Global study of ICU patients finds 10 per cent have often-fatal Acute Respiratory Distress Syndrome
Toronto, February 22, 2016
By Leslie Shepherd
Dr. John Laffey
Just over 10 per cent of patients in intensive care units around the world have Acute Respiratory Distress Syndrome, a condition that continues to have a high mortality rate despite advances in care, according to one of the biggest studies ever conducted in critical care.
However, the study involving more than 450 ICUs in 50 countries on five continents found that that ARDS is under-recognized and under-treated, said Dr. John Laffey, the lead author and chief anesthesiologist at St. Michael’s Hospital in Toronto.
The study was published today in the journal JAMA.
“We know that 40 per cent of patients with ARDS die, either of this syndrome or their primary illness or injury, so this new, global understanding of this important public health issue and how we are treating it is enormously important for patients and clinicians,” said Dr. Laffey, who is also a scientist with the hospital’s Keenan Research Centre for Biomedical Science.
ARDS occurs in in patients with critical illnesses such as severe infections or following severe injuries. An uncontrolled inflammatory response damages the lining of the lungs causing fluid to build up in the tiny, elastic air sacs in the lungs known as alveoli, reducing the amount of oxygen that reaches the bloodstream. Patients with ARDS are unable to breathe on their own and require artificial ventilation.
The LUNG SAFE (Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE ) study was carried out by the European Society of Intensive Care Medicine, and enrolled 29,144 patients admitted to 459 ICUs in 2014. It found that while 10.4 per cent of those patients developed ARDS – about six patients per ICU bed per year -- 40 per cent of all cases were not diagnosed. The number of patients who died in hospital was 34 per cent, 40.3 per cent and 46.1 per cent for mild, moderate and severe ARDS respectively.
Dr. Laffey said the reasons for failing to recognize ARDS are likely complex, and include the fact there is no single test for diagnosing a syndrome made up of many symptoms. But making the diagnosis is important because it influences the care delivered. Another finding of the study was that approaches to managing patients with ARDS are inconsistent, indicating perhaps that more research is needed to provide evidence that certain treatments are effective.
For example, less than two-thirds of ARDS patients received “protective” forms of mechanical ventilation known to cause less damage to the lungs. The study defined “protective” tidal volumes – the volume of air inhaled or exhaled at a time – as being based on a person’s ideal weight rather than his or her actual weight. Lung size is related to ideal weight, which is derived from height, not actual body weight.
The study also found that clinicians used lower-than-expected levels of PEEP, or positive-end expiratory pressure, the amount of pressure applied by the ventilator at the end of an exhalation. This was somewhat surprising, especially for patients with more severe ARDS, Dr. Laffey said, raising concerns that these patients may not have had enough PEEP to prevent parts of their lungs from collapsing.
Only 14.5 per cent of patients in the study received ventilation while lying in the prone position, which improves oxygenation in most patients with ARDS.
The study also found geographic differences in the recognition and treatment of ARDS, although not as large as they expected. The highest incidence of ARDS was in Australia and New Zealand, followed by Europe and North America.
This paper is an example of how St. Michael's Hospital is making Ontario Healthier, Wealthier, Smarter.
About St. Michael's Hospital
St. Michael’s Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in 27 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, care of the homeless and global health are among the hospital’s recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Centre, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael's Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.
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