Context Asphyxia is the most common cause of death after avalanche burial. A
device that allows a person to breathe air contained in snow by diverting
expired carbon dioxide (CO2) away from a 500-cm3 artificial
inspiratory air pocket may improve chances of survival in avalanche burial.
Objective To determine the duration of adequate oxygenation and ventilation during
burial in dense snow while breathing with vs without the artificial air pocket
Design Field study of physiologic respiratory measures during snow burial with
and without the device from December 1998 to March 1999. Study burials were
terminated at the subject's request, when oxygen saturation as measured by
pulse oximetry (SpO2) dropped to less than 84%, or after 60 minutes
Setting Mountainous outdoor site at 2385 m elevation, with an average barometric
pressure of 573 mm Hg.
Participants Six male and 2 female volunteers (mean age, 34.6 years; range, 28-39
Main Outcome Measures Burial time, SpO2, partial pressure of end-tidal CO2 (ETCO2), partial pressure of inspiratory CO2(PICO2), respiratory rate, and heart rate at baseline (in open atmosphere)
and during snow burial while breathing with the device and without the device
but with a 500-cm3 air pocket in the snow.
Results Mean burial time was 58 minutes (range, 45-60 minutes) with the device
and 10 minutes (range, 5-14 minutes) without it (P=.001).
A mean baseline SpO2 of 96% (range, 90%-99%) decreased to 90% (range,
77%-96%) in those buried with the device (P=.01)
and to 84% (range, 79%-92%) in the control burials (P=.02).
Only 1 subject buried with the device, but 6 control subjects buried without
the device, decreased SpO2 to less than 88% (P=.005). A mean baseline ETCO2 of 32 mm Hg (range, 27-38
mm Hg) increased to 45 mm Hg (range, 32-53 mm Hg) in the burials with the
device (P=.02) and to 54 mm Hg (range, 44-63 mm Hg)
in the control burials (P=.02). A mean baseline PICO2 of 2 mm Hg (range, 0-3 mm Hg) increased to 32 mm Hg (range, 20-44
mm Hg) in the burials with the device (P=.01) and
to 44 mm Hg (range, 37-50 mm Hg) in the control burials (P=.02). Respiratory and heart rates did not change in burials with
the device but significantly increased in control burials.
Conclusions In our study, although hypercapnia developed, breathing with the device
during snow burial considerably extended duration of adequate oxygenation
compared with breathing with an air pocket in the snow. Further study will
be needed to determine whether the device improves survival during avalanche