Inspiratory muscle training (IMT) with normocapnic hyperventilation (NH) improves respiratory muscle strength, exercise performance and ventilatory pattern in COPD patients

Introduction: IMT by means of NH is effective in improving exercise endurance in healthy subjects but few data are available for COPD. Aim: To evaluate the effect of 4 weeks NH training (Spirotiger®) on respiratory function and exercise capacity in 21 moderate/severe COPD patients. Materials and methods: 19 M, 2 F, aged 42-80. Respiratory function tests (FEV1, FVC, Pimax), QoL (St George's Questionnarie), 6MWT and endurance exercise performed at 75-80% of peak-work rate measured during an incremental test to the limit of tolerance (tLIM). 7 of 21 patients were instrumented with a portable inductive plethysmografhy (Lifeshirt System) to evaluate breathing pattern during tLIM. After 1 month of weekly supervised training, the patients trained at home for 4 weeks: 10 min twice a day at a breathing rate 12-24/min with a tidal volume (TV) equal to 50% of CV. Results: 6 patients dropped out (poor compliance). IMT significantly improved Pimax, QoL, exercise capacity. Ventilatory pattern after IMT is characterized by a significantly higher TV with no change in VE. Table 1 FEV1 (%) FVC (%) Pimax (kPa) QoL (tot) tLIM (min) 6MWt (m) preIMT 55,2±16,9 82,3±22,8 8,9±3 22,7±16,6 6,4±3,4 436±74,5 postIMT 57,6±15,8 82,7±24,1 9,6±2,8* 17,5±12,2* 10,3±7,4* 466,2±79,7* Table 2 SpO2mean (%) VE (L/min) TV (L/min) Br (b/min) preIMT 91±2,2 28,6±16,1 0,8±0,4 33±4,2 postIMT 92,3±1,5* 29±16,4 0,9±0,4* 30,8±6,5 *p<0,05 (statistical analysis: T test and Wilcoxon signed rank test). Conclusion: After a short IMT with NH, COPD patients show a higher exercise capacity and an intriguing change in ventilatory pattern which improves oxygen saturation.