A pilot study of left tracheal pulse oximetry

We tested the hypothesis that left tracheal pulse oximetry (Spo(2)) is more accurate than finger Spo(2) when compared with oxygen saturation from arte rial blood samples (Sao(2)) in anesthetized patients with normal thoracic a natomy. We also tested the hypothesis that tracheal oximetry readings are p rimarily derived from the tracheal mucosa. We studied 20 hemodynamically st able, well oxygenated, anesthetized patients with normal anatomy (ASA physi cal status I-III, 18-80 yr old). A single-use pediatric pulse oximeter was attached to the left lateral surface of a tracheal tube cuff. Tracheal and finger Spo(2) (dominant index finger), and Sao(2) (nondominant radial arter y) were taken with the intracuff pressure at 0-60 cm H2O. Tracheal Spo(2) w as the same as Sao(2) at an intracuff pressure of 10-60 cm H2O, but was les s when the intracuff pressure was zero (P < 0.0001). Tracheal Spo(2) was hi gher than finger Spo(2) at an intracuff pressure of 10-60 cm H2O tall: P < 0.001), but was lower when the intracuff pressure was zero (P < 0.0001). Sa o(2) was always higher than finger Sao(2) (P < 0.0001). Tracheal Spo(2) was lower at an intracuff pressure of zero (P < 0.0001), but was otherwise sim ilar over the range of intracuff pressures. Sao, and finger Spo(2) did not vary with intracuff pressure. Tracheal Spo(2) agrees more closely with Sao( 2) than finger Spo(2) at an intracuff pressure of 10-60 cm H2O (mean differ ence < 0.2%). We conclude that left tracheal Spo(2) is feasible and provide s similar readings to arterial blood samples and more accurate readings tha n finger oximetry in hemodynamically stable, well oxygenated, anesthetized patients with normal thoracic anatomy. Tracheal oximetry readings are not p rimarily derived from the tracheal mucosa. The technique merits further eva luation.