in several disorders. In particular, VO 2 /t slope, which expresses the oxygen (O 2 ) debt, is less steep in several disorders including chronic heart failure 26,27 and cystic fibrosis. 28 However, there is no reported study of the early phase of recovery from exercise in OSA.…”

Impairment of Autonomic Nervous System Activity in Patients With Pulmonary Arterial Hypertension: A Case Control Study

“…To examine VO 2 kinetics during the early recovery phase, the first-degree slope of VO 2 for the first minute of recovery (VO 2 / t-slope, mL$kg$min 2 ) was calculated as previously 17 by a linear regression model, using an appropriate computerized statistical program. The time required for a 50% fall of VO 2 p (t 1/2 , min) during the recovery period was also calculated.…”