Left-ventricular function and autonomic cardiac adaptations after short-term inpatient cardiac rehabilitation: a prospective clinical trial.

OBJECTIVE: Cardiac rehabilitation is associated with cardiac autonomic and physiological benefits. However, it is unclear whether baseline left ventricular function (LVF) impacts on training-induced cardiac autonomic adaptations. The aim of this study was to assess the cardiac autonomic adaptations in patients with varying left ventricular function profiles undergoing coronary artery bypass grafting and cardiac rehabilitation. DESIGN: Assessor-blinded prospective trial. PATIENTS: Forty-four patients undergoing coronary artery bypass grafting, divided into normal LVFN (≥ 55%, n = 23) or reduced LVFR (35-54%, n = 21) were evaluated. METHOD: Cardiac autonomic function was evaluated by heart rate variability indexes obtained both pre- and post-cardiac rehabilitation. All patients participated in a short-term (approximately 5 days) supervised inpatient physiotherapy program. RESULTS: There were differences in heart rate variability indexes, correlation dimension and SD2 according to time and group (e.g. interaction time (effect of cardiac rehabilitation) vs group (LVFN vs LVFR), p = 0.04). Simple main effects analysis showed that the LVFR group benefited to a greater degree from cardiac rehabilitation compared with the LVFN group. Heart rate variability indexes increased significantly in the former group compared with the latter. CONCLUSION: Among post-coronary artery bypass grafting patients engaged in short-term inpatient rehabilitation, those with reduced left ventricular function are most likely to have better cardiac autonomic adaptations to exercise-based rehabilitation.

Short-term supervised inpatient physiotherapy exercise protocol improves cardiac autonomic function after coronary artery bypass graft surgery--a randomised controlled trial.

OBJECTIVE: Coronary artery bypass grafting (CABG) is accompanied by severe impairment of cardiac autonomous regulation (CAR). This study aimed to determine whether a short-term physiotherapy exercise protocol post-CABG, during inpatient cardiac rehabilitation (CR), might improve CAR. DESIGN: Seventy-four patients eligible for CABG were recruited and randomised into physiotherapy exercise group (EG) or physiotherapy usual care group (UCG). EG patients underwent a short-term supervised inpatient physiotherapy exercise protocol consisting of an early mobilisation with progressive exercises plus usual care (respiratory exercises). UCG only received respiratory exercises. Forty-seven patients (24 EG and 23 UGC) completed the study. Outcome measures of CAR included linear and non-linear measures of heart rate variability (HRV) assessed before discharge. RESULTS: By hospital discharge, EG presented significantly higher parasympathetic HRV values [rMSSD, high frequency (HF), SD1)], global power (STD RR, SD2), non-linear HRV indexes [detrended fluctuation analysis (DFA)alpha1, DFAalpha2, approximate entropy (ApEn)] and mean RR compared to UCG (p<0.05). Conversely, higher values of mean HR, low frequency (LF) (sympathetic activity) and the LF/HF (global sympatho-vagal balance) were found in the UCG. CONCLUSIONS: A short-term supervised physiotherapy exercise protocol during inpatient CR improves CAR at the time of discharge. Thus, exercise-based inpatient CR might be an effective non-pharmacological tool to improve autonomic cardiac tone in patient's post-CABG.

Acute application of bilevel positive airway pressure influences the cardiac autonomic nervous system.

INTRODUCTION: Noninvasive positive pressure has been used to treat several diseases. However, the physiological response of the cardiac autonomic system during bilevel positive airway pressure (Bilevel) remains unclear. OBJECTIVE: The aim of this study was to evaluate the heart rate variability (HRV) during Bilevel in young healthy subjects. METHODS: Twenty men underwent 10-minute R-R interval recordings during sham ventilation (SV), Bilevel of 8-15 cmH(2)O and Bilevel of 13-20 cmH(2)O. The HRV was analyzed by means of the parallel R-R interval (mean R-Ri), the standard deviation of all R-Ri (SDNN), the root mean square of the squares of the differences between successive R-Ri (rMSSD), the number of successive R-Ri pairs that differ by more than 50 milliseconds (NN50), the percentage of successive R-Ri that differ by more than 50 milliseconds (pNN50), the low frequency (LF), the high frequency (HF) and SD1 and SD2. Additionally, physiological variables, including blood pressure, breathing frequency and end tidal CO(2), were collected. Repeated-measures ANOVA and Pearson correlation were used to assess the differences between the three studied conditions and the relationships between the delta of Bilevel at 13-20 cmH(2)O and sham ventilation of the HRV indexes and the physiological variables, respectively. RESULTS: The R-Ri mean, rMSSD, NN50, pNN50 and SD1 were reduced during Bilevel of 13-20 cmH(2)O as compared to SV. An R-Ri mean reduction was also observed in Bilevel of 13-20 cmH(2)O compared to 8-15 cmH(2)O. Both the R-Ri mean and HF were reduced during Bilevel of 8-15 cmH(2)O as compared to SV, while the LF increased during application of Bilevel of 8-15 cmH(2)O as compared to SV. The delta (between Bilevel at 13-20 cmH(2)O and sham ventilation) of ETCO(2) correlated positively with LF, HF, the LF/HF ratio, SDNN, rMSSD and SD1. Acute application of Bilevel was able to alter the cardiac autonomic nervous system, resulting in a reduction in parasympathetic activity and an increase in sympathetic activity and higher level of positive pressure can cause a greater influence on the cardiovascular and respiratory system.

Non-invasive ventilation improves peripheral oxygen saturation and reduces fatigability of quadriceps in patients with COPD.

BACKGROUND AND OBJECTIVE: Non-invasive ventilation (NIV) might improve peripheral muscle function and exercise capacity in severely disabled patients. This study evaluated the physiological impact of NIV on isokinetic concentric strength and endurance of lower limb muscles in patients with severe COPD. METHODS: This clinical trial tested COPD patients (n = 24) and healthy subjects (n = 18). Subjects underwent isokinetic dynamometry tests while given either bi-level positive airway pressure ventilation (BV) or sham ventilation (SV), in a randomized order with 30 min of rest prior to each intervention. The inspiratory level of BV was set up to 14 cm H(2)O and expiratory pressure up to 6 cm H(2)O. Peripheral oxygen saturation (SpO(2)), heart rate (HR), systolic (SBP) and diastolic blood pressure (DBP) at the peak of exercise were measured for each intervention. RESULTS: Compared with controls, COPD patients had lower values of SpO(2) and HR (P < 0.01) during both BV and SV and lower values of DBP (P < 0.01) during BV. BV improved SpO(2) (P < 0.01), and reduced SBP in both COPD (P < 0.01) and control groups (P < 0.05) and reduced DBP in COPD patients (P < 0.01). BV also reduced the fatigue index in COPD patients when compared with SV (P = 0.003). Variation (BV-SV) of total work at the peak of the test was higher in the control group than in the COPD group (P < 0.05). CONCLUSIONS: BV improved SpO(2) and reduced the fatigability of the quadriceps muscle in patients with severe COPD. These results support the need for further evaluation of BV as adjunct during high-intensity strength exercise training in these patients.