1. COMPARING PRESSURE CHANGES AND AEROSOL DEPOSITION OF A
STANDARD SMALL-VOLUME NEBULIZER AND A MINI-HEART LOW FLOW
NEBULIZER DURING HFOV Shane Cheney, BS RRT-NPS; Jeff Wright, BS RRT-
NPS; Kevin Crezee, RRT-NPS; Tim Macknight, BS RRT-NPS, Department of
Respiratory Care Services, Primary Children’s Medical Center, Salt Lake City, Utah
Introduction: Aerosolized medications are often administered to intubated
neonates within the Newborn Intensive Care Unit at Primary Children’s Medical Center
(PCMC) via a Sensormedics (Cardinal Health, Yorba Linda, CA) 3100A High Frequency
Oscillator Ventilator (HFOV). The standard as the means of delivery for aerosolized
medications via the HFOV has been a Metered Dose Inhaler (MDI) with an ACE spacer
(DHD Healthcare, Canastota, NY)). Previous bench laboratory studies conducted at
PCMC showed that aerosol deposition was in fact much more effective via a Small
Volume Nebulizer (SVN) vs. MDI in a neonatal lung model (Davidson et al, 2005). To
build upon this information, we hypothesized that the efficiency of deposition would not
be compromised and the turbulence / resistance to exhalation caused by the increased
amount of flow at the closed suction catheter connection with the standard SVN setup
could be minimized by using a Mini-HEART Low-Flow nebulizer (Westmed, Tucson,
AZ.). A mini-heart nebulizer requires 2 lpm of flow vs. the 6 lpm needed by a most SVN
devices. It was hypothesized that the post ETT tube pressures would be higher than the
set pressures on the ventilator with the standard SVN because of the amount of flow
being introduced to the circuit at the patient “Y”. If the standard SVN increased post ET
tube pressures, thus increasing alveolar ventilation and intrapulmonary pressures during
the duration of the aerosol treatment, this could be potentially detrimental in neonatal
patient populations. An increase in medication deposition without an increase or a
minimal increase in intrapulmonary pressures could be a more optimal outcome.
Methods: To measure post ETT pressures, a neonatal lung model was attached to
2.5, 3.0, 3.5, and 4.0 mm endotracheal tube sizes and ventilated with the HFOV. The
neonatal lung model consisted of the following in the correct order of placement: “Y”
closed suction catheter adapter connected to the endotracheal tube, 15 mm adapter, 6
inches of large bore corrugated tubing, 15mm adapter, and the jet port adapter. The Mini-
Heart system and the Airlife Misty Max 10 SVN (Cardinal Health, McGraw Park, IL)
were connected to the suction port of the Ballard “Y” adapter and run at multiple settings.
The post ETT pressures were read and measured from the LifePort jet adapter connected
to the Bunnell High Frequency Jet Ventilator (Salt Lake City, UT).
To measure medication deposition, a neonatal lung model consisted of the
following in the correct order of placement: mini-heart nebulizer connected to “Y”,
closed suction adapter, ETT, ETT adapter, 15 mm adapter, 22 mm adapter, 15 mm
adapter, hyprophobic filter, and an approximately 300 ml test lung. The proximal end of
the ETT was fitted with the “Y” type closed suction catheter. A filter was placed distal to
the ETT to trap aerosolized albuterol delivered to the test lung. The filter was measured
with a pocket scale in grams both pre and post treatment to gauge results. The mini-heart
was fitted to adapt to the closed suction catheter site and placed below the neonatal lung
unit to decrease the susceptibility towards acquiring the deposition by means of “rainout”
in the ventilator circuit.. The mini-heart was flicked for 1 minute after the nebulizer

2. started sputtering. Five treatments were performed with each of the ETT sizes
respectively (2.5,3.0,3.5,4.0). Each treatment was conducted in a humidified circuit
measured at 37.0 degrees Celsius. The mini-heart dosage consisted of a pre-mixed unit
dose of 2.5 mg (0.5ml) albuterol and 2.5 ml normal saline. Ventilator settings comparing
aerosol deposition were as follows: Mean Airway Pressure (PAW)= 20 cmH20,
Amplitude= 30 cmH20, Hertz= 10. A wide spectrum of HFOV settings were used to test
post-ETT pressure differences with both types of nebulizers.
Results: Mean Albuterol delivery and range results for the mini-heart nebulizer
into the filter was the following: 2.5 ETT; Range = 6.0-7.33% Mean= 6.80 %, 3.0 ETT;
Range= 6.66-10.33% Mean= 8.80 %, 3.5 ETT; Range= 9.3-11.0% Mean=10.05 %,
4.0ETT; Range=4.0-18.0% Mean=10.07% . The average of the above means was 9.24%.
A previous study performed at PCMC with a standard SVN during HFOV showed
average deposition of 9.33% (Davidson et al, 2005). Mean Airway Pressure
measurement results using a mini heart SVN were the following: 2.5 ETT= 20.8, 3.0
ETT= 21.1, 3.5 ETT =20.5, 4.0 ETT= 20.5. Mean Airway Pressure measurement results
using a standard SVN were the following: 2.5 ETT= 23.0, 3.0 ETT= 23.1, 3.5 ETT=
21.2, 4.0 ETT= 21.4. Mean PAW increase as measured post-ETT was 1.95 cmH2O using
the standard SVN and 0.5 cmH2O using the mini-heart nebulizer. When comparing post-
ETT pressures, the mini-heart consistently demonstrated lower post-ETT pressures
(Table 1).
Conclusions: Post-ETT pressures were minimized with the mini-heart nebulizer
with similar deposition results of SVN aerosolized medication. Evidence suggests the
Mini-Heart nebulizer may provide the same benefit of a an aerosolized medication
without altering intrapulmonary pressures.