Ultra-high frequency lung ultrasound in preterm neonates: a test validation study on interpretation agreement and reliability

Abstract

ObjectiveTo verify if increasing frequency, through the use of ultra-high frequency transducers, has an impact on lung ultrasound pattern recognition.DesignTest validation study.SettingTertiary academic referral neonatal intensive care unit.PatientsNeonates admitted with respiratory distress signs.InterventionsLung ultrasound performed with four micro-linear probes (10, 15, 20 and 22 MHz), in random order. Anonymised images (600 dpi) were randomly included in a pictorial database: physicians with different lung ultrasound experience (beginners (n=7), competents (n=6), experts (n=5)) blindly assessed it. Conformity and reliability of interpretation were analysed using intraclass correlation coefficient (ICC), area under the curve (AUC) of the multi-class ROC analysis, correlation and multivariate linear regressions (adjusting for frequency, expertise and their interaction).Outcome measuresA (0–3) score based on classical lung ultrasound semiology was given to each image as done in the clinical routine.ResultsICC (0.902 (95% CI: 0.862 to 0.936), p<0.001) and AUC (0.948, p<0.001) on the whole pictorial database (48 images acquired on 12 neonates), and irrespective of the frequency and physicians’ expertise, were excellent. Physicians detected more B-lines with increasing frequency: there was a positive correlation between score and frequency (ρ=0.117, p=0.001); multivariate analysis confirmed the score to be higher using 22 MHz-probes (β=0.36 (0.02–0.7), p=0.041).ConclusionOverall conformity and reliability of interpretations of lung ultrasound patterns were excellent. There were differences in the identification of the B-patterns and severe B-patterns as increasing probe frequency is associated with higher score given to these patterns.

Quantitative Lung Ultrasonography to Guide Surfactant Therapy in Neonates Born Late Preterm and Later

“…Nonetheless, previous studies have demonstrated equally optimal interobserver agreement for lung ultrasonography interpretation with or without operators’ blinding. 3 , 23 , 24 Lung ultrasonography values of 6 and 8 were the prespecified positive cutoffs, as these have been associated with the highest global accuracy in early preterm neonates 7 , 14 ; thus, we used them to investigate noninferiority in the study population. The reference standard was an FiO 2 level of 0.30, as this is the threshold suggesting surfactant administration in the European guidelines 20 and is widely used.…”

“…In detail, clinicians not performing ultrasonography were unaware of the LUS, but it was impossible to conceal patient conditions, such as vital monitoring and clinical appearance, to investigators performing ultrasonography. Nonetheless, previous studies have demonstrated equally optimal interobserver agreement for lung ultrasonography interpretation with or without operators’ blinding . Lung ultrasonography values of 6 and 8 were the prespecified positive cutoffs, as these have been associated with the highest global accuracy in early preterm neonates; thus, we used them to investigate noninferiority in the study population.…”

Inspiratory-expiratory variation of pleural line thickness in neonates with and without acute respiratory failure

“…This can be interesting as these probes have higher superficial resolution and can be used for the same purpose in adults too. It remains to be established if ultra-high frequency probes can further improve the measurement [ 12 ]. It is conceivable that the inspiratory-expiratory difference could have a role in the detection of pneumothorax (where the lung sliding is abolished) or the evaluation of lung overdistention but these are interesting hypotheses to be verified in dedicated studies.…”