How are the respiratory complications of amyotrophic lateral sclerosis (ALS) monitored?

Updated: Jan 02, 2020
  • Author: Divakara Kedlaya, MBBS; Chief Editor: Ryan O Stephenson, DO  more...
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Routinely measure vital capacity in the sitting and recumbent positions. Most often, the recumbent measurement declines prior to the sitting measurement. Gravity assists in lowering the diaphragm as the patient's angle of inclination is increased. As respiratory weakness progresses, patients have increasing difficulty with diaphragmatic movement when supine because of the elimination of this effect from gravity. This results in alveolar hypoventilation and ultimate oxyhemoglobin desaturation.

Difficulty sleeping may be the first symptom of hypoventilation. Patients should be questioned routinely regarding sleep habits, and if a sleep disturbance develops, measure vital capacities sitting and supine. In addition, perform overnight oxygen saturation monitoring to assess for nocturnal hypoxemia and the need for nocturnal noninvasive intermittent positive pressure ventilation (IPPV).

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