Respiratory Muscle Strength and Control of Ventilation in Patients with Neuromuscular Disease

doi:10.1378/chest.99.2.330

Chest

Volume 99, Issue 2, February 1991, Pages 330-338

https://doi.org/10.1378/chest.99.2.330 Get rights and content

To assess the relationship between respiratory mechanics and muscle strength and control of ventilation in patients with neuromuscular disease (NMD), we compared PImax and PEmax at RV, FRC and TLC, total respiratory elastance (Ers) with VT, TI, TT, ${\dot{V}}_{E}$ , VT/TI, TI/TT, P0.1, and P0.1/(VT/TI) effective impedance in 21 patients with NMD and 21 healthy control (C) subjects, in seated position breathing room air. Ers in NMD patients was 79 percent higher than in the C subjects. While TI, TT, and VT in NMD were approximately half the corresponding C values, P0.1 was 66 percent greater than in the C subjects (both p<0.001). NMD Pimax and PEmax ranged from 37 to 52 percent of corresponding C values, respectively. Despite significant respiratory muscle weakness, only 7 of 16 patients demonstrated a PaCO₂>45 mm Hg. Ventilatory output in NMD was modulated by respiratory mechanics as indicated by the increased P0.1. In spite of muscle weakness, central drive in patients with NMD is not decreased, and in fact, is often increased. ${\dot{V}}_{E}$ is not an accurate measure of central drive because of abnormal intrinsic respiratory mechanics and the effects of conscious responses or reflexes.

Section snippets

MATERIALS AND METHODS

Twenty-one patients with neuromuscular disease (11 with Duchennes muscular dystrophy) volunteered for this study. Their physical characteristics and respiratory function data are shown in Table 1. Their mean (± SD) age was 26.0 ± 14.0 years, and mean (± SD) FVC was 42.0 ± 27.5 percent predicted.¹¹^,¹² They were compared with 21 nonsmoking subjects whose mean (± SD) age was 25.5 ± 13.5 years and mean (± SD) FVC was 108.1 ± 9.5 percent predicted (Table 2). Following approval for the study by our

RESULTS

Because initial tests showed no meaningful differences between the patients with Duchenne's muscular dystrophy and the patients with other neuromuscular diseases (for the 18 respiratory parameters, median Wilcoxon p value was 0.43, only one p<0.05), all 21 patients were combined for the purpose of comparison with the control group.

Tables 1 and 2 list indices of respiratory function and muscle strength at three lung volumes, for the control subjects and the patients with neuromuscular disease,

DISCUSSION

Generally, the maximum static mouth pressure during inspiration, as measured at FRC, is a simple means of assessing the combined strength of the inspiratory muscles. In some diseases (eg, Duchenne's muscular dystrophy), declines in PImax precede changes in vital capacity.⁴ The measurements of PImax are reproducible in normal subjects (coefficient of variation about 10 percent).²¹

Although measurement of Pmax values provides a useful indicator of inspiratory muscle strength in respiratory

ACKNOWLEDGMENTS

The author thanks Ms. Hilkat Aral for providing data processing and analysis. Dr. Michael Carlson provided statistical support. Dr. Irene Gilgoff and William Prentice, nurse specialist, assisted in referring patients. Mrs. Mary Beth Cude prepared the manuscript. This study was supported by the Weingart Foundation and Dreyfus Foundation.

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: Presented in part at the 54th Annual Scientific Assembly, American College of Chest Physicians, Anaheim, October 3-8, 1968.

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Chest

Clinical InvestigationsRespiratory Muscle Strength and Control of Ventilation in Patients with Neuromuscular Disease

Section snippets

MATERIALS AND METHODS

RESULTS

DISCUSSION

ACKNOWLEDGMENTS

Pulmonary function in Duchennes muscular dystrophy related to stage of disease

Am J Med

Respiratory function in the muscular dystrophies

Muscle Nerve

Pathogenesis of respiratory insufficiency in myotonic dystrophy: the mechanical factors

Am Rev Respir Dis

Practical problems in the respiratory care of patients with muscular dystrophy

N Engl J Med

Control and modulation of respiration in Steinert's myotonic dystrophy

Am Rev Respir Dis

Ultrastructure of the muscle spindle in dystrophia myotonica, I: the intrafusal muscle fibers

Neuropathol Appl Neurobiol

Ultrastructure of the muscle spindle in dystrophia myotonica, II: the sensory and motor nerve terminals

Neuropathol Appl Neurobiol

The pathology of the muscle spindle in the Duchenne muscular dystrophy

J Neurol Sci

Muscular dystrophies of childhood

Pediatr Ann

Spirometric standards for healthy nonsmoking adults

Am Rev Respir Dis

The maximal expiratory flow-volume curve: normal standards, variability, and effects of age

Am Rev Respir Dis

Occlusion pressure as a measure of the respiratory center output in conscious man

Respir Physiol

Occlusion pressures in men rebreathing CO2 under methoxyflurane anesthesia

J Appl Physiol

Maximum static respiratory pressures in generalized neuromuscular disease

Am Rev Respir Dis

Respiratory mechanics during halothane anesthesia and anesthesia-paralysis in humans

J Appl Physiol

Statistics

Central respiratory drive in acute respiratory failure of patients with chronic obstructive pulmonary disease

Am Rev Respir Dis

Effect of posture on ventilation and breathing pattern during room air breathing at rest

Lung

Clinical Investigations
Respiratory Muscle Strength and Control of Ventilation in Patients with Neuromuscular Disease

Occlusion pressures in men rebreathing CO₂ under methoxyflurane anesthesia