The lungs in congenital diaphragmatic hernia: do we understand?

The long-term follow-up of patients with a congenital diaphragmatic hernia: a broad spectrum of morbidity

Congenital diaphragmatic hernia (CDH) is a life-threatening anomaly with a mortality rate of approximately 40-50%, depending on case selection. It has been suggested that new therapeutic modalities such as nitric oxide (NO), high frequency oxygenation (HFO) and extracorporal membrane oxygenation (ECMO) might decrease mortality associated with pulmonary hypertension and the sequelae of artificial ventilation. When these new therapies indeed prove to be beneficial, a larger number of children with severe forms of CDH might survive, resulting in an increase of CDH-associated complications and/or consequences. In follow-up studies of infants born with CDH, many complications including pulmonary damage, cardiovascular disease, gastro-intestinal disease, failure to thrive, neurocognitive defects and musculoskeletal abnormalities have been described. Long-term pulmonary morbidity in CDH consists of obstructive and restrictive lung function impairments due to altered lung structure and prolonged ventilatory support. CDH has also been associated with persistent pulmonary vascular abnormalities, resulting in pulmonary hypertension in the neonatal period. Long-term consequences of pulmonary hypertension are unknown. Gastro-esophageal reflux disease (GERD) is also an important contributor to overall morbidity, although the underlying mechanism has not been fully understood yet. In adult CDH survivors incidence of esophagitis is high and even Barrett's esophagus may ensue. Yet, in many CDH patients a clinical history compatible with GERD seems to be lacking, which may result in missing patients with pathologic reflux disease. Prolonged unrecognized GERD may eventually result in failure to thrive. This has been found in many young CDH patients, which may also be caused by insufficient intake due to oral aversion and increased caloric requirements due to pulmonary morbidity. Neurological outcome is determined by an increased risk of perinatal and neonatal hypoxemia in the first days of life of CDH patients. In patients treated with ECMO, the incidence of neurological deficits is even higher, probably reflecting more severe hypoxemia and the risk of ECMO associated complications. Many studies have addressed the substantial impact of the health problems described above, on the overall well-being of CDH patients, but most of them concentrate on the first years after repair and only a few studies focus on the health-related quality of life in CDH patients. Considering the scattered data indicating substantial morbidity in long-term survivors of CDH, follow-up studies that systematically assess long-term sequelae are mandatory. Based on such studies a more focused approach for routine follow-up programs may be established.

Effects of maternal retinoic acid administration in a congenital diaphragmatic hernia rabbit model

Maternal retinoid administration has beneficial effects on lung development in the nitrofen rodent toxic model of congenital diaphragmatic hernia (DH). We wanted to investigate the effects in a surgical model, where the retinoid signaling pathway is not primarily disrupted by the toxic agent. We created DH in fetal rabbits at day 23 of gestation, administrated to the does all trans-retinoic acid (ATRA) or vehicle (VHC) intramuscularly for 8 consecutive days and harvested normal and operated (DH) fetuses at 31 d (n = 7 in each group). Normal lungs exposed to ATRA had increased surfactant protein mRNA levels without change in type II pneumocyte density. There was no measurable effect on lung-to-body weight ratio and airway morphometry by ATRA. In DH lungs (DH/VHC) surfactant protein mRNA levels were increased, as well as the density of type II pneumocytes. When supplemented with ATRA (DH/ATRA) these parameters returned to normal (VHC). Cell proliferation or apoptosis were not influenced by ATRA supplementation. In conclusion, maternal ATRA supplementation does not affect gross anatomic, morphologic or proliferation indices in hypoplastic lungs related to surgically induced DH in rabbit. However, ATRA lowers surfactant protein expression and normalizes type I/II pneumocyte ratio to what is observed in normal lungs.

H, Daltro PA, Antunes E, Fazecas T, Rodrigues L, Guerra F, Marchiori E, Gasparetto EL, Domingues RC. O valor da ultra-sonografia e da ressonância magnética fetal na avaliação das hérnias diafragmáticas

OBJETIVO: Demonstrar a significância dos achados da ressonância magnética e da ultra-sonografia na caracterização pré-natal e avaliação do prognóstico de pacientes com hérnia diafragmática congênita. MATERIAIS E MÉTODOS: Catorze gestantes (idade gestacional média de 28,7 semanas) examinadas com ultra-sonografia e apresentando fetos com suspeita de hérnia diafragmática congênita foram avaliadas por meio da ressonância magnética. Os exames foram realizados em aparelho de 1,5 tesla usando seqüências-padrão. Dois radiologistas avaliaram as imagens e estabeleceram os achados por consenso. RESULTADOS: Doze fetos tinham hérnia diafragmática à esquerda e dois, à direita. O fígado fetal foi localizado no interior do tórax de cinco fetos pela ultra-sonografia (três com hérnia diafragmática esquerda e dois com hérnia diafragmática direita) e de oito pela ressonância magnética (seis com hérnia diafragmática esquerda e dois com hérnia diafragmática direita). Herniação do estômago e alças de intestino delgado foi observada em todos os fetos com hérnia diafragmática esquerda (n = 12), tanto pela ultra-sonografia quanto pela ressonância magnética. Oito fetos sobreviveram após cirurgia (sete com hérnia diafragmática esquerda e um com hérnia diafragmática direita). CONCLUSÃO: A ultra-sonografia e a ressonância magnética são métodos de imagens complementares na avaliação das hérnias diafragmáticas congênitas. A ressonância magnética pode auxiliar a ultra-sonografia na avaliação da posição do fígado, o qual representa importante fator prognóstico.

