The maximal respiratory pressure measurements assess ventilatory muscle strength in persons with neuromuscular disorders such as poliomyelitis, emphysema, and pulmonary fibroses. The maximal expiratory pressure (MEP) is the greatest pressure that can be generated at or near TLC after a maximal inspiration, whereas the maximal inspiratory pressure (MIP) is measured at or near the RV after a maximal expiration.
Instruct the patient, who should be in a seated position and wearing a nose clip, to inspire maximally. Place the mouthpiece of the handheld pressure manometer into the mouth and have the patient perform a forced expiration. Record this maximal sustained (1–3 seconds) pressure against the internal occlusion of the manometer as the MEP.
Repeat this same procedure to obtain the MIP, except that this time, the patient fully exhales before placing the mouthpiece of the manometer in the mouth. Have the patient then inspire forcefully and record the maximal sustained (1–3 seconds) pressure.
Repeat each procedure and record the best of three measurements for each.
See Chapter 1 guidelines for intratest care.
Decreases in both MEP and MIP are seen in neuromuscular disorders (e.g., myasthenia gravis, poliomyelitis).
Decreased MEP is common in both severe obstructive disease (e.g., emphysema) and severe restrictive ventilatory impairment (e.g., interstitial pulmonary fibrosis).
Decreased MIP is observed in patients with chest wall abnormalities (e.g., kyphoscoliosis) and in hyperinflation (e.g., emphysema).
Pretest Patient Care
Explain the purpose and procedure of the test. Explain that it is a noninvasive, effort-dependent maneuver that requires patient cooperation.
Record the patient’s age and gender.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed.
Discuss with the patient the possible need for follow-up testing to monitor course of therapy.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
The MIP and MEP measurements depend on patient effort; low values may be caused by poor effort rather than loss of respiratory muscle strength. If the patient does not inspire or expire maximally before performing the pressure measurement, the value may be low. Also, sustained efforts longer than 3 seconds should be avoided because they can cause a decrease in cardiac output as a result of increased intrathoracic pressures.