Certified Respiratory Therapist Practice Exam

Negative inspiratory force (NIF) is used to assess what aspect of respiratory function?

1. Lung volumes

2. Airway resistance

3. Respiratory muscle strength

4. Diffusion capacity

The correct answer is: Respiratory muscle strength

Negative inspiratory force (NIF) is a crucial measurement used to assess respiratory muscle strength. By having a patient generate negative pressure while inspiring through a closed system, NIF evaluates the ability of the diaphragm and accessory respiratory muscles to perform effectively. A high NIF indicates strong respiratory muscle function, which is important for adequate ventilation. In clinical practice, measuring NIF can help identify patients at risk for respiratory failure due to muscle weakness, particularly in conditions like neuromuscular disorders or severe chest wall deformities. Hence, a lower NIF often signifies compromised respiratory muscle function, which may necessitate further interventions, such as non-invasive ventilation, to support breathing. Understanding NIF's role in evaluating respiratory muscle strength is vital for healthcare professionals, as it directly correlates with a patient's ability to generate adequate tidal volumes and maintain effective ventilation.