Prenatal intervention for isolated congenital diaphragmatic hernia

PURPOSE OF REVIEW

We aim to review the recent literature regarding early prenatal prediction of outcome in babies diagnosed with isolated congenital diaphragmatic hernia, as well as results of fetal therapy for this condition.

RECENT FINDINGS

Current survival rates in population-based studies are around 55-70%. Highly specialized centers report 80% and more, but discount the hidden mortality, mainly in the antenatal period. Fetuses presenting with liver herniation and a lung-to-head ratio of less than 1.0 measured in midgestation have a poor prognosis. Other volumetric techniques are being evaluated for use in midtrimester. Recently, a randomized trial failed to show benefit from prenatal therapy, but lacked power to document the potential advantage of prenatal therapy in severe cases. We proposed percutaneous fetal endoluminal tracheal occlusion with a balloon at 26-28 weeks through a 3.3 mm incision. In severe cases, fetal endoluminal tracheal occlusion increased lung size as well as survival, with an early (7 day) survival, late neonatal (28 day) survival and survival at discharge of 75, 58 and 50%, respectively, comparing favorably with 9% in contemporary controls. Airways can be restored prior to birth improving neonatal survival (83.3% compared with 33.3%). The procedure carries a risk for preterm prelabour rupture of the fetal membranes, although that may decrease with experience.

SUMMARY

Fetuses with severe congenital diaphragmatic hernia can be identified in the second trimester. Fetal endoluminal tracheal occlusion can be considered as a minimally invasive fetal therapy, improving outcome in such highly selected cases.

Current consequences of prenatal diagnosis of congenital diaphragmatic hernia

BACKGROUND

Today, the diagnosis of congenital diaphragmatic hernia (CDH) can readily be made in the prenatal period during screening ultrasound examination. Patients ought to be referred to rule out associated anomalies, and in isolated cases, prognosis is poor when the liver is intrathoracic and the lung-to-head ratio (LHR) is less than 1. In these patients, prenatal intervention aiming to reverse pulmonary hypoplasia can be considered.

METHODS

We present our current algorithm for counselling patients presenting with CDH. Patients with a poor prognosis are offered percutaneous fetal endoluminal tracheal occlusion (FETO) with a balloon, inserted at 26 to 28 weeks. We report on the evolution of technique and results in a consecutive homogeneous case series and compare outcome in cases with similar severity managed in the postnatal period.

RESULTS

Within a period of 28 months, FETO was performed between 26 and 28 weeks in 24 fetuses with severe left-sided CDH. Under general (n = 5), epidural (n = 17) or local (n = 2) anesthesia, the balloon was successfully positioned at first surgery (23/24) with a mean operation time of 20 minutes (range, 3-60 minutes). There were no serious maternal complications or direct fetal adverse effects. In the first 2 weeks after FETO, LHR increased from 0.7 to 1.7. Premature prelabour rupture of the membrane (PPROM) occurred in 16.7% and 33.3% at 28 and 32 weeks or earlier, respectively. Gestational age at delivery was 33.5 weeks. Patency of airways was restored either in the prenatal (n = 12) or perinatal period (n = 12). Early (7 days) and late (28 days) survival, and survival at discharge were 75% (18/24), 58.3% (14/24) and 50% (12/24), respectively. Half of nonsurvivors (n = 6) died of pulmonary hypoplasia and hypertension, in combination with PPROM and preterm delivery (n = 4) and balloon dislodgement (n = 2), which coincided with a short tracheal occlusion (TO) period (12 days). In the other 6, TO period was comparable to that in the 12 survivors (47 vs 42 days, respectively). In that group of 6 babies, only 2 died of pulmonary problems. Late neonatal survival (28 days) was higher with prenatal vs perinatal balloon retrieval 83.3% vs 33.3% (P = .013). In a multicentre study validating the criteria, survival till discharge in 37 comparable cases was 9% (3/32) and 13% (5/37) of parents opted for termination.

CONCLUSION

Fetuses with isolated left-sided CDH, liver herniation, and LHR of less than 1 have a poor prognosis. Percutaneous FETO is minimally invasive and may improve the outcome in these highly selected cases. Airways can be restored before birth, allowing vaginal delivery and return to the referring tertiary unit and may improve survival rate. The procedure carries a risk for PPROM, although that may decrease with experience.

