Current activity guidelines for CABG patients are too restrictive: Comparison of the forces exerted on the median sternotomy during a cough vs. lifting activities combined with Valsalva maneuver

Background: The current activity guidelines for coronary artery bypass graft surgery (CABG) patients are overly restrictive, hindering recovery. As the sternotomy repair must withstand repeated coughs during convalescence, this provides a benchmark for the force tending to separate the incision that can be tolerated. Methods: Nine volunteers performed 5 weightlifting activities (lifting 5 lbs 12.3 kg], lifting a 25-lb simulated grandchild [11.4 kg], lifting a 30-lb suitcase [13.6 kg], lifting two 20-lb weights [18.2 kg], and lifting a gallon of milk to a counter [3.7 kg]), plus coughing. Valsalva forces were detected using a mouthpiece configured with an Ashcroft Inc. expiratory pressure gauge (model N10-120CMW). Three measurements were taken for each activity to calculate the mean internal forces while external forces on the sternotomy were calculated using vector algebra. Total force exerted on the sternotomy by the cough was compared to the total force exerted by each of the 5 activities using paired t-tests. Results: The cough exerted a significantly greater force across the median sternotomy (mean 27.5 kg-mass) than any of the five weightlifting activities (p < 0.05). The greatest difference was observed was for lifting a 5-lb weight (22.5 kg-mass), and the smallest for lifting two 20-lb weights (4.4 kg-mass). Conclusion: Lifting even 40 lbs puts less force on the median sternotomy incision than a cough. The strength of the repair is significantly greater than is implied by the recommendation to "not lift More than 5 lbs".