A radiographic method for assessing lung area in neonates

Radiographic thoracic area in newborn infants with Down's syndrome

OBJECTIVES

Infants with Down's syndrome (DS) can suffer from lung hypoplasia. Our aim was to determine if the chest radiographic thoracic area (CRTA) on day one of life differed between infants with DS compared to term controls without respiratory disease and whether in infants with DS, the CRTA was related to a longer duration of ventilation and supplemental oxygen therapy.

METHODS

A review of infants with DS born between 2012 and 2023 at King's College Hospital NHS Foundation Trust, London, UK was conducted. The control group consisted of term, newborn infants matched for birth weight and ventilated for poor respiratory drive at birth. Chest radiographs on day one were analysed and the highest CRTA for each infant was included in the analysis.

RESULTS

The 40 infants with DS (18 male) had significantly lower median (IQR) CRTA [1,922 (1,571-2,261) mm2] compared to 80 controls [2,495 (2,108-2,908) mm2, p<0.001]. The CRTA was not related to a longer duration of invasive ventilation, a longer period of supplemental oxygen requirement and was not different in infants with DS with or without significant congenital heart disease or gastrointestinal atresia.

CONCLUSIONS

Newborn infants with Down's syndrome had lower chest radiographic thoracic area compared to healthy term controls, but this finding was not associated with clinical indices of lung disease severity.

Correlation of fetal lung area with MRI derived pulmonary volume

BACKGROUND

Neonatal chest-Xray (CXR)s are commonly performed as a first line investigation for the evaluation of respiratory complications. Although lung area derived from CXRs correlates well with functional assessments of the neonatal lung, it is not currently utilised in clinical practice, partly due to the lack of reference ranges for CXR-derived lung area in healthy neonates. Advanced MR techniques now enable direct evaluation of both fetal pulmonary volume and area. This study therefore aims to generate reference ranges for pulmonary volume and area in uncomplicated pregnancies, evaluate the correlation between prenatal pulmonary volume and area, as well as to assess the agreement between antenatal MRI-derived and neonatal CXR-derived pulmonary area in a cohort of fetuses that delivered shortly after the antenatal MRI investigation.

METHODS

Fetal MRI datasets were retrospectively analysed from uncomplicated term pregnancies and a preterm cohort that delivered within 72 h of the fetal MRI. All examinations included T2 weighted single-shot turbo spin echo images in multiple planes. In-house pipelines were applied to correct for fetal motion using deformable slice-to-volume reconstruction. An MRI-derived lung area was manually segmented from the average intensity projection (AIP) images generated. Postnatal lung area in the preterm cohort was measured from neonatal CXRs within 24 h of delivery. Pearson correlation coefficient was used to correlate MRI-derived lung volume and area. A two-way absolute agreement was performed between the MRI-derived AIP lung area and CXR-derived lung area.

RESULTS

Datasets from 180 controls and 10 preterm fetuses were suitable for analysis. Mean gestational age at MRI was 28.6 ± 4.2 weeks for controls and 28.7 ± 2.7 weeks for preterm neonates. MRI-derived lung area correlated strongly with lung volumes (p < 0.001). MRI-derived lung area had good agreement with the neonatal CXR-derived lung area in the preterm cohort [both lungs = 0.982].

CONCLUSION

MRI-derived pulmonary area correlates well with absolute pulmonary volume and there is good correlation between MRI-derived pulmonary area and postnatal CXR-derived lung area when delivery occurs within a few days of the MRI examination. This may indicate that fetal MRI derived lung area may prove to be useful reference ranges for pulmonary areas derived from CXRs obtained in the perinatal period.

Chest radiographic thoracic areas and respiratory outcomes in infants with anterior abdominal wall defects

OBJECTIVES

Infants with anterior abdominal wall defects (AWD) can suffer from pulmonary complications. Our aims were to determine if the chest radiographic thoracic areas (CRTAs) on day one differed between infants with exomphalos or gastroschisis, whether this related to differing severity of outcomes and if they were lower than those of controls indicating abnormal antenatal lung growth.

METHODS

A review of infants with exomphalos or gastroschisis born between January 2004 and January 2023 was conducted. The control group was term, newborn infants ventilated for poor respiratory drive at birth. Chest radiographs on day one were analysed and the highest CRTA in the first 24 h after birth for each infant included in the analysis.

