Comparison of the effects of voluntary and involuntary breath stacking techniques on respiratory mechanics and lung function patterns in tracheostomized patients: a randomized crossover clinical trial

OBJECTIVE: To compare the effects of voluntary breath stacking (VBS) and involuntary breath stacking (IBS) techniques on respiratory mechanics, lung function patterns, and inspiratory capacity in tracheostomized patients. METHODS: This was a randomized crossover clinical trial involving 20 tracheostomized patients admitted to the ICU and submitted to the VBS and IBS techniques, in random order, with an interval of 5 h between each. Ten cycles of each technique were performed with an interval of 30 s between each cycle. In VBS, patients performed successive inspirations for up to 30 s through a one-way valve, whereas in IBS, successive slow insufflations were performed with a resuscitator bag until the pressure reached 40 cmH(2)O. Respiratory mechanics, inspiratory capacity, and the lung function pattern were evaluated before and after the interventions. RESULTS: After IBS, there was an increase in static compliance (p = 0.007), which was also higher after IBS than after VBS (p = 0.03). There was no significant difference between the pre-VBS and post-VBS evaluations in terms of static compliance (p = 0.42). Inspiratory capacity was also greater after IBS than after VBS (2,420.7 ± 480.9 mL vs. 1,211.3 ± 562.8 mL; p < 0.001), as was airway pressure (38.3 ± 2.6 cmH(2)O vs. 25.8 ± 5.5 cmH(2)O; p < 0.001). There were no changes in resistance or lung function pattern after the application of either technique. CONCLUSIONS: In comparison with VBS, IBS promoted greater inspiratory capacity and higher airway pressure, resulting in an increase in static compliance.