Method for a homogeneous distribution of pollens in an environmental exposure chamber

Abstract

Background

A variety of different environmental exposure chambers (EECs) have been used to evaluate treatments for allergic rhinitis.

Objective

To describe and test a system for a homogenous distribution of grass pollen, Phleum Pratense, in an EEC to be used for controlled pollen exposure studies in allergic participants.

Methods

A chamber made of stainless steel with completely rounded corners, seating four individuals at a time, was used. Room pressure, temperature, humidity and the air change rate were kept constant throughout the study period.

A rotating pipette dispensed a uniform supply of pollen into a turntable's v-shaped grooves. A stainless-steel capillary tube sucked the pollens into a venturi throat at which time, the pollens were mixed with a high-pressure airstream of compressed HEPA filtered air and then transported to a spreading plate inside the EEC.

To achieve uniform concentrations in the EEC, the turntable's rotating speed was continuously adjusted using information from video-coupled feedback and feed forward mechanisms. Pollen levels were detected using standard volumetric air samplers and laser particle counters. The target pollen exposure level was 1,000 pollens/m³. 21 participants were exposed to pollens in the EEC twice for 210 minutes. Participants evaluated their symptoms every 30 minutes using a total nasal symptom score (TNSS) consisting of blocked nose, runny nose, nasal itching and sneezing.

Results

Across fifteen study days the average pollen level was 982 pollens/m³ (SD, 102 pollens/m³). On average, participants experienced a 10% difference in overall pollen levels between their two visits to the EEC. The mean TNSSs rose throughout the exposure period, with a low at baseline of 0.43 (SD, .68) to a high of 4.71 (SD, 2.43) just before exiting the EEC.

Conclusion and Clinical Relevance

This EEC provides a reproducible, precise and homogenous distribution of pollens making it suitable for single-centre allergy clinical trials.

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