INTRODUCTION:

1. Inspiratory muscle strength training improves weaning outcome in failure to wean patients: a randomized trial Cader et al. (cont) INTRODUCTION: Most 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. METHODS: We 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. RESULTS: Groups 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). CONCLUSIONS: An IMST program can lead to increased MIP and improved weaning outcome in FTW patients compared to SHAM treatment. Abstract Martin AD, Smith BK, Davenport PD, et al. Inspiratory muscle strength training improves weaning outcome in failure to wean patients: a randomized trial. Critical Care. 2011;15(2):R84 Research design was single-blinded with a SHAM control treatment group. Maximal inspiratory pressure measurement Measured using a one-way valve that attached to the patient’s tracheostomy tube which allowed for exhalation but blocked inspiration. Patient was instructed to breath as forcefully as possible for 20 seconds. Measurements were repeated three times with 2 minute rest breaks between sets. The most negative value achieved was recorded. Inspiratory muscle strength training • Performed 5 days per week with a threshold inspiratory muscle trainer which provided a load between -4 and -20 cmH2O. • Subjects were disconnected from MV and the IMST device was attached to the tracheostomy tube. • Four sets of 6-8 reps were performed each day with 2 minute MV rest breaks between each set. • Training device was set to the highest tolerated pressure that was consistently opened by the subject and was increased daily as tolerated. • Subjects were instructed to inhale and exhale as forcefully as possible during IMST. • Pressures were monitored with CO2SMO Plus with Analysis Plus software. SHAM training Used a resistive IMST device set to it’s largest opening. SHAM training involved removal from the MV and attachment of training device to tracheostomy tube. Subjects performed four sets of 6-10 long, slow breaths, five days per week. 2 minutes of MV rest were given between each set. Breathing trials Subjects participated in progressively lengthening BTs with little or no MV support 7 days per week. Subjects who successfully breathed for 72 hours free of MV were considered weaned. BTs became progressively longer each day unless the subject could not complete it, in which case the following day repeated the same length treatment. Methods and Materials The IMST rehabilitation program rapidly improved MIP which, in turn, improved weaning outcome compared to those subjects who completed the SHAM protocol. The amount of successfully weaned patients from the SHAM group (47%) is consistent with usual care conditions. Other works have shown that MIP is a poor predictor of weaning outcomes, the methods of these studies differ in the following categories: Subjects were in acute phase of MV Inclusion criteria for study Other studies did not use a strength training program During MV there is a relatively low motor drive to breath because of slow, deep MV respirations. Thus, when removed from MV, patients have a high respiratory demand and little perception of lung volume feedback. Inspiratory strength training can theoretically lower the perception of breathing work. Limitations of this study include: All subjects that were tested came from the same site. Small sample size This IMST method is not suitable for all FTW patients Discussion Introduction Training was stopped when contraindications to exercise became apparent. Maximal inspiratory pressure was the main outcome to be measured. Results of the study showed a significant increase in maximal inspiratory pressure (7.6 cmH2O ) and a significant decrease in weaning time (1.7 days sooner). Limitations to this study include a wide variety of medical conditions, lack of blinding, This study concludes that inspiratory muscle training improves inspiratory muscle strength in older intubated patients and may also reduce weaning time. Caruso P, Denari SD, Ruiz SA, et al. Inspiratory muscle training is ineffective in mechanically ventilated critically ill patients. Clinics (Sao Paulo). 2005;60(6):479-84 Caruso et al. A randomized control trial performed in a surgical ICU aimed to determine the effects of inspiratory muscle strength training on weaning success and reintubation rates. 25 participants were randomly assigned to experimental and control groups. The control group received usual care while the IMST group received 2 bouts of training per day using a one way tracheostomy device. Initial resistance of the inspiratory device was set at 20% of MIP and was increased in accordance with patient performance. The maximal resistance possible was 40% MIP. Training sessions were discontinued if the subject exhibited any contraindications to exercise. Subjects were declared weaning failures if they had to be reintubated within 48 hours of extubation. Weaning duration and reintubation rates showed no significant differences (P=0.24 and 0.67 respectively). This article states that it may be unfeasible to muscularly train a critically ill patient. The authors state that the load and duration of the IMST may not have been sufficient enough to show significant changes in inspiratory strength. Limitations in this study include variability among the MIP values throughout training and the volitional nature of the training procedures. The insignificant results in this study could possibly be attributed to the small sample size. This article concludes