Summary
Professor Denny Levett of Southampton presents on preoperative inspiratory muscle training (IMT) at the EBPOM conference. She explains that post-operative pulmonary complications (PPCs) are more common than cardiac complications after surgery, with incidence ranging from 5% to 40% depending on definitions. IMT involves breathing against resistance using a handheld device, with patients performing 30 breaths twice daily at above 30% of their maximum inspiratory pressure (MIP). A 2013 Cochrane review of 12 trials found a 55% reduction in PPCs with IMT, and a subsequent systematic review confirmed a 50% risk reduction. However, supervision is critical -- unsupervised patients showed no benefit. The minimum effective training period is about two weeks, making it practical even for tight surgical timelines. Levett introduces the upcoming INSPIRE trial, a 2,500-patient NHS-funded RCT with IMT, sham, and usual care arms to evaluate real-world effectiveness.
Key Points
- Post-operative pulmonary complications are more common than cardiac complications, causing over 1 million complications annually in the US
- IMT is essentially resistance training for respiratory muscles -- diaphragm, intercostals, and accessory muscles
- Protocol: 30 breaths twice daily at more than 30% of maximum inspiratory pressure, with progressive load increases
- Cochrane review showed 55% reduction in post-op pulmonary complications across 12 trials
- High-intensity training (above 60% MIP) produces faster improvements in shorter duration
- Supervision is essential -- unsupervised patients showed zero reduction in complications
- Minimum effective duration is about two weeks, with benefits continuing up to 8-12 weeks
- Electronic devices that reduce load toward end of breath provide more training per breath than mechanical devices
Key Moments
IMT is resistance training for respiratory muscles
Professor Levett explains that inspiratory muscle training is essentially exercise training for the diaphragm, intercostal muscles, and accessory muscles. In patients with cardiorespiratory disease, respiratory muscle deconditioning contributes to exercise limitation.
"You can really think of inspiratory muscle training as essentially exercise training for the respiratory muscles. By that I mean the diaphragm, the intercostal muscles and the accessory muscles."
30 breaths twice daily with progressive loading is the standard protocol
The standard IMT protocol uses 30 breaths twice daily at above 30% of maximum inspiratory pressure, with minimum two weeks for efficacy and plateau at 8-12 weeks. High-intensity training above 60% MIP produces faster improvements.
"And most of the studies that have looked at this technique in the vast majority of patient populations have used approximately 30 breaths twice a day. And the minimum period for efficacy appears to be around about two weeks."
Cochrane review shows 55% reduction in post-operative pulmonary complications
A 2013 Cochrane review of 12 trials in major abdominal and cardiac surgery found a 55% reduction in post-operative pulmonary complications with IMT, though these were small single-center trials.
"So there were 12 trials in major abdominal surgery and cardiac elective surgery. And you can see, probably more important than atelectasis, 55% reduction in post-op pulmonary complications."
Supervision is essential -- unsupervised IMT shows zero benefit
The most striking finding from subgroup analysis is that completely unsupervised IMT showed no reduction in complications at all. Patients need at least initial follow-up within 3-5 days to ensure proper technique.
"So that if you didn't supervise them at all, i.e. you sent them off into the dark blue yonder with the machine and said, come back in two weeks, there was no reduction whatsoever."
