Accuracy of two wavelength pulse oximetry in neonates and infants

Accuracy of Pulse Oximetry in the Presence of Fetal Hemoglobin-A Systematic Review

Continuous monitoring of arterial oxygen saturation by pulse oximetry (SpO2) is the main method to guide respiratory and oxygen support in neonates during postnatal stabilization and after admission to neonatal intensive care unit. The accuracy of these devices is therefore crucial. The presence of fetal hemoglobin (HbF) in neonatal blood might affect SpO2 readings. We performed a systematic qualitative review to investigate the impact of HbF on SpO2 accuracy in neonates. PubMed/Medline, Embase, Cumulative Index to Nursing & Allied Health database (CINAHL) and Cochrane library databases were searched from inception to January 2021 for human studies in the English language, which compared arterial oxygen saturations (SaO2) from neonatal blood with SpO2 readings and included HbF measurements in their reports. Ten observational studies were included. Eight studies reported SpO2-SaO2 bias that ranged from −3.6%, standard deviation (SD) 2.3%, to +4.2% (SD 2.4). However, it remains unclear to what extent this depends on HbF. Five studies showed that an increase in HbF changes the relation of partial oxygen pressure (paO2) to SpO2, which is physiologically explained by the leftward shift in oxygen dissociation curve. It is important to be aware of this shift when treating a neonate, especially for the lower SpO2 limits in preterm neonates to avoid undetected hypoxia.

A pilot study of neonatal and pediatric esophageal pulse oximetry

BACKGROUND

In this pilot study we explored the suitability of the esophagus as a new measuring site for blood oxygen saturation (Spo(2)) in neonates.

METHODS

A new miniaturized esophageal pulse oximeter has been developed. Five patients (one child and four neonates) were studied.

RESULTS

Spo(2) values were obtained in the esophagus of all patients. A Bland and Altman plot of the difference between Spo(2) values from the esophageal pulse oximeter and a commercial toe pulse oximeter against their mean showed that the bias and the limits of agreement between the two pulse oximeters were +0.3% and +1.7% to -1.0%, respectively.

CONCLUSIONS

This study suggests that the esophagus can be used as an alternative site for monitoring blood oxygen saturation in children and neonates.

The measurement of accurate fetal hemoglobin and related oxygen saturation by the hemoximeter

BACKGROUND

The purposes of this study were to examine the accuracy of fetal hemoglobin (HbF) as quickly measured by the hemoximeter, verified by the high-performance liquid chromatography method, and to examine related oxygen saturation (SO(2)) measurements in neonates.

METHODS

Thirty-nine neonates with gestational ages ranging from 25 to 38 weeks were investigated (n=280 blood samples). Twenty younger premature neonates had blood transfusions (n=188 blood samples, 72 before and 116 after transfusions), and 19 older neonates did not.

RESULTS

The bias of the hemoximeter was 23% (+/-9.1) against the HPLC; 25% (+/-7.9) before, and 19% (+/-8.6) after blood transfusions (all P<0.001), for HbF measurements. A regression line (HbFt by the HPLC=8.46+0.7 x HbF by the hemoximeter) has been provided for the prediction. Oxyhemoglobin dissociation curves with the status of (before and after) blood transfusions were presented. In relation to oxygen tension values of 50-75 mm Hg, in addition to the right-shifted oxyhemoglobin dissociation curves, pulse oximeter ranged from 95 to 98% before the transfusions, but decreased to 94 to 96% after the blood transfusions.

CONCLUSIONS

Accurate HbF and related oxygen saturation measurements need to be determined, especially for premature neonates, to minimize the risk of oxygen toxicity.

Operational evaluation of pulse oximetry in NICU patients with arterial access

OBJECTIVE

To investigate pulse oximetry in neonates who require arterial access as represented by the clinical data recorded to manage their care.

STUDY DESIGN

Analysis of simultaneous SpO(2) and SaO(2) from: 7-year historical NICU data (N=31905); 4-month prospective NICU data (N=566); verification data using two hemoximeters (N=52); and NICU data from two collaborating centers (N=95 and 168). The bias function (SpO(2)-SaO(2)) was regressed against the measured "gold" standard, SaO(2).

