Small Bowel Tonometry : Assessment of Small Gut Mucosal Oxygen Tension in Dog and Man

Abstract

VARIOUS methods have been used to assess tissue oxygen tension^1–3 and recently the gall bladder and urinary bladder have been used as hollow viscus tonometers⁴. We have applied this principle in an attempt to measure the oxygen tension of the small gut mucosa of dog and man. Six dogs were anaesthetized with ‘Nembutal’, intubated and arterial _pCO₂ maintained between 35 and 45 mm mercury by using a respirator; arterial _pO₂ was kept between 95 and 110 mm mercury by enriching the inspired air with oxygen. Loops of jejunum (23 cm) and ileum (29 cm) were prepared so that their contents could be sampled through an indwelling polyvinyl tube after they had been returned to the abdomen and the abdomen had been closed⁵. The temperature of the animals was maintained between 37° and 39.5° C. Nitrogen was bubbled through isotonic sodium chloride at 37° C; after deoxygenation was complete 40 ml. were instilled into each small bowel loop. Samples were removed at various times for the estimation of _pO₂ and _pCO₂ with a Severinghaus electrode assembly⁶ and pH with an Astrup micro-electrode.