Does dynamic hyperinflation impair submaximal exercise cardiac output in chronic obstructive pulmonary disease?
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Adult↗
Biomedical subjects
Hélène Perrault
Publications and source records attributed to Hélène Perrault.
Enhanced cardiac vagal efferent activity does not explain training-induced bradycardia.
Studies of heart rate variability (HRV) have so far produced contradictory evidence to support the common belief that endurance training enhances cardiac parasympathetic tone. This may be related to the fact that most studies failed to specifically isolate the vagally mediated influence of respiration. This study used a cross-sectional comparison of endurance athletes (n=20; ATHL) exhibiting resting bradycardia and age-matched nonathletes (n=12; CRTL) to indirectly assess training effects on amplitude and timing characteristics of respiratory sinus arrhythmia (RSA). Continuous electrocardiogram (ECG) and ventilatory flows were recorded during spontaneous breathing (SP), as well as during breathing at four cycles less than (M4) or more (P4) than SP, to also examine potential repercussions of training on the sensitivity of the cardiac vagal responses to breathing. A fast Fourier transform procedure was used to quantify the standard spectral high-frequency (HF) and low-frequency (LF) components and a respiratory-centered frequency (RCF) component of HRV. RSA was assessed using a breath-by-breath quantification of the amplitude and timing of the maximum change in instantaneous heart rate. Under baseline SP conditions, heart rate was lower in ATHL (62.6+/-6.5 vs. 75.2+/-9 beats/min; p<0.05) while blood pressure (BP), breath cycle duration, tidal volume, and ventilatory drive were similar in both groups. HRV total spectral power density, LF, HF, or RCF was not different between groups at either the SP, M4, or P4 conditions. Changes in total breath duration similarly affected RSA amplitude in all groups, while HR and BP remained unchanged from SP. RSA phase was not affected by training status or by changes in total breath duration. RSA amplitude was negatively related to breathing frequency in all groups (p<0.05), while the mean slope of the relationship (sensitivity) was not different between groups. In as much as RSA is an adequate marker of cardiac vagal efferent activity, these results add support to a contribution of a decrease in intrinsic heart rate to explain training-induced bradycardia.
Adolescent↗
Individual differences in respiratory sinus arrhythmia.
To investigate the interindividual differences in respiratory sinus arrhythmia (RSA), recordings of ventilation and electrocardiogram were obtained from 12 healthy subjects for five imposed breathing periods (T(TOT)) surrounding each individual's spontaneous breathing period. In addition to the spectral analysis of the R-R interval signal at each breathing period, RSA characteristics were quantified by using a breath-by-breath analysis where a sinusoid was fitted to the changes in instantaneous heart rate in each breath. The amplitude and phase (or delay = phase x T(TOT)) of this sinusoid were taken as the RSA characteristics for each breath. It was found that for each subject the RSA amplitude-T(TOT) relationship was linear, whereas the delay-T(TOT) relationship was parabolic. However, the parameters of these relationships differed between individuals. Linear correlation between the slopes of RSA amplitude versus T(TOT) regression lines and 1) mean breathing period and 2) mean R-R interval during spontaneous breathing were calculated. Only the correlation coefficient with breathing period was significantly different from zero, indicating that the longer the spontaneous breathing period the lesser the increase in RSA amplitude with increasing breathing period. Similarly, only the correlation coefficient between the curvature of the RSA delay-T(TOT) parabola and mean breathing period was significantly different from zero; the longer the spontaneous breathing period the larger the curvature of RSA delay. These results suggest that the changes in RSA characteristics induced by changing the breathing period may be explained partly by the spontaneous breathing period of each individual. Furthermore, a transfer function analysis performed on these data suggested interindividual differences in the autonomic modulation of the heart rate.
Adolescent↗
Baroreflex resetting after successful surgical repair of tetralogy of Fallot.
BACKGROUND: Tetralogy of Fallot (TOF) and its surgical repair are associated with alterations in right ventricular systolic and diastolic functions. The cardiopulmonary baroreflex describes the peripheral vasoconstriction response to the volume-unloading deactivation of left and possibly right ventricular receptors. Alterations in cardiac geometry or distensibility and pulmonary vasculature of operated TOF may affect the mechanical stimulation of sensitive cardiopulmonary receptors leading to an impaired baroreflex function. There has to date been no report on the integrity of baroreflex function in postoperative TOF. OBJECTIVE: To characterize the combined cardiopulmonary and baroreflex response of patients successfully operated for TOF in early childhood to central volume unloading using graded lower body negative pressure (LBNP) application. METHODS: Fifteen patients operated on for TOF (mean+/-SEM) 15.7+/-1.4 years previously and 13 healthy age-matched control subjects were submitted to four consecutive 5 min LBNP applications at -10, -20, -30 and -40 mmHg. Forearm blood flow and vascular resistance, left ventricle end-diastolic diameter (LVEDD), arterial blood pressure and heart rate were obtained. RESULTS: TOF exhibited a lower LVEDD (42.7+/-1.5 mm) than control subjects (51.9+/-1.6). The forearm vascular resistance to LVEDD relationship was shifted left and upward in TOF compared with that of control subjects, but the slope of the relationship was not different between groups. LBNP -40 mmHg induced a lesser change in heart rate in TOF (+10.6+/-1.5%) than in control subjects (+14.7 +/-2.4%) and an increase (P<0.05) in diastolic blood pressure in TOF (-2.4+/-2.5%), which was not seen in control subjects (+4.3+/-2.9%). CONCLUSIONS: Young adults successfully operated on for TOF in early childhood exhibit a resetting of the cardiopulmonary baroreflex to operate at smaller LVEDD and at a higher level of forearm vascular resistance. The blunted heart rate response to LBNP -40 mmHg is consistent with previous observations pointing to disturbances in the efferent arm of the baroreflex.
