Inspiratory muscle strength

Martin DA, Davenport PD, Franceschi AC, et al. Use of inspiratory muscle strength training to facilitate ventilator weaning. Chest 2002 122 192-196. 

Martin D, Davenport PW, Gonzalez-Rothi J, et al. Inspiratory muscle strength training improves outcome in failure to wean patients. Eur Respir J 2006 28 369s. 

The function of the ventilatory pump is critically dependent on three factors the respiratory workload, the respiratory muscle strength, and the ventilatory drive (Fig. 1). Chronic hypercapnic respiratory failure can result from one or more of these abnormalities inadequate ventilatory drive, excessive respiratory load, and inadequate inspiratory muscle... 

Figure 6 Relationship between muscle strength and mixed venous partial pressure of CO2 (PVCO2) in patients with respiratory muscle weakness. Respiratory muscle strength is the arithmetic sum of maximum static inspiratory and expiratory mouth pressures (P iax = + TEmax)- The open circles...

The patients who required a tracheostomy may subsequently manage spontaneous ventilation with improvements in their underlying condition and respiratory muscle strength and endurance. Resolution of dynamic hyperinflation also improves the length-tension relationships of the inspiratory muscles (56). Strengthening of the upper extremities or the inspiratory muscles has provided mixed results (57,58). 

A man of 19 years had been diagnosed with Duchenne s muscular dystrophy at 6 years and became wheelchair bound by the age of 14. He had no other symptoms beyond muscle weakness and specifically denied morning headaches or dyspnea. His VC was 44% predicted and his respiratory muscle strength was reduced, with a maximal inspiratory pressure (MIP) of 28% predicted and a maximal expiratory pressure (MEP) of 13% predicted. 

Uncontrolled studies have shown that in patients with CF, NIPPV will unload respiratory muscles, increase alveolar ventilation, and improve oxygenation during wakefulness, sleep, and an acute exacerbation. Inspiratory and expiratory muscle strengths improve following NIPPV, which may be important in facilitating secretion clearance (32). NIPPV also improves tolerance of physiotherapy (33,34). 

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