Fetal intervention for congenital diaphragmatic hernia: the European experience

Fetuses with CDH presenting with liver herniation and a lung area-to-head circumference ratio of less than 1.0 have a high chance for neonatal death due to pulmonary hypoplasia. Fetal tracheal occlusion (TO) prevents egress of lung liquid, which triggers lung growth. In animal experiments, we were able to develop a minimally invasive technique for Fetoscopic Endoluminal Tracheal Occlusion (FETO) with a detachable balloon. In 2001, we demonstrated feasibility of FETO by percutaneous access in fetuses with severe CDH. In a retrospective multicenter review, we obtained LHR measurements and position of the liver in 134 cases of isolated left-sided CDH between 24 and 28 weeks. Eleven patients (8%) with LHR < 1.4 opted for termination. Overall survival of liveborn babies was 47% (58/123). LHR and position of the liver correlated both to survival. Combination of both variables predicted neonatal outcome better: liver up and LHR < 1.0 predicted a survival of 9%. When LHR < 0.6, there were no survivors irrespective of liver position. We could successfully perform endotracheal placement of the balloon in 20 cases at a median gestational age of 26 weeks. The mean duration of the operation was 22 (range 5-54) minutes. In 11 (55%) of these patients, there was postoperative prelabor (ie, <37 weeks) amniorrhexis. Membranes ruptured before 32 weeks in 35%, with a decreasing trend as experience increased. Ultrasound scans after FETO demonstrated an increase in the echogenicity of the lungs within 48 hours and improvement in the LHR from a median 0.7 (range 0.4-0.9) before FETO to 1.8 (range 1.1-2.9) within 2 weeks after surgery. The median gestation at delivery was 33.2 (range 27-38) weeks, and in 14 (70%) this occurred after 32 weeks. Surgical repair of the diaphragmatic hernia could be done in 13 babies, and in all but 1 the defect was extensive and required the insertion of a patch. Survival to discharge was 50%. These 10 long-term surviving babies are now aged 7 to 26 (median 19) months without known neurologic morbidity. Eight babies died in the neonatal period due to complications of the underlying disease. Two nonsurvivors died from other causes but with appropriately developed lungs. Improved survival coincided with increasing experience, in turn related to reduced incidence of postoperative amniorrhexis, later delivery, and a change in the policy on the timing of removal of the balloon from intrapartum to the prenatal period. Survival in eligible contemporary controls was 1/12 (8%). The presence of liver herniation and a low lung-to-head ratio (LHR <1.0) is a good predictor of poor prognosis at different tertiary centers around the world. Severe CDH may be successfully treated with FETO, which is minimally invasive and may improve postnatal survival.

Developmental biology of the pulmonary circulation

From the earliest stage of lung development, there is an accompanying blood circulation. In the adult lung, the pulmonary arteries are closely associated with the airways. During early fetal development, the airways act as a template for pulmonary blood vessel development in that the vessels form by vasculogenesis around the branching airways. In later lung development, as the alveoli multiply, new capillaries form by angiogenesis. As blood vessels increase in size, they develop a muscle wall that is relatively thick during fetal life and shows a rapid reduction after birth. The control of development by growth factors and the physiological changes immediately after birth are described in this review. Abnormal pulmonary vascular development leading to pulmonary arterial hypertension and strategies for treatment are also discussed.

Les déficits secondaires en surfactant

Preterm babies born before the 33rd week of gestation often exhibit primary surfactant deficiency responsible for the respiratory distress syndrome or hyaline membrane disease. In that situation, there is a limited and insufficient production of surfactant by type II alveolar cells of the lung due to immaturity. Secondary surfactant deficiencies occur in patients with prior normal surfactant synthesis and can be related to sepsis, hypoxia, ventilator induced lung injury or surfactant inhibition by a variety of substances reaching the alveolar spaces. They occur in full-term newborns with meconium aspiration syndrome, acute respiratory distress syndrome and congenital diaphragmatic hernia. In children and adults, acute respiratory distress syndrome and respiratory syncytial virus bronchiolitis can be responsible. In prematures they occur after the initial primary deficiency during pulmonary hemorrhage, pneumonia and bronchopulmonary dysplasia. Treatment with exogenous surfactant may be beneficial. There is a need for randomized controlled studies for evaluation of this treatment. Next generation of surfactants containing recombinant surfactant protein or synthetic peptides appear as promising agents in these situations of secondary surfactant deficiencies.

Surfactant replacement therapy on ECMO does not improve outcome in neonates with congenital diaphragmatic hernia

BACKGROUND PURPOSE

Respiratory failure in neonates with congenital diaphragmatic hernia (CDH) may in part be caused by a primary or secondary surfactant deficiency. Knowledge of the optimal approach to surfactant replacement in neonates with CDH and respiratory failure is limited. The aim of this study was to determine if surfactant replacement on extracorporeal membrane oxygenation (ECMO) results in improved outcomes in neonates > or =35 weeks' gestation with unrepaired CDH.

METHODS

Using the CDH Study Group Registry, the authors identified 448 neonates with CDH who were > or =35 weeks' gestation, had no major anomalies, were treated with ECMO within the first 7 days of life, and underwent repair on or after ECMO therapy. Patients in 2 groups were compared: group 1 (- Surf, n = 334) consisted of patients who received no surfactant and group 2 (+ Surf, n = 114) consisted of patients who received at least 1 dose of surfactant while on ECMO. An analysis of all patients in both groups was performed. Additionally, subgroup analyses stratified by gestational age were performed for patients 351/7 to 366/7 weeks' gestation and for patients > or =37 weeks' gestation. Primary end-points for the study were survival and length of ECMO run. Secondary end-points were length of intubation, need for supplemental oxygen at 30 days of life, and at discharge to home. Demographic, clinical, and outcome variables were examined using Fisher's Exact tests for categorical variables and using unpaired t tests for continuous variables. Odds ratios were calculated for categorical end-point variables.

