Respiratory Muscle Function after Trauma

Respiratory muscle power is reduced during starvation, and respiratory muscles probably are not preferentially spared in the nitrogen losses after trauma (see Chapter 63 ). The effects of the prolonged use of muscle relaxant drugs and of the enforced immobilization of respiratory muscles on recovery of ventilatory strength and chest-wall coordination have not been adequately investigated. Specific deficiency states may contribute to reduced muscle power; for example, acute areflexic paralysis with respiratory failure resulting from hypophosphatemia has been described.^[14] As the malnourished patient with an associated hypermetabolic disease process becomes more depleted, strength is diminished, which can lead to use of the accessory muscles of respiration as well as compromised pulmonary function ( Fig. 77-10 ). Minute ventilation and ventilatory response to CO₂ breathing are increased in spontaneously breathing patients who receive an amino acid-enriched nutritional formula.^[15] Nutritional support with high nitrogen loads leads to improved respiratory muscle strength and ventilatory response.