American Board of Internal Medicine (ABIM) Certification Practice Exam

What pH level indicates permissive hypercapnia in patients with ARDS?

1. Less than 7.0

2. Between 7.0 and 7.2

3. Equal to or greater than 7.2

4. Greater than 7.4

The correct answer is: Equal to or greater than 7.2

Permissive hypercapnia is a management strategy utilized in the context of Acute Respiratory Distress Syndrome (ARDS) that intentionally allows for elevated levels of carbon dioxide (CO2) in the blood. The rationale behind this approach is to minimize ventilator-induced lung injury by allowing lower tidal volumes and a reduced risk of barotrauma and volutrauma while managing mechanical ventilation. In this context, a pH equal to or greater than 7.2 indicates that the patient is still able to adequately buffer the excess CO2 without leading to severe acidosis. When the pH is maintained at or above this level, it suggests that the body can tolerate elevated CO2 levels without significant physiological derangement, and it aligns with the concept of permissive hypercapnia. This allows for a more gentle approach to mechanical ventilation, reducing the potential for further lung injury while still providing adequate oxygenation and ventilation in patients with ARDS. A pH level below 7.2 would suggest more severe acidosis and potentially the need for aggressive interventions, whereas a pH below 7.0 indicates critical acidosis, which would generally point to the necessity of addressing the underlying respiratory failure more urgently. Thus, a pH of 7.2