Pre-op Breathing Therapy Halves Post-CABG Lung Risks

UTRECHT, The Netherlands. Oct. 17 -- Pre-op breathing exercises and respiratory muscle training help avoid pulmonary complications after a coronary artery bypass graft, according to researchers here.

Only 18% of high-risk CABG patients who underwent pre-op breathing exercises and respiratory muscle training had pulmonary complications compared with 35% of patients given usual care, found a study reported in the Oct. 18 issue of the Journal of the American Medical Association.

Pneumonia, a common CABG complication, occurred in 6.5% of the breathing-therapy intervention group, compared with 16.1% of the usual-care patients, wrote Erik Hulzebos, P.T., M.Sc, of the University Medical Center here, and colleagues.

Over the past decades, the rate of postoperative pulmonary complications, especially pneumonia, following CABG surgery has remained stable, possibly because CABG is performed in increasingly fragile patients often at greater risk because of comorbid conditions, they noted.

So, they concluded, the pre-hospitalization period before a CABG might be well used to improve a patient's pulmonary condition.

From July 2002 to August 2005, 299 of 655 patients (45.6%) referred for elective CABG surgery in Utrecht met criteria for being at high risk of developing postoperative pulmonary complications. Of these, 279 were enrolled in the study and followed until hospital discharge.

One hundred and forty patients were randomly assigned to preoperative inspiratory muscle training, while 139 received usual care. Both groups received the same postoperative physical therapy.

The inspiratory muscle training program included a 20-minute routine for at least two weeks prior to surgery. Patients performed individualized, tailored exercises six times a week. Once a week, their efforts were supervised by a therapist who measured the strength and endurance of the patients' inspiratory muscles after each week of training.

The patients recorded daily progress, complaints, and adverse events in a diary and were trained to breathe with an inspiratory threshold-loading device.

Breathing started for 20 minutes at a resistance equal to 30% of the patient's baseline maximal inspiratory mouth pressure and was then increased incrementally as the rate of perceived exertion changed.

The program's supportive educational component consisted of detailed instruction in active cycles of breathing techniques with an incentive spirometer and forced expiration technique.

Both groups were comparable at baseline. After CABG surgery, pulmonary complications occurred in 25 (18.0%) of 139 patients in the intervention group and in 48 (35.0%) of 137 patients in the usual-care group (odds ratio 0.52; 95% confidence interval 0.30-0.92, P=.02).

Pneumonia occurred in nine (6.5%) of 139 patients in the intervention group and in 22 (16.1%) of 137 patients in the usual-care group (OR, 0.40; CI, 0.19-0.84, P=.01).

The bacteriological spectrum was similar in both groups. Three of 22 patients in the usual-care group developed respiratory failure as a consequence of pneumomia and died after surgery, whereas none of the intervention patients died. One other patient in the usual-care group died after surgery as a result of cardiac failure.

Commenting on the nine pneumonia patients in the intervention group, the researchers said these participants had actually trained longer (40.7 days) than the intervention patients who did not develop pneumonia (28.95 days).

However, mean inspiratory muscle strength and endurance did not increase significantly between baseline and one day before surgery in these patients. This contrasted, the investigators said, with a significant mean increase in both of these values among the 130 intervention participants who did not develop pneumonia.

Median duration of postoperative hospitalization was seven days (range, five to 41 days) in the intervention group vs. eight days (six to 70 days) in the usual-care group, according to Mann-Whitney U statistic (z=-2.42; P=.02).

The generalizability of these findings may be restricted because the study had a few limitations, the researchers said. In this study, they noted, all the patients were trained by the same physical therapist, unlike daily clinical practice where different therapists would train patients.

Also, they said, although the randomization appeared effective, there were some variables (cigarette smoking, for example) that distinguished the two groups. It is possible, they said, that these along with other measures that were not significantly different after randomization may be confounding variables.

"To our knowledge," the investigators wrote, "this is the first randomized clinical trial of a preoperative prophylactic tailored physical therapy intervention in patients scheduled for primary elective CABG surgery who are at high risk of developing pulmonary complications."

Preventive physical therapy given to these high-risk patients was associated with an increase in inspiratory force and a decrease in lung complications and length of hospitalization, the researchers said. "We consider this to be an important presurgical intervention that appears to be effective at reducing morbidity," they concluded.