Increased ventilatory drive in hyperinflated patients with chronic obstructive pulmonary disease activates the accessory respiratory muscles (from neck, rib cage, abdomen) and upper airway muscles and occasionally leads to chest-abdomen asynchrony (not necessarily a sign of fatigue). This can also be observed during unsuccessful weaning trials. Hyperinflation and excessive activation of neck inspiratory muscles are associated with tachypnea and the feeling of dyspnea. In this situation, reduction of tidal volume and a slight increase in PaCO2 can be regarded as a strategy of minimizing effort rather than a manifestation of fatigue. Respiratory drive (P01) is increased in all situations of augmented load.

The reaction to external loading (external resistance) seems to be different to the reaction to internal loading (airway resistance). Under steady state conditions gas exchange is impaired only under large external loads, whereas during anesthesia mechanical loading rapidly leads to hypercapnia and hypoxemia.

Sleep Apnea

Sleep Apnea

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