RESULTS

Demographic and clinical variables were similar between groups. Analyses of aggregate data showed no significant differences between groups in length of ECMO run, survival, number of days intubated, and percent of patients requiring supplemental oxygen at 30 days or discharge. Subgroup stratification by gestational age did not show significant differences between groups in any of the outcome variables.

CONCLUSIONS

The data from this study suggest that surfactant replacement on ECMO for neonates with congenital diaphragmatic hernia does not provide significant benefit in the infant's clinical course with respect to survival, length of ECMO course, length of intubation, or subsequent need for supplemental oxygen.

Lung function in lambs with diaphragmatic hernia after reversible fetal tracheal occlusion

BACKGROUND/PURPOSE

Short-duration resuscitation (< or =4 hours) of lambs with diaphragmatic hernia treated in utero with tracheal occlusion have shown improved lung function compared with untreated diaphragmatic hernia. This may be a transient phenomenon in the treated diaphragmatic hernia lambs because of surfactant deficiency. Our objective was to analyze the effect of fetal tracheal occlusion with or without release of the occlusion 1 week before delivery on pulmonary function during a longer period of resuscitation (8 hours) in the diaphragmatic hernia lamb model.

METHODS

Four groups were compared: diaphragmatic hernia (n = 5), diaphragmatic hernia and tracheal occlusion until delivery (n = 5), diaphragmatic hernia and tracheal occlusion with release of the occlusion 1 week before delivery (n = 5), and normal controls (n = 4).

RESULTS

Despite persistently decreased surfactant levels, diaphragmatic hernia lambs treated with tracheal occlusion had normal-sized lungs with marked improvement in lung function and gas exchange over 8 hours when compared with untreated lambs with diaphragmatic hernia. Release of the tracheal occlusion 1 week before delivery added no benefit.

CONCLUSIONS

It appears that surfactant-independent mechanisms such as pulmonary growth and structural changes are of foremost importance in relating to improved compliance, oxygenation, and ventilation of diaphragmatic hernia lambs treated with tracheal occlusion.

Administration of prenatal betamethasone suppresses the adrenal-hypophyseal axis in newborns with congenital diaphragmatic hernia

BACKGROUND

Congenital diaphragmatic hernia (CDH) is a condition that is characterized by pulmonary hypoplasia and pulmonary hypertension. Prenatal betamethasone often is administered to fetuses with CDH to improve pulmonary function. In this study, the authors investigate the possible role of the adrenal-hypophyseal axis in CDH in an animal model and subsequently in human infants with CDH.

METHODS

Twin fetal sheep underwent creation of DH or a sham thoracotomy, and levels of plasma and lung ACTH and plasma cortisol were compared. For the human studies, plasma levels of ACTH, cortisol, and DHEA were measured in cord blood samples collected from 9 CDH (5 that received prenatal betamethasone) and compared with those of 14 normal newborns. In both studies, ACTH and cortisol levels were determined by radioimmunoassay (RIA). Human (DHEA) levels were determined by ELISA.

RESULTS

Plasma ACTH and cortisol levels were elevated in fetal DH sheep compared with sham-operated controls; however, levels of ACTH in lung tissues were not different. Human newborns with CDH who have been exposed to prenatal steroids have significantly lower plasma ACTH, cortisol, and DHEA levels than normal newborns and CDH newborns not exposed to prenatal betamethasone.

CONCLUSIONS

In an ovine model of CDH, the adrenal-hypophyseal axis appears up-regulated in DH fetuses compared with sham-operated animals. Conversely, the adrenal-hypophyseal axis in human CDH newborns appears normal but is suppressed by the administration of prenatal betamethasone.

Pulmonary vascular morphology in a fetal rabbit model for congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Although the pulmonary vascular abnormalities in congenital diaphragmatic hernia (CDH) are described from a morphologic point of view, the treatment of pulmonary hypertension (PH) remains one of the main unsolved problems in clinical daily practice. For this reason, detailed studies in well-validated animal models could still be of significance in our understanding of the pathogenesis of CDH.

METHODS

In does of 23 days' gestational age (GA), 39 fetuses underwent creation of diaphragmatic hernia (DH) and 15 fetuses a sham thoracotomy (SHAM). Thirty-nine nonoperated littermates served as internal controls (CTR). Fetuses were harvested by cesarean section on days 25, 27, 29, and 30 of gestation. Lung specimens were obtained and formalin fixed for further vascular morphometry studies.

RESULTS

Lung vessels from DH fetuses started to show significantly smaller internal diameter (ID), external diameter (ED), larger arterial wall thickness (WT), and, in particular, a proportionally higher medial thickness (%MT) and adventitial thickness (%AT) from day 27 onward when compared with control fetuses. SHAM fetuses, which were harvested at term, showed no differences with CTR.

