What happens to tidal volume (Vt) and peak inspiratory pressure (PIP) when a patient with bronchospasm is on a volume cycled ventilator?

When a patient with bronchospasm is on a volume-cycled ventilator, the tidal volume (Vt) remains consistent, as the ventilator is set to deliver a predetermined volume of air per breath. However, the presence of bronchospasm, which is characterized by airway obstruction and increased airway resistance, can lead to an increase in peak inspiratory pressure (PIP). This occurs because the ventilator must generate greater pressure to deliver the set tidal volume against the increased resistance of constricted airways.

The increased PIP reflects the effort required to overcome the narrowed airways, while the tidal volume being delivered remains constant at the set level of the ventilator. This relationship illustrates the impact of airway resistance on ventilatory parameters and highlights the distinction between the volume output and the pressures generated during mechanical ventilation in a patient with compromised airway mechanics.