Airway

Overventilation in asthma failure

Asthmatic airways empty slowly. Stacking bag-valve-mask breaths before exhalation finishes traps air, inflates the chest, and raises intrathoracic pressure.

That pressure impairs venous return— air trapping decreases preload , stroke volume, cardiac output, and blood pressure. Ventilate gently with time to exhale; do not chase saturation with oversized or rapid breaths.