In pressure cycled ventilators, which variable can fluctuate due to changes in airway resistance and pulmonary compliance?

In pressure-cycled ventilators, the primary variable that is maintained is the pressure delivered to the airway. The volume of air that is actually delivered to the patient's lungs can fluctuate based on changes in airway resistance and pulmonary compliance.

When airway resistance increases (such as in cases of bronchospasm or mucus obstruction), or when pulmonary compliance decreases (as seen in conditions like ARDS or pulmonary fibrosis), the volume of gas delivered with each breath can be significantly affected. Despite the ventilator aiming to maintain a set pressure, the change in these parameters means that the actual volume may drop or rise, depending on the state of the lungs and airways.

Therefore, it is crucial to understand that in a pressure-cycled mode, while the pressure remains constant to avoid barotrauma, the volume is a variable that can change based on the patient's respiratory mechanics. This understanding is vital for correctly interpreting ventilator settings and patient responses during mechanical ventilation.