title: Detection of upper airway muscle involvement in neuromuscular disorders using the flow-volume loop.
abstract: Abnormal contours of the flow-volume loop, ie, flow oscillations and inspiratory flow plateaux, have been noted in disorders affecting upper-airway muscular function. In this study, we assessed the incidence and the value of these contours as a test of bulbar and upper-airway muscular involvement in neuromuscular disease. We therefore compared flow-volume loops and pulmonary function test results between ten patients with (group 1) and 20 patients without (group 2) clinically apparent bulbar muscle involvement in neuromuscular disease. An abnormal flow-volume loop occurred significantly more often in group 1 than in group 2 (9/10 or 90 percent vs 3/20 or 15 percent, respectively; p less than 0.001) and predicted bulbar and upper-airway muscle involvement with high sensitivity (90 percent), specificity (85 percent) and efficiency (87 percent). Based on commonly used spirometric criteria, upper-airway obstruction was not more common in group 1 than in group 2 (1/10 vs 2/20); however, all three patients with upper-airway obstruction suggested by these criteria had an abnormal flow-volume loop. Following this study, three patients incurred severe respiratory complications. All three patients had previously shown an abnormal flow-volume loop. We conclude that in patients with neuromuscular disease, involvement of the bulbar and upper-airway muscles is frequently associated with an abnormal contour of the flow-volume loop. Recognition of flow oscillations or flow plateaux on flow-volume loops in these patients seems important, since they may be potential markers of severe respiratory complications.
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D009460:Neurologic Examination; D009468:Neuromuscular Diseases / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology; D012123:Pulmonary Ventilation; D012129:Respiratory Function Tests; D014797:Vital Capacity