# 4992
At the risk of blogging on a subject a little too `inside baseball’, a study caught my eye this morning in the BMJ on the survival rates of COPD (Chronic Obstructive Pulmonary Disease) patients treated by paramedics with either high concentrations or low concentrations of oxygen.
This has been a contentious subject in the medical community for a long time.
I was taught – back in the stone age of emergency medicine (early 1970s) – not to give more than 2 liters of oxygen to a COPD patient (we didn’t have pulse-ox meters onboard back then).
Oxygen, as my paramedic instructor often said, was a drug. And too much O2 for patients with COPD could result in respiratory failure.
For many years, however, it has been standard protocol for a lot of EMS services not to deprive COPD patients in serious respiratory distress high flow rates of oxygen.
Running contrary to that opinion, in 2008 the British Thoracic Society came up with guidelines that restricted in-the-field oxygen delivery for COPD patients – and those were adopted by British Ambulance services in 2009.
The guideline recommends that oxygen is administered to patients whose oxygen saturation falls below the target saturation ranges (94-98% for most acutely ill patients and 88-92% for those at risk of type 2 respiratory failure with raised carbon dioxide level in the blood), and that those who administer oxygen therapy should monitor the patient and keep within those specified target saturation ranges.
But elsewhere in the world, delivery of high flow rates of oxygen for COPD patients (both pre-hospital and in-hospital) remains common.
This new study (BMJ 2010; 341:c5462), which appeared in yesterday’s British Medical Journal as an open access research article, may shake up that practice.
It has relevance for emergency responders, and for those who have in-home oxygen setups for someone with COPD (primarily Emphysema).
Effect of high flow oxygen on mortality in chronic obstructive pulmonary disease patients in prehospital setting: randomised controlled trial
- Michael A Austin,Karen E Wills, Leigh Blizzard, Eugene H Walters, Richard Wood-Baker
Accepted 19 August 2010
Abstract
Objectives To compare standard high flow oxygen treatment with titrated oxygen treatment for patients with an acute exacerbation of chronic obstructive pulmonary disease in the prehospital setting.
Design Cluster randomised controlled parallel group trial.
Setting Ambulance service in Hobart, Tasmania, Australia.
Participants 405 patients with a presumed acute exacerbation of chronic obstructive pulmonary disease who were treated by paramedics, transported, and admitted to the Royal Hobart Hospital during the trial period; 214 had a diagnosis of chronic obstructive pulmonary disease confirmed by lung function tests in the previous five years.
Interventions High flow oxygen treatment compared with titrated oxygen treatment in the prehospital (ambulance/paramedic) setting.
Main outcome measure Prehospital or in-hospital mortality.
The results? Again from the abstract:
Titrated oxygen treatment reduced mortality compared with high flow oxygen by 58% for all patients (relative risk 0.42, 95% confidence interval 0.20 to 0.89; P=0.02) and by 78% for the patients with confirmed chronic obstructive pulmonary disease (0.22, 0.05 to 0.91; P=0.04).
Patients with chronic obstructive pulmonary disease who received titrated oxygen according to the protocol were significantly less likely to have respiratory acidosis (mean difference in pH 0.12 (SE 0.05); P=0.01; n=28) or hypercapnia (mean difference in arterial carbon dioxide pressure −33.6 (16.3) mm Hg; P=0.02; n=29) than were patients who received high flow oxygen.
Remarkable numbers, assuming that future studies corroborate the results.
There were limitations to this study, including a failure to obtain arterial blood gases for many of the patients within 30 minutes of their arrival at the ER, and a lack of in-hospital monitoring of treatment.
Breaches in protocol were apparently common during this study, with more oxygen being administered in some cases than specified by the study.
And of course, this study was limited in size as well.
Which means that the controversy over which protocol to use isn’t resolved.
It is, after all, counter-intuitive to deprive someone who is in serious respiratory distress abundant oxygen. And so more studies will certainly be needed before titering oxygen rates for COPD patients gains wide acceptance.
Amazing, though, that what we believed back in the early 1970s – and what was subsequently discarded - may end up coming back as the standard today.
The authors write:
Conclusions and policy implications
This randomised controlled trial found that titrated oxygen treatment in the prehospital setting resulted in a 78% reduction in the risk of in-hospital respiratory failure and subsequent mortality, compared with high flow oxygen treatment, and a decreased risk of hypercapnia and respiratory acidosis for patients with an acute exacerbation of chronic obstructive pulmonary disease.
Our findings provide the first high quality evidence from a randomised controlled trial for the development of universal guidelines and support the British Thoracic Society’s recent guidelines on acute oxygen treatment, which recommend that oxygen should be administered only at concentrations sufficient to maintain adequate oxygen saturations.
Although our findings may need to be confirmed in larger studies across other health systems, implementation of the new guidelines will now be easier. However, resources for an aggressive campaign of education will still be needed to change the “more is better” oxygen culture that may ignore the potential dangers of hyperoxia.
What is already known on this topic
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Audits have shown increased mortality, acidosis, and hypercarbia in patients with acute exacerbations of chronic obstructive pulmonary disease treated with high flow oxygen
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High flow oxygen is still used routinely in prehospital and hospital areas for breathless patients with chronic obstructive pulmonary disease
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A “more is better” oxygen culture is strong in prehospital management
What this study adds
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Titrated oxygen treatment reduces mortality, acidosis, and hypercarbia in patients with acute exacerbation of chronic obstructive pulmonary disease treated before arrival at hospital
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The risk of death was reduced by 78% by use of titrated oxygen rather than high flow oxygen, with a number needed to harm of 14
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These findings provide strong evidence that titrated oxygen treatment should be used for hypoxic or breathless patients with chronic obstructive pulmonary disease in prehospital settings