RESULTS

The 127 infants with gastroschisis had a lower gestational age and birthweight than the 62 exomphalos infants and 130 controls (all p<0.001) The CRTAs of the controls were greater than the CRTAs of the exomphalos and the gastroschisis infants (p = 0.001). The median CRTA corrected for birthweight was lower in the exomphalos infants [688, IQR 568-875 mm2/kg] than the gastroschisis infants [813, IQE 695-915 mm2/kg] No gastroschisis infant developed bronchopulmonary dysplasia (BPD). A CRTA of 1759 mm2 had a sensitivity of 81 % and specificity of 71 % in predicting BPD in infants with exomphalos.

CONCLUSIONS

Infants with gastroschisis or exomphalos had lower CRTAs than controls suggesting both groups had abnormal antenatal lung development. The CRTA was lower in the exomphalos infants who also had worse respiratory outcomes, hence CRTA assessment may a useful prognostic aid.

Prediction of bronchopulmonary dysplasia by the chest radiographic thoracic area on day one in infants with exomphalos

OBJECTIVES

To determine if infants with exomphalos had abnormal antenatal lung growth as indicated by lower chest radiographic thoracic areas (CRTA) on day one compared to controls and whether the CRTA could predict the development of bronchopulmonary dysplasia (BPD).

METHODS

Infants with exomphalos cared for between January 2004 and January 2023 were included. The controls were term, newborn infants ventilated for absent respiratory drive at birth, without lung disease and had no supplemental oxygen requirement by 6 h of age. The radiographs were imported as digital image files by Sectra PACS software (Sectra AB, Linköping, Sweden). Free-hand tracing of the perimeter of the thoracic area was undertaken and the CRTA calculated by the software.

RESULTS

Sixty-four infants with exomphalos and 130 controls were included. Infants with exomphalos had a lower median (IQR) CRTA (1,983 [1,657-2,471] mm2) compared to controls (2,547 [2,153-2,932] mm2, p<0.001). Following multivariable regression analysis, infants with exomphalos had lower CRTAs compared to controls (p=0.001) after adjusting for differences in gestational age and male sex. In the exomphalos group, the CRTAs were lower in those who developed BPD (n=14, 1,530 [1,307-1,941] mm2) compared to those who did not (2,168 [1,865-2,672], p<0.001). Following multivariable regression analysis, the CRTA was associated with BPD development (p=0.021) after adjusting for male sex and gestational age.

CONCLUSIONS

Lower CRTAs on day one in the exomphalos infants compared to the controls predicted BPD development.

Critical functional lung volumes in neonatal intensive care: evidence and clinical applications

Respiratory disease is common in premature and sick newborn infants and can often necessitate the initiation of intensive care. Newborn infants often suffer from conditions that are associated with decreased lung volumes that occur as a result of abnormal or incomplete lung development. Such conditions are prematurity and respiratory distress syndrome, preterm premature rupture of membranes and the ensuing pulmonary hypoplasia and congenital lung anomalies such as congenital diaphragmatic hernia. These diseases have a structural component manifesting with lower lung volumes and a functional component that can present with increased oxygen and ventilatory requirements. The corresponding decreased functional lung volume is possibly responsible for some unfavourable pulmonary outcomes. Some infants are unable to wean off invasive respiratory support and, in extreme cases, unable to sustain independent breathing that can lead to long-term invasive ventilation or subsequent death. The aim of this review is to summarise the available evidence behind the concept of a critical functional lung volume in neonatal intensive care and describe the clinical implications that arise from decreased functional lung volumes in the main high-risk populations of newborn infants. IMPACT: Newborn infants suffer from diseases such as respiratory distress syndrome, pulmonary hypoplasia and congenital diaphragmatic hernia that are associated with a decrease in the total lung volume and impaired lung function. Critically decreased functional lung volumes during neonatal care are associated with failure to wean off invasive respiratory support, increased mortality and possibly longer-term respiratory complications.

Postnatal Imaging for Prediction of Outcome in Patients with Left-sided Congenital Diaphragmatic Hernia

OBJECTIVE

To evaluate associations between postnatal imaging features and outcome of left-sided congenital diaphragmatic hernia, as defined by overall survival and a requirement for extracorporeal membrane oxygenation (ECMO).

