Respiratory muscle strength

Pulmonary i Respiratory muscle strength i Chest wall compliance i Total alveolar surface i Vital capacity i Maximal breathing capacity... 

Pulmonary 4 Respiratory muscle strength 4 Chest wall compliance 4 Total alveolar surface 4 Vital capacity 4 Maximal breathing capacity... 

A relatively new approach to nutrition assessment is to evaluate muscle function as an end-organ response. Hand-grip strength (forearm muscle dynamometry), respiratory muscle strength, and muscle re-... 

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... 

Table 3 Causes of Reduced Respiratory Muscle Strength...

Arora NS, Rochester DF. Respiratory muscle strength and maximal voluntary ventilation in patients in undernourished patients. Am Rev Respir Dis 1982 126 5-8. 

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...

Malnutrition is highly prevalent among patients requiring PMV (37) and LTMV (70) and is assoeiated with poor prognosis (71). Malnutrition decreases muscle mass and respiratory muscle strength and enduranee (40). These effects on the respiratory muscles are partially reversible with nutritional support. The process, however, is slow, and in laboratory animals, it can take months of refeeding for muscle mass to return to normal values (72). To date, it remains unclear whether malnutrition by itself ean cause sufficient respiratory muscle weakness to produce ventilator dependence. It is more likely for malnutrition to be a contributing factor and not a sole cause of ventilator dependence. 

In addition to monitoring symptoms, regular monitoring of respiratory function is essential. The vital capacity (VC) is one of the most reproducible tests for lung function. Although it may not fall below the normal range rmtil there is a 50% reduction in respiratory muscle strength (RMS) (26), its rate of decline can predict survival (27). Opinions vary as to how often pulmonary function should be evaluated. Some clinicians propose that if the VC is > 60% predicted, it should be performed every six months, while if the VC is < 60% predicted, it should be performed at every three to four months (28). 

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. 

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