Humidified High Flow Nasal Cannula as Compared to Nasal Continuous Positive Airway Pressure

In the face of exogenous surfactant and use of antenatal steroids, respiratory distress
syndrome (RDS) remains a leading cause of morbidity and mortality in premature infants. RDS
is the result of a series of complex, interrelated events, including atelectasis,
ventilation-perfusion mismatching, and lung inflammation/injury (1). The cascade of events
which typifies RDS and its long-term counterpart, chronic lung disease (CLD), is rooted in
the intrinsic deficits of the premature lung as well as exacerbated by mechanical
ventilation, a mainstay of therapy. For this reason, scientists and clinicians alike
continue to search for treatment modalities which will not only treat RDS but also decrease
the incidence of chronic lung disease.

The use of non-invasive ventilatory strategies, such as nasal continuous positive airway
pressure (NCPAP), in the treatment of RDS is thought to provide positive distending pressure
while minimize lung inflammation and injury associated with mechanical ventilation (2).
Avoidance of intubation and increased use of NCPAP to treat respiratory distress syndrome
has been shown to decrease the incidence of chronic lung disease (3,4). However, NCPAP does
have some common clinical limitations. First, the administration of NCPAP has inherent
mechanical difficulties in appropriately maintaining the nasal prong apparatus within the
small neonatal nose. Secondly, the nasal prongs used to deliver NCPAP can cause nasal septal
trauma. Lastly, some premature infants do not tolerate the NCPAP apparatus which must be
tightly affixed to their nose and face. This intolerance is often demonstrated by increased
patient movement, and subsequently, the risk of mechanical difficulties and septal trauma
increase during these times. Although NCPAP continues to be used in most neonatal intensive
care units (NICUs), due to its aforementioned drawbacks, we continue to look for other
effective, non-invasive modes of ventilation to provide support to premature infants with
respiratory distress.

Humidified high flow nasal cannula (HFNC) has recently been introduced into neonatal
respiratory care as a means of providing positive distending pressure to the neonate with
respiratory distress. HFNC aims to maximize patient tolerance by employing heated,
humidified gas flow through the standard neonatal nasal cannula that is used routinely in
neonatal intensive care units. HFNC provides positive distending pressure by using high gas
flow (>1 liter per minute) (5). Although numerous neonatal intensive care units are using
HFNC, including both NICUs at Children's Hospitals of Minnesota, there are very few studies
regarding its use in this population. Anecdotally, the premature babies tolerate the
administration of HFNC quite well. However, like any new therapy, there are many unknowns.

There is only one study to date which investigates HFNC versus NCPAP in the preterm neonate
(6). Sreenan and colleagues found HFNC to be as effective as NCPAP in the management of
apnea of prematurity and also demonstrated that the positive distending pressure provided by
HFNC varied with the patient's weight. Sreenan's study as well as preliminary data presented
in abstract form cite HFNC use with various amounts of gas flow, ranging from 1 liter per
minute up to 6 liters per minute (6,7,8). The choice of how much gas flow to use with the
HFNC system is unclear. This decision is actually a three-fold question: 1) the initial
amount of liter flow to use, 2) what does a particular liter flow provide for positive
distending pressure to that patient, and 3) are these values system-specific? We aim to
evaluate these questions in our study. Until recently, NCPAP has been the mainstay of
non-invasive ventilatory support for premature babies. However, as HFNC is better tolerated
and uses a nasal cannula that is less prone to mechanical mishaps than NCPAP, it is clear
that we need more information to accurately treat babies with HFNC. The results of this
study will help guide the use of HFNC in preterm babies with respiratory insufficiency, as
knowledge of the positive distending pressures derived from the HFNC system are crucial in
minimizing barotrauma to the fragile, premature lung.

Inclusion Criteria:

- 1) receiving NCPAP ventilatory support at > 72 hrs. of age and 2) requiring FiO2
21-50% on NCPAP.

Exclusion Criteria:

- FiO2 >50%, presence of pneumothorax or pleural effusion, anatomical abnormalities of
the airway, lungs, or esophagus, or cyanotic congenital heart defect.