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Supine fall in lung volumes in the assessment of diaphragmatic weakness in neuromuscular disorders,☆☆

https://doi.org/10.1053/apmr.2001.18053Get rights and content

Abstract

Fromageot C, Lofaso F, Annane D, Falaize L, Lejaille M, Clair B, Gajdos P, Raphaël JC. Supine fall in lung volumes in the assessment of diaphragmatic weakness in neuromuscular disorders. Arch Phys Med Rehabil 2001;82:123-8. Objective: To determine whether diaphragmatic function can be determined by noninvasive respiratory indices in neuromuscular disease. Design: Vital capacity (VC) and mouth pressure generated during a maximal static inspiratory effort (Pi max) were measured with patients in both sitting and supine positions. Setting: Rehabilitation hospital. Patients: Twenty-four patients with generalized neuromuscular disease. Main Outcome Measures: Changes in indices from sitting to supine position were compared with invasive diaphragmatic function indices consisting of transdiaphragmatic pressures during maximal sniff (Pdi sniff) and the ratio of gastric pressure (Pga) increases over transdiaphragmatic pressure (ΔPga/ΔPdi) during quiet breathing. Results: The fall in VC in the supine position was greater in the 15 patients who had spontaneous paradoxical diaphragmatic motion (ΔPga/ΔPdi < 0) than in the 9 patients who did not. Specificity and sensitivity of a greater than 25% supine fall in VC for the diagnosis of diaphragmatic weakness (ΔPga/ΔPdi < 0 and/or Pdi sniff < 30cmH2O) were 90% and 79%, respectively. Stepwise multiple regression analysis of Pdi sniff showed that both the supine fall in VC and Pi max were associated with diaphragmatic weakness (R2 =.66; p <.0001). These factors contributed 52% and 14% of the Pdi sniff variance, respectively. Conclusions: Simple VC measurement in the sitting and supine positions may be helpful in detecting severe or predominant diaphragmatic weakness. © 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Section snippets

Methods

Between 1990 and 1998, 24 patients with generalized neuromuscular disease from various causes, but who did not have chronic obstructive pulmonary disease, were referred to our laboratory for pulmonary function testing and transdiaphragmatic pressure measurement. All patients had experienced a recent increase in breathlessness and/or a clinical suspicion of diaphragmatic dysfunction and/or unexplained hypercapnia.

The tests were performed after a 2-week period of stability for all subjects. Blood

Statistics

Data were expressed as mean ± standard deviation. Comparison of groups with and without paradoxical diaphragmatic motion (ΔPga/ΔPdi < 0) was performed by using the nonparametric Mann-Whitney test. In addition, we looked for correlations between noninvasive and invasive variables, by using least-square linear regression techniques. Univariate analysis was used to evaluate the independent contribution of each variable. A full model, stepwise, multiple, linear regression analysis was then

Results

A total of 18 men and 6 women were studied. Individual data are summarized in table 1.Paradoxical diaphragmatic motion (ΔPga/ΔPdi < 0) was noted in 14 patients, of whom 7 were on nocturnal mechanical ventilation, versus none of the 10 patients without paradoxical diaphragmatic motion. No variation in expiratory abdominal activity, as judged by analysis of the shape of the Pga curve, was found in any of the patients. Age and height were similar in the 2 groups (table 1). Pdi sniff and Pdi max

Discussion

Almost all neuromuscular disorders causing limb weakness can affect the respiratory muscles, including the diaphragm. In some patients, the diaphragm is selectively or disproportionately affected.1 Assessment of diaphragmatic function is important because several studies have found that the prognosis in neuromuscular disease was worse when diaphragmatic function was disproportionately impaired than when it was relatively spared.2, 3

There is a need for a simple test that can identify patients in

Conclusion

Our data indicate clearly a need to perform lung volume measurements in both the sitting and the supine positions when respiratory function impairment caused by neuromuscular disorders is being evaluated. Patients with neuromuscular disorders are supine much of the time and detecting a supine fall in VC will help diagnose predominant diaphragmatic weakness and, therefore, predict the occurrence of hypercapnic respiratory failure.

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Reprint requests to Dr. Frédéric Lofaso, Service de Physiologie-Explorations Fonctionnelles, Hôpital Raymond Poincaré, 92380 Garches, France, e-mail: [email protected].

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a. ABL 330; Radiometer Medical A/S, DK 2700 Brønshøj, Denmark.

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b. Model DP45 Low Pressure Transducer; Validyne Engineering Corp, 8626 Wilbur Ave, Northridge, CA 91324.

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c. Marquat Gbm, BP11, 94471 Boissy-St. Leger Cedex, France.

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