STUDY DESIGN

Newborns diagnosed prenatally with left-sided congenital diaphragmatic hernia between January 2013 and September 2021 were studied retrospectively. The esophageal deviation index was newly defined as the largest diameter from the midline to deviated gastric tube divided by the largest transverse diameter of the thoracic cavity on the radiograph. Regression analyses were performed to identify postnatal imaging features associated with overall survival and a requirement for ECMO. The predictive power (ie, area under the curve [AUC] of a time-dependent receiver operating characteristic curve) of prenatal, postnatal, and intraoperative findings for predicting survival were calculated.

RESULTS

Ninety-seven patients (54 males; mean gestational age, 38.3 ± 1.9 weeks; mean birth weight, 2956.5 ± 540.0 g) were analyzed. The esophageal deviation index (adjusted hazard ratio [HR], moderate [≥0.19 to <0.24], 6.427 [P = .029]; severe [≥0.24], 33.007 [P < .001]) and right pneumothorax (adjusted HR, 8.763; P = .002) were associated with overall survival and with a requirement for ECMO. Liver herniation on postnatal ultrasound also was associated with overall survival (P < .001) and need for ECMO (P = .001). In addition, the AUC for prediction of 1-year survival from postnatal ultrasound was comparable with that of prenatally or intraoperatively detected liver herniation (0.93; 95% CI, 0.88-0.97).

CONCLUSIONS

The esophageal deviation index, right pneumothorax, and liver herniation observed by postnatal imaging have prognostic value in patients with left-sided congenital diaphragmatic hernia.

Brief research report: Chest radiographic thoracic area in term ventilated infants without respiratory disease

OBJECTIVE

To report values of the chest radiographic thoracic area (CRTA) in ventilated, term-born infants without respiratory disease and to evaluate whether CRTA is related to demographic data at birth.

METHODS

Retrospective, observational cohort study in a tertiary neonatal unit at King's College Hospital NHS Foundation Trust, London, UK.Newborn infants born after 36 completed weeks of gestation, ventilated for poor perinatal adaptation or hypoxic ischaemic encephalopathy without respiratory disease and admitted in a recent eight-year period (2014-2022).The CRTA was assessed by free-hand tracing of the perimeter of the thoracic area as outlined by the diaphragm and the rib cage excluding the mediastinal structures and was calculated using the Sectra PACS software.

RESULTS

One hundred and twenty-one infants (75 male) were included with a median (IQR) gestation of 40 (38-41) weeks and birth weight of 3.41 (3.04-3.75) kg. The median (IQR) CRTA was 2,589 (2,167-2,943) mm² and was significantly related to birth weight (r = 0.316, p = 0.003), gestation at birth (r = 0.193, p = 0.032) and birth weight z-score (r = 0.187, p = 0.038).

CONCLUSIONS

We report values of the chest radiographic thoracic area in ventilated term-born infants which could be used as reference for determining respiratory disease severity.

The Chest Radiographic Thoracic Area Can Serve as a Prediction Marker for Morbidity and Mortality in Infants With Congenital Diaphragmatic Hernia

Objective: Valid postnatal prediction parameters for neonates with congenital diaphragmatic hernia (CDH) are lacking, but recently, the chest radiographic thoracic area (CRTA) was proposed to predict survival with high sensitivity. Here, we evaluated whether the CRTA correlated with morbidity and mortality in neonates with CDH and was able to predict these with higher sensitivity and specificity than prenatal observed-to-expected (O/E) lung-to-head ratio (LHR). Methods: In this retrospective cohort study, all neonates with CDH admitted to our institution between 2013 and 2019 were included. The CRTA was measured using the software Horos (V. 3.3.5) and compared with O/E LHR diagnosed by fetal ultrasonography in relation to outcome parameters including survival, extracorporeal membrane oxygenation (ECMO) support, and chronic lung disease (CLD). Results: In this study 255 neonates were included with a survival to discharge of 84%, ECMO support in 46%, and 56% developing a CLD. Multiple regression analysis demonstrated that the CRTA correlates significantly with survival (p = 0.001), ECMO support (p < 0.0001), and development of CLD (p = 0.0193). The CRTA displayed a higher prognostic validity for survival [area under the curve (AUC) = 0.822], ECMO support (AUC = 0.802), and developing a CLD (AUC = 0.855) compared with the O/E LHR. Conclusions: Our data suggest that the postnatal CRTA might be a better prognostic parameter for morbidity and mortality than the prenatal O/E LHR.

