Dataset Information

Nonlinear Imputation of Pao2/Fio2 From Spo2/Fio2 Among Patients With Acute Respiratory Distress Syndrome.

ABSTRACT:

Background

ARDS is an important clinical problem. The definition of ARDS requires testing of arterial blood gas to define the ratio of Pao2 to Fio2 (Pao2/Fio2 ratio). However, many patients with ARDS do not undergo blood gas measurement, which may result in underdiagnosis of the condition. As a consequence, a method for estimating Pao2 on the basis of noninvasive measurements is desirable.

Methods

Using data from three ARDS Network studies, we analyzed the enrollment arterial blood gas measurements to compare nonlinear with linear and log-linear imputation methods of estimating Pao2 from percent saturation of hemoglobin with oxygen as measured by pulse oximetry (Spo2). We compared mortality on the basis of various measured and imputed Pao2/Fio2 ratio cutoffs to ensure clinical equivalence.

Results

We studied 1,184 patients, in 707 of whom the Spo2 ? 96%. Nonlinear imputation from the Spo2/Fio2 ratio resulted in lower error than linear or log-linear imputation (P < .001) for patients with Spo2 ? 96% but was equivalent to log-linear imputation in all patients. Ninety-day hospital mortality was 26% to 30%, depending on the Pao2/Fio2 ratio, whether nonlinearly imputed or measured. On multivariate regression, the association between imputed and measured Pao2 varied by use of vasopressors and Spo2.

Conclusions

A nonlinear equation more accurately imputes Pao2/Fio2 from Spo2/Fio2 than linear or log-linear equations, with similar observed hospital mortality depending on Spo2/Fio2 ratio vs measured Pao2/Fio2 ratios. While further refinement through prospective validation is indicated, a nonlinear imputation appears superior to prior approaches to imputation.

SUBMITTER: Brown SM

PROVIDER: S-EPMC4980543 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Publications

Nonlinear Imputation of Pao2/Fio2 From Spo2/Fio2 Among Patients With Acute Respiratory Distress Syndrome.

Brown Samuel M SM Grissom Colin K CK Moss Marc M Rice Todd W TW Schoenfeld David D Hou Peter C PC Thompson B Taylor BT Brower Roy G RG

Chest 20160119 2

<h4>Background</h4>ARDS is an important clinical problem. The definition of ARDS requires testing of arterial blood gas to define the ratio of Pao2 to Fio2 (Pao2/Fio2 ratio). However, many patients with ARDS do not undergo blood gas measurement, which may result in underdiagnosis of the condition. As a consequence, a method for estimating Pao2 on the basis of noninvasive measurements is desirable.<h4>Methods</h4>Using data from three ARDS Network studies, we analyzed the enrollment arterial bloo ...[more]

PMID: 26836924

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Project description:OBJECTIVES:In the contemporary ICU, mechanically ventilated patients may not have arterial blood gas measurements available at relevant timepoints. Severity criteria often depend on arterial blood gas results. Retrospective studies suggest that nonlinear imputation of PaO2/FIO2 from SpO2/FIO2 is accurate, but this has not been established prospectively among mechanically ventilated ICU patients. The objective was to validate the superiority of nonlinear imputation of PaO2/FIO2 among mechanically ventilated patients and understand what factors influence the accuracy of imputation. DESIGN:Simultaneous SpO2, oximeter characteristics, receipt of vasopressors, and skin pigmentation were recorded at the time of a clinical arterial blood gas. Acute respiratory distress syndrome criteria were recorded. For each imputation method, we calculated both imputation error and the area under the curve for patients meeting criteria for acute respiratory distress syndrome (PaO2/FIO2 ? 300) and moderate-severe acute respiratory distress syndrome (PaO2/FIO2 ? 150). SETTING:Nine hospitals within the Prevention and Early Treatment of Acute Lung Injury network. PATIENTS:We prospectively enrolled 703 mechanically ventilated patients admitted to the emergency departments or ICUs of participating study hospitals. INTERVENTIONS:None. MEASUREMENTS AND MAIN RESULTS:We studied 1,034 arterial blood gases from 703 patients; 650 arterial blood gases were associated with SpO2 less than or equal to 96%. Nonlinear imputation had consistently lower error than other techniques. Among all patients, nonlinear had a lower error (p < 0.001) and higher (p < 0.001) area under the curve (0.87; 95% CI, 0.85-0.90) for PaO2/FIO2 less than or equal to 300 than linear/log-linear (0.80; 95% CI, 0.76-0.83) imputation. All imputation methods better identified moderate-severe acute respiratory distress syndrome (PaO2/FIO2 ? 150); nonlinear imputation remained superior (p < 0.001). For PaO2/FIO2 less than or equal to 150, the sensitivity and specificity for nonlinear imputation were 0.87 (95% CI, 0.83-0.90) and 0.91 (95% CI, 0.88-0.93), respectively. Skin pigmentation and receipt of vasopressors were not associated with imputation accuracy. CONCLUSIONS:In mechanically ventilated patients, nonlinear imputation of PaO2/FIO2 from SpO2/FIO2 seems accurate, especially for moderate-severe hypoxemia. Linear and log-linear imputations cannot be recommended.

Project description:Managing the oxygen saturation of preterm infants to a target range has been the standard of care for a decade. Changes in target ranges have been shown to significantly impact mortality and morbidity. Selecting and implementing the optimal target range are complicated not only by issues of training, but also the realities of staffing levels and demands. The potential for automatic control is becoming a reality. Results from the evaluation of different systems have been promising and our own experience encouraging.This study was conducted in two tertiary level newborn nurseries, routinely using an automated FiO2-SpO2 control system (Avea-CLiO2, Yorba Linda CA, USA). The aim of this study was to compare the performance of the system as used routinely (set control range of 87-93% SpO2), to a narrower higher range (90-93%). We employed a 12-hour cross-over design with the order of control ranges randomly assigned for each of up to three days. The primary prospectively identified end points were time in the 87-93% SpO2 target range, time at SpO2 extremes and the distribution of the SpO2 exposure.Twenty-one infants completed the study. The infants were born with a median EGA of 27 weeks and studied at a median age of 17 days and weight of 1.08 kg. Their median FiO2 was 0.32; 8 were intubated, and the rest noninvasively supported (7 positive pressure ventilation and 6 CPAP). The control in both arms was excellent, and required less than 2 manual FiO2 adjustments per day. There were no differences in the three primary endpoints. The narrower/higher set control range resulted in tighter control (IQR 3.0 vs. 4.3 p < 0.001), and less time with the SpO2 between 80-86 (6.2% vs. 8.4%, p = 0.006).We found that a shift in the median of the set control range of an automated FiO2-SpO2 control system had a proportional effect on the median and distribution of SpO2 exposure. We found that a dramatic narrowing of the set control range had a disproportionally smaller impact. Our study points to the potential to optimize SpO2 targeting with an automated control system.

Dataset Information

Nonlinear Imputation of Pao2/Fio2 From Spo2/Fio2 Among Patients With Acute Respiratory Distress Syndrome.

Background

Methods

Results

Conclusions

Publications

Nonlinear Imputation of Pao2/Fio2 From Spo2/Fio2 Among Patients With Acute Respiratory Distress Syndrome.

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