Effects of Acute Exposure to Low Oxygen Tension on the Circulation of Vagotomized Nonnarcotized Dogs

¹ From the Laboratory of Experimental Physiology, Fondation Marie Lannelongue, Paris, France

Bilateral cervical vagotomy was performed in two stages on five dogs that survived for periods of 14 to 68 days following the second surgical procedure. These animals were trained to breathe through a head mask, once under local anesthesia, catheters were introduced into the pulmonary artery and femoral artery. After 3 minutes of exposure to a mixture of 8% oxygen in nitrogen when average arterial oxygen saturation was 52% mean pulmonary artery pressure, (referred to mean intrapulmonary pressure which was simultaneously measured) increased by 3 mm Hg. During the same time, heart rate and cardiac output, measured by the dye dilution technique were also increased. Calculated pulmonary resistance did not change, a result also observed in the intact dog. Calculate peripheral resistance fell by 23% which would indicate that in the vagotomized dog the local vasodilator effect of low oxygen is predominant.