NeoAPACHE II. Relationship Between Radiographic Pulmonary Area and Pulmonary Hypertension, Mortality, and Hernia Recurrence in Newborns With CDH

Congenital diaphragmatic hernia is a rare disease with high mortality and morbidity due to pulmonary hypoplasia and pulmonary hypertension. The aim of the study is to investigate the relationship between radiographic lung area and systolic pulmonary artery pressure (sPAP) on the first day of life, mortality, and hernia recurrence during the first year of life in infants with a congenital diaphragmatic hernia (CDH). A retrospective data collection was performed on 77 CDH newborns. Echocardiographic sPAP value, deaths, and recurrence cases were recorded. Lung area was calculated by tracing the lung's perimeter, excluding mediastinal structures, and herniated organs, on the preoperative chest X-ray performed within 24 h after birth. Logistic and linear regression analyses were performed. Deceased infants showed lower areas and higher sPAP values. One square centimeter of rising in the total, ipsilateral, and contralateral area was associated with a 22, 43, and 24% reduction in mortality risk. sPAP values showed a decreasing trend after birth, with a maximum of 1.84 mmHg reduction per unitary increment in the ipsilateral area at birth. Recurrence patients showed lower areas, with recurrence risk decreasing by 14 and 29% per unit increment of the total and ipsilateral area. In CDH patients, low lung area at birth reflects impaired lung development and defect size, being associated with increased sPAP values, mortality, and recurrence risk. Clinical Trial Registration: The manuscript is an exploratory secondary analysis of the trial registered at ClinicalTrials.gov with identifier NCT04396028.

The NeoAPACHE Study Protocol I: Assessment of the Radiographic Pulmonary Area and Long-Term Respiratory Function in Newborns With Congenital Diaphragmatic Hernia

In newborns with congenital diaphragmatic hernia (CDH), the radiographic lung area is correlated with functional residual capacity (FRC) and represents an alternative method to estimate lung hypoplasia. In a cohort of newborn CDH survivors, we retrospectively evaluated the relationship between radiographic lung area measured on the 1st day of life and long-term respiratory function. As a secondary analysis, we compared radiographic lung areas and respiratory function between patients undergoing fetal endoscopic tracheal occlusion (FETO) and patients managed expectantly (non-FETO). Total, ipsilateral, and contralateral radiographic areas were obtained by tracing lung perimeter as delineated by the diaphragm and rib cage, excluding mediastinal structures and herniated organs. Tidal volume (V_T), respiratory rate (RR), and their Z-Scores when compared to the norm were collected from pulmonary function tests (PFTs) performed at 12 ± 6 months of age. Linear regression analyses using the absolute Z-Score values for each parameter were performed. In CDH survivors, an increase in total and ipsilateral lung area measured at birth was related to a reduction in the absolute Z-Score for V_T in PFTs (p = 0.046 and p = 0.023, respectively), indicating a trend toward an improvement in pulmonary volumes and V_T normalization. Radiographic lung areas were not significantly different between FETO and non-FETO patients, suggesting a volumetric lung increase due to prenatal intervention. However, the mean Z-Score value for RR was significantly higher in the FETO group (p < 0.001), probably due to impaired diaphragmatic motility in the most severe cases. Further analyses are necessary to better characterize the role of the radiographic pulmonary area in the prognostic evaluation of respiratory function in patients with CDH. Clinical Trial Registration: This trial was registered at ClinicalTrials.gov with the identifier NCT04396028.

Prediction of Mortality in Newborn Infants With Severe Congenital Diaphragmatic Hernia Using the Chest Radiographic Thoracic Area

OBJECTIVES

To evaluate whether the preoperative chest radiographic thoracic area in newborn infants with congenital diaphragmatic hernia was related to the length of mechanical ventilation and the total length of stay and whether chest radiographic thoracic area predicted survival to discharge from neonatal care.

DESIGN

Retrospective observational cohort study.

SETTING

Tertiary neonatal unit at King's College Hospital National Health Service Foundation Trust, London, United Kingdom.

PATIENTS

Newborn infants admitted with congenital diaphragmatic hernia at King's College Hospital in a 10-year period (2007-2017).

INTERVENTIONS

The chest radiographic thoracic area was assessed by free hand tracing of the perimeter of the thoracic area as outlined by the diaphragm and the rib cage and excluded the mediastinal structures and abdominal contents in the thorax and calculated using the Sectra PACS software (Sectra AB, Linköping, Sweden).

