Rationale:
A significant concern following coronary artery bypass graft (CABG) surgery is sternal injury, oftentimes leading to conservative post-CABG exercise prescriptions. Current guidelines advocate motivating patients to resume physical activities, yet advise them not to perform select actions unavoidable in daily living. Therefore, it is necessary to evaluate which activities can be safely performed during recovery - encouraging a return to normal life.
Objectives:
To compare forces experienced during common activities on the pathway home of a CABG patient with those implied as "safe" under the advice "don't lift more than 5 pounds".
Methodology:
10 healthy subjects (5 female, 5 male; age 24-77 years; weight 110-322 lbs), performed 10 activities simulating a pathway home for a post-CABG patient. Expiratory pressures were taken "during task" using a sterile mouthpiece interfaced to an analog pressure gauge (Ashcroft Inc. model N10/120CMW). Mechanical forces on the sternum resulting from these activities were estimated using vector algebra. Subjects were coached in use of the gauge and practiced normal breathing patterns while connected to the system prior to testing.
Results:
Coughing exerted the greatest expiratory pressures (averaging 84.2 cm H2O), along with a 30.9 kg vector force across the median sternotomy. "Pathway home" activities exerted expiratory pressures averaging 13.8-17.8 cm H2O. Total vector forces across the median sternotomy averaged 19.9-23.3 kg. The average vector force associated with lifting a 5 lb weight, a common post-surgical limitation, was 5.0 kg.
Conclusion:
Typically contraindicated patient activities on the pathway home from surgery (eg, lifting a child/suitcase, rising from bed/chair) put less thoracic pressure and vector force on the median sternotomy incision than a cough. The repair tolerates separating forces significantly larger than the "safe" force implied in the advice "don't lift more than 5 lbs". Since over-cautious guidelines may cause unnecessary fear and inactivity among patients, hindering recovery, post-CABG exercise prescriptions should be revised.