To study whether the proximal and distal facial artery have a constant blood pressure after the facial artery is cut and whether the retrograde flow of the distal, paramandibular part of the facial artery would provide sufficient pressure to perfuse the flap for survival.

We seleted 25 oral squamous cell carcinoma cases from Mar. 2017 to July 2017 treated in Sun Yet-san Memorial Hospital (lymphatic metastasis was excluded) . All patients were informed before surgery and agreed to accept the experiment. We dissected the facial artery and occluded the branch of it, the facial artery was occluded with two vessel clamps at the level of the mandible and prepared to allow for insertion of a standard intravenous polyethylene. The tube was connected to a pressure transducer. Arterial pressure and the pulsatile wave of the facial artery were recorded, and then with the ligation of the lower lip artery. The blood pressure of retrograde and the anterograde in facial artery was recorded and analyzed.

The mean systolic blood pressure in the distal facial atery was (88.00 ± 17.46) mmHg (1 mmHg= 0.133 kPa) . The mean distolic blood pressure in the distal facial atery was (60.33 ± 7.49) mmHg. The mean systolic blood pressure in the proximal facial atery was (113.36 ± 21.22) mmHg. The mean distolic blood pressure in the proximal facial atery was (68.80 ± 11.63) mmHg. Systolic blood pressure arterial pressure in the distal facial artery with retrograde flow was 77.68% of the anterograde arterial pressure. Diastolic blood pressure arterial pressure in the distal facial artery with retrograde flow was 88.43% of the anterograde arterial pressure. The systolic blood pressure in the distal facial atery was compared with the systolic blood pressure in the proximal facial atery (t= 10.210, P<0.001) . The mean distolic blood pressure in the distal facial atery was compared with the distolic blood pressure in the proximal facial atery (t= 6.643, P<0.001) . After ligation of the lower lip artery, the blood pressure of the retrograde and the anterograde showed no significant fluctuations.

Although the retrograde blood pressure in the facial artery descend compared to the anterograde, there is no significant difference between them. Thus, there is a good blood flow basis for retrograde facial artery, which could provide good blood supply for tissue flap survival.