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 (6MSTSCC) or rest (6MSTCONTROL), 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 6MSTSCC and 6MSTCONTROL were similar. There was a greater reduction in EELV after 6MSTSCC compared to 6MSTCONTROL (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.

A performance comparison of the 20 and 30 meter six-minute walk tests among middle aged and older adults.

Objective: To compare the performance of the Six-Minute Walk Test on 20-meter (6MWT20) and 30-meter (6MWT30) tracks and to test the validity and reliability of the 6MWT20 in middle-aged and older adults.Method: The subjects underwent lung function assessment and performed the 6MWT30 and 6MWT20. Student´s t-tests or Wilcoxon tests were used to compare the variables. The Pearson or Spearman correlation coefficients were used to evaluate the validity of the 6MWT20 and the reliability of the 6MWT20. The 6MWT30 was tested by the two-way mixed model of the Intraclass Correlation Coefficient (ICC 3,1).Results: Twenty-five subjects (age: 60 ± 10 years) walked, on average, 11.0 ± 21.9 m more in the 6MWT30 than in the 6MWT20 (p < .05). The walking distance, the number of steps, the energy expenditure and the movement intensity between the 6MWT20 and 6MWT30 was correlated (r = 0.95; r = 0.81; r = 0.91; r = 0.67; respectively, p < .001). The walking distances showed high reliability and were similar between test and re-test in the 6MWT30 (544 ± 72.1 vs. 551 ± 70.5; p < .05; ICC = 0.97) and in the 6MWT20 (533 ± 73.1 vs. 532 ± 59.1; p < .05; ICC = 0.87).Conclusion: The 6MWT20 performance is lower than the 6MWT30 However, this difference is not clinically relevant. Additionally, the 6MWT20 is a valid and reproducible test to assess the functional capacity of middle-aged and older adults.