Abstract
IntroductionMost patients are readily liberated from mechanical ventilation (MV) support, however, 10% - 15% of patients experience failure to wean (FTW). FTW patients account for approximately 40% of all MV days and have significantly worse clinical outcomes. MV induced inspiratory muscle weakness has been implicated as a contributor to FTW and recent work has documented inspiratory muscle weakness in humans supported with MV.MethodsWe conducted a single center, single-blind, randomized controlled trial to test whether inspiratory muscle strength training (IMST) would improve weaning outcome in FTW patients. Of 129 patients evaluated for participation, 69 were enrolled and studied. 35 subjects were randomly assigned to the IMST condition and 34 to the SHAM treatment. IMST was performed with a threshold inspiratory device, set at the highest pressure tolerated and progressed daily. SHAM training provided a constant, low inspiratory pressure load. Subjects completed 4 sets of 6-10 training breaths, 5 days per week. Subjects also performed progressively longer breathing trials daily per protocol. The weaning criterion was 72 consecutive hours without MV support. Subjects were blinded to group assignment, and were treated until weaned or 28 days.ResultsGroups were comparable on demographic and clinical variables at baseline. The IMST and SHAM groups respectively received 41.9 ± 25.5 vs. 47.3 ± 33.0 days of MV support prior to starting intervention, P = 0.36. The IMST and SHAM groups participated in 9.7 ± 4.0 and 11.0 ± 4.8 training sessions, respectively, P = 0.09. The SHAM group's pre to post-training maximal inspiratory pressure (MIP) change was not significant (-43.5 ± 17.8 vs. -45.1 ± 19.5 cm H2O, P = 0.39), while the IMST group's MIP increased (-44.4 ± 18.4 vs. -54.1 ± 17.8 cm H2O, P < 0.0001). There were no adverse events observed during IMST or SHAM treatments. Twenty-five of 35 IMST subjects weaned (71%, 95% confidence interval (CI) = 55% to 84%), while 16 of 34 (47%, 95% CI = 31% to 63%) SHAM subjects weaned, P = .039. The number of patients needed to be treated for effect was 4 (95% CI = 2 to 80).ConclusionsAn IMST program can lead to increased MIP and improved weaning outcome in FTW patients compared to SHAM treatment.Trial RegistrationClinicalTrials.gov: NCT00419458
Highlights
Most patients are readily liberated from mechanical ventilation (MV) support, 10% - 15% of patients experience failure to wean (FTW)
There were no adverse events observed during inspiratory muscle strength training (IMST) or SHAM treatments
The number of patients needed to be treated for effect was 4
Summary
Most patients are readily liberated from mechanical ventilation (MV) support, 10% - 15% of patients experience failure to wean (FTW). MV induced inspiratory muscle weakness has been implicated as a contributor to FTW and recent work has documented inspiratory muscle weakness in humans supported with MV. Numerous animal studies have documented ventilator-induced diaphragm dysfunction following as little as six hours of controlled MV [6,7,8], but less data examining the effects of MV on the human diaphragm are available. Levine et al [10] documented approximately 55% atrophy in human diaphragms following 19 to 56 hours of controlled MV. Hussain et al documented upregulation of catabolic process in human diaphragms following 15 to 276 hours of controlled MV [12], and Jaber et al documented a 32% reduction in endotracheal tube pressure following magnetic diaphragm stimulation in humans following six days of MV support [13]
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