Ultrassonografia como método de avaliação da aeração pulmonar e da função diafragmática em recém-nascidos

Abstract

Ultrasound (US) is a non-invasive, radiation-free, safe, and bedside technique that overcomes many limitations of other imaging methods. Functional assessment of the diaphragm and dynamic evaluation of lung aeration in various clinical situations using US have been incorporated into physiotherapeutic practice to optimize clinical management and improve outcomes. However, the use of respiratory system ultrasonography in neonatology remains underexplored, with a scarcity of studies supporting its specific application in this population. This thesis comprises two studies. Objective of the first study: To establish reference values and assess intra- and inter-examiner reliability of inspiratory diaphragmatic thickness (IDT), expiratory diaphragmatic thickness (EDT), diaphragmatic thickening fraction (DTF), and diaphragmatic excursion (DE) by ultrasonography, including lower (LLN) and upper (ULN) limits of normality in neonates. A cross-sectional study was conducted including healthy neonates from a public hospital between July 2022 and December 2023. IDT, EDT, DTF, and DE were measured by physiotherapist 1 (experienced examiner). Reliability was assessed by having physiotherapist 1 and physiotherapist 2 (ultrasound specialist) independently analyze the examinations using ImageJ software. Intraclass correlation coefficients (ICC) and 95% confidence intervals (CI) were used to evaluate intra- and inter-examiner reliability. Among 100 neonates [39 (38–40) weeks, 3168 ± 475 g, 49 (47.5–50) cm], normal values were: EDT: 2.17 ± 0.59 mm, LLN: 2.05 mm, ULN: 2.29 mm; IDT: 1.71 ± 0.48 mm, LLN: 1.62 mm, ULN: 1.80 mm; DTF: 28.02 ± 9.88%, LLN: 26.08%, ULN: 29.96%; DE: 2.47 ± 0.72 mm, LLN: 2.33 mm, ULN: 2.61 mm. No significant differences were observed between physiotherapist 1 and physiotherapist 2 (p > 0.05). Intra- and inter-examiner reliability were ICC ≥ 0.98 (0.97–1.00) (p < 0.001) and ICC ≥ 0.91 (0.85–0.99) (p < 0.001), respectively. Objective of the second study: To describe and assess diaphragmatic function and lung aeration by ultrasound during the weaning and post-extubation phases in preterm newborns. This cross-sectional study included intubated preterm newborns eligible for extubation. IDT, EDT, DTF, DE, and lung aeration (lung ultrasound score, LUS) were evaluated at three time points: T1 — during invasive mechanical ventilation (IMV); T2 — during the spontaneous breathing trial (SBT); and T3 — during nasal intermittent positive pressure ventilation (NIPPV). The Friedman test and Wilcoxon signed-rank post hoc test were used for comparisons (p < 0.05). Fifty preterm newborns were evaluated. Forty-five (mean gestational age 30.9 ± 2.2 weeks; mean weight 1377.5 ± 432 g) received IMV for 4 ± 3 days and were successfully extubated (extubation failure rate 10%). Due to the small number of failures (n = 5), only descriptive analyses were performed. In successfully extubated newborns, IDT and DE increased at T2 and T3 compared to T1 (p < 0.05), with IDT highest at T2. Lung aeration decreased at T3 (p < 0.05), but LUS remained low throughout, consistent with milder respiratory disease and minimal impact on lung aeration. No significant changes were observed in EDT or DTF, which remained consistently elevated. Conclusion: The established reference values provide support for interpreting neonatal diaphragmatic function and detecting alterations in contractility and motion amplitude, demonstrating high intra- and inter-examiner reliability for EDT, IDT, DTF, and DE. Moreover, in preterm newborns successfully extubated, diaphragmatic thickness and excursion increased during the spontaneous breathing trial and remained elevated after extubation, while lung aeration showed a transient decrease but remained adequate. These findings may support the use of diaphragmatic and lung ultrasound to guide extubation readiness and monitor post-extubation adaptation in preterm infants.