ALS From Both Sides


What is BiPAP used for?

BiPAP (and its predecessor, CPAP) are most commonly used for people with sleep apnea or with hypopnea.


How does this apply to ALS?

All three of the problems discussed above can occur in ALS. Bulbar weakness (weakness of the muscles controlled by the cranial nerves that arise from the bulb-shaped medulla portion of the brainstem) causes swallowing and speech problems and may also allow collapse of the upper airway during sleep when muscles relax. This results in obstructive apnea. If ALS affects the motor pathways the brain stem uses to send the impulses to trigger breathing, central apnea can occur. And of course ALS can affect the muscles used in breathing and cause hypopnea. Hypopnea is probably the most common problem in ALS but it certainly is possible for a combination of these problems to occur in ALS.

Whether it is a form of apnea or hypopnea, the patient does not get good quality sleep. Quality of sleep is not just dependent on the total number of hours, but also how that time is broken up by awakenings. In order to feel rested, it is necessary to get blocks of sleep that lasts at least 90 minutes -- that is when REM sleep occurs and REM sleep is apparently the stage of sleep where the brain has a chance to "recharge" itself. Without this good quality sleep, the patient becomes increasingly tired, has trouble staying awake during the day (yet has apnea and awakens if he falls asleep), finds it harder think clearly, concentrate, remember. Depression is very common. In addition the mental effects, the lack of sleep begins to affect physical health too.


CPAP or BiPAP?

CPAP isn't bad for people with neuromuscular weakness of the respiratory muscles in the sense that it is dangerous, it just doesn't work for them. CPAP is designed to give Continuous Positive Airway Pressure to keep the airway from collapsing on exhalation. In effect it keeps the lungs partially inflated to the same amount during inhalation and exhalation. That makes it more difficult to exhale and that is why it is difficult for anyone to adjust to. For neuromuscular patients, the muscle weakness makes it even more difficult to exhale against the pressure. BiPAP has separate pressure settings for inhaling (higher) and exhaling (lower). The lower pressure during exhalation makes easy so it is the correct choice for ALS patients.

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