MEASUREMENTS AND MAIN RESULTS

Eighty-four infants with congenital diaphragmatic hernia (70 left-sided) were included with a median (interquartile range) gestation of 36 weeks (34-39 wk). Fifty-four (64%) survived to discharge from neonatal care. In the infants who survived the chest radiographic thoracic area was not related to the length of mechanical ventilation (r = 0.136; p = 0.328) or the total duration of stay (r = 0.095; p = 0.495). The median (interquartile range) chest radiographic thoracic area was higher in infants who survived (1,780 mm [1,446-2,148 mm]) compared with in the deceased infants (1,000 mm [663-1,449 mm]) after correcting for confounders (adjusted p = 0.01). Using receiver operator characteristics analysis, the chest radiographic thoracic area predicted survival to discharge from neonatal care with an area under the curve of 0.826. A chest radiographic thoracic area higher than 1,299 mm predicted survival to discharge with 85% sensitivity and 73% specificity.

CONCLUSIONS

The chest radiograph in infants with severe congenital diaphragmatic hernia can predict survival from neonatal care with high sensitivity and moderate specificity.

Correlation of radiographic thoracic area and oxygenation impairment in bronchopulmonary dysplasia

We hypothesized that radiographically-assessed hyperinflation in bronchopulmonary dysplasia (BPD) is related to the degree of oxygenation impairment. Our objective was to explore the relation of chest radiographic thoracic area (CRTA) with right-to-left shunt, right shift of the oxyhemoglobin dissociation curve and ventilation/perfusion ratio (VA/Q) in infants with BPD. Twenty-two infants born at median (IQR) gestation of 26 (24-28) weeks with BPD were prospectively studied at 39 (30-69) days. Inspired oxygen (FiO2) was varied to obtain transcutaneous oxygen saturation (SpO2) values between 85 and 96%. Shunt, shift and VA/Q were derived by plotting and analysing pairs of SpO2 and FiO2. CRTA was measured by free hand-tracing the perimeter of the thoracic area in anterio-posterior chest radiographs. Median (IQR) shunt was 8 (1-14)%, shift was 13 (11-19)kPa and VA/Q 0.42 (0.30-0.48). Median (IQR) CRTA/kg was 2495 (1962-2838)mm(2) and was significantly related to shift (r=0.674, p<0.001), VA/Q (r=-0.633, p<0.001), weight at study (r=-0.457, p=0.003) and day of life (r=-0.406, p=0.009), but not to shunt. CRTA in BPD is significantly related to oxygenation impairment as quantified by shift and VA/Q. CRTA can be used as a simple radiographic test to quantify BPD severity.

Chest radiograph thoracic areas and lung volumes in infants developing bronchopulmonary dysplasia

OBJECTIVES

To determine whether chest radiograph (CXR) thoracic areas and lung volumes differed between infants who did and did not develop BPD and according to the severity of BPD developed.

WORKING HYPOTHESIS

Infants developing BPD, particularly if moderate or severe, would have low CXR thoracic areas and lung volumes in the perinatal period.

STUDY DESIGN

Prospective study. PATIENT-SUBJECT SELECTION: 53 infants with a median gestational age of 28 (range 24-32) weeks.

METHODOLOGY

CXR thoracic areas were calculated using a Picture Archiving and Communicating System (PACS) and lung volume assessed by measurement of functional residual capacity (FRC) in the first 72 hr after birth. BPD was diagnosed if the infants were oxygen dependent beyond 28 days, mild BPD in infants no longer oxygen dependent at 36 weeks post-menstrual age (PMA) and moderate/severe BPD in infants who required supplementary oxygen with or without respiratory support at 36 weeks PMA.

RESULTS

Thirty two infants developed BPD, 21 had moderate/severe BPD. The median CXR thoracic areas were higher (P < 0.0001) and FRCs were lower (P < 0.0001) in the BPD compared to no BPD infants. The median CXR thoracic areas of the moderate/severe group (P < 0.001) and the mild group (P < 0.05) were greater than that of the no BPD group and the median FRC of the moderate/severe BPD group was lower than the no BPD group (<0.001) and the mild BPD group (P < 0.05).

CONCLUSION

These results highlight that in the perinatal period infants developing BPD, particularly if moderate/severe, have low functional lung volumes and may have gas trapping, which likely reflects ventilation inhomogeneity.

