Heart rate variability in chronic obstructive pulmonary disease patients during bilevel positive airway pressure

Objectives

Ventilation by bilevel positive airway pressure (BIPAP) was been applied in chronic obstructive pulmonary disease (COPD) with the aim of increasing oxygenation, and reducing dyspnea and respiratory work. However, the positive pressure may produce harmful effects on the cardiovascular system. The aim of this study was to evaluate the autonomic modulation of the heart by the heart rate response and heart rate variability analysis (HRV) during BIPAP ventilation in COPD patients.

Methods

Seven patients aged 65.2 ± 6 years with FEV₁ < 50% predicted were selected for the study. The COPD diagnostic was based on the clinical history and spirometry test. The study protocol was approved by the Universidade Federal de São Carlos Human Ethics Committee. All patients were informed of the nature of the study and signed a consent document for participation (CNS no. 03/2000). The patients were submitted to clinical and resting electrocardiograph evaluation before the study. The experimental protocol consists of the collection of the heart rate beat to beat and RR intervals (RRi) (in milliseconds) using a cardiac rate meter (Polar-Vantage). Heart rate data and RRi were collected over a period of 10 min during rest in the supine and sitting positions. After this, the BIPAP (Respironics) was applied with inspiratory pressure (IPAP) of 14 cmH₂O and expiratory pressure (EPAP) of 6 cmH₂O, during 20 min with a nasal mask, and then HR and RRi values were collected. The data analysis evaluated the RRi values and HRV using the calculation of the RMSSD index of the RRi (in milliseconds), the square root of the mean sum of squares of the differences between the adjacent normal RRi in the record divided by the number of RRi within a given time minus one RRi. Data were analyzed statistically by the Friedman and Dunn test, with the level of significance set at P < 0.05.

Results

There were no significant differences in the absolute results of RRi and HRV by the RMSSD index in different situations (P > 0.05).

Conclusion

The results suggest that the BIPAP with pressures levels applied did not promote changes in the vagal-sympathetic control of the heart and in HVR. These procedures thus do not involve additional cardiovascular risks for the patients with COPD.