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A Porcine Model of Acute Autologous Pulmonary Embolism
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Venous Gas Emboli and Ambulation at 4.3 psia.
Johnny Conkin1, Neal W Pollock, Michael J Natoli
1NASA Johnson Space Center, Houston, TX, USA.
Aerospace Medicine and Human Performance
|May 19, 2017
Summary
Walking before or during low-pressure exposure increases venous gas emboli (VGE) risk. Mild ambulation in a supersaturated state significantly elevates high-grade VGE and decompression sickness symptoms.
Area of Science:
- Space medicine
- Human physiology
- Aerospace medicine
Background:
- Extravehicular activity (EVA) on Mars presents risks, including decompression sickness due to potential bubble formation.
- Understanding the physiological effects of ambulation during hypobaric exposure is critical for astronaut safety.
Purpose of the Study:
- To determine if walking (ambulation) before or during a hypobaric exposure protocol affects the incidence of venous gas emboli (VGE).
- To investigate the relationship between ambulation timing, nitrogen supersaturation, and VGE formation at reduced pressure.
Main Methods:
- Compared VGE incidence in three groups: control (no ambulation), Group I (ambulation before and during 4.3 psia exposure), and Group II (ambulation before exposure only).
- Utilized precordial Doppler ultrasound to monitor VGE in the pulmonary artery.
- Categorized VGE severity, with Grade III or IV classified as high-grade VGE.
Main Results:
- Group I exhibited a significantly higher incidence of high-grade VGE (57%) compared to control (17%) and Group II (15%).
- Incidence of pain-only decompression sickness was also greater in Group I (20%) than control (0%) and Group II (5%).
Conclusions:
- Mild ambulation increases high-grade VGE when performed under a supersaturated nitrogen state.
- Ambulation during a saturated state alone did not increase VGE incidence, suggesting timing and physiological state are key factors.
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