Respiratory Muscle Evaluation of the Patient with Neuromuscular Disease

Abstract

This review presents clinically relevant issues regarding the assessment of respiratory muscles in individuals with neuromuscular disorders, and discusses the advantages and disadvantages of methods generally available to the clinician. Vital capacity (VC) and total lung capacity (TLC) are routinely measured in pulmonary function laboratories and are typically reduced in the context of severe respiratory muscle weakness, but the sensitivity and specificity of these measures are limited. Better measures of respiratory muscle weakness are maximal static inspiratory and expiratory pressures (PI max and PE max). PI max is reduced even with mild or moderate degrees of inspiratory muscle weakness, but low values also may be related to submaximal effort. To circumvent this problem, pressures can be measured using simpler maneuvers such as a maximal sniff. Specific tests of diaphragm function such as measurements of maximal transdiaphragmatic pressure are invasive and not routinely available to the clinician. Recently, noninvasive methods that specifically assess diaphragm function, such as diaphragm ultrasound of the zone of apposition and magnetic or electrophrenic nerve stimulation, have shown promise as new techniques for clinical use.

Maximum inspiratory pressure as a clinically meaningful trial endpoint for neuromuscular diseases: a comprehensive review of the literature

“…The results demonstrated the limitations of using K CO in the diagnosis of respiratory muscle weakness. Gas exchange anomalies can also be multifactorial in their origin, for example, mechanical problems and airway obstructions can affect results [67]. …”

“…While the above discussed spirometry tests have utility, they can be considered insensitive measures of respiratory muscle function since a significant reduction in lung volume may not be observed until severe impairment of respiratory muscles has occurred [67]. Also, other factors such as airway obstruction due to asthma or lower airway obstruction may affect the reliability of some spirometry results [5, 68–70].…”

Phase I/II Trial of Adeno-Associated Virus–Mediated Alpha-Glucosidase Gene Therapy to the Diaphragm for Chronic Respiratory Failure in Pompe Disease: Initial Safety and Ventilatory Outcomes

“…Significant changes in MIP can be detected early in mild to moderate respiratory muscle weakness, but it has been found less sensitive to changes in severe disease (DePalo and McCool, 2002;Nicot et al, 2006). Further, the particular reliance of the MIP test on fast motor unit recruitment could have limited its ability to detect change.…”

Paresia diafragmática bilateral idiopática

“…(5) A test that results in a highly negative maximal inspiratory pressure (approximately 80 cmH 2 O) or in a positive maximal expiratory pressure (90 cmH 2 O) rules out clinically significant inspiratory or expiratory muscular weakness. (7) In this patient, the maximal inspiratory pressure measured was 25 cmH 2 O (38% of predicted) and the maximal expiratory pressure was 90 cmH 2 O (normal). (8) The principal alteration found in the polysomnography was a decrease in the percentage of phase 3 sleep, phase 4 sleep and REM sleep.…”