Measurement of right atrial oxygen saturation by fiberoptic oximetry accurately reflects mixed venous oxygen saturation in swine

Abstract

Continuous fiberoptic measurement of mixed venous oxygen saturation (SvO2) via a pulmonary artery catheter is a useful, though invasive, monitoring technique. Continuous right atrial venous oxygen saturation measurement by oximetry offers the potential of a significantly less invasive SvO2 measurement. However, catheter motion, character of the vessel, chamber wall reflection, the filtering technique involved in calculating oxygen saturation, and the streaming of venous blood prior to ventricular mixing may influence the feasibility of continuous right atrial (RA) SvO2 measurement. This study investigated the performance of fiberoptically measured RA SvO2, at a position 2 cm from the tricuspid valve, relative to simultaneously measured pulmonary artery (PA) SvO2. Ten pigs were subjected to circulatory shock or chemically induced lung damage. Over a total monitoring period of approximately 40 hours, 464 paired data points were sampled at 5-minute intervals. The difference between the overall means of RA and PA SvO2 was 0.91% with a standard error of the estimate of 4.7%, a regression equation of RA SvO2 = PA SvO2 (0.94 + 2.1) PA So2, and a correlation coefficient of 0.94. Our conclusion, although extrapolated from a pig model, is that fiberoptic SvO2 monitoring may be accomplished less invasively and at a lower cost with a right atrial catheter.

The value of venous oximetry

“…High correlation coefficients between ScvO 2 and SvO 2 under various conditions have been reported [13]. As in the experimental setting, a good correlation between ScvO 2 and SvO 2 could be found in critically ill patients [1,11 • ].…”

Central venous oxygen saturation monitoring in the critically ill patient

“…Scalea et al [57] Baquero-Cano et al [58] Schou et al [59] Davies et al [60] Shah et al [61] Lee et al Patients in the ICU with low, medium, and high cardiac indexes.…”

Continuous central venous oxygen saturation (ScvO2) measurement using a fibre optic catheter in newborn infants.

“…Measurement of the ScvO2 in the right atrium instead of in the pulmonary artery has been reported. 30 31 No evidence was found for a systematic difference between right atrial and pulmonary arterial oxygen saturations over a wide range of haemodynamic conditions, both in animal models and in adults.30-32 Other reports describe a poor correlation between right atrial and pulmonary arterial oxygen saturation when comparing absolute numerical values.33 However, a better correlation was observed comparing subsequent changes of right atrial and pulmonary arterial saturations. 34 In neonatal medicine the use of a pulmonary artery catheter is difficult and hazardous, but umbilical venous catheters have been used frequently with a low incidence of complications.…”