Pulmonary function testing is safe in patients with thoracic aortic aneurysms (TAA), with no evidence of acute rupture of even large aneurysms or poorer outcomes following spirometry, UK research shows.
Researchers from the Liverpool Heart and Chest Hospital, led by Respiratory Fellow Dr Freddy Frost, reviewed the outcomes of 519 patients who had undergone spirometry as part of the work up for TAA surgery between 2011 and 2017.
The results published in the European Respiratory Journal showed that the forced respiratory manoeuvre necessary for spirometric measurement was not associated with adverse outcomes in patients undergoing elective or urgent surgery for TAA. There was no increase in 30-day mortality, length of stay or the need for unplanned urgent or emergency surgery in patients having undergone spirometry. The findings were similar across all sizes of TAA.
The researchers also found that lung function is an important predictor of post-operative length of stay, which they say underlines the value of its assessment.
AARC guidelines refuted
The new findings refute the American Association of Respiratory Care (AARC) 1996 Spirometry Clinical Practice Guidelines which listed thoracic aneurysms as a relative contraindication to forced respiratory manoeuvres due to the theoretical risk of rupture from increased thoracic pressure.
Although the AARC guideline is now retired, the contraindications are still often referred to because little is known about the risk of rupture in TAA following forced expiratory manoeuvres, says Dr Frost.
He told the limbic: “Physiologists and technicians have anecdotally suspected there is no increased danger with spirometry but local policies often dictate they must seek clinician approval prior to testing.
“We hope that our findings will help reassure clinicians, physiologists and patients alike that spirometry is a safe procedure in people with thoracic aortic aneurysms.”
“We hope our data can help support a standardisation of practice so that people who need spirometry can do it without undue concern,” he added.
“Currently there is wide variation in practice with some centres requiring formal written consent before patients with aortic aneurysms can undergo spirometry and others happy to proceed regardless.”
Expert welcomes research
Professor Brendan Cooper, a Consultant Clinical Scientist and Professor of Respiratory & Sleep Physiology at the University Hospitals Birmingham (Queen Elizabeth Hospital) NHS Foundation Trust and author of the 2010 update on contraindications for lung function testing published in Thorax, has welcomed the research.
“The risks associated with spirometry are pretty low generally but we need evidence like this just to be absolutely sure that we can make these general statements that ‘spirometry isn’t a high risk but take it on its own merits’,” he told the limbic.
“Now we’ve actually got some concrete evidence you can make a much more informed decision about the relative risks, so I think clinicians will go much more towards common sense and reasonable risk management.”
Professor Cooper says one of the final conclusions on research recommendations in his contraindications update was that there should be an audit of patients who have had aneurysms to investigate whether lung function tests do actually present any risks.
“Freddy Frost’s paper is absolutely perfect because it’s answered one of those questions for us,” he said.
“I’d like more people to do similar work and for people to remember that contraindications really are all relative, down to each case judged on its own merit,” he added.
Dr Frost also thinks it’s important for high-throughput centres to continue to report and publish outcomes so that an evidence base for the safety of spirometry can be built up, and noted that his research supports recent data from the Royal Brompton and Harefield NHS Foundation Trust on the safety of spirometry in general over 20 years, published in Thorax earlier this year.