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August 1979

Reduced Flow Rates in Amyotrophic Lateral Sclerosis-Reply

Author Affiliations

Institutes of Medical Sciences Pacific Medical Center San Francisco, CA 94120

Arch Neurol. 1979;36(8):523. doi:10.1001/archneur.1979.00500440093026

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In Reply.—  We agree with Dr Bensam that the vast majority of reduced flow rates in amyotrophic lateral sclerosis (ALS) are caused by the neuromuscular disease. Airway obstruction was only diagnosed when there were other objective findings to indicate airway obstruction, eg, curvature of the flow volume loop or a delayed helium mixing time. Thus, 19% of our patients were considered to suffer from airway obstruction in addition to neuromuscular impairment. This is not surprising since more than 50% of those studied were cigarette smokers.We disagree that tracheostomy would always be needed when the vital capacity falls below 1,200 cc. Some patients maintain adequate gas exchange with vital capacities much less than 1 L or less than 20% predicted. Conversely, some patients with larger vital capacities have frequent respiratory difficulties due to bulbar involvement, causing recurrent aspiration, pneumonia, or atelectasis. When such clinical problems arise, we generally try to avoid tracheostomy

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