ATS Pulmonary Function Laboratory Manual

ATS Pulmonary Function Laboratory Management & Procedure Manual | 3rd Edition

Effective Date: 2014 Version #1

Chapter 11

Procedure Name: Maximum Respiratory Pressures

Purpose or Principle The measurement of respiratory muscle forces (or strength), maximum inspiratory pressure (MIP or Pimax), and maximum expiratory pressure (MEP or Pemax), are direct tests that are simple to perform, and are well tolerated by patients. The test assesses the aggregate force or pressure that respiratory muscles can generate against an occlu- sion at the mouth (1). Pimax is an index of diaphragm strength, while Pemax measures the strength of abdominal and intercostal muscles (1, 2). The most commonly reported method of measuring respiratory muscle force is that reported by Black and Hyatt (3). The equipment required is a pressure gauge, manometer, or transducer that can be a handheld device, or part of a more complex pulmonary function (PF) system. The technician must be a motivating coach and encourage the patient to give maximal efforts on a test that is very effort-dependent and may be uncomfortable (2). Pemax is measured at or near total lung capacity (TLC), and Pimax is measured at or near residual volume (RV).

Indications and Contraindications Some indications for measuring maximum respiratory pressures are provided in Table 11.1.

Table 11.1

Indications for Maximum Respiratory Pressures • Assess and quantify the degree of respiratory muscular weakness that may occur with neuromuscular diseases (e.g., amyotrophic lateral sclerosis, myasthenia gravis, Guillain-Barré syndrome, muscular dystrophy, stroke, and poly- myositis), obstructive lung disease causing hyperinflation (e.g., emphysema, chronic bronchitis, and cystic fibrosis), and conditions requiring chronic steroid use, conditions with chest deformities, and unexplained dyspnea (3). • Abnormal diagnostic test results (e.g., decreased forced vital capacity [FVC], peak flow, maximal voluntary venti- lation [MVV], or abnormal chest radiograph). • The Pemax gives information about the potential for effective cough and ability for secretion clearance (4). • Diagnosis and management of a patient with actual or suspected injury to the diaphragm or other respiratory muscles (4). • Evaluate the effectiveness of therapy designed to improve respiratory muscle strength.

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