The Control of Breathing during Weaning from Mechanical Ventilation (15)

The Control of Breathing during Weaning from Mechanical Ventilation (15)If respiratory pump failure is truly the consequence of an imbalance between load and strength, why could groups 1 and 2 not be distinguished on the basis of respiratory system impedance and maximal inspiratory muscle pressures? Although many patients with weaning-induced respiratory distress had profound inspiratory muscle weakness and suffered from severe airways obstruction, there was sufficient overlap among the measurements of strength and load (Table 2) such that a clear separation between groups was not possible. Pimax is effort dependent and may, there-
fore, not reflect the maximal force generating capacity of the inspiratory muscles. Similarly, we cannot share the enthusiasm of others for measuring P01 as a discriminator of weaning outcome. The determinants of P0.| are exceedingly complex, particularly in the presence of airways obstruction. While the increased mechanical impedance of the respiratory system requires a greater than normal muscle pressure output, ie, a raised P01, dynamic hyperinflation and an insufficient time for equilibration between mouth occlusion pressure and intrathoracic pressure swings may mask the presence of a high respiratory drive.

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