Objective: To check the effectiveness of Conventional Physiotherapy and Threshold Inspiratory Muscle Training(TIMT) on the weaning period of mechanically ventilated patients. Background: Prolonged Mechanical ventilation (MV) of ICU patients is associated with high health care costs and respiratory muscle weakness which also has been suggested as a possible cause of delayed weaning from MV. Hence, TIMT may be seen as a possible accelerator for successful weaning. Study Design: Experimental and comparative design. Methods: Total 30 subjects were selected on the basis of inclusion criteria and divided randomly with 15 subjects in each group. To the Group-A Conventional Physiotherapy was given whereas in the Group-B TIMT was also added. The Maximal Inspiratory Pressure (MIP) was measured before commencement of the treatment and post-extubation. Result: The data was analyzed using unpaired ‘t’ test. In Group-B (TIMT), MIP mean increased to -43.87 ± 8.01 cm H2O (post extubation) from pre-treatment value of -29.29 ± 3.61 cm H2O, as compared to Group-A’s values of -35.68 ± 4.49 cm H2O (post extubation) from -28.77 ± 2.93 cm H2O (pre-treatment). Also the weaning period was reduced more significantly in Group-B (mean duration of 4.27 ± 1.49 days) than the Group-A (mean duration of 6.27±1.71 days). Conclusion: The results of the study indicate that TIMT along with conventional physiotherapy produces more significant changes in MIP and weaning period of patients receiving mechanical ventilation as compared to conventional physiotherapy alone.

This report describes the use of specific inspiratory muscle training to enhance weaning from mechanical ventilation in a patient who had failed conventional weaning strategies. A 79-year-old man remained ventilator-dependent 17 days following laparotomy. A program of daily inspiratory muscle training was initiated. The mean training threshold increased progressively during the program and simultaneously the periods of unassisted breathing achieved gradually increased. By day 27, mechanical ventilation was no longer required. Inspiratory muscle training can be implemented effectively in the difficult to wean patient and should be considered for patients who have failed conventional weaning strategies.
PMID: 17933168 DOI: 10.1177/0310057X0703500520

The review by Nguyen et al. [1] acknowledges the substantially lower baseline central venous oxygen saturation (ScvO2) values reported by Rivers et al. [2] (48.6 ± 11.2 %) when compared to those for ProCESS [3] (71 ± 13 %), ARISE [4] (72.7 ± 10.5 %) and ProMISe [5] (64 ± 20 %) trials. Assuming normality, the distribution of baseline ScvO2 values in the study by Rivers et al. differed from those of the other trials (Fig. 1; p < 0.0001 by t test). Nguyen et al. ascribed this difference to “earlier central venous catheter (CVC) placement, greater shock severity or imbalances between O2 delivery and O2 consumption before corrective interventions”. One aspect of these trials that has been ignored up to now is the CVC position in the superior vena cava. According to accepted guidelines, the tip of the CVC should lie below the anterior first rib and above the right atrium, placing the tip of the CVC below the opening of the azygos vein, a vessel carrying venous blood from the intercostal muscles and portions of the diaphragm. In the study by Rivers et al., 53.8 % of patients randomized to the early goal-directed therapy (EGDT) group required invasive mechanical ventilation during the first 6 h of treatment, a greater rate (p < 0.0001; Chi Square test) than those reported by ProCESS (26.4 %), ARISE (22.2 %), and ProMISe (19 %). Furthermore, the baseline respiratory rate for the EGDT cohort in Rivers et al. (31.8 ± 10.8 bpm) was greater (p < 0.001) than those reported by ProCESS (25.4 ± 7.0 bpm) and ARISE (24. ± 7.5 bpm). The baseline respiratory rate for patients in the ProMISe trial was not reported. These data infer that patients in the study of Rivers et al. experienced considerable respiratory distress prior to the initiation of mechanical ventilation. This condition was likely associated with an increased work of breathing and the discharge of highly desaturated blood by the azygos vein into the superior vena cava, in close proximity to the fiber optic lumen of the catheter tip, precisely where ScvO2 was measured spectrophotometrically. It is reasonable, therefore, to propose that the low ScvO2 values reported in the study of Rivers et al. reflected work by the muscles of respiration and not sepsis-associated systemic tissue dysoxia. In that instance, the ScvO2 increases observed during the first 6 h of treatment in the study by Rivers et al. may have been in response to unloading of respiratory muscles by mechanical ventilation and not to red blood cell transfusion or dobutamine infusion as proposed by their treatment algorithm.
doi: 10.1186/s13054-016-1476-1

