Lower Distending Pressure Improves Respiratory Mechanics in Congenital Diaphragmatic Hernia Complicated by Persistent Pulmonary Hypertension

Infants With a Congenital Diaphragmatic Hernia Had Favourable Pulmonary Hypertension Outcomes at 1 Year of Age

AIM

Pulmonary hypertension is frequent in neonates with a congenital diaphragmatic hernia, but long-term data have been scarce. Our aim was to examine its prevalence, evolution and management and identify factors associated with its persistence.

METHODS

This French retrospective cohort study compared the characteristics of neonates who had persistent pulmonary hypertension, or died with it, and those with normalised pulmonary pressures at 1 month and 1 year of age.

RESULTS

Most (92%) of the 88 neonates we studied underwent surgery. Two-thirds (67%) had preoperative pulmonary hypertension and they included 10 of the 11 who died after surgery. Pulmonary hypertension resolved after a median of 31 days in the 70 who were discharged alive and 27% required prolonged sildenafil treatment. At 1 year, 6 (9%) of the 65 children with echocardiographic data available still had elevated pulmonary pressures. Preoperative pulmonary hypertension, associated malformations and longer invasive ventilation were independently associated with persistent pulmonary hypertension at 1 month. Only prolonged invasive ventilation remained significant at 1 year.

CONCLUSION

Despite its high initial prevalence and impact on mortality, pulmonary hypertension resolved within weeks of surgery in the surviving neonates. The duration of invasive ventilation may have been a key factor in its persistence.

Lung-protective ventilation in the management of congenital diaphragmatic hernia

Prioritizing lung-protective ventilation has produced a clear mortality benefit in neonates with congenital diaphragmatic hernia (CDH). While there is a paucity of CDH-specific evidence to support any particular approach to lung-protective ventilation, a growing body of data in adults is beginning to clarify the mechanisms behind ventilator-induced lung injury and inform safer management of mechanical ventilation in general. This review summarizes the adult data and attempts to relate the findings, conceptually, to the CDH population. Critical lessons from the adult studies are that much of the damage done during conventional mechanical ventilation affects normal lung tissue and that most of this damage occurs at the low-volume and high-volume extremes of the respiratory cycle. Consequently, it is important to prevent atelectasis by using sufficient positive end-expiratory pressure while also avoiding overdistention by scaling tidal volume to the amount of functional lung tissue rather than body weight. Paralysis early in acute respiratory distress syndrome improves outcomes, possibly because consistent respiratory mechanics facilitate avoidance of both atelectasis and overdistention-a mechanism that may also apply to the CDH population. Volume-targeted conventional modes may be advantageous in CDH, but determining optimal tidal volume is challenging. Both high-frequency oscillatory ventilation and high-frequency jet ventilation have been used successfully as 'rescue modes' to avoid extracorporeal membrane oxygenation, and a prospective trial comparing the two high-frequency modalities as the primary ventilation strategy for CDH is underway.

Ventilator strategies in congenital diaphragmatic hernia

This review focuses on contemporary mechanical ventilator practices used in the initial management of neonates born with congenital diaphragmatic hernia (CDH). Both conventional and non-conventional ventilation modes in CDH are reviewed. Special emphasis is placed on the rationale for gentle ventilation and the current evidence-based clinical practice guidelines that are recommended for supporting these fragile infants. The interplay between CDH lung hypoplasia and other key cardiopulmonary elements of the disease, namely a reduced pulmonary vascular bed, abnormal pulmonary vascular remodeling, and left ventricular hypoplasia, are discussed. Finally, we provide insights into future avenues for mechanical ventilator research in CDH.

Mechanical ventilation in special populations

Optimal respiratory support can only be achieved if the ventilator strategy utilized for each individual patient at any given point in the evolution of their disease process is tailored to the underlying pathophysiology. The critically ill newborn infant requires individualized patient care when it comes to mechanical ventilation. This can only occur if the clinician has a good understanding of the different pathophysiologies of a variety of conditions that can lead to respiratory failure. In this chapter we describe the key pathophysiological features of bronchopulmonary dysplasia, meconium aspiration syndrome and lung hypoplasia syndromes with emphasis on congenital diaphragmatic hernia. We review available evidence to guide management an provide specific recommendations for pathophysiologically-based mechanical ventilation support.

