What happens to tidal volume (Vt) if lung compliance decreases significantly?

When lung compliance decreases significantly, the ability of the lungs to expand diminishes, which directly affects tidal volume (Vt). In this scenario, as compliance decreases, the lungs become stiffer and require greater pressure to achieve the same volume during ventilation.

If tidal volume were to remain constant in the face of decreased compliance, this would typically require an increase in pressure to maintain that constant volume, which is not supported in this context. Therefore, a decrease in tidal volume is the most logical response to reduced compliance because the lungs can't accommodate as much air per breath without a corresponding increase in pressure.

In this situation, while peak inspiratory pressure often rises due to the increased effort required to inflate the stiffer lungs, maintaining a constant Vt is not typically possible, as it would necessitate adjustments in pressure that aren't sustainable given the reduced compliance. Thus, it is reasonable to conclude that tidal volume decreases in response to decreased lung compliance, even if peak inspiratory pressure remains unchanged in some scenarios. This understanding highlights the mechanics of respiratory physiology where changes in lung properties directly correlate with measurable ventilatory outcomes.