Respiratory muscle dysfunction is associated with prolonged and difficult weaning from mechanical ventilation. This dysfunction in ventilator-dependent patients is multifactorial: there is evidence that inspiratory muscle weakness is partially explained by disuse atrophy secondary to ventilation, and positive end-expiratory pressure can further reduce muscle strength by negatively shifting the length-tension curve of the diaphragm. Polyneuropathy is also likely to contribute to apparent muscle weakness in critically ill patients, and nutritional and pharmaceutical effects may further compound muscle weakness. Moreover, psychological influences, including anxiety, may contribute to difficulty in weaning. There is recent evidence that inspiratory muscle training is safe and feasible in selected ventilator-dependent patients, and that this training can reduce the weaning period and improve overall weaning success rates. Extrapolating from evidence in sports medicine, as well as the known effects of inspiratory muscle training in chronic lung disease, a theoretical model is proposed to describe how inspiratory muscle training enhances weaning and recovery from mechanical ventilation. Possible mechanisms include increased protein synthesis (both Type 1 and Type 2 muscle fibres), enhanced limb perfusion via dampening of a sympathetically-mediated metaboreflex, reduced lactate levels and modulation of the perception of exertion, resulting in less dyspnoea and enhanced exercise capacity.
PMID: 22417017 DOI: 10.1177/0310057X1204000205

BACKGROUND: The benefits of inspiratory muscle training (IMT) in patients with chronic heart failure (CHF) have been inadequately studied.
DESIGN AND METHODS: Using a prospective, age and sex-matched controlled study, we investigated 35 patients with moderate to severe CHF (NYHA class II-III and left ventricular ejection fraction 24.4+/-1.3% [mean+/-SEM]). An incremental respiratory endurance test using a fixed respiratory workload was provided by software with an electronic mouth pressure manometer interfaced with a computer. The training group (n=20) exercised at 60% of individual sustained maximal inspiratory pressure (SMIP) and the control group (n=15) at 15% of SMIP. All patients exercised three times weekly for 10 weeks. Pulmonary function, exercise capacity, dyspnea and quality of life were assessed, pre- and post-training.
RESULTS: The training group significantly increased both maximum inspiratory pressure (Pimax), (111+/-6.8 versus 83+/-5.7 cmH2O, P<0.001), and SMIP (527822+/-51358 versus 367360+/-41111 cmH2O/sec x 10(-1), P<0.001). Peak VO2 increased after training (17.8+/-1.2 versus 15.4+/-0.9 ml/kg/min, P<0.005), as did the six-minute walking distance (433+/-16 versus 367+/-22 meters, P<0.001). Perceived dyspnea assessed using the Borg scale was reduced for both the treadmill (12.7+/-0.57 versus 14.2+/-0.48, P<0.005) and the walking (9+/-0.48 versus 10.5+/-0.67, P<0.005) exercise tests and the quality of life score was also improved (21.1+/-3.5 versus 25.2+/-4, P<0.01). Resting heart rate was significantly reduced with training (77+/-3.3 versus 80+/-3 beats/min, P<0.05). The control group significantly increased Pimax (86.6+/-6.3 versus 78.4+/-6.9 cmH2O, P<0.05), but decreased SMIP (274972+/-32399 versus 204661+/-37184 cmH2O/sec x 10(1), P<0.005). No other significant effect on exercise capacity, heart rate, dyspnea, or quality of life was observed in this group.
CONCLUSION: Inspiratory muscle training using an incremental endurance test, successfully increases both inspiratory strength and endurance, alleviates dyspnea and improves functional status in CHF.
PMID: 15580060 DOI: 10.1097/01.hjr.0000152242.51327.63