Bi-level ventilation: breathing new life into patients

1 July 2012

Respiratory nurse practitioner Diana Hart helps the morbidly obese breathe easily again at night. FIONA CASSIE learns more about her successful bi-level ventilation clinics.

It all started for Diana Hart with just one patient back in 2001.

Back then, having a patient frequently hospitalised with obesity-related respiratory failure was still unusual enough for Middlemore Hospital to search for a novel solution.

It was decided to send the particular patient home with one of the hospital’s own bi-level ventilation machines to sleep with to see what happened.

“We saw what happened – she didn’t need to be re-admitted again. It all started from there,” recalls Hart.

Hart was the respiratory clinical nurse specialist assigned to go home with that first patient and support her using the machine at night.

With the global obesity epidemic speeding up in the past decade, Hart’s role with bi-level ventilation patients has just kept snowballing. She now has more than 60 home-based bi-level patients on her books – the majority morbidly obese – and these patients make up to 25 per cent of her workload as a respiratory nurse practitioner (NP) for Counties Manukau District Health Board.

Her morbidly obese patients are the truly big, most with BMIs (body mass indexes) averaging between the 50s and 60s, and with one – now deceased – client reaching a BMI of over 90.

What they have in common is ventilatory failure caused by their obesity (known as obesity hypoventilation syndrome) that has seen them hospitalised more than four times in a year with type II (hypercapnic) respiratory failure. This has led to them being offered bi-level ventilation and a minority of them also need oxygen during the day or night.

Ventilatory failure is when the breathing response is not strong enough to rid the body of carbon dioxide, particularly when sleeping at night, when having a very large tummy can “squash” their lungs and cause their breathing rate to drop.

This ineffective breathing means the carbon dioxide levels in the body can rise to detrimental levels putting them ultimately at risk of coma and death.

When the patients turn up at hospital, they are often very unwell, very sleepy, and their arterial blood gas results show abnormal levels of carbon dioxide. Hart says often contributing is an early chest infection or cardiac problems.

The success of preventing hospital admissions for Hart’s first patient highlighted a need for home bi-level ventilation for the morbidly obese. Despite precarious funding, then and now, within a few years, Hart had 20 patients and was increasingly working in the community. Soon after becoming an NP in 2006, she set up a monthly outpatient clinic for complex patients using home bi-level ventilation..

Hart carried out an impromptu audit and found the hospital admission rates of the 60 patients in the previous year was only five per cent. These were patients that previously had been hospitalised at least three to four times a year and some of them three to four times a month.

“It’s been amazingly successful, really,” Hart says.

She says other centres in New Zealand use bi-level ventilation but patients are monitored by physicians. The Counties Manukau service is an NP-led clinic but draws on the support of respiratory physicians and the multidisciplinary team because of the patients’ often very complex multiple co-morbidities.

Some of her patients have now lived eight to ten years on bi-level ventilation and rarely, if ever, again suffer respiratory failure. A number of them are able to work, particularly the younger patients. The average age of her Pacific and Māori patients is mid 40s and late 40s, respectively.

“These machines make them feel so much more energised, more awake, and more able to cope with working.”

After a decade of caring for patients often sidelined because their BMI was seen as just too high, Hart now has greater understanding of how very difficult it is for the morbidly obese to lose weight.

“It’s certainly not as simple as just exercise and diet. To be successful, any treatment must affect life-long behavioural changes rather than short-term weight loss.”

A large part of her work with her home bi-level patients is ongoing education to help convince them, and when possible, their family, to make the major lifestyle changes needed.

Her successes include one patient who lost 100 kgs with the help of a supportive sister who returned from Australia to live with him.

She has also had two patients successfully undergo bariatric surgery. But the barrier to bariatric surgery for most of her clients is they need to be 180 kg or under to be considered. Otherwise, they are considered to be too much of an anaesthetic risk.

None of her patient stories are simple, but sadly, her very first patient – Mrs Folole Muliaga – was to die in tragic and fraught circumstances that polarised the country in 2007. Hart was drawn into the inquest into her patient’s death that followed a Mercury Energy contractor disconnecting the family’s electricity, which disabled her oxygen supply. As Mrs Muliaga’s leading caregiver, Hart says she was put “through the mill” for some time. Hart says an audit of her care by a senior respiratory physician concluded she had provided excellent care of a patient she had admired for her “strength and determination” to live as normally as she could.

While the improvement the nocturnal ventilation machines can bring motivates many of her patients, others can never adjust to wearing the mask at night, and she has had two patients return their machines.

“They had to have the consequences of not using the machine explained to them. As long as people have informed choices, that’s fine, as you can’t expect everybody to do what you think is the correct thing.”

For others, bi-level ventilation has literally given them a new breath of life.

Surprisingly low levels of diabetes

While the vast majority of Hart’s morbidly obese patients have co-morbidities like hypertension or cardiomyopathy (heart muscle disease), very few have diabetes.

“Nobody can really explain it,” Hart says.

For example, only four of her 30 Pacific Island patients have diabetes. She has no evidence to back it up but she believes her patients being successfully ventilated at night for a number of years has reduced the diabetes incidence.

“All things being equal, the majority of them should have been diabetic, but they’re not”.

She says it is one of the many topics ripe for research if she could find the time.


Bi-level ventilation

Bi-level ventilation is a non-invasive form of ventilation, using a full-face or nose mask that responds to the patient’s breathing patterns.

The machine – unlike those used for obstructive sleep apnoea – provides not just one but two different levels of air pressure that are triggered by the patient breathing in and out.

The result is breathing is more effective, as when the patient breathes out, the machine switches to a lower pressure level that prevents the lower airways collapsing and carbon dioxide building up.