Influence of physical rehabilitation on heart rate dynamics in patients with idiopathic pulmonary fibrosis

Abstract

This study sought to determine whether a 6-week physical rehabilita-tion programme has a measurable influence on heart rate responsive-ness to changing metabolic demand in patients with pulmonary fibrosis. Fifteen individuals (13 with idiopathic pulmonary fibrosis and two with pulmonary fibrosis associated with rheumatoid disease) underwent as-sessments of physical function (6-min walk test), ventilatory function (spirometry), and cardio-respiratory function (respiratory gas analysis and electrocardiogram [ECG] recording during a protocol consisting of periods of rest, incremental bicycle exercise to maximal effort, and post-exercise recovery). RR (beat-to-beat cardiac intervals) data were derived from the ECG and used to quantify (a) heart rate variability (HRV) and (b) cardiac acceleration (AC) and deceleration capacities (DC) (via phase rectified signal averaging). Following the rehabilitation pro-gramme, heart rate was elevated by 11%-18% during exercise and re-covery states. HRV was not statistically influenced by rehabilitation during any stage of the assessment protocol; however, qualitative changes were apparent with HRV increasing by 68%-75% during all stages of the protocol. Statistically, AC and DC were similar pre- and postrehabilitation (AC=-2.7 and -3.2 msec; DC=2.3 and 3.2 msec, re-spectively) but again we observed qualitative improvements in these in-dices of 19% and 38%, respectively. These results provide initial evi-dence that physical rehabilitation improves heart rate dynamics (via modulation of autonomic control of heart rate) in idiopathic pulmonary fibrosis patients, even when respiratory and physical functions are un-changed or diminished.