The Gas Mask: the Effects on Respiration!

Summary

Background: The gas mask is used to protect military and non-military subjects exposed to respiratory hazards (CBRN agents). The aim of the study was to evaluate the impact of the gas mask on respiratory patterns and indexes of the respiratory effort. Methods: We are completing our study with 14 healthy subjects to evaluate breathing patterns, index of respiratory efforts and blood gases. Seven conditions have been tested in a randomized order: at rest, during effort (on a tread mill, standardized at 7 METs for all subjects) and during induced hypoxemia with and without a mask (C4, Airboss Defence, Bromont, Canada). Airway pressure, inspiratory and expiratory flows were measured. An esophageal catheter was introduced at the beginning of the study to measure esophageal pressure (Peso) and calculate indexes of respiratory effort (PTPeso, WOB). SpO2 was continuously measured and capillary blood bases were drawn at the end of each condition. Each condition lasted 10 minutes, data of the last 2 minutes at a steady state were considered for analyses. Results: The preliminary analyses based on 10 subjects are presented here. Comparing the wearing of the gas mask and without, most of the respiratory index increased in the tested conditions (at rest, during induced hypoxemia and during effort). At rest, in 8 out of 10 healthy subject the indexes of effort were higher with the gas mask, a statistical trend was observed with the WOB (0.22±0.13 vs. 0.28±0.10 J/cycle; p = 0.059), the PTPes (101±35 vs. 122±47 cmH2O\*s; p=0.21) and SwingPeso (4.4±2.0 vs. 5.3±2.0 cmH2O; p=0.13). During the effort, the respiratory index increased (WOB 4.0±2.6 vs. 5.6±3.2; p=0.10; PTPeso 406±211 vs. 606±65; p=0.04; SwingPeso 14.8±8.1 vs. 21.8±9.0; p=0.13). There was no difference for the breathing pattern and arterial blood gases data with and without mask. Data for induced hypoxemia are under analysis. We measured on bench the inspiratory and expiratory resistances of the tested gas mask (C4: inspiratory resistances = 3.2 cmH2O at 1 L/sec; expiratory resistances = 0.9 cmH2O at 1 L/sec). This may explain in part the increased work of breathing with masks. Conclusions: This study demonstrated an increase of the indexes of respiratory effort during an exercise with the gas mask. This study is the first to directly assess the indexes of efforts with esophageal pressure in this situation. Our results and method may be used as a reference for evaluating tolerance with different designs of gas masks.

Conditions

• Work of Breathing

Interventions

OTHER

measurement of the work of breathing

We have been evaluating breathing patterns, index of respiratory efforts and blood gases in all randomized conditions. A gas mask has been used mask (C4, Airboss Defence, Bromont, Canada). Airway pressure, inspiratory and expiratory flows have been measured. An esophageal catheter has been introduced at the beginning of the study to measure esophageal pressure (Peso) and calculate indexes of respiratory effort (PTPeso, WOB). SpO2 has been continuously measured and capillary blood bases were drawn at the end of each condition. Each condition lasted 10 minutes, data of the last 2 minutes at a steady state has been considered for analyses.

DEVICE

Gas mask

During the conditions that involved a gas mask, the measurement of the work of breathing is achieved with a oesophageal catheter and two disposable pneumotachs. While the oesophageal catheter has been fixed to the mandibular with an hypo-allergic tape, the two pneumotachs are hooked respectively on the canister and exhalation port of the gas mask. Investigators have induced the hypoxemia with a mixture nitreous and medical gas in a plastic bag that has been setted up to the canister. The FiO2 level has been kept to 14 percent.

Sponsors & Collaborators

• Pierre-Alexandre Bouchard, RT.

  collaborator UNKNOWN

• Captain (Ret) Stephane Bourassa, RN.

  collaborator UNKNOWN

• Laval University

  lead OTHER

Principal Investigators

• Francois Lellouche, Doctorate · Institut de Recherche Universitaire de Cardiologie et Pneumologie de Québec

Study Design

Allocation

RANDOMIZED

Purpose

HEALTH_SERVICES_RESEARCH

Masking

DOUBLE

Model

SINGLE_GROUP

Eligibility

Min Age

18 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2015-06-30

Primary Completion

2016-07-31

Completion

2016-07-31

Countries

• Canada

Study Locations