Validation of oxygen saturation monitoring in neonates

Abstract

Background: Pulse oximetry is commonly used to monitor oxygenation in neonates, but cannot detect variations in hemoglobin. Venous and arterial oxygen saturations are rarely monitored. Few data are available to validate measurements of oxygen saturation in neonates (venous, arterial, or pulse oximetric). Purpose To validate oxygen saturation displayed on clinical monitors against analyses (with correction for fetal hemoglobin) of blood samples from neonates and to present the oxyhemoglobin dissociation curve for neonates.

Method: Seventy-eight neonates, 25 to 38 weeks' gestational age, had 660 arterial and 111 venous blood samples collected for analysis.

Results: The mean difference between oxygen saturation and oxyhemoglobin level was 3% (SD 1.0) in arterial blood and 3% (SD 1.1) in venous blood. The mean difference between arterial oxygen saturation displayed on the monitor and oxyhemoglobin in arterial blood samples was 2% (SD 2.0); between venous oxygen saturation displayed on the monitor and oxyhemoglobin in venous blood samples it was 3% (SD 2.1) and between oxygen saturation as determined by pulse oximetry and oxyhemoglobin in arterial blood samples it was 2.5% (SD 3.1). At a Pao(2) of 50 to 75 mm Hg on the oxyhemoglobin dissociation curve, oxyhemoglobin in arterial blood samples was from 92% to 95%; oxygen saturation was from 95% to 98% in arterial blood samples, from 94% to 97% on the monitor, and from 95% to 97% according to pulse oximetry.

Conclusions: The safety limits for pulse oximeters are higher and narrower in neonates (95%-97%) than in adults, and clinical guidelines for neonates may require modification.

Figure 1

Arterial oxyhemoglobin sigmoid curves with Pao₂, for arterial oxyhemoglobin, Sao₂, monitor Sao₂, and Spo₂. Abbreviations: Sao₂, arterial oxygen saturation; Spo₂, pulse oximetry oxygen saturation.

Figure 2

Venous oxyhemoglobin sigmoid curves with Pvo₂, for venous oxyhemoglobin, Svo₂, monitor Svo₂, and Spo₂. Abbreviations: Pvo₂, venous oxygen tension; Spo₂, pulse oximetry oxygen saturation; Svo₂, venous oxygen saturation.

Figure 3

Oxyhemoglobin sigmoid curves for total merged arterial and venous blood samples with Po₂, for oxyhemoglobin, oxygen saturation, monitor oxygen saturation, and Spo₂. Abbreviation: Spo₂, pulse oximetry oxygen saturation.