Background: Arterial spasm is described as an event occurring after internal mammary artery (IMA) harvesting. Endothoracic papaverine and carbon dioxide application have been used to prevent IMA spasm before surgical dissection. This technique may make harvest quicker and easier. The aim of this study is to evaluate the effect of room air injection into the endothoracic fascia on IMA blood flow and harvest time. Methods: Eighty-four consecutive ischemic patients were randomly assigned to four groups: group 1 (n = 21, no treatment), group 2 (n = 21, papaverine), group 3 (n = 21, air), group 4 (n = 21, air and papaverine). The room air was injected with a blunt needle through the endothoracic fascia before harvest. Each dissection time was recorded and the flows were measured before cardiopulmonary bypass. Results: Mean blood flows and harvest time were: group 1 = 65.7 +/- 16.3 mL/min, 37.2 +/- 8.5 minutes; group 2 = 86.6 +/- 16.4 mL/min, 25.6 +/- 5.5 minutes; group 3 = 85.7 +/- 13.1 mL/min, 22.4 +/- 4.8 minutes; and group 4 = 90.2 +/- 16.4 mL/min, 21.7 +/- 5.7 minutes. IMA flow and harvest time in groups 2, 3, and 4 were different than the control group (p < 0.001), but there was no significant statistical difference between treatment groups (2, 3, and 4) (p > 0.05). Conclusions: Injection of room air beneath the endothoracic fascia before IMA dissection may prevent spasm and shorten harvest time, which avoids any risk of intimal injury.