Session 4: Living with and managing nocturnal hypoventilation in MND

Living with and managing nocturnal hypoventilation in MND Ventilation has to be supported… or less commonly The airway supported How do we do it?

It used be with one of these… Or one of these..

Then it was with one of these…

And now with one of these

What is NIV? Non-invasive ventilation (NIV) refers to the provision of ventilatory support through the upper airway using a mask or similar device. Initially and most frequently at night

Two types of NIV CPAP: Continuous positive airway pressure splints upper airway and recruits unused alveoli. (OSA, Acute type 1 respiratory failure). BiPAP: Bilevel Positive airway pressure (type 2 respiratory failure) (nippy, nippv, vpap). When used outside of hospital NIV is often referred to as Home Mechanical Ventilation (HMV).

How does BiPAP help ? generally NIV supports the patients own breathing increases tidal volume supports and rests tired respiratory muscles supports upper airway improves sleep efficiency and quality improves mortality and morbidity improves quality of life. 8

When to introduce in MND Best time to introduce is when people have symptoms of sleep disordered breathing or nocturnal hypoventilation. Few people tolerate NIV without symptoms. Some patients, particularly those with MND, have what appears to be normal lung function and normal sleep study. Caveat: Not everyone will want ventilation or tolerate it. We are trying to improve quality of life not worsen it.

Does it work? In short…Yes

General outcomes mortality excellent outcome at 5 years for post polio syndrome 100% survival rate over 50% of those with DMD now survive to over 25 because of HMV excellent outcome in stable muscular skeletal and neuromuscular disease (73% of kyphoscoliosis pts 5 year survival (60% O2 alone) improving mortality in MND (200 days median improvement in length expectancy) poorer outcome in bronchiectasis, CF and COPD.

The evidence NB Probability of continuing NIV is equivalent to survival as the main reason for discontinuation was death. (Simonds and Elliott 1995)

The evidence DMD NIV significantly improves length of life in DMD, more so than tracheostomy ventilation.

The evidence in MND Non-invasive ventilation Can improve QoL and length of life in non-bulbar MND. Can Improve QoL but not length of life in severe bulbar MND.

Effects of non-invasive ventilation on survival and quality of life in patients with amyotrophic lateral sclerosis: a randomised controlled trial Bourke et al 2006

Oxygen in MND Target saturation range is 88-92%. Only employ oxygen to keep patients in that range.

Hypoxaemic drive Control of ventilation is complex but includes a hypercapnic respiratory drive. A small percentage of patients who hypoventilate can have chronically high CO2. Such patients become insensitive to CO2 and use a hypoxaemic drive to their respiration. As paO2 increases ventilation will fall raising paCO2 and decreasing pH.

VQ mismatch due to increased alveolar oxygen Poorly ventilated alveolar capillary units become hypoxic and therefore poorly perfused due to hypoxic pulmonary vasoconstriction. If widespread, then vasoconstriction across the pulmonary circulation.

VQ mismatch due to increased alveolar oxygen High flow oxygen improves alveolar hypoxia and therefore pulmonary vasoconstriction. The alveolar units remain poorly ventilated and CO2 pours into the blood stream, raising paCO2 and decreasing pH. The patient becomes narcosed and can die of acidaemia.

Oxygen in MND Target saturation range is 88-92%. Only employ oxygen to keep patients in that range. Oxygen alerts and venture packs may help acute teams.

Supporting the Mucociliary escalator mobilise the phlegm hydration mucolytics breathing techniques. mucociliary escalator video