In-Vitro (Bench) Analysis of Bypass HMEs

Introduction

Bypass Heat Moisture and Exchangers (BHMEs)

simplifies aerosol delivery to ventilated patients

utilizing passive humidification without breaking

the circuit. A BHME provides the ability to optimize

aerosol delivery by positioning the medication

delivery device in the most ideal position of 6” to

18” back from the patienti.

An ideal or perfect Bypass HME would not influence

an aerosolized particle, simply letting it pass

through the device unchanged. Quantifying the

change of aerosol through BHMEs is a complex

process dependent upon a variety of clinical and

device-related variables. Patient breathing

patterns, the choice and dilution of drug and

device selection all have the potential to affect

aerosol. In-vitro (benchmark) testing can provide

the clinician with useful information regarding the

bypass performance.

Purpose

The purpose of this technical bulletin is to illustrate

the in-vitro (bench) bypass performance

characteristics of the AirLife® BHMEs. Two

different test methods were used to demonstrate

the aerosol impact on the BHME called the

Andersen Cascade Impactor and Laser Diffraction

Test.

Andersen Cascade Impactor Analysis

Products Tested

Testing was conducted on the following products:

� 003020, AirLife® Adult Nonfiltered Bypass Heat

and Moisture Exchanger (BHME)

� 003021, AirLife® Adult Filtered Bypass Heat and

Moisture Exchanger (BHME)

� No HME in-line. Dry Circuit only. Illustrate what

would be the perfect “BHME”

Particle Size Test Method

An Andersen eight-stage cascade impactor (ACI)

with USP inlet was used and assayed with a

spectrophotometer (277 nm). Particle size

characterization was performed using an

albuterol/saline solution. Cascade impaction was

chosen for the following reasons:

� Cascade impaction measures aerodynamic

diameter directly, which accounts for the density

and irregular shape of drug particles. It is

believed that aerodynamic diameter more

accurately predicts the behavior of aerosol as it

is delivered into the patient’s lungs

� There is more historical data on particle size

measurement using cascade data than any other

method. Relative comparison with historical data

can be readily made.

� Cascade impaction is one of the USP methods for

characterization of particle distributions.

Definition of Respirable Fraction

“Respirable fraction” is the percent of aerosol

generated, by mass, which falls below an

aerodynamic diameter of 5µm. It has been

reported that particles less than 5µm will penetrate

beyond the upper airways and deposit into the

tracheobronchial and pulmonary regions of the

lung. This measurement is often used to describe

the quality of aerosol. The mass collected between

the cascade plate cutoff points of 0.4µm and

4.7µm were utilized to quantify the mass below

5µm.

Aerosol Optimization

and the AirLife® BHME

Andersen Cascade Impactor Analysis

91.2% 91.1% 90.8%

75.0%

80.0%

85.0%

90.0%

95.0%

100.0%

% M

ass

of

Alb

ute

rol

Su

lfa

te

be

twe

en

0.4

- 4

.7 μ

m

No Device 003020 003021

Conclusions

There is no statistically significant difference in the respirable fraction between delivering aerosol through the

AirLife® BHMEs (003020 & 003021) and delivering aerosol with the devices removed (p-values > 0.445, 95%

confidence).

Laser Diffraction Test for Aerosol

Products Tested

Testing was conducted on the following test

groups:

� 003020, AirLife® Adult Nonfiltered Bypass Heat

and Moisture Exchanger (BHME)

� 003021, AirLife® Adult Filtered Bypass Heat

and Moisture Exchanger (BHME)

� 19912, Gibeck Humid-Flo® Heat and Moisture

Exchanger

� 68-1000, CircuVent® HME/HCH Bypass

(Assembled with AirLife 003005, Adult Filtered

HCH)

� No HME in-line. Dry Circuit only. Illustrate

what would be the perfect “BHME”

Particle Size Test Method

Laser diffraction was performed using a Malvern

Spraytech with an inhalation cell. A constant

extraction flow rate of 14 Lpm through the Malvern

Spraytech was used. Particle size characterization

was performed using an albuterol/saline solution.

Laser diffraction was chosen because the laser

diffraction test method is less time consuming than

the cascade impactor test method, facilitating

testing of competitive products.

Conclusions

� There is a statistically significant difference in

the respirable fraction between delivering

aerosol through the any of the tested devices

and delivering aerosol with the devices

removed (p-values < 0.002, 95% confidence).

� The AirLife® BHMEs (003020 & 003021)

influence the respirable fraction less than the

DHD CircuVent® (p-values < 0.001, 95%

confidence).

� There no statistically significant difference in

the respirable fraction between delivering

aerosol through the AirLife® 003021 and

delivering aerosol through the Gibeck Humid-

Flo® (p-value = 0.638, 95% confidence).

Summary Conclusion

In either test method, the AirLife® BHME has comparable performance to using no HME device on

ventilated patients and should be considered minimal risk of aerosol knockdown to ventilated

patients.

i Patrick J Dunne MEd RRT FAARC (December 2004). Respiratory Care Protocols: Benefits for Patients, Therapists and Hospitals. www.aarc.org/protocol_course/protocols_book.pdf

James B Fink, MS RRT, Martin J Tobin MD, and Rajiv Dhand MD. Bronchodilator Therapy in Mechanically Ventilated Patients Respiratory Care. Jan 1999: 44-1, pg. 57.

Timothy B. Op’t Holt, EdD, RRT. Ventilation for Life. Aerosol Therapy during Mechanical Ventilation. AARC Times. July 2000: pg. 22.

Laser Diffraction Test for Aerosol

80.8%

85.7%

82.9%83.3%

88.2%

50

55

60

65

70

75

80

85

90

95

100

% V

olu

me

< 5

.0 μ

m

No HME

AirLife 003020

AirLife 003021

Gibeck Humid-Flo

DHD CircuVent

© Cardinal Health, Inc. or one of its subsidiaries. All rights reserved. AirLife is a registered trademark of Cardinal Health, Inc. or one of its subsidiaries. Humid-Flo is a registered trademark of Teleflex Medical or one of its subsidiaries. CircuVent is a registered trademark of Smiths Medical one of its subsidiaries. Lit. No. 3RT2925

Cardinal Health 22745 Savi Ranch Pkwy. Yorba Linda, CA 92887 www.cardinalhealth.com/respiratory