Impact of CO2 Absorption on Gas Exchange and Ventilation Patterns While Breathing Into a Snow Air Pocket

NCT06895759 | Completed

• 1 other identifier: AVACO2R
• Study Type: interventional
• Target: 22
• Locations: 1 country
• Sites: 1

Brief Summary

Asphyxia is by far the most common cause of death after critical avalanche burial. The presence of an air pocket increases the survival chances, but expired air rich in carbon dioxide (CO2) progressively displaces oxygen (O2) in the air pocket, a phenomenon known as displacement asphyxia. In addition, an increase in the inspired concentration of CO2 (FiCO2) reduces the alveolar partial pressure of O2 (PAO2), as explained by the alveolar gas equation. Underlining this, a recent experimental porcine study showed that an increased FiCO2 is the leading cause of the decrease in PaO2. By removing CO2 in an experimental avalanche burial, normoxia persisted even after 90 minutes of burial, while, in the absence of CO2 removal, hypoxemia and hypercapnia occurred after only 10 minutes. Additionally, hypercapnia increases pulmonary vascular resistance, reduces cardiac output and can lead to life-threatening hemodynamic instability. Hypercapnia can speed up the cooling rate, and the combination of hypothermia with hypoxia and hypercapnia may result in a worse neurological outcome in completely buried avalanche patients compared to patients suffering solely hypothermic cardiac arrest. Taken together, these findings suggest that removing CO2 from the air-pocket could prevent, or at least delay, the hypercapnic condition with its deleterious consequences and consequently increase the survival after complete avalanche burial. The main aim of the study is to investigate the effectiveness of soda lime in removing CO2 while breathing into a snow air pocket, and to assess its impact on gas exchange, ventilation patterns, and hemodynamics.

Conditions

Avalanche Burial

Outcome Measures

Primary Outcomes (2)

• Time to reach an end-tidal CO2 or partial pressures of carbon dioxide in arterial blood (PaCO2)

  Time to reach an end-tidal CO2 (etCO2) of 70 mmHg or partial pressures of carbon dioxide in arterial blood (PaCO2) of 65 mmHg

  35 minutes

• Time to reach an oxygen saturation (SpO2)

  Time to reach an oxygen saturation (SpO2) ≤75%

  35 minutes

Secondary Outcomes (9)

• Difference in end-tidal CO2 (etCO2) and partial pressures of carbon dioxide in arterial blood (PaCO2)

  35 minutes

• Partial pressure of oxygen

  35 minutes

• Differences in inspiratory fraction of CO2 (FiCO2) and O2 (FiO2)

  35 minutes

• Difference in minute ventilation (VE)

  35 minutes

• Difference in cardiac output (CO)

  35 minutes

Study Arms (2)

Breathing with soda lime

EXPERIMENTAL

Respiration into a snow air pocket through an experimental rebreathing circuit with the integration of a soda lime canister.

Device: Soda lime

Breathing without soda lime

SHAM COMPARATOR

Respiration into a snow air pocket through an experimental rebreathing circuit without the integration of a soda lime canister.

Device: Sham

Interventions

Soda lime DEVICE

Respiration into a snow air pocket through an experimental rebreathing circuit with the integration of a soda lime canister.

Breathing with soda lime

Sham DEVICE

Respiration into a snow air pocket through an experimental rebreathing circuit without the integration of a soda lime canister.

Breathing without soda lime

Eligibility Criteria

• Age: 18 Years - 60 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Age: 18 - 60 yrs.
• Body mass index \< 30 kg/m2
• ASA class ≤2
• Providing informed and written consent

You may not qualify if:

• ASA \>2
• Pregnancy
• Smoking

Sponsors & Collaborators

• Institute of Mountain Emergency Medicine: lead

Study Sites (1)

terraXCube

Bolzano, Italy/BZ, 39100, Italy

Location

Study Officials

• Simon Rauch, MD, PhD

  Eurac research, Institute of Mountain Emergency Medicine

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: PARTICIPANT
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: March 14, 2025
• First Posted: March 26, 2025
• Study Start: March 20, 2025
• Primary Completion: March 30, 2025
• Study Completion: December 31, 2025
• Last Updated: March 11, 2026

Record last verified: 2026-03

Data Sharing

• IPD Sharing: Will not share

Locations

IT (1)