CPAP and EPAP elicit similar lung deflation in a non-equivalent mode in GOLD 3-4 COPD patients

Acute effects of expiratory positive pressure on autonomic cardiac modulation during spontaneous and slow deep breathing in COPD patients

AIM

to evaluate the acute effects of expiratory positive airway pressure on cardiac autonomic modulation in chronic obstructive pulmonary disease patients during spontaneous breathing and slow deep breathing.

METHODS

17 patients were evaluated. The R-R intervals were collected (Polar® S810i) during spontaneous breathing (10 minutes) and slow deep breathing (4 minutes), with and without 5 cmH2O expiratory positive airway pressure. Stable signals were analyzed by Kubios®. Heart rate variability indices were computed in time domain and in frequency domain.

RESULTS

Expiratory positive airway pressure application affected low frequency (spontaneous breathing: 62.5±4.1 vs slow deep breathing: 28.2±4.2, p<0.001) and high frequency (spontaneous breathing: 37.4±17.3 vs slow deep breathing: 58.9±18.1, p<0.001). Interactions were observed between expiratory positive airway pressure effect and slow deep breathing effect for low frequency (p<0.001), high frequency (p<0.001) and low frequency/high frequency ratio (p<0.001). When patients were stratified by disease's severity, we identified a significant low frequency reduction (p<0.001) and high frequency increase (p<0.001) for all stages when slow deep breathing was associated with expiratory positive airway pressure.

CONCLUSION

A 5 cmH2O expiratory positive airway pressure during spontaneous and slow deep breathing can elicit an acute response, resulting in a cardiac autonomic control improvement in moderate-to-very severe patients.

Inspiratory Muscle Training Potentiates the Beneficial Effects of Proportional Assisted Ventilation on Exertional Dyspnea and Exercise Tolerance in COPD: A Proof-of-Concept Randomized and Controlled Trial

During pulmonary rehabilitation, a subset of subjects with COPD requires adjunct therapy to achieve high-intensity training. Both noninvasive ventilation (NIV) and inspiratory muscle training (IMT) are available to assist these subjects. We aimed to prime the respiratory muscles before NIV with IMT, anticipating additive effects for maximal exercise tolerance (T _lim) and dyspnea/leg fatigue relief throughout the exercise as primary outcomes. Changes in the respiratory pattern were secondary outcomes. COPD subjects performed a total of four identical constant work rate tests on a cycle ergometer at 75% of maximum work rate, under control ventilation (SHAM, 4 cm H₂O) or proportional assisted ventilation (PAV, individually adjusted), before and after 10 sessions of high-intensity IMT (three times/week) during 30 days. Two-way RM ANOVA with appropriate corrections were performed. Final analysis in nine subjects showed improved T _lim (Δ = 111 s) and lower minute-ventilation (Δ = 4 L^.min^-1) at exhaustion, when comparing the IMT effects within the PAV modality (p = 0.001 and p = 0.036, respectively) and improved T _lim for PAV vs. SHAM (PAV main-effect, p = 0.001; IMT main-effect, p = 0.006; PAV vs. IMT interaction, p = 0.034). In addition, IMT + PAV association, compared to PAV alone, resulted in lower respiratory frequency (IMT main-effect, p = 0.009; time main-effect, p < 0.0001; IMT vs. time interaction, p = 0.242) and lower inspiratory time related to duty cycle (IMT main-effect, p = 0.018; time main-effect, p = 0.0001; IMT vs. time interaction, p = 0.004) throughout exercise. The addition of IMT prior to a PAV-supported aerobic bout potentiates exercise tolerance and dyspnea relief and induces favourable changes in ventilatory pattern in severe COPD during high-intensity training (Brazilian Registry of Clinical Trials, number RBR-6n3dzz).

Influence of expiratory positive airway pressure on cardiac autonomic modulation at rest and in submaximal exercise in COPD patients

The aim of this study was to evaluate the effect of expiratory positive airway pressure (EPAP) on heart rate variability (HRV) indices at rest and during 6-min walk test (6MWT) in chronic obstructive pulmonary disease (COPD) patients. Fifteen moderate to severe COPD patients were randomized and evaluated with and without (Non-EPAP) a 5 cmH₂O EPAP device. Respiratory rate (RR) was collected at rest (5 min), during the 6MWT (5 min), and at recovery (5 min). Indices of HRV were computed in the time domain, in the frequency domain, and nonlinear analysis. For EPAP and Non-EPAP during the 6MWT, we found an increased mean heart rate (HR) (P=0.001; P=0.001) while mean RR (P=0.001; P=0.015) and RR tri index decreased (P=0.006; P=0.028). Peripheral oxygen saturation (P=0.019) increased at rest only in the EPAP group. In EPAP, correlations were found between forced expiratory volume in 1 s (FEV₁) and low frequency (LF) sympathetic tonus (P=0.05; r=-0.49), FEV₁ and high frequency (HF) parasympathetic tonus at rest (P=0.05; r=0.49), lactate at rest and LF during the 6MWT (P=0.02; r=-0.57), and lactate at rest and HF during 6MWT (P=0.02; r=0.56). Through a linear regression model, we found that lactate at rest explained 27% of the alterations of LF during 6MWT. The use of 5 cmH₂O EPAP improved autonomic cardiac modulation and its complexity at rest in COPD patients. Although it did not influence the performance of the 6MWT, the EPAP device caused alterations in resting lactate concentration with an effect on sympatho-vagal control during the test.