Final answer:
Pressure-controlled inverse ratio ventilation (PCIRV) is designed to prevent alveolar collapse and improve oxygenation by altering the inspiratory to expiratory ratio to allow more time for gas exchange, utilizing the principles of Boyle's law and pressure differences within the lungs.
Step-by-step explanation:
The mode of pressure-controlled ventilation that is designed to prevent alveoli with short time constants from collapsing and thereby improving oxygenation is pressure-controlled inverse ratio ventilation (PCIRV). In PCIRV, the timing of the ventilator cycle is inverted so that the inspiratory time is longer than the expiratory time. This method increases the mean airway pressure and alveolar recruitment which can prevent alveolar collapse (atelectasis) and facilitate better oxygenation.
By altering the inspiratory to expiratory ratio in favor of inspiration, PCIRV allows more time for gases to equilibrate in the alveoli, which can help open and maintain patency of alveoli that might otherwise be prone to collapse. This is particularly important in conditions where alveolar collapse is common, such as Acute Respiratory Distress Syndrome (ARDS).
The act of pulmonary ventilation is essentially the movement of air into and out of the lungs, controlled by the difference between intra-alveolar and intrapleural pressures. According to Boyle's law, the pressure within the alveoli is inversely proportional to the volume of the thoracic cavity. Therefore, the manipulation of breath timing in PCIRV can create more favorable pressure conditions for preventing alveolar collapse.