Slow chest compression acutely reduces dynamic hyperinflation in people with chronic obstructive pulmonary disease: a randomized cross-over trial.

Background: Strategies to minimize dynamic hyperinflation (DH) and dyspnea, such as slow chest compression (SCC), are relevant in people with chronic obstructive pulmonary disease (COPD).
Objectives: To analyze the acute effects of SCC after exercise on DH and dyspnea in people with COPD and to identify responders to the technique.
Methods: This is a cross-over study with 40 patients. Two six-minute step tests (6MSTs) were performed followed by a one-minute application of SCC (6MST _SCC ) or rest (6MST _CONTROL ), at random. End-expiratory lung volume (EELV) and dyspnea were assessed. A difference ≥76 ml in ΔEELV between SCC and control characterized the responders.
Results: The performance in 6MST _SCC and 6MST _CONTROL were similar. There was a greater reduction in EELV after 6MST _SCC compared to 6MST _CONTROL (124 ± 193 ml vs. 174 ± 183 ml; p = .049), while there was no difference in change in dyspnea between the SCC and control groups. Twenty-one participants were SCC responders and had higher functional residual capacity [FRC: 5.36 ± 1.09 vs. 4.58 ± 0.94; p = .02; cutoff point: 4.56; sensitivity = 76%; specificity = 53%; AUC = 0.71 (95%CI: 0.54 to 0.87); p = .02].
Conclusion: SCC applied immediately after exercise reduced DH, but did not reduce dyspnea in people with COPD. The technique is beneficial only for some patients and FRC can help to identify them.