RESULTS

A significant negative correlation was found for each of the data sets between the bias function and SaO(2). This bias was similar for devices from several manufacturers (Datex-Ohmeda, Masimo, Nellcor, and Spacelabs). Maximum operational performance occurred with peaks between 92 and 97% SaO(2), but declined markedly above and below this narrow range. In all, 71 to 95% of patients exhibited data with significant bias(.)

CONCLUSION

These operational data suggest that with the methodology and devices currently in use, SpO(2) values in most all neonates who require arterial lines inaccurately correlate with measured arterial saturation.

Oxygen therapy for infants with chronic lung disease

Supplemental oxygen is a safe and effective treatment for infants with established chronic lung disease who are not at risk of further progression of retinopathy of prematurity (ROP). Oxygen saturations of < 92% should be avoided and a target range of at least 94-96% aimed for. The saturation target range for very preterm infants at risk of developing ROP is more controversial, but the therapeutic index is probably considerably narrower.

Accuracy of two pulse oximeters at low arterial hemoglobin-oxygen saturation

OBJECTIVE

To evaluate the performance of two pulse oximeters in the measurement of arterial hemoglobin saturation in hypoxemic children.

DESIGN

Prospective, repeated-measures observational study.

SETTING

A 16-bed pediatric intensive care unit in a children's tertiary hospital.

PATIENTS

Sixty-six patients with arterial saturation of <90%.

INTERVENTIONS

Three arterial blood samples were taken from each subject during a 48-hr period. Pulse oximeter measurements of arterial saturation were compared with arterial saturation determined by cooximetry.

MEASUREMENTS AND MAIN RESULTS

Arterial saturation was measured using one or both pulse oximeters (SpO2) and compared with the arterial hemoglobin saturation determined by cooximetry (SaO2). Sixty-two subjects were studied, using the Ohmeda pulse oximeter giving 185 data points (78 with saturations <75% [defined by the average of pulse oximeter and cooximeter]); 53 subjects were studied, using the Hewlett-Packard pulse oximeter yielding 155 data points (60 with saturations <75%). SpO2 ranged from 24% to 94%. Bias and precision of the Ohmeda pulse oximeter were -2.8% and 4.8% >75% and -0.8% and 8.0% <75%. Bias and precision of the Hewlett-Packard pulse oximeter were -0.5% and 5.1% >75% and 0.4% and 4.6% <75%. Intrapatient regression coefficient (r) for the differences between pulse oximeter and cooximeter was 0.58 for the Ohmeda and 0.59 for the Hewlett-Packard. Regression coefficients for predicting change in cooximeter value given a change in the Ohmeda pulse oximeter were 0.59 and 0.71 <75% and >75%, respectively. Similar coefficients for the Hewlett-Packard pulse oximeter were 0.50 and 0.70, respectively.

CONCLUSION

The performance of the Ohmeda pulse oximeter deteriorated below an SpO2 of 75%. The Hewlett-Packard pulse oximeter performed consistently above and below an SpO2 of 75%. The ability of both pulse oximeters to reliably predict change in SaO2 based on change in pulse oximetry was limited. We recommend measurement of PaO2 or SaO2 for important clinical decisions.

Episodes of spontaneous desaturations in infants with chronic lung disease at two different levels of oxygenation

The optimal range of pulse oximeter oxygen saturation (SaO2) for infants with chronic lung disease (CLD) has not been well established. We quantified episodes of spontaneous desaturation, at two different ranges of SaO2. For 1 hr each, we alternatively administered inspired O2 concentrations (FiO2) necessary to maintain an SaO2 of 94-96% or 87-91% to 21 patients (mean birth weight, 865 g; gestational age, 27.3 weeks; postnatal age 40.6 days) with CLD (defined by FiO2 > 0.21 at > or = 28 days and radiographic evidence). SaO2 was monitored with the Nellcor N-200 oximeter and analyzed by a computer program (SatMaster). The percentage of time the infants desaturated to levels of SaO2 < 85 and < 80% revealed significantly fewer spontaneous episodes during the hour of higher baseline SaO2 (P < 0.0002). Comparison of episodes of spontaneous desaturation to SaO2 < 80 and < 85%, lasting 0-15, 16-30, 31-45 sec also showed significant differences between the two levels of SaO2. We conclude that when infants with CLD are maintained at a higher SaO2 they probably experience fewer episodes of spontaneous desaturations, because of less alveolar hypoxia. We believe that attempts at weaning the FiO2 should be tempered with the need of maintaining an adequate SaO2. Therefore, prolonged monitoring of oxygenation in infants with CLD at different levels of SaO2 could be helpful during the weaning process.

