Research

A preliminary study on the monitoring of mixed venous oxygen saturation through the left main bronchus

Xiang-rui Wang¹ , Yong-jun Zheng² , Jie Tian² , Zheng-hong Wang² and Zhi-ying Pan²

¹Professor of anesthesiology, Department of Anesthesiology, Renji Hospital affiliated to Shanghai Second Medical University, 1630 Dongfang Road, Shanghai, 200127, China

²Resident, Department of Anesthesiology, Renji Hospital affiliated to Shanghai Second Medical University, 1630 Dongfang Road, Shanghai, 200127, China

author email corresponding author email

Critical Care 2006, 10:R7doi:10.1186/cc3914

Published:	6 December 2005

Abstract

Introduction

The study sought to assess the feasibility and accuracy of measuring mixed venous oxygen saturation (SvO₂) through the left main bronchus (SpO_2trachea)

Methods

Twenty hybrid pigs of each sex were studied. After anesthesia, a Robertshaw double-lumen tracheal tube with a single-use pediatric pulse oximeter attached to the left lateral surface was introduced toward the left main bronchus of the pig by means of a fibrobronchoscope. Measurements of SpO_2trachea and oxygen saturation from pulmonary artery samples (SvO_2blood) were performed with an intracuff pressure of 0 to 60 cmH₂O. After equilibration, hemorrhagic shock was induced in these pigs by bleeding to a mean arterial blood pressure of 40 mmHg. With the intracuff pressure maintained at 60 cmH₂O, SpO_2trachea and SvO_2blood were obtained respectively during the pre-shock period, immediately after the onset of shock, 15 and 30 minutes after shock, and 15, 30, and 60 minutes after resuscitation.

Results

SpO_2trachea was the same as SvO_2blood at an intracuff pressure of 10, 20, 40, and 60 cmH₂O, but was reduced when the intracuff pressure was zero (p < 0.001 compared with SvO_2blood) in hemodynamically stable states. Changes of SpO_2trachea and SvO_2blood corresponded with varieties of cardiac output during the hemorrhagic shock period. There was a significant correlation between the two methods at different time points.

Conclusion

Measurement of the left main bronchus SpO₂ is feasible and provides similar readings to SvO_2blood in hemodynamically stable or in low saturation states. Tracheal oximetry readings are not primarily derived from the tracheal mucosa. The technique merits further evaluation.