Am. J. Respir. Crit. Care Med., Volume 156, Number 1, July 1997, 133-139

Relationship Between Chronic Hypercapnia and Inspiratory-Muscle Weakness in Myotonic Dystrophy

PAUL BÉGIN, JEAN MATHIEU, JOSÉ ALMIRALL, and ALEJANDRO GRASSINO

Department of Medicine, University of Montréal; Complexe Hospitalier de la Sagamie, Chicoutimi; Department of Human Sciences, University of Québec at Chicoutimi; Department of Medicine, McGill University; and Hôpital Notre-Dame, Montréal, Québec, Canada

We studied 134 patients with Steinert's myotonic dystrophy (MD) in order to determine the prevalence of chronic hypercapnia, the level of muscle weakness and forced expiratory volume at which hypercapnic respiratory failure is likely to occur, and how clinical assessment might help predict hypercapnic respiratory failure. Subjects were divided into five classes with a muscular disability rating scale (MDRS): 0 = no clinical impairment (n = 9), I = minimal signs of impairment (n = 11), II = distal weakness (n = 41), III = moderate proximal weakness (n = 62), and IV = nonambulatory (n = 11). The prevalence of hypercapnia (Pa_CO2  43 mm Hg) was found to be 0%, 27%, 29%, 45% and 55% for MDRS 0 to 4, respectively (p = 0.03). A multiple regression analysis limited to clinical data showed that daytime hypersomnolence was a significant cofactor with the MDRS (p = 0.01) in predicting Pa_CO2 (r = 0.40). Among respiratory parameters, FVC, respiratory muscle strength (RMS), and maximal inspiratory pressure against occluded airways (PI_max) were found to be predictors of nearly equal strength, explaining 16%, 15%, and 14% of the Pa_CO2 variance, respectively. In multiple regression analysis, sex, daytime sleepiness, and the expected/observed FVC ratio for a given RMS were found to be significant cofactors with PI_max in predicting Pa_CO2 (r = 0.51). It is concluded that respiratory insufficiency should be suspected in MD patients with proximal weakness or daytime sleepiness. The likelihood of hypercapnia also increases with volume restriction and respiratory muscle weakness. Our study suggests that the combination of inspiratory muscle weakness and loading plays a predominant role in the pathogenesis of chronic alveolar hypoventilation in MD patients. The occurrence of daytime hypersomnolence suggests that other factors, such as low central ventilatory drive or sleep apnea, might play an additional role.

This article has been cited by other articles:

				N. Terzi, D. Orlikowski, C. Fermanian, M. Lejaille, L. Falaize, A. Louis, J-C. Raphael, B. Fauroux, and F. Lofaso Measuring inspiratory muscle strength in neuromuscular disease: one test or two? Eur. Respir. J., January 1, 2008; 31(1): 93 - 98. [Abstract] [Full Text] [PDF]

				C. Gagnon, L. Noreau, R. T Moxley, L. Laberge, S. Jean, L. Richer, M. Perron, S. Veillette, and J. Mathieu Towards an integrative approach to the management of myotonic dystrophy type 1 J. Neurol. Neurosurg. Psychiatry, August 1, 2007; 78(8): 800 - 806. [Full Text] [PDF]

				S P Kumar, D Sword, R K. Petty, S W Banham, and K R Patel Assessment of sleep studies in myotonic dystrophy Chronic Respiratory Disease, February 1, 2007; 4(1): 15 - 18. [Abstract] [PDF]

				M. Toussaint, M. Steens, and P. Soudon Lung Function Accurately Predicts Hypercapnia in Patients With Duchenne Muscular Dystrophy Chest, February 1, 2007; 131(2): 368 - 375. [Abstract] [Full Text] [PDF]

				N Shahrizaila, W J M Kinnear, and A J Wills Respiratory involvement in inherited primary muscle conditions J. Neurol. Neurosurg. Psychiatry, October 1, 2006; 77(10): 1108 - 1115. [Abstract] [Full Text] [PDF]

				N Shahrizaila, W S Lim, D K Robson, W J Kinnear, and A J Wills Tubular aggregate myopathy presenting with acute type II respiratory failure and severe orthopnoea Thorax, January 1, 2006; 61(1): 89 - 90. [Abstract] [Full Text] [PDF]

				F. Laghi and M. J. Tobin Disorders of the Respiratory Muscles Am. J. Respir. Crit. Care Med., July 1, 2003; 168(1): 10 - 48. [Abstract] [Full Text] [PDF]

				A.-M. Nugent, I. E. Smith, and J. M. Shneerson Domiciliary-Assisted Ventilation in Patients With Myotonic Dystrophy Chest, February 1, 2002; 121(2): 459 - 464. [Abstract] [Full Text] [PDF]

				B. Lanini, G. Misuri, F. Gigliotti, I. Iandelli, A. Pizzi, I. Romagnoli, and G. Scano Perception of Dyspnea in Patients With Neuromuscular Disease Chest, August 1, 2001; 120(2): 402 - 408. [Abstract] [Full Text] [PDF]

				V. Ugalde, S. Walsh, R. T. Abresch, H. W. Bonekat, and E. Breslin Respiratory abdominal muscle recruitment and chest wall motion in myotonic muscular dystrophy J Appl Physiol, July 1, 2001; 91(1): 395 - 407. [Abstract] [Full Text] [PDF]

				J. Mathieu, H. Boivin, D. Meunier, M. Gaudreault, and P. Begin Assessment of a disease-specific muscular impairment rating scale in myotonic dystrophy Neurology, February 13, 2001; 56(3): 336 - 340. [Abstract] [Full Text] [PDF]

				G. Misuri, B. Lanini, F. Gigliotti, I. Iandelli, A. Pizzi, M. G. Bertolini, and G. Scano Mechanism of CO2 Retention in Patients With Neuromuscular Disease Chest, February 1, 2000; 117(2): 447 - 453. [Abstract] [Full Text] [PDF]

				J. Mathieu, P. Allard, L. Potvin, C. Prevost, and P. Begin A 10-year study of mortality in a cohort of patients with myotonic dystrophy Neurology, May 1, 1999; 52(8): 1658 - 1658. [Abstract] [Full Text] [PDF]