Adolescent↗
Impaired exercise response in sarcoid patients with normal pulmonary functio.
BACKGROUND AND AIM OF THE WORK: Sarcoidosis is a granulomatous disease with frequent pul monary involvement. Patients generally exhibit a 25-30% reduction in maximal aerobic capacit (VO2max). As most investigations have included patients with both normal and abnormal resting pulmonary function tests (PFT), the mechanisms responsible for this limitation remain unclear. We initiated a prospective study to characterize the cardio-respiratory response to exercise in sarcoid patients with normal resting PFT. METHODS: 19 untreated male patients with biopsy-proven sarcoidosis and 19 age- an sex-matched sedentary healthy controls (38 +/- 8.7 vs 37 +/- 8.7 yrs ; Body Mass Index: 24 +/- 3.05 vs 23 +/- 3.05) were included in the study. All patients had normal resting PFT including diffusing capacity for CO (DLCO) > 80% predicted and normal cardiac status at rest as assessed by EKG and echocardiography. A maximal cycling test was performed in all subjects. RESULTS: True maximal effort was obtaine in all subjects (plasma lactate 9.1 +/- 2.6 vs 11.0 +/- 2.2 mmol l(-1), pH 7.35 +/- 0.04 vs 7.34 +/- 0.04) (patients vs controls). Patients exhibited a 30% lower maximal workload and/or VO2max (2,128 +/- 413 vs 2,909 +/- 387 ml x min(-1)) than controls. Maximal ventilation (79 +/- 21.7 vs 110 +/- 21.7 l x min(-1)) and tital volume (VT) (2,313 +/- 517 ml vs 2,856 +/- 339) were significantly lower in patients than in controls while dead space t tital volume ratio (VD/V(T)) (0.18 +/- 0.09 vs 0.11 +/- 0.04) was higher in patients than in controls. PaO2, PAiO2, and PAi-aO2 at VO2max were not significantly different between patient and controls. Peak exercise EKG was normal in all but one patient. Interestingly, heart rate was significantly lower in patients for all relative exercise intensities > or = 60% VO2max including maximum (159 +/- 21.7 vs 182 +/- 13) CONCLUSION: The present observations indicate a significant maximal exercise limitation in sarcoid patients without significant pulmonary impairment which could be related at least in part to an impaired heart rate response to exercise.
Adult↗
A Canadian, multicentre, randomized clinical trial of home-based pulmonary rehabilitation in chronic obstructive pulmonary disease: rationale and methods.
BACKGROUND: Pulmonary rehabilitation remains largely underused. Self-monitored, home-based rehabilitation is a promising approach to improving the availability of pulmonary rehabilitation. OBJECTIVE: To report the rationale and methods of a trial comparing the effectiveness of self-monitored, home-based rehabilitation with hospital-based, outpatient rehabilitation in patients with chronic obstructive pulmonary disease (COPD). STUDY DESIGN: A parallel-group, randomized, noninferiority, multicentre trial will be performed with 240 patients with moderate to severe COPD. INTERVENTION: Patients will be randomly assigned to conventional, supervised, hospital-based outpatient rehabilitation or self-monitored, home-based rehabilitation. Both interventions will include a standardized, comprehensive self-management program, in addition to the hospital-based outpatient or home-based exercise program. After the three-month intervention, patients in both groups will be encouraged to continue exercising at home. Patients will be assessed monthly with telephone interviews and in person at enrollment, three months and 12 months. OUTCOMES: The dyspnea domain of the Chronic Respiratory Questionnaire (CRQ) at 12 months is the primary outcome variable. Secondary outcome variables include total and domain-specific CRQ scores; exercise tolerance and activity of daily living; health service use over the one-year study period; and direct and indirect costs of COPD treatment. ANALYSIS: An intent-to-treat approach will be used as the primary analysis. The primary analysis will focus on the change in the CRQ dyspnea score using a two-sided t distribution based on 95% CIs. The same approach will be used for secondary continuous outcome variables. CONCLUSION: The present trial will address two unresolved issues in pulmonary rehabilitation for patients with COPD: the short-term and long-term effectiveness of home-based pulmonary rehabilitation strategies. The authors will also determine if home-based pulmonary rehabilitation can reduce health service use (eg, hospitalizations and emergency visits) and if it can be done at a lower cost than the traditional hospital-based outpatient pulmonary rehabilitation.
Adult↗