Quizlet flashcards list the normal range for negative inspiratory force, also called maximum inspiratory pressure, as -80 to -100. Critical Care Medicine Tutorials explains that negative inspiratory force measures the ability of the patient to inhale air against an obstruction.
The Merck Manual states that maximum inspiratory pressure measures respiratory muscle strength, which is inversely related to lung volume. According to Critical Care Medicine Tutorials, negative inspiratory force tests are often used to determine if a patient is ready to be weaned off a ventilator. The patient requires sufficient, negative inspiratory force in order to be able to cough out secretions or fully expand the lungs.