Congenital Diaphragmatic Hernia: Pulmonary Hypertension and Pulmonary Vascular Disease

This review provides a comprehensive summary of the current understanding of pulmonary hypertension (PH) in congenital diaphragmatic hernia, outlining the underlying pathophysiologic mechanisms, methods for assessing PH severity, optimal management strategies, and prognostic implications.

Congenital diaphragmatic hernia: quality improvement using a maximal lung protection strategy and early surgery-improved survival

To evaluate the effectiveness of a novel protocol, adopted in our institution, as a quality improvement project for congenital diaphragmatic hernia (CDH). A maximal lung protection (MLP) protocol was implemented in 2019. This strategy included immediate use of high-frequency oscillatory ventilation (HFOV) after birth, during the stay at the Neonatal Intensive Care Unit (NICU), and during surgical repair. HFOV strategy included low distending pressures and higher frequencies (15 Hz) with subsequent lower tidal volumes. Surgical repair was performed early, within 24 h of birth, if possible. A retrospective study of all inborn neonates prenatally diagnosed with CDH and without major associated anomalies was performed at the NICU of Schneider Children's Medical Center of Israel between 2009 and 2022. Survival rates and pulmonary outcomes of neonates managed with MLP were compared to the historical standard care cohort. Thirty-three neonates were managed with the MLP protocol vs. 39 neonates that were not. Major adverse outcomes decreased including death rate from 46 to 18% (p = 0.012), extracorporeal membrane oxygenation from 39 to 0% (p < 0.001), and pneumothorax from 18 to 0% (p = 0.013).

CONCLUSION

 MLP with early surgery significantly improved survival and additional adverse outcomes of neonates with CDH. Prospective randomized studies are necessary to confirm the findings of the current study.

WHAT IS KNOWN

• Ventilator-induced lung injury was reported as the main cause of mortality in neonates with congenital diaphragmatic hernia (CDH). • Conventional ventilation is recommended by the European CDH consortium as the first-line ventilation modality; timing of surgery is controversial.

WHAT IS NEW

• A maximal lung protection strategy based on 15-Hz high-frequency oscillatory ventilation with low distending pressures as initial modality and early surgery significantly reduced mortality and other outcomes.

Unique Cardiopulmonary Interactions in Congenital Diaphragmatic Hernia: Physiology and Therapeutic Implications

Congenital diaphragmatic hernia (CDH) results in abdominal contents entering the thoracic cavity, affecting both cardiac and pulmonary development. Maldevelopment of the pulmonary vasculature occurs within both the ipsilateral lung and the contralateral lung. The resultant bilateral pulmonary hypoplasia and associated pulmonary hypertension are important components of the pathophysiology of this disease that affect outcomes. Despite prenatal referral to specialized high-volume centers, advanced ventilation strategies, pulmonary hypertension management, and the option of extracorporeal membrane oxygenation, overall CDH mortality remains between 25% and 30%. With increasing recognition that cardiac dysfunction plays a large role in morbidity and mortality in patients with CDH, it becomes imperative to understand the different clinical phenotypes, thus allowing for individual patient-directed therapies. Further research into therapeutic interventions that address the cardiopulmonary interactions in patients with CDH may lead to improved morbidity and mortality outcomes.

Intact cord resuscitation in newborns with congenital diaphragmatic hernia: insights from a lamb model

Introduction

Congenital diaphragmatic hernia (CDH) is a rare condition characterized by pulmonary hypoplasia, vascular dystrophy, and pulmonary hypertension at birth. Validation of the lamb model as an accurate representation of human CDH is essential to translating research findings into clinical practice and understanding disease mechanisms. This article emphasizes the importance of validating the lamb model to study CDH pathogenesis and develop innovative therapeutics.