CONCLUSIONS

This is the first report documenting changes over time in the vascular system in a rabbit fetal model of surgically induced DH. These changes mimic pathologic findings observed in human fetuses and are also concordant with earlier observations in the surgical ovine model and the toxic nitrofen rat model.

Cardiopulmonary anatomy and function in long-term survivors of mild to moderate congenital diaphragmatic hernia

BACKGROUND/PURPOSE

In the last decades, several studies regarding cardiopulmonary sequelae in survivors of congenital diaphragmatic hernia (CDH) have been published, but results often are conflicting, and controversies still exist. The aim of this study was to assess cardiopulmonary anatomic and functional outcome in a group of long-term survivors of CDH of mild to moderate degree.

METHODS

Twenty-four children aged 8.15 +/- 2.80 years underwent clinical examination with growth assessment, chest radiographs, echocardiography, pulmonary perfusion scintigraphy, static lung volumes measurement, and spirometry.

RESULTS

Mean Z scores of weight for age and height for age were within normal values. Echocardiography showed normal anatomy and function in all but 3 patients with isolated CDH, in whom minor alterations were detected. Mean perfusion to the affected side was significantly lower (45.16 +/- 5.30%; P <.0001) but still within normal range. Four children showed a substantial impairment of perfusion to the hernia side. The mean spirometric values and pulmonary volumes were normal. However, a mild restrictive pattern was evident in 6 children (27.3%), an obstructive pattern in 3 (13.6%), and a mixed obstructive and restrictive impairment in 1.

CONCLUSIONS

Hypoplastic lungs of mild to moderate CDH survivors continue to cause pulmonary morbidity in some children many years after the correction of the defect. In particular, lung perfusion appears to be impaired in 20% of the patients and pulmonary function in 45%, without any significant cardiac or developmental sequelae. The negative correlation between FEV1 and duration of ventilation at presentation (r = -0.49; P =.026) may be caused by the consequences of lung hypoplasia, but initial ventilatory management may contribute to increased pulmonary morbidity. Relationship between perfusion and FEF25-75 (r = 0.61; p = 0.004) could reflect an equivalent degree of reduction in the caliber of distal airways and pulmonary vascular tree.

Pulmonary surfactant protein A, B, and C mRNA and protein expression in the nitrofen-induced congenital diaphragmatic hernia rat model

Neonates with congenital diaphragmatic hernia (CDH) suffer from a diaphragmatic defect, lung hypoplasia, and pulmonary hypertension, with poor lung function forming the major clinical challenge. Despite prenatal diagnosis and advanced postnatal treatment strategies, the mortality rate of CDH is still high. CDH has been subject of extensive research over the past decades, but its etiology remains unknown. A major problem with CDH is the failure to predict the individual response to treatment modalities like high-frequency ventilation, inhaled nitric oxide, and extracorporeal membrane oxygenation. In this study, we tested the possibility that CDH lungs are surfactant protein deficient, which could explain the respiratory failure and difficulties in treating CDH infants. We investigated this hypothesis in the nitrofen-induced CDH rat model and assessed the cellular concentrations of surfactant protein (SP)-A, -B, and -C mRNA with a quantitative radioactive in situ hybridization technique. No differences were observed between control and CDH lungs for SP mRNA expression patterns. The cellular concentration (mean OD) of SP-A and SP-B mRNA was similar at all stages whereas the mean OD of SP-C mRNA and the volume fraction of cells (% Area) expressing SP mRNA was higher in CDH lungs at term. Immunohistochemical analysis revealed no differences between control and CDH lungs for SP protein expression. No differences in the mean OD or % Area for the SP mRNAs were found between the ipsi- and contralateral side of CDH lungs. We conclude that there is no primary deficiency of surfactant proteins in the nitrofen-induced CDH rat model.

Partial liquid ventilation combined with two different gas ventilatory strategies in acute lung injury in piglets: Effects on gas exchange, respiratory mechanics, and hemodynamics

BACKGROUND/PURPOSE

Partial liquid ventilation (PLV) has been shown to improve oxygenation and lung mechanics in different models of acute lung injury. This study was designed to investigate the effects of 2 gas ventilatory strategies during PLV on gas exchange, respiratory mechanics, and hemodynamics in acute lung injury in piglets.

METHODS

After induction of acute lung injury, the animals were assigned randomly to 2 groups with different positive end-expiratory pressure (PEEP) levels and tidal volumes (Vt) (group A, Vt > 12.5 mL/kg; PEEP = 6 cm H2O, n = 7; group B, Vt < 9 mL/kg, PEEP = 12 cm H2O, n = 7). Thereafter, the perfluorocarbon (PFC) liquid (30 mL/kg) was instilled into the endotracheal tube. Cardiorespiratory parameters were measured at baseline, after induction of acute lung injury, and every 30 minutes up to 120 minutes.

