BACKGROUND Directed cough maneuvers are often included in physiotherapy management aimed at preventing postoperative pulmonary complications after open heart surgery, but there is little scientific evidence of the effectiveness of directed cough maneuvers. METHODS We conducted a randomized intra-subject crossover trial to evaluate the effect of thoracic support (patient holds his or her hands over the incision) and maximal inspiration on cough peak expiratory flow (CPEF), cough expiratory volume (CEV), and incision pain during cough in the early period after open heart surgery. Cough evaluation was undertaken on the first and second morning after surgery. On both measurement days the subject did a baseline cough (baseline cough 1) then, in a random sequence, performed 3 cough conditions: an additional baseline cough (baseline cough 2), supported cough, and supported cough preceded by maximal inspiration. In these test conditions a P < .008 was deemed to indicate a statistically significant difference. RESULTS Twenty-one subjects participated. Thoracic support alone did not significantly affect CPEF or CEV (Bonferroni adjusted P > .008). With a maximal inspiration and thoracic support, CPEF and CPEV were significantly higher than in all other cough conditions (Bonferroni adjusted P < .008). Pain during cough was not influenced by the different cough conditions (P > .05). There was no significant difference in the cough variables or pain during the different cough conditions on the first day versus the second measurement day. CONCLUSIONS Maximal inspiration increased CPEF and CEV, but the method of thoracic support we used did not reduce pain during cough or influence the cough values we measured.