Summary
Professor Denny Levett presents on preoperative inspiratory muscle training at the POETTS 2018 congress. She covers the epidemiology of post-operative pulmonary complications (PPCs), noting they cause over 1 million complications annually in the US and result in nearly 5 million additional hospital days. The ARISCAT score is introduced as a tool for identifying high-risk patients using patient and surgical factors. IMT is described as resistance training for respiratory muscles -- the diaphragm, intercostals, and accessory muscles -- using devices where patients breathe against an adjustable load. The evidence shows a consistent 50% reduction in PPCs across multiple systematic reviews and a Cochrane analysis. Levett details the protocol (30 breaths, twice daily, progressive loading) and emphasizes that supervision is essential for effectiveness. She announces the upcoming INSPIRE trial, a 2,500-patient NHS pragmatic RCT.
Key Points
- Post-operative pulmonary complications cause more than 1 million complications and 5 million extra hospital days annually in the US
- ARISCAT score combines patient factors and surgical factors to stratify pulmonary complication risk
- IMT protocol: 30 breaths twice daily at above 30% of MIP, with weekly 5% load progression
- High-intensity IMT (above 60% MIP) produces faster improvements in shorter duration
- Cochrane review of 12 RCTs showed 55% reduction in pulmonary complications
- Without supervision, IMT provides zero benefit -- at minimum, follow-up within 3-5 days is needed
- Incentive spirometry has no evidence base for reducing PPCs, unlike IMT
- INSPIRE trial: 2,500-patient three-arm pragmatic NHS RCT (IMT vs sham vs usual care)
Key Moments
IMT trains the diaphragm and intercostals against adjustable resistance
IMT is explained as resistance training specifically for the respiratory muscles. In healthy people breathing is not limiting, but in patients with cardiorespiratory disease or deconditioning, respiratory muscle weakness creates a dangerous supply-demand imbalance during surgery.
"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."
Consistent 50% reduction in pulmonary complications across systematic reviews
Multiple systematic reviews show a consistent 50% reduction in post-operative pulmonary complications with IMT. The effect is seen across thoracic, abdominal, and cardiac surgery, and even training under 14 days provides meaningful benefit.
"So you can see the overall relative risk is about 0.5 for post-op pulmonary complications. So again, 50% reduction. Reassuringly, that's the same."
IMT has evidence while incentive spirometry does not
Professor Levett points out that incentive spirometry, commonly used preoperatively, has no evidence supporting its effectiveness. IMT is a fundamentally different intervention with actual evidence from randomized controlled trials.
"So it is a different intervention to incentive in spirometry, and there is actually good evidence in randomized controlled trials that IMT works."
