Lung ultrasound to predict the duration of respiratory support in newborn infants with respiratory distress

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Dokumentart: PhDThesis
Date: 2023-08-08
Language: English
Faculty: 4 Medizinische Fakultät
Department: Medizin
Advisor: Poets, Christian Friedrich (Prof.Dr.)
Day of Oral Examination: 2023-07-25
DDC Classifikation: 610 - Medicine and health
Keywords: Säugling , Atemnot , Ultraschall , Lunge , CPAP
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Delayed transition and transient tachypnea of the newborn (TTN) are common causes of respiratory distress in term and near-term infants caused by delayed postnatal lung liquid clearance. Risk factors for delayed transition and TTN are prematurity, elective cesarean section, male sex, and perinatal asphyxia. Risk factors associated with a prolonged course of TTN and respiratory support are low umbilical cord pH, Apgar score, decreased SpO2, increased respiratory rates, and increased CO2. Treatment includes close cardiorespiratory monitoring, supplemental oxygen, and nasal continuous positive airway pressure (nCPAP). Usually bearing a benign clinical course, delayed transition and TTN may nonetheless lead to neonatal intensive care unit (NICU) admission with varying duration and associated mother-child separation. Identifying bedside applicable prognostic parameters to estimate the duration of nCPAP therapy as a surrogate for the clinical course of TTN and delayed transition potentially reduces NICU admission. We designed a prospective observational study to estimate the duration of nCPAP therapy in term and near-term infants ≥ 36 0/7 weeks of gestation with delayed transition and TTN. The main outcome parameter was nCPAP therapy duration (< 1 vs. ≥ 1 hour). Additional study aims were clinical and lung ultrasound findings and evaluating interrater agreement of lung ultrasound scores. Thirty and 60 minutes postnatally, nCPAP duration was estimated based on the following parameters: lung ultrasound score, Silverman-Andersen score, respiratory rate, FiO2, SpO2, and respiratory acidosis in blood gas analysis. We also included the previously described risk factors birth weight, gestational age, pH in cord blood analysis, 1-minute Apgar score, and sex in our analysis. We used univariate and multivariate analysis to evaluate the risk factors' influence on nCPAP therapy duration and the intraclass correlation coefficient to test interrater agreement. Thirty minutes postnatally, a lung ultrasound score > 5, FiO2 > 0.21, and respiratory acidosis were associated with nCPAP therapy ≥ 1 hour. We determined two probability cutoffs aiming at either a high sensitivity or high specificity predicting nCPAP therapy ≥ 1 hour. We confirmed our model using classification and regression tree analysis. With an area under the curve of 0.87 in receiver operating characteristic analysis, our model proved to be a good diagnostic test, potentially serving as a basis for developing a prognostic tool. Sixty minutes postnatally, a Silverman-Andersen-Score ≥ 5 and a respiratory rate > 60/min were associated with nCPAP therapy ≥ 1 hour. Due to unevenly distributed data, we refrained from further analyses at the 60-minute time point. None of the already known risk factors were associated with prolonged nCPAP therapy in our cohort, but we confirmed several already known lung ultrasound findings in TTN and, for the first time, in delayed transition. We identified the double lung point and pleural line abnormalities as potential candidates for further prognostic studies in TTN and delayed transition. We demonstrated a good interrater agreement for lung ultrasound scoring between different raters: two neonatologists and two pediatric radiologists. With regard to our study’s main limitation of determining the lung ultrasound score cutoff statistically based on our cohort’s data, our findings on risk factors for prolonged nCPAP therapy and their potential use as a diagnostic tool must be validated in an independent sample.

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