Mourot, Laurent PhD; Teffaha, D. MSc; Bouhaddi, M. PhD; Ounissi, F. MD; Vernochet, P. MD; Dugue, B. PhD; Regnard, J. MD, PhD; Monpère, C. MD
Laboratoire de Physiologie, Faculté de Médecine et de Pharmacie, EA 3920–IFR 133 Université de Franche Comté (Drs Mourot, Bouhaddi, and Regnard), Clinical Investigation Centre Inserm, Hôpital St. Jacques (Dr Mourot), and Explorations fonctionnelles Physiologie, Centre Hospitalier Universitaire (Drs Bouhaddi and Regnard), Besançon, France; Laboratoire des Adaptations Physiologiques aux Activités Physiques, Université de Poitiers, Poitiers, France (Ms Teffaha and Drs Dugue and Monpère); and Centre de Réadaptation Cardiovasculaire Bois-Gibert, Ballan Miré, France (Drs Ounissi, Vernochet, and Monpère).
Corresponding Author: Laurent Mourot, PhD, Laboratoire de Physiologie, Faculté de Médecine et de Pharmacie, EA 3920–IFR 133 Université de Franche Comté, F-25030 Besançon Cedex, France (firstname.lastname@example.org).
PURPOSE: Rehabilitation programs increasingly involve immersed exercising, including inpatients suffering from severe cardiovascular diseases such as coronary artery disease (CAD) or chronic heart failure (CHF). The hemodynamic responses to short-term head-out water immersion are not well defined in these diseases. This study was aimed at evaluating (1) the cardiac and peripheral hemodynamic responses to short-term head-out water immersion in patients with CHF (n = 12) and CAD (n = 12) and (2) the effect of a rehabilitation program on these responses.
METHODS: Wrist arterial tonometry was performed in the upright posture before and during immersion (1.30-m depth) once before and once after a 3-week rehabilitation program including gymnic water exercises.
RESULTS: In patients with CAD, water immersion triggered a significant increase in stroke volume, cardiac output, and pulse pressure and a significant decrease in pulse rate, diastolic blood pressure, and systemic vascular resistances, both before and after the rehabilitation program. In patients with CHF, no significant immersion-linked changes in cardiovascular variables were observed before rehabilitation. However, after completion of the rehabilitation program, it was found that water immersion caused significant increases in stroke volume, cardiac output, and pulse pressure.
CONCLUSION: In patients with CHF, this 3-week rehabilitation program restored the usual central responses to head-out water immersion (increase in stroke volume and cardiac output). In both patients with CHF and CAD, acute water immersion did not change arterial compliance.
The buoyancy provided by water makes any form of water exercise attractive for individuals seeking ways to improve fitness without the inherent risk of musculoskeletal injuries. Rehabilitation programs involving immersed exercises appear to be increasingly used, including inpatients suffering from severe cardiovascular diseases such as coronary artery disease (CAD) or chronic heart failure (CHF).1–6
At variance with central hemodynamic adaptations, changes in the peripheral circulation have been little studied. However, they are of importance since systemic vascular resistance (SVR) and total arterial compliance have a major impact on cardiac work. In healthy young subjects, water immersion increases total arterial compliance,7 but this is not the case in older subjects.8 To the best of our knowledge, change in arterial compliance has not been studied in patients with reduced cardiac function. Moreover, the effects of cardiovascular rehabilitation involving immersed exercises on acute immersion-induced hemodynamic responses in patients with cardiac disease are unknown. Therefore, the aim of this study was to (1) evaluate the hemodynamic adaptation triggered by short-term head-out water immersion in patients with CHF or with CAD and (2) assess if this acute adaptation is modified by a rehabilitation program involving regular immersed exercises.