that acute critically ill patients inspiratory muscle training from the beginning of mechanical ventilation neither abbreviated weaning duration nor decreased the reintubation rate. Initial and final maximal inspiratory pressures were lower than normal in the majority of patients and did not change during mechanical ventilation. Summary The initiation of an inspiratory muscle strengthening program, grounded in proper strength training standards, has been shown to increase maximal inspiratory pressure of patients who require mechanical ventilation. Increases in maximal inspiratory pressure have been shown to decrease weaning time and increase weaning success rates in mechanically ventilated ICU patients. Decreased weaning time may lead to a higher quality of physical therapy care and a shorter overall hospital stay. Physical therapist, among other health care professionals, should advocate the use of IMST in order to more efficiently reach patient’s goals upon discharge from ICU. References Failure to wean (FTW) from mechanical ventilation (MV) is a significant clinical and economic problem. In the USA in 2003, approximately 300,000 patients were mechanically ventilated for longer than 96 hours costing $16 billion. MV has been shown to cause rapid atrophy of the diaphragm muscle in animals. Strength training of the inspiratory muscles emerges as a possible treatment. Preoperative IMST has been shown to reduce the incidence of post-operative respiratory complications in high risk cardiac surgery patients and has also been demonstrated t preserve post-operative inspiratory muscle strength following major abdominal surgery. To date, no adequately powered studies have examined the effects of inspiratory muscle strength training (IMST) on weaning outcomes. A randomized control trial was carried out in a hospital intensive care unit in Brazil. Participants were >70 years old, intubated, and had been on MV for >48 hours. The experimental group received inspiratory muscle training twice daily in addition to usual care while the control group received usual care. Usual care consisted of changes in ventilator support, positioning, physical therapy, and chest compressions. IMST was achieved using a one way valve tracheostomy. Resistance to inspiration could be changed via a spring on the device. Subjects were supine in a 45 degree recumbent position. Training took place twice daily in 5 minute increments 7 days a week until weaned. Training was stopped when contraindications to exercise became apparent. Maximal inspiratory pressure was the main outcome to be measured. Cader AS, de Souza Vale RG, Castro JC, et al. Inspiratory muscle training improves maximal inspiratory pressure and may assist weaning in older intubated patients: a randomised trial. Journal of Physiotherapy. 2010;56 One way tracheostomy tube device Clinical Significance • This article has direct implications on physical therapy and the question of how physical therapists should handle a patient who is receiving respiratory support from a mechanical ventilator. • 10-15% of all MV patients fail to wean and remain ventilated for more than 96 hours. • Time to discharge is important in the outpatient setting. • Successfully weaned patients are discharged significantly sooner than patients who fail to be weaned. • This study provides evidence that the utilization of an IMST can reduce the amount of time a patient requires mechanical ventilation which will directly affect physical therapy treatment time, leading to an earlier discharge. Conclusions In conclusion, an improved MIP and weaning outcome with IMST compared with SHAM training in medically complex, long-term FTW patients. IMST is a clinically practical and safe method to improve weaning outcome in selected FTW patients. Results • Mean training pressure setting on the IMST device was 7.2 ± 2.6 vs. 12.8 ± 3.6 cmH2O for the initial and final training bouts respectively. The SHAM training device was set at its lowest resistance for all sessions. • The IMST group developed -9.54 ± 3.70 and -14.52 ± 4.59 cm H2O of inspiratory pressure during the initial and final IMST bouts (P=0.0004). • The SHAM group developed -3.10 ± 1.54 and -3.36 ± 2.08 cmH2O of pressure at initial and final bouts (P=0.86). • The SHAM group showed no significant change (P=0.39) in MIP from pre to post-training (-43.5 ±17.8 vs. -45.1 ± 19.6 cmH2O). • The IMST group showed a significant increase (P<0.0001) in MIP (-44.4 ± 18.4 vs. -54.1 ± 17.8 cm H2O). • 71% of IMST patients weaned, 47% of SHAM patients were also weaned. • Pre and post test measures for the successfully weaned groups were -44.0 ± 20.2 and -53.5 ± 20.7 cmH2O while the same measures for the failed weaning group were -43.9 ± 14.8 and -43.9 ± 15.0. • The change in MIP values for the successfully weaned group were significantly greater (P<0.0001) than the failed weaning group. Purpose The purpose of this study is to examine the relationship between maximal inspiratory pressure and successful weaning outcomes in FTW patients. Martin et al. hypothesize that an IMST program, grounded in accepted principles of muscle strength training, coupled with progressively lengthening breathing trials would improve weaning outcome compared to patients receiving a SHAM treatment. -Martin AD, Smith BK, Davenport PD, et al. Inspiratory muscle strength training improves weaning outcome in failure to wean patients: a randomized trial. Critical Care. 2011;15(2):R84 Drew Cecil, SPT Bellarmine University Physical Therapy