Oxygen Saturation Index and Severity of Hypoxic Respiratory Failure

Abstract

Background: The oxygenation index (OI = mean airway pressure, MAP × FiO₂ × 100 : PaO₂) is used to assess the severity of hypoxic respiratory failure (HRF) and persistent pulmonary hypertension of the newborn (PPHN). An indwelling arterial line or arterial punctures are necessary to obtain PaO₂ for the calculation of OI. Oxygenation can be continuously and noninvasively assessed using pulse oximetry. The use of the oxygen saturation index (OSI = MAP × FiO₂ × 100 : SpO₂) can be an alternate method of assessing the severity of HRF. Objective: To evaluate the correlation between OSI and OI in the following: (1) neonates with HRF and (2) a lamb model of meconium aspiration syndrome. Methods: Human neonates: a retrospective chart review of 74 ventilated late preterm/term neonates with indwelling arterial access and SpO₂ values in the first 24 h of life was conducted. OSI and OI were calculated and correlated. Lamb model: arterial blood gases were drawn and preductal SpO₂ was documented in 40 term newborn lambs with asphyxia and meconium aspiration. OI and OSI were calculated and correlated with pulmonary vascular resistance (PVR). Results: Mean values of OSI and OI showed a correlation coefficient of 0.952 in neonates (mean value of 308 observations in 74 neonates) and 0.948 in lambs (mean value of 743 observations in 40 lambs). In lambs, with increasing PVR, there was a decrease in OI and OSI. Conclusion: OSI correlates significantly with OI in infants with HRF. This noninvasive measure may be used to assess the severity of HRF and PPHN in neonates without arterial access.

Assessing Initial Response to High-Frequency Jet Ventilation in Premature Infants With Hypercapnic Respiratory Failure

“…OSI was a secondary outcome observed between cohorts to assess the severity of hypoxic respiratory failure as described by Rawat et al 16 OSI was similar between groups before and 1 h after conversion to HFJV and was significantly higher in non-responders at hour 4. Additionally, F IO 2 was significantly higher for non-responders during this time, at similar ventilating pressures, which may suggest that these subjects may have benefited from increased PEEP.…”

“…However, these metrics have been validated in children. 16,21 Fourth, long-term follow up was limited due to the nature of the study; therefore, important long-term pulmonary, neurologic, and developmental outcomes were not assessed. Last, we did not utilize severity scoring because many of these systems (eg, newborn respiratory distress scoring system, clinical risk index for babies, and score for neonatal acute physiology) were developed to evaluate the initial risk at time of admission and are limited to the first hours and days of life.…”

An Investigation of Various Inspiratory Times and Inflation Pressures during Airway Pressure Release Ventilation

“…Data was transferred into SPSS® for statistical analyses. Subject pre-APRV dosing and post-APRV dosing P/F ratio, OI, OSI, and MSOFA scores were calculated to represent validated predictors of clinical outcomes [28][29][30][31][32].…”

“…A p-value < 0.2 to start was considered statistically significant for all covariates. The P/F ratio, OI, OSI, and MSOFA scores were calculated utilizing original versions of each applicable equation -listed in the "Metrics" section [28][29][30][31][32].…”

“…A standard equation was used for calculating OI: (FiO 2 × MAWP)/PaO 2 × 100 [29]. Due to the intermittent unavailability of certain subject's PaO 2 , pulsatile oxygen saturation (SpO 2 ) was used as a replacement as necessary, allowing the calculation of a modified OI (OSI): (FiO 2 × MAWP/SpO 2 × 100) [28]. The MSOFA score was calculated based on the original table by Grissom, et al [32].…”