Male patients with stable CHF (n = 12) and CAD with preserved left ventricular function (n = 12) were involved in this study. A description of the patients is presented in Table 1. Patients with CHF had left ventricular systolic dysfunction defined as ejection fraction of 45% or less. Heart failure resulted from ischemic cardiomyopathy or idiopathic dilated cardiomyopathy. Patients with CAD had preserved left systolic function with normal ejection fraction (>45%) and no history or symptoms of heart failure. They were referred for cardiac rehabilitation after an acute coronary syndrome with or without ST-segment elevation. All patients were involved in a 3-week rehabilitation program and had not previously participated in comparable studies. Patients were able to swim and were in a stable clinical condition. Exclusion criteria were water phobia, cutaneous pathology, urinary incontinence, contraindications to exercise stress testing, major change in treatment, or other disabling diseases that might interfere with the protocol. The study protocol complied with the Declaration of Helsinki and was reviewed and accepted (no. 2005–25) by the ethical committee of Tours (France). Subjects were informed about the study procedure and gave their written informed consent.
In this study, each subject served as his own control. Patients were investigated at the beginning of the afternoon, 2 hours after a light meal. Cardiovascular evaluations in upright posture were performed first on land and then in water at the beginning and end of a 3-week rehabilitation program involving immersed exercises. Evaluations on land (dry ambience) were done in a quiet, dimly lit room with a stable ambient temperature (22°C–25°C). Evaluations during immersion (immersed ambience) were performed in the swimming pool of the Bois-Gibert Cardiovascular Rehabilitation Center (1.30 m deep with water temperature around 30°C–32°C). In both ambiences, evaluations were performed while standing, after 15 minutes of rest.
The cardiovascular status of patients was evaluated with a noninvasive method, which computed small and large vessel compliance from radial artery measurements (HDI/PulseWave CR-2000 Hypertension Diagnostics, Inc, Eagan, Minnesota). An acoustic transducer (tonometer), made from medical-grade stainless steel, was positioned over the radial artery (right wrist) and held in place using a holding and positioning device on a manually adjustable shaft. The arm was supported by a wrist stabilizer for optimal positioning and minimal movements during the measurements. The arm with the transducer was placed in the same position in the dry and immersed ambiences so that posture changes did not interfere with the measurements. Optimal pressure pulse waveforms were recorded by carefully placing the device and the attached sensor and adjusting the hold-down pressure by setting the knob on top of the device to the highest relative signal strength. The recorded waveforms (mean of 30-second recording) were calibrated by the oscillometric method, with the cuff on the contralateral arm and a calibration system inside the device. A report was generated containing the results, that is, systolic (SAP), diastolic (DAP), and mean (MAP) arterial blood pressures; pulse pressure (PP); pulse rate (PR); estimated cardiac ejection time; estimated stroke volume (SV); estimated cardiac output (CO); large (C1) and small (C2) artery compliance indices; SVR; and total vascular impedance. Three measures were performed at 2- to 3-minute intervals: the mean of the 2 closest values was recorded. Percentage of change for C1 and C2 over 2 to 5 weeks is reported to be between 1% and 11%.9,10 In addition, systemic arterial compliance was calculated by dividing SV by PP.7 Also, an echocardiography device (Sequoia C256 Siemens Echocardiography catheter 3V2c-S) was utilized to assess resting ejection fraction in the supine position in air before the upright evaluations.
The rehabilitation program comprised aerobic exercises performed on land using a cycle ergometer (30 minutes, 4–5 times a week, intensity equal to roughly 60%–70% of patient heart rate reserve) and gymnastic sessions in immersed conditions (40 minutes, 3–4 times a week).
Cycle ergometer exercise tests were conducted in an upright position (ERG 900, GE Medical System, CASE Exercise Testing System Case, Milwaukee, Wisconsin,). A ramp protocol was utilized with a 10-W increase every minute until exhaustion. Peak oxygen uptake (V̇O2peak) was measured breath-by-breath using a Vmax spectra system (SensorMedics Corporation, Yorba Linda, California). The peak values reported were averaged over 10 seconds.
Statistical analyses were performed using SigmaStat software (SPSS Inc, Chicago, Illinois). Standard statistical methods were used for the calculation of mean ± SD. Among subgroups with different diseases, differences between the data observed in dry and immersed ambiences and differences observed after the rehabilitation program compared with before rehabilitation were tested by 2-way repeated measures analysis of variance. Differences between before and after the rehabilitation program for the absolute and relative changes between dry and immersed ambiences were also tested with a paired t test. A P value of less than .05 was considered significant.
In patients with CAD, water immersion triggered a significant increase in SV, CO, PP, and total vascular impedance, both before and after the rehabilitation program. This was accompanied by a significant decrease in PR, DAP, and SVR (Table 2 and Figure 1).
