The Role of High-Frequency Ventilation in Neonates: Evidence-Based Recommendations

Andrea L. Lampland

Clin Perinatol 34 (2007) 129–144

Respiratory failure in neonates, commonly defined as retention of carbon dioxide with a resultant decrease in the arterial blood pH and accompanied by hypoxemia, has multiple etiologies. It remains the most common complication of premature birth and the number one reason that neonates require assisted mechanical ventilation. Respiratory failure is a result of impaired pulmonary gas exchange mechanisms, such as can be seen with surfactant deficiency, atelectasis, or obstructive airway disease. Less common causes of respiratory failure may be a result of airway, musculature, or central nervous system abnormalities. The specific etiology of neonatal respiratory failure can, at times, be unclear and potentially multifactorial. Nonetheless, insights into the potential etiologies and pathophysiology of respiratory failure weigh heavily in the clinician’s decisions regarding initiation of assisted mechanical ventilation.

Much progress has been made in the treatment of neonatal respiratory failure over the past few decades. In particular, antenatal steroids and exogenous surfactant replacement have decreased neonatal mortality and morbidity in premature infants . However, lung injury and pulmonary morbidities secondary to mechanical ventilation remain an ongoing problem in the care of premature infants. Of most concern, chronic lung disease (CLD) develops in up to one third of preterm infants who have respiratory distress syndrome (RDS) who receive positive pressure mechanical ventilation . Dilemmas still remain regarding optimization of both timing

and mode of mechanical ventilation to decrease neonatal pulmonary

morbidities.

High-frequency ventilation (HFV) is a form of mechanical ventilation that uses small tidal volumes and extremely rapid ventilator rates. It first came to the attention of the medical community during the 1970s, when a number of scattered reports appeared. Lunkenheimer and colleagues reported the use of high-frequency oscillatory ventilation (HFOV) in apneic dogs, Sjostrand used high-frequency positive pressure ventilation in adults who have respiratory failure, and Carlon and colleagues used a type of jet ventilation in adults who have bronchopleural fistula. Early reports of neonatal use came from Frantz and colleagues in Boston, Massachussetts,

and Pokora and colleagues in St. Paul, Minnesota. In an attempt to clarify how it is possible to maintain pulmonary gas exchange when the tidal volumes used are often smaller than the anatomic dead space, Chang described  the multiple modes of gas transport that occur during HFV, including bulk convection, high-frequency ‘‘pendulluft,’’ convective dispersion, Taylor-type dispersion, and molecular diffusion. There are various high-frequency ventilator designs, including HFOV, high-frequency jet ventilation (HFJV), as well as ‘‘mixed’’ forms of HFV (eg, flow interrupters, high-frequency positive pressure ventilation). In the United States, the most commonly used high-frequency ventilators include the SensorMedics 3100A (SensorMedics Inc., Yorba Linda, California), which provides HFOV; the LifePulse high-frequency jet ventilator (Bunnell Inc., Salt Lake City, Utah), which provides HFJV; and the Infant Star ventilator (Infra- Sonics Inc., San Diego, California), which is a high-frequency flow interrupter (HFFI).

Potential advantages of HFV over conventional mechanical ventilation (CMV) include the use of small tidal volumes, the ability to independently manage ventilation and oxygenation, and the safer use of mean airway pressure that is higher than that generally used during CMV [11]. Animal studies suggest that HFV works at lower proximal airway pressures than CMV, reduces ventilator-related lung injury, improves gas exchange in the face of air leaks, and decreases oxygen requirements [12–17]. Most causes of neonatal respiratory insufficiency requiring mechanical ventilation are amenable to treatment with HFV or CMV. For either technique to be successful, lung volumes need to be optimized for the underlying condition, and pressure exposures must likewise be similarly regulated. Only by the careful application of the chosen technique can ventilator-induced lung injury be avoided. The question remains, however: is one form of ventilation better than the other?

Despite the wealth of laboratory and clinical research on HFV, there are no established guidelines for prioritizing the use of HFV versus CMV in neonatal respiratory failure. Since 1997, approximately 25% of infants born at 1500 g or less reported to the Vermont–Oxford Network have been treated at some time with HFV [18]. Some clinicians choose to use HFV as the primary mode of mechanical ventilation for small infants. Others elect to only use HFV as a ‘‘rescue’’ method when CMV is failing. Most clinicians stand somewhere in the middle of this spectrum. This article is not a ‘‘how to’’ guide for the use of HFV. Rather, it reviews and evaluates the available literature to determine the evidence base for the use of HFV in neonatal respiratory failure.

Evidence review

An evidence review was performed to answer the following questions:

1. In the presence of acute neonatal respiratory failure or respiratory distress syndrome, does elective use of HFV provide benefit over the use of CMV?

2. In the presence of ongoing, severe neonatal respiratory failure, does the use of HFV as a rescue mode of ventilation provide benefit over the continued use of CMV?

3. Are there specific etiologies to neonatal respiratory failure in which HFV has been superior to CMV?