RESULTS

During PLV, oxygenation significantly improved with no difference between both gas ventilatory strategies. The high PEEP-moderate Vt gas ventilatory strategy reduced the inspiratory airway resistance and was associated with moderate hypercapnia. There were no significant differences in hemodynamics and respiratory compliance between both gas ventilatory strategies.

CONCLUSIONS

The results of this pilot study suggest that oxygenation was equally improved during PLV. This effect was independent of the mode of gas ventilation. However, the high PEEP-moderate Vt gas ventilatory technique resulted in moderate hypercapnia.

Airway and blood vessel interaction during lung development

In the adult lung the pulmonary arteries run alongside the airways and the pulmonary veins show a similar branching pattern to the arteries, though separated from them. During early fetal development the airways act as a template for pulmonary blood vessel development in that the vessels form by vasculogenesis around the branching airways. In later lung development the capillary bed is essential for alveolar formation. This paper reviews evidence for the interaction of the airways and blood vessels in both normal and abnormal lung development.

Altered gene level expression of thyroid hormone receptors alpha-1 and beta-1 in the lung of nitrofen-induced diaphragmatic hernia

PURPOSE

Thyroid receptor alpha-1 (TR-alpha1) and thyroid receptor beta-1 (TR-beta1) are thought to be essential for the fetal and postnatal development of the lung. The authors investigated gene level expression of TR-alpha1 and TR-beta1 in the lung of nitrofen-induced congenital diaphragmatic hernia (CDH) using reverse transcription polymerase chain reaction (RT-PCR).

METHODS

CDH was induced in pregnant rats after administration of 100 mg nitrofen on day 9.5 of gestation. Cesarean section was performed on day 21 of gestation. The fetuses were divided into 3 groups: normal controls (n = 16), nitrofen-induced CDH (n = 16), and nitrofen-treated without CDH (n = 16). mRNA was extracted from the left lung in each group. RT-PCR was performed to evaluate mRNA expressions of TR-alpha1 and TR-beta1. Levels of mRNA were expressed as a ratio of the band density divided by that of beta-actin, a house-keeping gene.

RESULTS

TR-alpha1 mRNA expression was decreased significantly in CDH lung (1.618 +/- 0.148) compared with controls (2.658 +/- 0.251; P <.01) and nitrofen-treated without CDH lung (2.232 +/- 0.193; (P <.05). TR-beta1 mRNA expression also was significantly decreased in CDH lung (2.223 +/- 0.270) compared with controls (3.569 +/- 0.262; P <.01) and nitrofen-treated without CDH lung (3.235 +/- 0.299; P <.05).

CONCLUSION

These data suggest that the downregulation of thyroid hormone signaling pathway through altered expression of TR-alpha1 and TR-beta1 during lung morphogenesis may be a contributory factor in the pathogenesis of pulmonary hypoplasia in nitrofen-induced CDH.

Pulmonary structural maturation and pulmonary artery remodeling after reversible fetal ovine tracheal occlusion in diaphragmatic hernia

PURPOSE

Congenital diaphragmatic hernia (CDH) is associated with thickened pulmonary arteries (PA) contributing to pulmonary hypertension. In the current study, the effects of antenatal glucocorticoids and reversible tracheal occlusion (TO) on PA structure were assessed in a hypoplastic lung model.

METHODS

A left-sided CDH was created in fetal lambs at 80 days gestation, TO at 108 days, and release of the occlusion (TR) at 129 days. All were given 1 dose of maternal glucocorticoids at 135 days. At 136 days (term, 145 days), the fetus was delivered by cesarian section. CDH (n = 7), CDH + TO (n = 6), CDH + TO + TR (n = 6), and unoperated twin controls (n = 16) were compared. Outcome measurements were (1) lung growth, represented by lung weight to body weight ratio (LW/BW), (2) lung structural maturation, which is inversely proportional to mean terminal bronchiole density (MTBD), (3) PA medial and adventitial areas (square micrometers), (4) lung capillary load, which is the ratio of vessel surface area (SA) to tissue SA ratio.

RESULTS

CDH lungs were hypoplastic with a low LW/BW and high MTBD. The small PAs (<75 microm) of CDH had an increased medial area, indicating increased muscle mass and an increased adventitial area. CDH + TO +/- TR increased LW/BW and achieved normal structural lung maturity with a low MTBD. Only CDH + TO thinned the PA medial area closer to control values. The adventitial area remained thick in CDH +/- TO +/- TR when compared with controls. All 4 groups had similar capillary load.

CONCLUSIONS

TO may be especially important for PA remodeling in the latter part of gestation, because TR 1 week before delivery prevents thinning of the small PAs in CDH. The shaping achieved by TO in terms of lung growth, structural maturity, and pulmonary artery medial area thinning may prove beneficial in lessening the severity of the associated pulmonary hypertension in CDH.

Surfactant levels after reversible tracheal occlusion and prenatal steroids in experimental diaphragmatic hernia

BACKGROUND/PURPOSE

In normal lungs, fetal tracheal occlusion (TO) induces lung growth but decreases the number of type II cells; this is remedied if TO is released (TR) before delivery. In the current study, the effects of TO with or without TR on pulmonary structure and surfactant were assessed in the ovine model in which lung hypoplasia was induced by creation of a diaphragmatic hernia (CDH).

