page_title: Amyotrophic lateral sclerosis
section_title: Non-invasive ventilation
hierarchical_section_title: Amyotrophic lateral sclerosis / Management / Breathing support / Non-invasive ventilation
caption_attribution_description: English: BiPAP using a ventilator
context_page_description: Amyotrophic lateral sclerosis, also known as motor neurone disease or Lou Gehrig's disease, is a disease that causes the death of neurons controlling voluntary muscles. Some also use the term motor neuron disease for a group of conditions of which ALS is the most common. ALS is characterized by stiff muscles, muscle twitching, and gradually worsening weakness due to muscles decreasing in size. It may begin with weakness in the arms or legs, or with difficulty speaking or swallowing. About half of the people affected develop at least mild difficulties with thinking and behavior and most people experience pain. Most eventually lose the ability to walk, use their hands, speak, swallow, and breathe.
  The cause is not known in 90% to 95% of cases, but is believed to involve both genetic and environmental factors. The remaining 5–10% of cases are inherited from a person's parents. About half of these genetic cases are due to one of two specific genes. The underlying mechanism involves damage to both upper and lower motor neurons. The diagnosis is based on a person's signs and symptoms, with testing done to rule out other potential causes.
  No cure for ALS is known.
context_section_description: Non-invasive ventilation (NIV) is the primary treatment for respiratory failure in ALS and was the first treatment shown to improve both survival and quality of life in people with ALS. NIV uses a face or nasal mask connected to a ventilator that provides intermittent positive pressure to support breathing. Continuous positive pressure is not recommended for people with ALS because it makes breathing more difficult. Initially, NIV is used only at night because the first sign of respiratory failure is decreased gas exchange (hypoventilation) during sleep; symptoms associated with this nocturnal hypoventilation include interrupted sleep, anxiety, morning headaches, and daytime fatigue. As the disease progresses, people with ALS develop shortness of breath when lying down, during physical activity or talking, and eventually at rest. Other symptoms include poor concentration, poor memory, confusion, respiratory tract infections, and a weak cough. Respiratory failure is the most common cause of death in ALS.
  It is important to monitor the respiratory function of people with ALS every three months, because beginning NIV soon after the start of respiratory symptoms is associated with increased survival. This involves asking the person with ALS if they have any respiratory symptoms and measuring their respiratory function. The most commonly used measurement is upright forced vital capacity (FVC), but it is a poor detector of early respiratory failure and is not a good choice for those with bulbar symptoms, as they have difficulty maintaining a tight seal around the mouthpiece. Measuring FVC while the person is lying on their back (supine FVC) is a more accurate measure of diaphragm weakness than upright FVC. Sniff nasal inspiratory pressure (SNIP) is a rapid, convenient test of diaphragm strength that is not affected by bulbar muscle weakness. If someone with ALS has signs and symptoms of respiratory failure, they should undergo daytime blood gas analysis to look for hypoxemia (low oxygen in the blood) and hypercapnia (too much carbon dioxide in the blood). If their daytime blood gas analysis is normal, they should then have nocturnal pulse oximetry to look for hypoxemia during sleep.
  Non-invasive ventilation prolongs survival longer than riluzole. A 2006 randomized controlled trial found that NIV prolongs survival by about 48 days and improves quality of life; however, it also found that some people with ALS benefit more from this intervention than others. For those with normal or only moderately impaired bulbar function, NIV prolongs survival by about seven months and significantly improves quality of life. For those with poor bulbar function, NIV neither prolongs survival nor improves quality of life, though it does improve some sleep-related symptoms. Despite the clear benefits of NIV, about 25–30% of all people with ALS are unable to tolerate it, especially those with cognitive impairment or bulbar dysfunction. Results from a large 2015 cohort study suggest that NIV may prolong survival in those with bulbar weakness, and so NIV should be offered to all people with ALS, even if it is likely that they will have difficulty tolerating it.
caption: Non-invasive ventilation supports breathing with a face or nasal mask connected to a ventilator.
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