Snow Physical Properties and Human Ventilatory Response

Study Overview
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Brief Summary
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Sufficient oxygenation is critical for completely buried avalanche victims to avoid life-threatening consequences during hypoxic exposure. Snow contains a remarkable capacity to maintain air availability; it was suspected that the snow physical properties affect the development of hypoxia and hypercapnia. The aim of this study was to evaluate the influence of different snow physical properties on the development of hypoxia and hypercapnia in subjects breathing into an artificial air pocket in snow. Twelve male healthy subjects breathed through an airtight face-mask and 40cm tube into an artificial air pocket of 4L. Every subject performed three tests on different days with varying snow characteristics. Symptoms, gas and cardiovascular parameters were monitored up to 30min. Tests were interrupted at SpO2 <75% (primary endpoint); or due to subjective symptoms like dyspnea, dizziness, and headache (i.e. related to hypercapnia). Snow density was assessed via standard methods and micro-computed tomography (CT) analysis, and permeability and penetration with the snow micro-penetrometer (SMP).

Official Title
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Evaluation of Air Pocket Factors That Contribute to the Development of Hypoxia and Hypercapnia

Conditions
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Hypoxic Respiratory Failure, Hypercapnic Respiratory Failure, Avalanche Burial, Snow Physical Properties

Intervention / Treatment
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* Other: Breathing in snow


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy volunteers with an age above 18yr-old, physically active. Volunteers have been informed and have signed consent. Exclusion Criteria: Lack of consent. Chronic previous illness of the respiratory tract or of the cardiovascular system. Acute disease at or immediately prior to the test (eg, flu-like infection, fever of unknown origin). Eurac employees.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Winter snow<br>First test series breathing in dry snow in winter | Other: Breathing in snow<br>* Breathing in snow with different physical properties<br>|
| Experimental: Intermediate snow<br>Second test series breathing in dry/wet snow in intermediate season | Other: Breathing in snow<br>* Breathing in snow with different physical properties<br>|
| Experimental: Spring snow<br>Third test series breathing in very wet snow in spring | Other: Breathing in snow<br>* Breathing in snow with different physical properties<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| SpO2 (%) | Continuous monitoring | Changes from baseline (measurement at 0min) -> snow-breathing phase (5min, 15min, and timepoint immediately before interruption of snow-breathing phase [max 30min]) -> 2.5min and 5min after snow-breathing phase | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| EtCO2 (mmHg) | Continuous monitoring | Changes from baseline (measurement at 0min) -> snow-breathing phase (5min, 15min, and timepoint immediately before interruption of snow-breathing phase [max 30min]) -> 2.5min and 5min after snow-breathing phase | 
| Cause of interruption | SpO2 <75% or subjectives symptoms due to hypercapnia (like dyspnea, dizziness, and headache) | Timepoint immediately before interruption of snow-breathing phase (max 30min) | 
| VE (L/min) | Continuous monitoring | Changes from baseline (measurement at 0min) -> snow-breathing phase (5min, 15min, and timepoint immediately before interruption of snow-breathing phase [max 30min]) -> 2.5min and 5min after snow-breathing phase | 
| rSO2 (%) | Continuous monitoring | Changes from baseline (measurement at 0min) -> snow-breathing phase (5min, 15min, and timepoint immediately before interruption of snow-breathing phase [max 30min]) -> 2.5min and 5min after snow-breathing phase |