Oxygen no relief for breathlessness?

October 2010 Vol 11 issue 6

This month’s clinically-appraised topic asks the question does prescribing oxygen offer relief to palliative care patients experiencing breathlessness?

 

CLINICAL BOTTOM LINE:web97537749
Oxygen provides no additional benefit over room air in relief of dyspnoea – either in terms of breathlessness or in terms of quality of life. Side effects profiles are the same. Simply prescribing oxygen via cannula is unlikely to benefit palliative care patients experiencing breathlessness.

CLINICAL SCENARIO:
One of your palliative care patients is experiencing breathlessness. He is prescribed oxygen via nasal prongs but finds them uncomfortable and keeps removing them despite his breathlessness. He doesn’t seem to get any benefit from the oxygen and while others of your colleagues believe it is because he doesn’t keep the nasal prongs on, you wonder if the oxygen is of any benefit anyway.

QUESTION:
Among palliative care patients does oxygen relieve breathlessness and dyspnoea?

CITATION:
Abernethy AP et al. Effect of palliative oxygen versus room air in relief of breathlessness in patients with refractory dyspnoea: a double-blind, randomised controlled trial. Lancet 2010; 376:784-93.

STUDY SUMMARY:
A two-arm, blinded, multi-centre randomised controlled trial conducted in nine centres (five in Australia, two in the USA and two in the United Kingdom). Participants were recruited through outpatient pulmonary, palliative care, oncology and primary care clinics. Inclusion criteria were: adults aged 18 years or more, PaO2 > 7.3 kPa, refractory dyspnoea related to a life-limiting illness, received maximum treatment for underlying disease, reported dyspnoea at rest or with negligible exertion of three or more on MRC categorical dyspnoea scale, were on stable medications for one week before enrolment in trial and were judged by their physicians to have expected survival of at least one month. Exclusion criteria were if they meet inclusion criteria for long-term oxygen therapy, had history of hypercarbic respiratory failure, had anaemia, hypercarbia, cognitive impairment, smoked or had had a respiratory or cardiac event within the previous seven days. More than 560 possible participants were referred, 488 were screened, 256 were eligible and 239 were randomised. All groups received a medical gas concentrator with instructions to use for at least 15 hours per day.
Intervention (n=120):
Unmodified medical gas concentrator that delivered two litres of oxygen was delivered via nasal cannula.
Control (n=119):
Modified medical gas concentrator that dispensed room air via nasal cannula.

OUTCOMES:
Primary outcomes were self-reported breathlessness (right now) recorded by the patient twice a day: firstly within 30 minutes of waking up (morning) and secondly when going to bed (evening). Results were recorded in a diary with zero being no breathlessness and 10 being breathlessness as bad as you can imagine. A one point reduction in breathlessness is generally considered clinically relevant. Secondary outcomes included breathlessness over the previous 24 hours, relief of dyspnoea over the previous 24 hours, and ordered categorical scales of impact on function, sleep disturbance, anxiety, nasal irritation, nose bleeds, quality of life and side effects.

VALIDITY:
Computer generated randomisation was used and allocation concealment was by central telephone randomisation or via web through the pharmacy service at Adelaide Hospital using balanced blocks of four. Loss to follow up was eight (7%) in the treatment group and 20 (17%) in the control group. Analysis was by intention-to-treat with all randomised participants who completed an assessment included in the analysis (88%). Patients, individuals delivering the interventions, investigators and nurses were blinded to the intervention. The groups were balanced at baseline. Overall impression – a high quality study.

RESULTS:
Participants at baseline were on average aged 73 years, 62% were men, and the range of diseases causing dyspnoea were similarly broad (COPD and lung cancer accounted for 74% of cases). Breathlessness did not differ between the groups either at baseline or at endpoint (table). There were similar improvements in morning breathlessness in both groups. Change in quality of life was also similar in both groups. Side effects were similar in both groups as was frequency of extreme drowsiness (10% vs 13%). Two patients reported extreme nasal irritation in the oxygen group compared to seven in the room air group.

COMMENTS:
The trial was publicly funded by the National Institutes of Health and the Australian National Health and Medical Research Council. ✚

Reviewer:
Dr Andrew Jull, RN PhD, associate professor (School of Nursing), nurse advisor – quality, Auckland District
Health Board.