Heart rate monitor watches are becoming increasingly popular in outdoor sports. That has resulted in some interesting case reports where heart rate recordings have been downloaded and analysed from victims´watches. The most recent one was published in Resuscitation. It details the heart rate variations of a person buried in an avalanche. It is an absolutely chilling demonstration of death from asphyxia.
Avalanche death from asphyxia with an obstructed airway
The victim was backcountry-skiing alone when he was caught by an avalanche and buried completely at a depth of 1,5m. He wasn´t located and extricated by the rescue services until after 290 minutes. After extrication he displayed no vital signs, no signs of trauma and had core temperature of 24°C. The cooling rate was 2,7 °C/h which is fairly normal for skiers buried in avalanches. Importantly, his airways were found to be obstructed by packed snow. The man was pronounced dead according to avalanche ALS guidelines. (´Complete avalanche burial cannot be survived for more than 35 minutes with an completely obstructed airway.´)
The data from his Polar(tm) watch was downloaded and is displayed in the graph below.
Period 1 has a duration of approximately one minute. Sympathetic activation and tachycardia peaking at 180 bpm. It likely describes the initial panic and violent struggle against burial. Period 2, lasts for about 20 minutes. The pulse rate varies wildly between brady and tachycardia. The authors offer no explanation for why that happens. Then in period 3 the heart rate steadily decreases towards asystole and death. Asystole occurs after about 30 minutes. The pulse watch cannot record bradycardias below 20 bpm.
Those readings can be compared with those from a similar case-report where the airway was not obstructed.
Avalanche death from asphyxia with an unobstructed airway
The other case, by Strappazon et al, was similar. A skier of similar age was completely buried in an avalanche before being located and extricated 230 minutes after burial. The big difference was how the rescuers observed an airspace in the snow front of his mouth and nose of 15x15x15 cm. In avalanche rescue, the presence of an air pocket is important. It means the victim potentially had an unobstructed airway after being buried. It also means the rescuers can´t estimate the time of death with any certainty. The futility call becomes impossible and CPR should probably proceed until the patient is evacuated to a hospital.
The first 20 minutes: Variable pulse rate 28-144 bpm.
18-35 minutes: Sustained tachycardia. 155 bpm. The victim from the first case was dead by now.
35-70 minutes: Sustained bradycardia. 51 bpm.
70-235 minutes: Sustained takycardia. 176 bpm with variability during the last minutes before extrication. Obviously we cant know if the patient was really perfusing at this stage.
235 minutes and onwards: Cardiac arrest after extrication.
Unfortunately, despite being alive until the moment of extrication, CPR was not performed on this patient. This apparently had to do with severe weather and objective dangers threatening the rescuers who by then had to evacuate themselves and the dead victim out of the avalanche area.
These case reports likely demonstrate the enormous impact the presence of an obstructed airway has on our chances to survive avalanche burial. The observation of an obstructed airway in the first patient means the patient had asphyxia from the start and died after 30 minutes or so. At extrication, after 290 minutes, he could correctly be declared dead.
The second patient, on the other hand, displayed vital signs for 253 minutes before dying of increasing hypoxia. The team observed an air-pocket and couldn´t with any certainty estimate the time of death. CPR should then be commenced and go on all the way to the ED/ICU.
Why this patient died the moment he was extricated remains unknown. All patients who are critically ill are sensitive to movement and handling. The violent digging around the patient before he was pulled out of the snow could have triggered an v.fib or an arrest. Hypothermic patients are also notorious for becoming hemodynamically unstable or even arresting if not handled carefully.
Case 1 lives here:
Resuscitation. 2013 Jul 26. pii: S0300-9572(13)00365-1. doi: 10.1016/j.resuscitation.2013.07.014. [Epub ahead of print] Electrical cardiac activity in an avalanche victim dying of asphyxia. Heschl S, Paal P, Farzi S, Toller W.