Reliability of Pulse Oximetry in Titrating Supplemental Oxygen Therapy in Ventilator-Dependent Patients

doi:10.1378/chest.97.6.1420

Chest

Volume 97, Issue 6, June 1990, Pages 1420-1425

https://doi.org/10.1378/chest.97.6.1420 Get rights and content

Pulse oximetry is widely used in the critical care setting, but few studies have examined its usefulness in clinical decision making. One area where pulse oximetry might be useful is in the titration of fractional inspired O₂ concentration (FIo₂) in ventilator-dependent patients. Unfortunately, documented guidelines for this use do not exist, and in a survey of directors of intensive care units, we found that they employed a wide range of target O₂ saturation (SpO₂) values. Consequently, we undertook a study to determine if SpO₂ could be reliably substituted for measurements of arterial O₂ tension (PaO₂) when adjusting FIo₂ in ventilator-dependent patients. We examined a number of SpO₂ target values in 54 critically ill patients aiming for a PaO₂ of ≥60 mm Hg, while minimizing the risk of O₂ toxicity. In white patients, we found that a SpO₂ target of 92 percent was reliable in predicting a satisfactory level of oxygenation. However, in black patients, such a SpO₂ reading was commonly associated with significant hypoxemia (PaO₂ as low as 49 mm Hg), and a higher SpO₂ target, 95 percent, was required. In addition, inaccurate oximetry readings (ie, >4 percent difference between SpO₂ and direct SaO₂ measurements) were more common in black (27 percent) than in white patients (11 percent, p>0.05). In conclusion, a SpO₂ target of 92 percent was reliable when titrating supplemental O₂ in white patients receiving mechanical ventilation; however, in black patients, such a SpO₂ reading was commonly associated with significant hypoxemia, and a higher SpO₂ target, 95 percent, was required to ensure a satisfactory level of oxygenation.

Section snippets

Hospital Survey

A telephone survey was conducted to determine if pulse oximetry is being used to evaluate the response to titrations in FIo₂. The medical directors of 25 hospitals (both university affiliated and private community hospitals) from various geographic locations throughout the United States were contacted. The medical director was asked whether he/she used pulse oximetry to titrate FIo₂ in ventilator-dependent patients, and, if so, what target SpO₂ he/she employed.

Patient Study

Patients: Fifty-four patients

Hospital Survey

The target SpO₂ values employed by the directors of ICUs at the various institutions that we surveyed are displayed in Figure 1. A wide scatter of target SpO₂ values is apparent (85 percent to 95 percent). In addition, one physician decreased FIo₂ until a SpO₂ of 90 percent was reached, at which time, FIo₂ was increased by 0.10. Of note was the fact that 64 percent of the physicians employed a SpO₂ target of 90 percent or less. Although 22 (88 percent) of the ICU directors stated that they used

DISCUSSION

This study indicates that physicians employ a wide variety of target SpO₂ values when using pulse oximetry to assess the response to titrations of FIo₂ in ventilator-dependent patients (Fig 1). Although we found that pulse oximetry was reliable when assessing the response to adjustments of FIo₂, the optimal SpO₂ target value depended on the patient’s skin color. In white patients, a SpO₂ target of 92 percent was reliable in predicting a satisfactory level of oxygenation. In black patients,

ACKNOWLEDGMENT

The authors gratefully thank Drs. Robert F. Lodato and Gilbert D’Alonzo for their helpful comments, and the medical residents and nursing staff for their assistance with this project. In addition, we are indebted to the young woman whose medical problem stimulated this study.

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Increasing evidence suggest a racial bias in pulse oximetry measurement, but this was under investigated in Asian pediatric populations.
Via the Pediatric Intensive Care database, this retrospective study included pediatric patient records of arterial oxygen saturation (SaO₂) and oxygen saturation on pulse oximetry (SpO₂) measured within 10 min. Discrepancy was examined, and potential predictors of occult hypoxemia (defined as SaO₂ <88% with the paired SpO₂ ≥92%) as well as its association with outcomes were explored by logistic regression.
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To determine whether there is racial/ethnical discrepancy between pulse oximetry (SpO₂) and oxygen saturation (SaO₂) in patients receiving extracorporeal membrane oxygenation (ECMO).
This was a retrospective observational study at a tertiary academic ECMO center with adults (>18 years) on venoarterial (VA) or venovenous (VV) ECMO. Datapoints were excluded if oxygen saturation ≤70% or SpO₂–SaO₂ pairs were not measured within 10 minutes. The primary outcome was the presence of a SpO₂–SaO₂ discrepancy between different races/ethnicities. Bland–Altman analyses and linear mixed-effects modeling, adjusting for prespecified covariates, were used to assess the SpO₂–SaO₂ discrepancy between races/ethnicities. Occult hypoxemia was defined as SaO₂ <88% with a time-matched SpO₂ ≥92%.
Of 139 patients receiving VA-ECMO and 57 patients receiving VV-ECMO, we examined 16,252 SpO₂–SaO₂ pairs. The SpO₂–SaO₂ discrepancy was greater in VV-ECMO (1.4%) versus VA-ECMO (0.15%). In VA-ECMO, SpO₂ overestimated SaO₂ in Asian (0.2%), Black (0.94%), and Hispanic (0.03%) patients and underestimated SaO₂ in White (−0.06%) and nonspecified race (−0.80%) patients. The proportion of SpO₂–SaO₂ measurements considered occult hypoxemia was 70% from Black compared to 27% from White patients (P < .0001). In VV-ECMO, SpO₂ overestimated SaO₂ in Asian (1.0%), Black (2.9%), Hispanic (1.1%), and White (0.50%) patients and underestimated SaO₂ in nonspecified race patients (−0.53%). In linear mixed-effects modeling, SpO₂ overestimated SaO₂ by 0.19% in Black patients (95% confidence interval, 0.045%-0.33%, P = .023). The proportion of SpO₂–SaO₂ measurements considered occult hypoxemia was 66% from Black compared with 16% from White patients (P < .0001).
SpO₂ overestimates SaO₂ in Asian, Black, and Hispanic versus White patients, and this discrepancy was greater in VV-ECMO versus VA-ECMO, suggesting the need for physiological studies.

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Manuscript received September 21; revision accepted December 18.

Reprint requests: Dr. Jubran, University of Texas at Houston, 6431 Fannin, Houston 77030

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Chest

Reliability of Pulse Oximetry in Titrating Supplemental Oxygen Therapy in Ventilator-Dependent Patients

Section snippets

Hospital Survey

Patient Study

Hospital Survey

DISCUSSION

ACKNOWLEDGMENT

Chest

Chest

Pulse oximetry: a technology that needs direction

Respir Care

History of blood gas analysis. VI. Oximetry

J Clin Monit

State of the art: respiratory monitoring in the intensive care unit

Am Rev Respir Dis

A clinical evaluation of the accuracy of the Nellcor N-100 and Ohmeda 3700 pulse oximeters

J Clin Monit

Adult respiratory distress syndrome

Measurement in medicine: the analysis of method comparison studies

Statistician

Continuous or nocturnal oxygen therapy in hypoxemic chronic obstructive pulmonary disease: a clinical trial

Ann Intern Med

Pulse oximetry

Anesthesiology