METHODS

A left-sided CDH was created in fetal lambs at 80 days gestation; TO was done at 108 days; and TR at 129 days. All ewes were given 1 dose of glucocorticoids at 135 days. At 136 days, the fetus was delivered. Lung weight to body weight ratio, mean terminal bronchiole density, type II cell density, bronchoalveolar lavage fluid (BAL) phosphatidylcholine (PC), BAL surfactant protein A (SP-A) and B (SP-B), and lung tissue SP-A and SP-B were assessed in CDH, CDH with TO, CDH with TO and TR, and controls.

RESULTS

CDH lungs were hypoplastic and structurally immature, but had increased type II cell density. TO with or without TR caused lung growth with normalization of lung parenchymal architecture and type II cell density. Although the BAL SP-A and BAL SP-B were similar in all 4 groups, the BAL PC was low in CDH with or without TO or TR. Also, lung tissue SP-B levels were low in CDH with or without TO or TR. However, lung tissue SP-A levels were normal in CDH, but low in CDH with TO with or without TR.

CONCLUSIONS

Despite the finding that lung morphology was improved in CDH with TO with or without TR animals, surfactant content and composition remained abnormal. Although surfactant secreted early by the fetus into alveolar spaces contained normal levels of BAL SP-A and BAL SP-B, the low levels of BAL PC and low lung tissue stores of SP-B indicate that these experimental lambs may experience respiratory insufficiency soon after birth. This implies that prophylactic surfactant at birth might be beneficial for CDH.

Lung development following diaphragmatic hernia in the fetal rabbit

Diaphragmatic hernia was created in 39 rabbit fetuses on day 23 of gestation. Fifteen fetuses underwent a sham thoracotomy (SHAM). Thirty-nine non-operated littermates served as internal controls (CTR). Fetuses were harvested by Caesarean section on days 25, 27, 29 and 30 of gestation. Pulmonary response was evaluated by lung to body weight ratio (LBWR), morphometry, and density of type II pneumocytes. No difference was found between CTR and SHAM fetuses at term. CDH fetuses had smaller lungs (LBWR 0.014 +/- 0.004 versus 0.030 +/- 0.04 in CTR, P < 0.0001), a less complex acinus [mean terminal bronchial density (MTBD) 1.786 +/- 0.408 versus 0.917 +/- 0. 188, P < 0.0001], thicker alveolar septa [mean wall transection length (LMW) 0.0221 +/- 0.008 versus 0.0142 +/- 0.002, P = 0.0003], and a lower type II cell count (144.5 +/- 19.33 versus 216.2 +/- 27.85 per high power field, P < 0.0001). The differences in MTBD and LMW were significant from gestational day 25 onwards, and the differences in type II cell count from day 27 onwards. Surgical diaphragmatic hernia in rabbit fetuses in the late pseudoglandular phase reproduces many features of the pulmonary hypoplasia associated with human congenital diaphragmatic hernia, including the delayed maturation. The effects are present within 2 days following experimental diaphragmatic hernia and progress over time.

In vitro effects of growth factors on lung hypoplasia in a model of congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Pulmonary hypoplasia, a leading contributor to the lethality of congenital diaphragmatic hernia (CDH), precedes diaphragmatic malformation in the nitrofen model and persists to allow experimental manipulations in organ culture. Fibroblast growth factors (FGFs) are crucial to early lung development. Acidic FGF (FGF-1) binds to all FGF receptors and enhances in vitro branching morphogenesis. Basic FGF (FGF-2) is localized to developing airway epithelium, basement membrane, and extracellular matrix. Heparin (HEP) modulates FGF kinetics and inhibits smooth muscle proliferation in lung primordia. The aim of this study was to examine the morphological effects of fibroblast growth factors and heparin on lung hypoplasia in an organ culture model.

METHODS

Sprague-Dawley rats were fed nitrofen on day 9.5 of pregnancy to induce lung hypoplasia and CDH in newborns. Control rats received olive oil. Normal and hypoplastic lung primordia were microdissected on day 13.5 of gestation and cultured up to 78 hours in plain media with or without FGF-1 or FGF-2, with or without HEP. In vitro morphological development was studied by serial measurements of terminal bud count, lung area, and lung perimeter.

RESULTS

Over 120 fetal lung specimens were studied (n > or = 4 per group). Significant increases in area, perimeter, and bud count were seen in normal lungs cultured with FGF-1 plus HEP compared with control media (P < .05). In the nitrofen lungs, FGF1 plus HEP yielded reductions in all parameters compared with those in control media (P < .05), whereas FGF-2 produced significant expansion in lung area but marked reductions in bud count and lung perimeter divided by square root of area (P < .05). Heparin did not produce substantial or sustained alteration of morphology in normal or hypoplastic lungs.

CONCLUSIONS

These observations may indicate an intrinsic abnormality of FGF processing in the hypoplastic nitrofen lung before diaphragmatic malformation. Heparin did not rescue abnormal lung development. Mechanisms underlying the differential effects of these agents now need to be explored to target fetal lung growth and improve the dismal prognosis of human CDH.