Material and methods

At 78 days of gestation, the fetal lamb's left forelimb was exposed through a midline laparotomy and hysterotomy, and a supra diaphragmatic thoracotomy was performed to allow the digestive organs to ascend into the thoracic cavity. At 138 ± 3 days of gestation, lambs were delivered via a cesarean section; then, with umbilical cord intact during 1 hour, the lambs were mechanically ventilated with gentle ventilation in a pressure-controlled mode for 2 h.

Results

CDH lambs exhibited a lower left lung-to-body weight ratio of 5.3 (2.03), p < 0.05, and right lung-to-body weight ratio of 8.2 (3.1), p < 0.05. They reached lower Vt/kg (tidal volume per kg) during the course of the resuscitation period with 1.2 (0.7) ml/kg at 10 min and 3 (1.65) ml/kg at 60 min (p < 0.05). Compliance of the respiratory system was lower in CDH lambs with 0.5 (0.3) ml/cmH2O at 60 min (p < 0.05) and 0.9 (0.26) ml/cmH2O at 120 min (p < 0.05). Differences between pre- and postductal SpO2 were higher with 15.1% (21.4%) at 20 min and 6.7% (14.5%) at 80 min (p < 0.05). CDH lambs had lower differences between inspired and expired oxygen fractions with 4.55% (6.84%) at 20 min and 6.72% (8.57%) at 60 min (p < 0.05). CDH lamb had lower left ventricle [2.73 (0.5) g/kg, p < 0.05] and lower right ventricle [0.69 (0.8), p < 0.05] to left ventricle ratio.

Discussion

CDH lambs had significantly lower tidal volume than control lambs due to lower compliance of the respiratory system and higher airway resistance. These respiratory changes are characteristic of CDH infants and are associated with higher mortality rates. CDH lambs also exhibited pulmonary hypertension, pulmonary hypoplasia, and left ventricle hypoplasia, consistent with observations in human newborns. To conclude, our lamb model successfully provides a reliable representation of CDH and can be used to study its pathophysiology and potential interventions.

Neonatal pneumothorax in congenital diaphragmatic hernia: Be wary of high ventilatory pressures

Background

Patients with congenital diaphragmatic hernia (CDH) require invasive respiratory support and higher ventilator pressures may be associated with barotrauma. We sought to evaluate the risk factors associated with pneumothorax in CDH neonates prior to repair.

Methods

We retrospectively reviewed newborns born with CDH between 2014 and 2019 who developed a pneumothorax, and we matched these cases to patients with CDH without pneumothorax.

Results

Twenty-six patients were included (n=13 per group). The pneumothorax group required extracorporeal life support (ECLS) more frequently (85% vs 54%, p=0.04), particularly among type A/B defects (31% vs 7%, p=0.01). The pneumothorax group had higher positive end-expiratory pressure (PEEP) within 1 hour of birth (p=0.02), at pneumothorax diagnosis (p=0.003), and at ECLS (p=0.02). The pneumothorax group had a higher mean airway pressure (Paw) at birth (p=0.01), within 1 hour of birth (p=0.01), and at pneumothorax diagnosis (p=0.04). Using multiple logistic regression with cluster robust SEs, higher Paw (OR 2.2, 95% CI 1.08 to 3.72, p=0.03) and PEEP (OR 1.8, 95% CI 1.15 to 3.14, p=0.007) were associated with an increased risk of developing pneumothorax. There was no difference in survival (p=0.09).

Conclusions

Development of a pneumothorax in CDH neonates is independently associated with higher Paw and higher PEEP. A pneumothorax increases the likelihood of treated with ECLS, even with smaller defect.

Clinical trials and outcome reporting in congenital diaphragmatic hernia overlook long-term health and functional outcomes-A plea for core outcomes

Aim

To review the selection, measurement and reporting of outcomes in studies of interventions in Congenital Diaphragmatic Hernia (CDH).

Methods

We searched the Cochrane Central Register of Controlled Trials from 2000–2020 for randomised trials and observational studies. Outcomes reported were classified into seven key domains modelled on the patient journey.