In patients with CHF, compared to dry ambience, water immersion caused no significant changes in hemodynamic variables before training. On the contrary, SV, CO, and PP were significantly higher during immersion than on land at the end of the rehabilitation program. Furthermore, the PR during immersion after rehabilitation was significantly lower than before rehabilitation (Table 2 and Figure 1). Neither the absolute nor the relative cardiovascular changes triggered by water immersion were significantly changed by the rehabilitation program (Table 3).
V̇O2peak increased significantly from 27.7 ± 5.8 to 30.1 ± 6.7 mL · kg-1 · min-1 for patients with CAD and from 20.0 ± 6.9 to 21.8 ± 6.5 mL · kg-1 · min-1 for patients with CHF. Peak power output increased from 130.7 ± 9.5 to 152.2 ± 11.5 W for patients with CAD and from 103.7 ± 8.3 to 112.7 ± 9.3 W for patients with CHF.
The main results of the present study were that (1) in patients with CHF, the rehabilitation program restored the main central hemodynamic responses to head-out water immersion (ie, increases in SV and CO), which were absent before the training, and (2) arterial compliance was not changed by water immersion in patients with either CAD or CHF.
During thermoneutral head-out water immersion, the ambient hydrostatic pressure reduces the vascular capacitance leading to the translocation of peripheral blood into the abdominal and thoracic vascular beds. The venous return and the central venous pressure increase,11 in turn, supporting increase in SV and CO, which are the main central responses usually observed in healthy subjects.7,8 In patients suffering from cardiovascular disease, the increased preload could overstrain the cardiovascular adaptive mechanisms. A decreased SV was indeed observed in patients with a severe disease.3,12 Nevertheless, recent studies reported that patients with severely reduced left ventricular function, but stable clinical conditions, as well as patients with CAD with preserved left ventricular function, are able to increase SV and CO indexes adequately during water immersion and swimming,3–5 implying that controlled immersed activities might be safe for these patients.6 Both before and after rehabilitation, the results obtained here in patients with CAD were in accordance with these previous observations. Conversely, no significant change in SV and CO occurred upon immersion in patients with CHF at the beginning of the rehabilitation program. However, after 3 weeks of training and regular immersion, the immersion-induced changes in main functional cardiac variables were observed in these patients. The restoration of this adaptive response might be due to regular exposure to water immersion and/or to a better functional adaptation due to the enhanced cardiorespiratory capacity (V̇O2peak and peak power output improved after training). On the whole, these changes suggest a better adaptation of the patients with CHF to conditions of increased preload, which may be of importance for their health and quality of life.
The major part of cardiac afterload is linked to SVR and also to the inverse of total arterial compliance. Studies on arterial compliance during water immersion are scarce and, to the best of our knowledge, these changes have not been investigated in patients with cardiac disease. In healthy subjects, total arterial compliance, estimated by SV to PP ratio, and small and large artery compliance indices increase with immersion to the midchest, mainly due to neuroendocrine and autonomic mechanisms.7 On the contrary, arterial compliance indexes were not significantly altered by water immersion both in patients with CAD and CHF in the present study. However, the neuroendocrine responses to water immersion have been found to be similar in patients with heart failure and their healthy counterparts.13 Thus, the lack of immersion-linked change in arterial compliance might be explained by other factors, for example, likely disease-linked endothelial dysfunction.14
Inpatients with CHF, a 3-week rehabilitation program involving regular immersed exercises and endurance training restored the water immersion–induced increase in SV and CO, suggesting that these patients displayed a better adaptation to conditions of increase preload. This may be of importance for the health and quality of life of these patients. Conversely, thermoneutral head-out water immersion did not induce any significant lowering of arterial compliance in patients with CHF or CAD. The precise clinical implications of this result remain to be determined.
This work was funded by grants from the French Ministry of National Education, of Research and of Technology (UPRES EA3920) by the Fédération Française de Cardiologie and the Fondation de l'Avenir. The authors thank the subjects for their time and cooperation. They also thank A. Pianeta for supervision of the training sessions and Frances Sheppard of the Clinical Investigation Center for correcting and improving the English.
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