Hyperbaric oxygen decreases intimal thickness and area after carotid artery balloon injury in a rat model

Clinical studies have suggested a benefit for hyperbaric oxygen (HBO) treatment in decreasing symptomatic restenosis after coronary angioplasty. We hypothesize that HBO treatment will decrease hyperplastic intimal area after arterial balloon injury in a rat.

Fifty-four male Sprague-Dawley rats (Charles River Laboratories, Wilmington, MA) were randomly assigned either to room air (n = 27) or a treatment group (n = 27) receiving HBO treatment (2 hyperbaric treatments of 100% oxygen at 2 bars for 90 min). A 2F balloon-tipped catheter was used to injure the right common carotid arteries, which were harvested at 7, 14, and 28 days. Postinjury intimal thickness and area were measured from hematoxylin-eosin-stained specimens at each time point. Computer-assisted histomorphometry was used to calculate maximal intimal thickness, relative intimal thickness (ratio of intimal to intimal plus medial thickness), intimal area, and the intimal to medial area ratio.

There was a 42.3% reduction in maximal intimal thickness (P = 0.0012) and a 36.5% reduction in intimal area (P = 0.0337) at day 28 in the HBO-treated group (mean ± standard error [SE], 0.0425 ± 0.0054 mm for maximal thickness and 0.065 ± 0.0056 mm(2) for area) when compared to the normoxic group (0.0737 ± 0.004 mm for maximal thickness and 0.0413 ± 0.0074 mm(2) for area). The relative intimal thickness also showed a 28.3% reduction at day 28 in the HBO-treated group (ratio of 0.38 ± 0.0329) compared to the normoxic group (ratio of 0.53 ± 0.0141; P = 0.0065).

Our results indicate that HBO treatment decreases maximal intimal thickness and intimal area of the carotid artery after balloon injury. This could have significant clinical implications on the increasing number of endovascular interventions in vascular surgery and cardiology.