Alterations in Intercostal Muscle Morphology and Biochemistry in Patients with Obstructive Lung Disease1,2

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Abstract
Patients (22) undergoing thoracotomy for diagnosis or treatment of a suspected pulmonary neoplasm had separate biopsies taken from their external intercostal muscles at the time of surgery. Pulmonary function abnormalities ranged from none to moderate airway obstruction. Of the 22 patients, 17 had morphologic changes (targeting, variation in fiber size, splitting and atrophy) in both respiratory muscles, but not in the control latissimus dorsi. Fiber atrophy was more marked in the internal intercostal muscle and was significantly related to the degree of airway obstruction, but not to age, malignancy or weight loss. Biochemical anlyses revealed decreased ATP and phosphocreatine (PC) in 47 of 52 muscles, including the latissimus dorsi. Increasing airway obstruction may be related to decreasing amounts of phosphocreatine in both intercostal muscles. This relationship may enhanced by the presence of malignancy or weight loss. There was a selective decrease in muscle glycogen only in the external intercostal muscle that was not affected by airway obstruction, malignancy or weight loss. Intercostal muscle abnormalities are common in patients with obstructive lung disease who undergo thoracotomy, and are probably multifactorial in origin. These abnormalities may affect the natural history of lung disease in some patients.