Patients with Chronic Paralytic/Restrictive Ventilatory Dysfunction (4)
The reflex activity of the dilator muscles of the upper airway, which normally occurs at the onset of active inspiration, may be inhibited by many factors, including the onset of REM sleep. Typical REM episodes of dSa02 are 6- to 18-s drops of 3 to 5 percent below the normal baseline Sa02, which is 95 percent or greater. Otherwise, dSa02 is ^2 percent despite the normal non-REM sleep alveolar hypoventilation with increases of alveolar Pco2 of 3 to 7 mm Hg.
For patients using BVs, obstructive apneas or hypopneas may occur or be exacerbated because of suppression of the reflex activity of upper airway dilator muscles by the elimination of the initiation of active inspiratory effort. The weakness of the upper airway dilator musculature in patients with neuromuscular disease may potentiate the tendency to develop obstructive apneas during negative pressure ventilatory support. Patients with OSAS or neuromuscular/ restrictive or pulmonary disease may also develop chronic alveolar hypoventilation (CAH) with a drop in arterial Sa02 baseline below 95 percent. buy ventolin inhalers
Decreased mixed venous Sa02 and CAH tend to increase the severity of dSa02 that occurs during an obstructive event.