Snow Physical Properties and Human Ventilatory Response

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

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).

Study Overview

• Status: Completed
• Conditions: Hypercapnic Respiratory Failure; Hypoxic Respiratory Failure; Avalanche Burial; Snow Physical Properties
• Intervention / Treatment: Other: Breathing in snow

• Study Type: Interventional
• Enrollment (Actual): 12
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Italy
  • Bz
    • Bolzano, Bz, Italy, 39100
      • Institute of Mountain Emergency Medicine, Eurac Research

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

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.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

3

Arms and Interventions

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

What is the study measuring?

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

Collaborators and Investigators

• Sponsor: Institute of Mountain Emergency Medicine
• Collaborators: Medical University Innsbruck
• Investigators: Study Director: Giacomo Strapazzon, MD PhD, EURAC Research; Study Director: Hermann Brugger, MD, EURAC Research

Publications and helpful links

General Publications

• Brugger H, Sumann G, Meister R, Adler-Kastner L, Mair P, Gunga HC, Schobersberger W, Falk M. Hypoxia and hypercapnia during respiration into an artificial air pocket in snow: implications for avalanche survival. Resuscitation. 2003 Jul;58(1):81-8. doi: 10.1016/s0300-9572(03)00113-8.
• Haegeli P, Falk M, Brugger H, Etter HJ, Boyd J. Comparison of avalanche survival patterns in Canada and Switzerland. CMAJ. 2011 Apr 19;183(7):789-95. doi: 10.1503/cmaj.101435. Epub 2011 Mar 21.

Study record dates

Study Major Dates

• Study Start (Actual): December 1, 2013
• Primary Completion (Actual): March 9, 2014
• Study Completion (Actual): March 9, 2014

Study Registration Dates

• First Submitted: March 8, 2017
• First Submitted That Met QC Criteria: March 10, 2017
• First Posted (Actual): March 17, 2017

Study Record Updates

• Last Update Posted (Actual): March 17, 2017
• Last Update Submitted That Met QC Criteria: March 10, 2017
• Last Verified: March 1, 2017

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Respiratory Tract Diseases; Respiration Disorders; Respiratory Insufficiency
• Other Study ID Numbers: V/16/13

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: No

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No