Agreement between arterial partial pressure of carbon dioxide and saturation of hemoglobin with oxygen values obtained by direct arterial blood measurements versus noninvasive methods in conscious healthy and ill foals.

The research article investigates the accuracy of noninvasive procedures in determining the arterial partial pressure of carbon dioxide and hemoglobin oxygen saturation levels in newborn foals. The study suggests that both noninvasive methods, nasal capnography and pulse oximetry, offer clinically applicable and reliable estimates, however, should not replace standard direct measurements.

Research Background

• The study’s primary aim is to ascertain the level agreement between noninvasive measures – end-tidal partial pressure of carbon dioxide (PetCO(2)) and oxygen saturation of hemoglobin as determined by pulse oximetry (SpO(2)) – with the direct measurements of PaCO(2) and the calculated oxygen saturation of hemoglobin in arterial blood (SaO(2)) in conscious healthy and sick foals.

Methodology

• In this validation study, the researchers conducted arterial blood gas analysis on 10 healthy and 21 ill foals examined at a veterinary teaching hospital. They kept note of direct measurements of PaCO(2) and PaO(2), along with SaO(2).
• Simultaneously, they measured PetCO(2) using a capnograph inserted into a foal’s nostril, and SpO(2) was determined using a reflectance probe placed at the base of the foal’s tail.
• Paired values were then analyzed using Pearson correlation coefficients, and the level of agreement was assessed using the Bland-Altman method.

Results

• The average difference between the PaCO(2) and PetCO(2) measurements was 0.1 ± 5.0 mm Hg. These results demonstrated a significant, strong correlation (r = 0.779) and a good agreement between PaCO(2) and PetCO(2).
• Between SaO(2) and SpO(2), the average difference was found to be 2.5 ± 3.5%. These values exhibited a significant moderate correlation (r = 0.499) and an acceptable agreement.

Conclusion

• The results establish that both noninvasive techniques, nasal capnography for PetCO(2) determination and pulse oximetry for SpO(2) measurement, offer valid and precise indirect methods for estimating and monitoring PaCO(2) and SaO(2) in newborn foals.
• However, the study emphasizes these noninvasive methods should not replace periodic direct measurement of the corresponding parameters.