Clinical and demographic data
The GA of this study population ranged from 27 ± 3 weeks to 41 ± 1 week.The study population consisted of 99 preterm infants and 189 full-term infants.The birth weight ranged from 880–4210 g.There were 156 males and 132 females. A total of 176 infants were delivered by vaginal delivery,while 112 infants were delivered by cesarean section.
The study subjects included 48 patients with PTX and 240 controls.The control subjects included 48 infants with healthy lungs,and 192 infants with different types of lung disease (48 cases of RDS,48 cases of TTN,48 cases of MAS,and 48 cases of pneumonia). There were no significant differences in GA and birth weight among the subgroups.
Normal LUS manifestations
Healthy neonatal lung demonstrates a bamboo sign on B-mode LUS (Fig. 1A) and a seashore sign (Fig. 1B) on M-mode LUS.Lung sliding is clearly evident on real-time LUS (Video 1) [12, 13].In addition,the heart image in the left precardiac area is visible in healthy newborns.Moreover,heart movement should be visible on real-time LUS (Video 2).
Ultrasound manifestations of PTX
The major LUS manifestations of PTX are summarized in Table 1.These include (1) disappearance of lung sliding on real-time LUS (in this study,disappearance of lung sliding was observed in all patients with PTX);(2) absence of B lines (all patients lacked B lines at PTX sites);(3) presence of pleural and A lines (all patients demonstrated pleural and A lines at PTX sites);(4) lung point (which was observed in 30 cases [62.5%] of mild and moderate PTX);(5) spared areas (which were observed in 12 patients with PTX [35%]);(6) the stratosphere sign (which was seen in all patients with PTX at the PTX site);and (7) PHI disappearance (8 patients with PTX [16.7%] demonstrated PHI disappearance).
Sensitivity and specificity of PHI disappearance in PTX diagnosis
Many LUS signs,such as presence of pleural and A lines,absence of B lines,lung sliding disappearance, lung point in mild-to-moderate PTX,spared areas in patients with mild PTX,and the stratosphere sign on M-mode LUS,are used to diagnose PTX [10–14, 16, 17].However,PHI disappearance has not been described previously.Thus,we investigated the value of PHI disappearance for the diagnosis of neonatal PTX using LUS in this study. Specifically,PHI disappearance was used as a parameter to calculate the sensitivity and specificity of LUS to diagnose neonatal PTX.The results indicate that PHI disappearance exhibits a sensitivity of 16.7% and a specificity of 100% for diagnosing neonatal PTX (Table 2).
Effectiveness of thoracentesis
Among the 48 patients with PTX,needle aspiration was performed in 42 patients (87.5%) with significant clinical symptoms under LUS monitoring.Satisfying results were obtained in 40 patients (95.2%),and gas was completely removed after puncture.The remaining 2 cases underwent closed thoracic drainage for 1–3 days.The drainage gas volume was 55–520 mL.
The puncture site was at the second intercostal space of the left or right midclavicular line (the traditional puncture site) in 14 cases;at the fifth to sixth intercostal space of the left or right midaxillary line in 12 cases;at the seventh to eighth intercostal space of the left or right subscapular line in 8 cases;and at the precardiac area in 8 cases,including 5 cases at the sixth intercostal space of the left midclavicular line and 3 cases 1 cm medial to the fifth intercostal space of the left midclavicular line.
Typical case presentation
To aid understanding of the results,we herein present a typical case.An infant with a GA of 32 ± 1 week,who was delivered by caesarean section with a birth weight of 1980 g,was admitted to the NICU because of severe dyspnea 3 hours after birth.LUS confirmed RDS in the right lung.Pleural lines and A lines were observed in the regions of L1–L2, L3–L4, and L5–L6, but no heart image or heart movement was observed (Video 3).Lung sliding also disappeared (Videos 4 & 5).
When 75 mL of gas was removed by pleural puncture from the sixth intercostal space at the left midclavicular line (Fig. 2),dyspnea was relieved,and heart rate decreased from more than 180 ~ 200 beats/min to approximately 140 beats/min.LUS showed that the heart image and heart movement emerged in the left precardiac region (L1–L2) (Video 6) after thoracic puncture.Therefore,it was confirmed that PHI disappearance was caused by left-sided PTX.