Results

Our search yielded 118 papers; 27 were eligible. The most frequent domains measured were ‘short‐term markers of disease activity’ (17/27), whereas long‐term outcomes (3/27) and outcomes relating to functional health status (8/27) were reported infrequently. There was heterogeneity in the methods and timing of outcome reporting. Primary outcomes were varied and not always clearly stated.

Conclusion

Long‐term health and functional outcomes involving interventional studies in CDH are infrequently reported, which hinders the process of shared decision‐making and evidence‐based healthcare. A CDH core outcome set is needed to standardise outcome reporting that is relevant to both families and healthcare teams.

Congenital diaphragmatic hernia: a narrative review of controversies in neonatal management

The consequences of most hernias can be immediately corrected by surgical repair. However, this isn't always the case for children born with a congenital diaphragmatic hernia. The derangements in physiology encountered immediately after birth result from pulmonary hypoplasia and hypertension caused by herniation of abdominal contents into the chest early in lung development. This degree of physiologic compromise can vary from mild to severe. Postnatal management of these children remains controversial. Although heavily studied, multi-institutional randomized controlled trials are lacking to help determine what constitutes best practice. Additionally, the results of the many studies currently within the literature that have investigated differing aspect of care (i.e., inhaled nitric oxide, ventilator type, timing of repair, role of extracorporeal membrane oxygenation, etc.) are difficult to interpret due to the small numbers investigated, the varying degree of physiologic compromise, and the contrasting care that exists between institutions. The aim of this paper is to review areas of controversy in the care of these complex kids, mainly: the use of fraction of inspired oxygen, surfactant therapy, gentle ventilation, mode of ventilation, medical management of pulmonary hypertension (inhaled nitric oxide, sildenafil, milrinone, bosentan, prostaglandins), the utilization of extracorporeal membrane oxygenation, and the timing of surgical repair.

Respiratory Support of Infants With Congenital Diaphragmatic Hernia

Optimisation of respiratory support of infants with congenital diaphragmatic hernia (CDH) is critical. Infants with CDH often have severe lung hypoplasia and abnormal development of their pulmonary vasculature, leading to ventilation perfusion mismatch. It is vital that lung protective ventilation strategies are employed during both initial stabilisation and post-surgical repair to avoid ventilator induced lung damage and oxygen toxicity to prevent further impairment to an already diminished gas-exchanging environment. There is a lack of robust evidence for the routine use of surfactant therapy during initial resuscitation of infants with CDH and thus administration cannot be recommended outside clinical trials. Additionally, inhaled nitric oxide has been shown to have no benefit in reducing the mortality rates of infants with CDH. Other therapeutic agents which beneficially act on pulmonary hypertension are currently being assessed in infants with CDH in randomised multicentre trials. The role of novel ventilatory modalities such as closed loop automated oxygen control, liquid ventilation and heliox therapy may offer promise for infants with CDH, but the benefits need to be determined in appropriately designed clinical trials.

Left-sided congenital diaphragmatic hernia: can we improve survival while decreasing ECMO?

BACKGROUND

Mortality and ECMO rates for congenital diaphragmatic hernia (CDH) remain ~30%. In 2016, we changed our CDH guidelines to minimize stimulation while relying on preductal oxygen saturation, lower mean airway pressures, stricter criteria for nitric oxide (iNO), and inotrope use. We compared rates of ECMO, survival, and survival without ECMO between the two epochs.

DESIGN/METHODS

Retrospective review of left-sided CDH neonates at the University of Utah/Primary Children's Hospital NICUs during pre (2003-2015, n = 163) and post (2016-2019, n = 53) epochs was conducted. Regression analysis controlled for defect size and intra-thoracic liver.

RESULTS

Following guideline changes, we identified a decrease in ECMO (37 to 13%; p = 0.001) and an increase in survival without ECMO (53 to 79%, p = 0.0001). Overall survival increased from 74 to 89% (p = 0.035).

CONCLUSION(S)

CDH management guideline changes focusing on minimizing stimulation, using preductal saturation and less aggressive ventilator/inotrope support were associated with decreased ECMO use and improved survival.