American Board of Internal Medicine (ABIM) Certification Practice Exam

What does a maximum inspiratory pressure of less than -30 cm H2O indicate in respiratory evaluation?

1. Normal respiratory function

2. Possible need for ventilator support

3. Obstructive lung disease

4. Restrictive lung disease

The correct answer is: Possible need for ventilator support

A maximum inspiratory pressure of less than -30 cm H2O is indicative of respiratory muscle weakness or reduced inspiratory capacity. This measurement reflects the strength of the respiratory muscles and their ability to create negative pressure to draw air into the lungs. When this threshold is crossed, it often signals a significant impairment in the patient’s ability to initiate and sustain adequate ventilation. In this context, a pressure reading lower than -30 cm H2O suggests that the individual may not be able to breathe effectively on their own, potentially leading to respiratory failure if support is not provided. While it may suggest underlying conditions like neuromuscular disorders or significant restrictive lung disease, the primary implication of this finding is the need for mechanical assistance. Therefore, ventilator support may be necessary to facilitate adequate gas exchange and prevent respiratory complications. Normal respiratory function would typically show higher inspiratory pressure values, while obstructive lung disease would more commonly present with other findings related to airflow limitation rather than maximum inspiratory pressure. Restrictive lung disease may contribute to decreased inspiratory capacity but would need to be assessed alongside other parameters to define the overall respiratory function accurately.