Evaluation of Correlation and Agreement between SpO2/FiO2 ratio and PaO2/FiO2 ratio in Neonates

Objectives This article evaluates correlation and agreement between oxygen saturation (SpO2)/fraction of inspired oxygen (FiO2) (SF) ratio and partial pressure of oxygen (PaO2)/FiO2 (PF) ratio. It also derives and validates predictive PF ratio from noninvasive SF ratio measurements for clinically relevant PF ratios and derives SF ratio equivalent of PF ratio cutoffs used to define acute lung injury (ALI, PF < 300) and acute respiratory distress syndrome (ARDS, PF < 200).

Methods Retrospective cohort study including neonates with respiratory failure over a 6-year study period. Correlation and agreement between PF ratio with SF ratio was analyzed by Pearson's correlation coefficient and Bland–Altman analysis. Generalized estimating equation was used to derive PF ratio from measured PF ratio and derive corresponding SF ratio for PF ratio cutoffs for ALI and ARDS.

Results A total of 1,019 paired measurements from 196 neonates with mean 28 (± 4.7) weeks' gestational age and 925 (± 1111) g birth weight were analyzed. Strong correlation was noted between SF ratio and PF ratio (r = 0.90). Derived PF ratios from regression (1/PF = –0.0004304 + 2.0897987/SF) showed strong accuracy measures for PF ratio cutoffs < 200 (area under the curve [AUC]: 0.85) and < 100 (AUC: 0.92) with good agreement. Equivalent SF ratio to define ALI was < 450, moderate ARDS was < 355, and severe ARDS was < 220 with strong accuracy measures (AUC > 0.81, 0.84, and 0.93, respectively).

Conclusion SF ratio correlated strongly with PF ratio with good agreement between derived PF ratio from noninvasive SpO2 source and measure PF ratio. Derived PF ratio may be useful to reliably assess severity of respiratory failure in neonates. Further studies are needed to validate SF ratio with clinical illness severity and outcomes.

Evaluation of Oxygen Saturation Index Compared With Oxygenation Index in Neonates With Hypoxemic Respiratory Failure

IMPORTANCE

Oxygenation index (OI), an invasive measurement, is routinely used as a marker of severity of hypoxemic respiratory failure in neonates. Oxygen saturation index (OSI) is a noninvasive measurement and has been shown to be a reliable surrogate marker of OI in children and adults with respiratory failure.

OBJECTIVES

To evaluate the correlation of OI with OSI and to derive and validate predictive OI from noninvasive OSI measurements for clinically relevant OI values.

DESIGN, SETTING, AND PARTICIPANTS

For this retrospective cohort study, 220 neonates requiring invasive mechanical ventilation for hypoxic respiratory failure during the first 3 days of admission were recruited from a level III neonatal intensive care unit during a 6-year period, from January 1, 2012, to December 31, 2017. Data were analyzed from January 2017 to December 2017.

MAIN OUTCOMES AND MEASURES

The primary outcome was correlation of OI with OSI, analyzed using Pearson correlation coefficient. The secondary outcome was derivation and validation of OI from OSI. The data were split into derivative samples, from which a predictive equation for OI was derived using generalized linear model, and a validation sample was used to assess the predictive ability of the derived OI. Bland-Altman plot was used to assess agreement between derived OI and measured OI.

RESULTS

A total of 1442 paired OI and OSI measurements from 220 infants (190 preterm and 30 term; median [interquartile range] gestational age, 29 [26-33] weeks; mean [SD] birth weight, 1602 [1092] g) were recorded during the study. The median (interquartile range) number of samples was 5 (3-9) per patient. Overall, OI and OSI showed strong correlation (r = 0.89). The correlation was stronger in preterm infants (<28 weeks, r = 0.93; 28-33 weeks, r = 0.93) and within an oxygen saturation range of 85% to 95% (r = 0.94). The predictive derivative equation showed a strong linear association and good agreement in both derivation and validation data sets, with strong accuracy measures of derived OI for OI cutoffs of 5, 10, 15, 20, and 25.

CONCLUSIONS AND RELEVANCE

A strong correlation of OI with OSI was found. Derived OI from OSI was in good agreement and strongly predictive of clinically relevant OI cutoffs from 5 to 25. Oxygenation index derived from noninvasive sources may be useful to reliably assess severity of respiratory failure and response to therapy on a continuous basis.

Premedication Use Before Nonemergent Intubation in the Newborn Infant

OBJECTIVE

In 2010, an American Academy of Pediatrics (AAP) clinical report recommended that except for emergent situations, premedication should be used for all endotracheal intubations in newborns. The purpose of this study is to ascertain the current practice of premedication before elective intubation.

STUDY DESIGN

An online, survey-based questionnaire on the practice of premedication before nonemergent intubations was distributed via e-mail to neonatologists who are members of the Perinatal Section of the AAP.

RESULTS

Although 72% of respondents believed premedication should be used in nonemergent intubations, only 34% of the respondents report frequently premedicating before intubation with significant variation among the neonatal units (46% among level 4 units and 27% in level 3 and 2 units) p = 0.000. About 44% of respondents report having a written protocol or guideline on premedication which significantly correlated with the use of premedication (62% in level 4, 33% in level 3, and 16% in level 2 units), p = 0.000.

CONCLUSION

Despite a recent AAP clinical report recommending the use of premedication before nonemergent endotracheal intubation, only one-third of neonatologists report frequent use of premedication and less than half of the institutions have a written protocol on premedication.