[Late revealing of congenital diaphragmatic hernia: diagnostic difficulties]

Two patients, aged four and six months, with congenital diaphragmatic hernias, and who presented outside of the neonatal period, are reported. Clinical presentation was a progressive respiratory failure, and radiographic findings showed a consolidation of the left lung, associated with a pneumothorax in one and an ascites in the other. One had previous normal chest X-rays. All cases with herniated bowel showed connecting bowel segments passing through the diaphragmatic defect. All were repaired via an abdominal approach. Delay in presentation of congenital diaphragmatic hernias is not uncommon. Long-term prognosis is favourable and postoperative morbidity is minimal, despite late presentation and undesirable time delay between first sign and surgery.

Remodeling of pulmonary arteries in human congenital diaphragmatic hernia with or without extracorporeal membrane oxygenation

PURPOSE

The aim of this study was to describe in detail the perinatal developmental profile of the pulmonary vasculature in congenital diaphragmatic hernia (CDH) and to examine the potential beneficial effects of extracorporeal membrane oxygenation (ECMO) on the vascular morphology. Additionally the authors aimed to identify the differences in pulmonary vascular morphology among CDH cases according to the primary cause of death: either extreme lung hypoplasia (LH) or persistent pulmonary hypertension (PPH).

METHODS

The authors studied autopsy sections from 30 high-risk CDH cases with respect to the pulmonary arteries in relation to gestational age (GA) and ECMO treatment. They were grouped into CDH-I: 20 cases with GA greater than 34 weeks who were not subjected to ECMO and CDH-II: 10 cases with GA greater than 34 weeks, who were subjected to ECMO for an average time of 237 hours. Five age-matched neonates who died from placental insufficiency or birth asphyxia without evidence of lung hypoplasia served as controls (CON). Medial and adventitial thicknesses of pulmonary arteries were measured in lung sections stained with Elastic van Gieson by 2 investigators blinded for the clinical data. Immunohistological staining with anti-alpha-smooth muscle actin (alpha-SMA) was performed to confirm the precise location of the arterial media before morphometry. CDH cases were subgrouped and compared according to the primary cause of death. Unpaired Student t test was used for statistics, with significant P value < or =.05.

RESULTS

In CDH newborns, a significant increase in medial, adventitial, and total wall thickness was found in pulmonary arteries with an external diameter of less than 200 microm as compared with age-matched controls (P<.004, .0001, and .0009, respectively). ECMO-treated CDH newborns showed a significantly thinner arterial adventitia than CDH patients who did not receive this treatment (P<.0001), approaching normal values. However, the medial thickness remained increased. Morphometrically, no significant differences in CDH cases between patients dying of PPH or severe LH could be determined.

CONCLUSIONS

(1) In CDH, there is failure of the normal arterial remodeling processes occurring in the perinatal period. (2) Pulmonary vascular morphology in CDH does not differ between the groups with lung hypoplasia or persistent pulmonary hypertension as primary cause of death. (3) Adventitial thinning of these arteries might be one of the mechanisms by which ECMO alters PPH in CDH cases.

Cell proliferation and apoptosis in experimental lung hypoplasia

BACKGROUND/PURPOSE

Current treatment for lethal pulmonary hypoplasia in congenital diaphragmatic hernia (CDH) may be hampered by uncertainty over its origin. Herniation of abdominal organs into the chest was thought to produce lung hypoplasia by compression. Experimental CDH models suggest that disturbed lung growth precedes these events. Mammalian development comprises cell differentiation, proliferation and programmed cell death or apoptosis. Could lung hypoplasia in CDH result from alterations in these processes well before visceral herniation takes place? The aim of this study was to compare cell proliferation and apoptosis in normal and hypoplastic embryonic lungs before normal diaphragmatic closure using a CDH model.

METHODS

Sprague-Dawley rats were given 100 mg of nitrofen on day 9.5 of pregnancy to create lung hypoplasia and CDH in newborns (term, 22 days). Control rats received olive oil. Cell proliferation in embryonic lung specimens was measured by bromodeoxyuridine (BrdU) incorporation at 13.5 to 15.5 days' gestation, before normal diaphragmatic closure in this species (day 16.5). Apoptosis was measured by the in situ end-nick labelling (TUNEL) method in lung sections obtained from rat embryos of 13.5 to 16.5 days' gestation.

RESULTS

High levels of cell proliferation were seen in both normal control and nitrofen-exposed lungs. However, 24 hours before normal diaphragmatic closure, nitrofen-exposed lungs had significant reductions in cell proliferation on day 15.5 of gestation (P = .009 v controls). Apoptosis occurred at low levels throughout the developmental stages examined (< 0.3%) without significant differences encountered between the study groups.

CONCLUSIONS

These findings have shown high rates of cell division during normal lung development before diaphragmatic closure. Decreased levels over this critical period in gestation may contribute to early lung anomalies in the nitrofen CDH model. Strategies to promote cell proliferation in the fetal lung may therefore hold future promise in human CDH. Apoptosis appears not to play a major role in hypoplastic lung development. Therapies to inhibit apoptosis would seem unlikely to improve this early lung growth.