Noninvasive Ventilation in Preterm Infants: Factors Influencing Weaning Decisions and the Role of the Silverman-Andersen Score

Abstract

The factors influencing weaning of preterm infants from noninvasive ventilation (NIV) are poorly defined and the weaning decisions are often driven by subjective judgement rather than objective measures. To standardize quantification of respiratory effort, the Silverman-Andersen Score (SAS) was included in our nursing routine. We investigated the factors that steer the weaning process and whether the inclusion of the SAS would lead to more stringent weaning. Following SAS implementation, we prospectively evaluated 33 neonates born ≤ 32 + 0 weeks gestational age. Age-, weight- and sex-matched infants born before routine SAS evaluation served as historic control. In 173 of 575 patient days, NIV was not weaned despite little respiratory distress (SAS ≤ 2), mainly due to bradycardias (60% of days without weaning), occurring alone (40%) or in combination with other factors such as apnea/desaturations. In addition, “soft factors” that are harder to grasp impact on weaning decisions, whereas the SAS overall played a minor role. Consequently, ventilation times did not differ between the groups. In conclusion, NIV weaning is influenced by various factors that override the absence of respiratory distress limiting the predictive value of the SAS. An awareness of the factors that influence weaning decisions is important as prolonged use of NIV has been associated with adverse outcome. Guidelines are necessary to standardize NIV weaning practice.

Inter-rater reliability of the Silverman and Andersen index-a measure of respiratory distress in preterm infants

“…The poor inter-rater agreement indicates that the use of the SA index might not provide enough information to identify when to scale up and when to start weaning from respiratory support. Nussbaum et al showed that low SA index scores did not necessarily lead to weaning from NIV, yet higher scores were predictive against weaning [11]. The authors highlighted that bradycardias, apneas and desaturations might have a higher impact on the weaning decision than low scores of respiratory distress [11].…”

“…Nussbaum et al showed that low SA index scores did not necessarily lead to weaning from NIV, yet higher scores were predictive against weaning [11]. The authors highlighted that bradycardias, apneas and desaturations might have a higher impact on the weaning decision than low scores of respiratory distress [11]. It is possible that the SA index is more useful in an "either-or" situation regarding whether the preterm infants need respiratory support or not.…”

“…In a former study evaluating the use of SA index in the clinical routine, the authors found only slight inter-rater agreement among the raters when assessing preterm infants breathing on various types of non-invasive ventilation (NIV) [11]. The authors speculated that the SA index was inaccurate due to the difficulty in observing nasal flaring when infants wear an interface with masks or prongs [11]. Setty et al removed the indices of nares dilation and expiratory grunt and found that this simplified versions of the SA index had a predictive value in line with the full SA index [12].…”

Regional pulmonary oxygen saturations in late preterm and term infants with respiratory distress at birth

“…Each category was scored from 0 to 2, with an infant breathing comfortably receiving a score of “0” and an infant in severe respiratory distress receiving a score of “10” point 12,13 . For the SAS, 0‐2 points were accepted as no/mild respiratory distress, 3 points as moderate respiratory distress and SAS ≥ 4 points as significant respiratory distress as it has been reported by Nussbaum et al 14 All infants with a SAS score ≥3 points received standardized noninvasive ventilatory support as nasal continuous positive airway pressure (n‐CPAP) with a positive end‐expiratory pressure (PEEP) of 6 cmH 2 O. Infants <35 weeks of gestational age, infants with congenital malformations and whose parents disagreed to participate were all excluded.…”

“…Each category was scored from 0 to 2, with an infant breathing comfortably receiving a score of "0" and an infant in severe respiratory distress receiving a score of "10" point. 12,13 For the SAS, 0-2 points were accepted as no/mild respiratory distress, 3 points as moderate respiratory distress and SAS ≥ 4 points as significant respiratory distress as it has been reported by Nussbaum et al 14…”