Accuracy and trending capability of haemoglobin measurement by noninvasive pulse co-oximetry in anaesthetized horses.

This study evaluated the reliability of the Masimo Radical-7 pulse co-oximeter, a non-invasive device used to measure and monitor haemoglobin concentration, oxygen saturation and oxygen content in anaesthetized horses. The results show that the device generally gave slightly underestimated readings, but demonstrated acceptable overall accuracy. However, further research is required to understand the device’s ability to accurately track changes in these measurements over time, especially in horses with significant variation in haemoglobin levels during anaesthesia.

Study Background

• Pulse co-oximetry is a non-invasive method to continuously monitor haemoglobin concentration [Hb], oxygen saturation (SaO) and oxygen content (CaO) in a patient’s body.
• The Masimo Radical-7 pulse co-oximeter is one such device studied in this research.
• The examination focused on assessing its accuracy and trending capabilities, particularly under conditions of inhalational anaesthesia in horses.

Study Methodology

• The study was conducted on a group of 23 adult horses that were healthy but undergoing elective surgical procedures.
• Throughout the anaesthesia, paired measurements were collected. These consisted of the pulse co-oximetry-based measurements (SpHb, SpO, and SpOC) and simultaneous arterial blood samples.
• The blood samples were then analysed by a laboratory co-oximeter for total haemoglobin (tHb), SaO and manually calculated CaO.
• The pulse co-oximeter’s precision and trending capability were assessed using various statistical tools including Bland-Altman plots, linear regression analysis, error grid analysis, four-quadrant plot and Critchley polar plot.

Study Results

• Analysis of 101 data pairs indicated that the pulse co-oximeter slightly underestimated tHb, SaO, and CaO.
• However, 99% of data pairs for SpHb were found within Zone A of the error grid, implying an acceptable level of accuracy.
• The perfusion index (PI), a measure of the strength of a patient’s pulse, was monitored to assess the influence of blood flow on the readings.
• The concordance rate for consecutive changes in SpHb and tHb was determined to be 80% for cases with PI ≥ 1% and 91% for cases with PI < 1% using a four-quadrant plot, and 45.8% and 66.6% with a Critchley polar plot.

Conclusions

• The study concluded that pulse co-oximetry with the Masimo Radical-7 device provides acceptably accurate measurements, even with low perfusion index values.
• However, its capability to accurately trend changes in measurements, especially in horses with higher variations in haemoglobin concentration during anaesthesia, necessitates further research.