Functional residual capacity measurement by heptafluoropropane in ventilated newborn lungs: in vitro and in vivo validation

OBJECTIVE

Heptafluoropropane is an inert gas commercially used as propellant for inhalers. Since heptafluoropropane can be detected in low concentrations, it could also be used as a tracer gas to measure functional residual capacity and ventilation homogeneity. The aim of the present study was to validate functional residual capacity measurements by heptafluoropropane wash-in/wash-out (0.8%) during mechanical ventilation in small, surfactant-depleted lungs using a newborn piglet model.

DESIGN

Prospective laboratory and animal trial.

SETTING

Animal laboratory in a university setting.

SUBJECTS

Sixteen newborn piglets (age<12 hrs, median weight 1390 g [705-4200 g]) before and after surfactant depletion (Pao2<100 torr in Fio2=1.0) by lung lavage.

INTERVENTIONS

Heptafluoropropane was measured with a new infrared mainstream sensor connected with the flow sensor of the Dräger Babylog 8000. Accuracy and precision of the measurement technique were tested in a mechanical lung model with a volume range from 11 to 35 mL. Reproducibility of the method and its sensitivity to detect changes of functional residual capacity were assessed in vivo by variation of ventilatory variables.

MEASUREMENTS AND MAIN RESULTS

In vitro the absolute error of functional residual capacity was <1 mL (relative errors<3%) with a coefficient of variation<4%. The coefficient of variation of consecutive in vivo measurements was only slightly higher (<5.1%). Measurement of heptafluoropropane concentrations in blood showed no significant accumulation for repeated functional residual capacity measurements within short time periods. After lung lavage, the functional residual capacity decreased from 20.9 mL/kg to 14.5 mL/kg (p<.05) despite increased ventilatory pressures, and lung clearance index (p<.001) and moment ratios (p<.01) increased significantly due to uneven alveolar ventilation. In healthy lungs, the increase in peak inflation pressure and positive end-expiratory pressure by 3-4 cm H2O had only a moderate effect on functional residual capacity (20.9+/-8.6 vs. 26.0+/-11.9 mL/kg, p=.17) and no effect on ventilatory homogeneity, whereas in surfactant-depleted lungs the functional residual capacity increased from 14.5+/-6.7 mL/kg to 29.9+/-12.6 mL/kg (p<.001) and lung clearance index and moment ratios decreased significantly (p < .01).

CONCLUSIONS

Heptafluoropropane is a suitable tracer gas for precise functional residual capacity measurements tested in vitro and allows for reproducible measurements in ventilated small lungs without any adverse effects on mechanical ventilation. The sensitivity of the method is sufficiently high to demonstrate the effect of changes in ventilatory settings on the functional residual capacity and ventilation homogeneity.

Comparison of lung area by chest radiograph, with estimation of lung volume by helium dilution during prone and supine positioning in mechanically ventilated preterm infants: a pilot study

Measurement of lung volume may be useful in determining the degree of lung disease and for optimizing an infant's mechanical ventilator settings. A chest radiograph (CXR) is often used to estimate lung volume, because direct measurement, e.g., functional residual capacity (FRC), is neither practical nor possible in the neonatal intensive care unit. In supinely positioned infants, good correlation was found between lung area determined by CXR and lung volume, e.g., functional residual capacity (FRC). Whether this is true for the prone position is unknown. Since positioning may affect oxygenation and pulmonary function, we studied the relationship between lung area measured from CXR and FRC during both supine and prone positioning in 14 mechanically ventilated preterm infants. Lung area was determined from CXRs using computed radiography and FRCs obtained by helium dilution at end-expiration in both supine and prone positions. Reproducibility of lung area measurements was demonstrated by high correlations between two observers (R2 = 0.92 and 0.99 for supine and prone, respectively). When supine, lung area was 15.4 +/- 3.1 cm2, and FRC was 19.5 +/- 7.3 ml. In prone position, lung area was 16.7 +/- 4.2 cm2, and FRC 23.0 +/- 9.4 ml. There was a moderate to strong positive correlation between lung area and FRC for both positions (supine: r = 0.57, P < 0.03; prone: r = 0.63, P < 0.02). Lung area measured by computed radiography is a reproducible and practical method for estimating lung volume from routine chest X-rays in both supine and prone positions in mechanically ventilated preterm infants.

