Advances in Neonatology

Overall survival of infants with congenital diaphragmatic hernia (CDH) has improved over the past 30 years, due in large part to better understanding of the underlying pulmonary pathophysiology, advances in medical and ventilator management, and refinements in the role and timing of surgery. Preoperative stabilization of patients is vitally important and often involves mechanical ventilation. In patients who fail to stabilize with conventional mechanical ventilation (CMV), high frequency oscillatory ventilation (HFOV) is often the first-line rescue ventilation strategy. While HFOV is thought to improve gas exchange, promote uniform lung inflation, and decrease production of inflammatory mediators, this approach has a number of limitations. Few hospitals utilize the transport ventilator required for intra- or inter-hospital patient transfer on HFOV. In addition, the use of HFOV during surgery is complex and poses challenges for the anesthesia and surgery team.

Patients born at NewYork-Presbyterian Morgan Stanley Children’s Hospital who are prenatally diagnosed with CDH with large defects or nonreassuring fetal parameters of severity are immediately intubated at birth starting with synchronized intermittent mandatory ventilation. Gentle ventilation with permissive hypercapnia and oxygen saturation goals of 85 to 95 percent guide further ventilation setting and mode changes. In infants who fail conventional ventilation, the Hospital’s neonatologists and pediatric surgeons often employ high-frequency positive pressure ventilation (HFPPV) as a rescue mode of ventilation. This time-cycled pressure-controlled ventilation method uses high respiratory rate delivered at 100bpm with low-positive end-expiratory pressure supplied via a conventional ventilator. HFPPV eliminates the need for specialized training in HFOV management and allows for wider use, for example, during inter-hospital transfer and during surgery.

Recently, Vincent P. Duron, MD, Co-Director of Fetal Therapy and Surgical Director of the Pediatric ICU; Rakesh Sahni, MBBS, Medical Director of the Neonatal Intensive Care Unit and Director of the Infant Physiology Laboratory; and Anna Penn, MD, PhD, Chief of Neonatology at NewYork-Presbyterian Morgan Stanley Children’s Hospital and Columbia, along with Claire Gerall, MD, pediatric ECMO fellow, and colleagues in neonatology, pediatric surgery, and the Department of Biostatistics at Columbia, conducted a study on the use of HFPPV and HFOV in the treatment of critically ill patients with CDH. Their goal was to compare outcomes from a stepwise progression from HFPPV to HFOV to the outcomes from progression directly to HFOV.

In their study, the Columbia researchers retrospectively reviewed 77 patients diagnosed with congenital diaphragmatic hernia at NewYork-Presbyterian Morgan Stanley Children’s Hospital between January 2005 and September 2019 who required rescue mechanical ventilation – either an acceleration from conventional mechanical ventilation to HFOV or progression from HFPPV to HFOV for at least three hours. Of the 77 patients, 45 patients underwent HFPPV followed by HFOV; 32 underwent HFOV only.

Their findings, published in the December 16, 2021, issue of the American Journal of Perinatology, showed:

• Survival to discharge, the primary outcome, was significantly different between the HFOV-only group (58.4 percent) and the HFPPV plus HFOV group (79.5 percent)
• In the HFOV-only group, 16 patients (51.6 percent) did not survive to discharge, while 9 patients (20.5 percent) treated with both HFPPV and HFOV did not survive to discharge
• More patients in the HFPPV plus HFOV group (95.6 percent vs. 68.8 percent) survived to operative repair
• Patients who underwent stepwise escalation of mechanical ventilation from HFPPV to HFOV were medically optimized and stable for repair on average of 2 days earlier than those escalated directly to HFOV from CMV

Overall, the authors note that the study demonstrated that high-frequency positive pressure ventilation:

• may be used as an intermediary mode of rescue ventilation prior to high frequency oscillatory ventilation without adverse effect;
• is more widely available and can mitigate the limitations faced when using high frequency oscillatory ventilation; and
• allows for intra- or inter-hospital transfer of neonates with CDH.