Hemoglobin desaturation during sleep and daytime in patients with cystic fibrosis and severe airway obstruction

Transcutaneous hemoglobin saturation by pulse oximetry was evaluated during sleep and for 2-3 h during the day in 31 patients with cystic fibrosis (median age 15.2 years; range 7.6-33.6 years) and severe airway obstruction. Pulse oximetry readings were analyzed as a cumulative percentage of time in which oxygen saturation was < 90% during both sleep and daytime. Each patient was also examined using clinical and radiological scores, spirometry and arterial blood-gas analysis. The agreement between arterial and transcutaneous saturation was evaluated in 29 patients. The difference between transcutaneous and arterial saturation was 2.4 +/- 2.0% and it increased as arterial saturation decreased. Clinical and radiological scores and spirometry parameters showed a poor correlation with both overnight and daytime desaturation. An arterial saturation < 94% may indicate a risk of consistent desaturation. This occurred for more than 50% of the time in 11 of 20 patients during sleep and in 5 of 20 patients during daytime hours.

Potential errors in pulse oximetry. III: Effects of interferences, dyes, dyshaemoglobins and other pigments

Electrosurgery, patient motion and some types of lighting can cause errors in saturation readout; it is recommended that probes should be shielded from ambient lighting. Intravenous dyes can introduce gross but transient errors, which may also be present in in vitro measurements. Carboxyhaemoglobin causes overestimation of fractional saturation by an amount less than, but possibly close to, the percent of carboxyhaemoglobin present. Methaemoglobin causes the pulse oximeter readout to tend towards 85%. Fetal haemoglobin and bilirubin introduce no significant error, although they may interfere with in vitro measurements. Skin pigmentation can result in a slight decrease in accuracy. Nail polish may cause up to 6% underestimation of saturation; it is recommended that probes should be mounted sideways on fingers with nail polish or long nails. Adhesive tape or a vinyl glove across the probe has no demonstrable effect on accuracy. A blood sample should be analysed by a multiwavelength in vitro oximeter when an erroneous pulse oximeter reading is suspected, although errors may be introduced in the in vitro reading by fetal haemoglobin, bilirubin and intravenous dyes.

Pulse oximetry versus measured arterial oxygen saturation: a comparison of the Nellcor N100 and the Biox III

Pulse oximetry is noninvasive, fast, and simple, making it a very popular way of assessing oxygenation in pediatric patients. However, there are few studies that establish the accuracy of this technology over a wide range of oxygen saturations in children. This study, done in 47 children aged from 1 day to 16 years with congenital heart disease and undergoing cardiac catheterization, compared the direct measurement of arterial oxygen saturation to values from pulse oximetry. Oxygen saturation was measured by an IL-282 Co-oximeter, which also measured carboxyhemoglobin and methemoglobin, and was compared to values obtained from both a Biox III and Nellcor N100. Both pusle oximeters gave values that closely correlated with the actual saturation (r = 0.91 and 0.93, respectively) with standard errors of the estimate of 4.1 and 3.2%, respectively. For both devices, the error increased with decreasing saturations, being progressively larger below a saturation of 80%. The difference between the actual saturation and that measured by pulse oximetry bore no relationship to the presence of carboxyhemoglobin, methemoglobin, fetal hemoglobin, bilirubin, cardiac index, or age of the patient. In conclusion, pulse oximetry, while a very useful technology in pediatrics, must be interpreted with some caution in children with severe cyanosis.