Chest radiograph scores in preterm infants: interobserver agreement and relation to respiratory function

To evaluate scoring systems for chest radiographs, we determined interobserver agreement and relation to the lung function during the 1st week of life in ventilated preterm infants. Three independent observers examined chest radiographs by applying radiological scores according to Lischka, Yuksel, Greenough, Toce, and Giedion on postnatal days 2 and 7. Kappa statistics was used to assess the interobserver agreement. By means of regression analysis, mean scores and individual radiological scores of the three observers were studied in relation to ventilation and oxygenation indices and respiratory system resistance and compliance. Forty-eight radiographs were evaluated on day 2 and 17 radiographs on day 7. All scoring systems showed kappa values equal to or <0.5. Regression analysis revealed no significant associations between radiological scores and ventilator requirements or respiratory mechanics. We conclude that in ventilated preterm infants radiological scoring systems showed a poor interobserver agreement and that they were not related to the actual respiratory function.

Prediction of outcome by computer-assisted analysis of lung area on the chest radiograph of infants with congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Pulmonary hypoplasia is a major cause of mortality and morbidity in infants with congenital diaphragmatic hernia (CDH). Pulmonary hypoplasia is characterized by low volume lungs, and affected infants are likely to have a low lung area on their chest radiograph. The authors assessed whether, in CDH infants, computer-assisted analysis of the chest radiograph lung area gave an accurate indication of lung volume, and if a low lung area was a better predictor of poor outcome (death or oxygen dependency at 28 days) than other test results.

METHODS

Comparisons were made of the radiographic lung area derived by computer-assisted analysis and lung volume, assessed by measurement of functional residual capacity (FRC) on day 1 before surgical intervention and on the first postoperative day. Compliance was measured, and the maximum and modified ventilation indices and maximum Paco2 also was noted. Twenty-five CDH infants with a median gestational age of 38 weeks were studied; 18 had FRC measurements preoperatively.

RESULTS

Both preoperatively and postoperatively, the lung areas and FRCs correlated significantly (r = 0.51, P<.05; r = 0.76, P<.02, respectively). Eleven infants had a poor outcome (5 infants died without an operation); that group preoperatively differed significantly from those with a good outcome with respect to having a lower compliance (P<.02) and higher maximum ventilation index (P<.01) and maximum modified ventilation index (P<.05). Only postoperatively did infants with a poor outcome versus good outcome have a significantly lower lung area (P<.05); they also had a lower increase in lung area preoperatively to postoperatively (P<.01). Receiver operator characteristic curves were constructed; comparison of the areas under the curves showed that preoperatively, a low compliance and high ventilation index were the best predictors of poor outcome. Postoperatively, a low lung area performed as well as the ventilation indices.

CONCLUSION

Computer-assisted analysis of the lung area on the chest radiograph is useful in predicting outcome in CDH infants postoperatively but not preoperatively.

Computer assisted analysis of the chest radiograph lung area and prediction of failure of extubation from mechanical ventilation in preterm neonates

Post-extubation chest radiographs (CXRs) are frequently requested on the neonatal intensive care unit, but it is controversial whether they generate useful information. A low lung volume assessed by measurement of functional residual capacity (FRC) post extubation has been demonstrated to predict extubation failure, which is a subsequent requirement for increased respiratory support. We have previously shown that the CXR lung area obtained by computer assisted analysis significantly correlated with FRC and, therefore, speculated that a low CXR lung area post extubation would reliably predict extubation failure. The aim of this study was to test the hypothesis by analysing CXRs from 20 infants, with median gestational age of 28 weeks (range 25-33 weeks) and postnatal age 4 days (range 1-11 days). CXRs were obtained within 4 h of extubation and were scanned and analysed using a Power Macintosh computer with a Wacom A5 Ultra pad and NIH image software. The cardiac, mediastinal and thymic shadows, and areas of perihilar and lobar consolidation were subtracted from the thoracic area to give the lung area. Seven infants failed extubation and differed significantly from the rest of the cohort only with regard to their CXR lung area, median gestational age, birth weight and postnatal age. Receiver operator characteristic (ROC) curves were constructed and the areas under each ROC curve were compared. Analysis demonstrated that a low CXR lung area and an older postnatal age were the best predictors of extubation failure. A post-extubation CXR lung area of < 8.5 cm2 had the highest specificity (100%) in predicting extubation failure. We conclude that routine post-extubation CXRs can have a useful role.