The high altitude adversely affected the quality of the chest compressions of skilled rescuers without them realizing it, experiments have shown.
At simulated altitudes of 200, 3000, or 5000 meters in a hypobaric chamber, helicopter EMS personnel began with optimal chest compressions on dummies, but gradually lost both the depth of their compressions and the appropriate pace. effective compressions over time, according to Giacomo. Strapazzon, MD, PhD, from the Italian Institute for Mountain Emergency Medicine at Eurac Research in Bolzano, and colleagues.
Chest compression depths dropped below the guideline recommended minimum of 50mm after just 60-90 seconds of CPR at heights reached by EMS helicopters serving mountainous and rural areas.
“There is a significant risk that the depth of CC [chest compressions] can drop below the recommended 50 mm already within 2 minutes, when the change of CC supplier is recommended by international RCP guidelines. Failure to meet the lower limits set for depth could lead to a worse clinical outcome, ”the researchers noted in their article in Journal of the American Heart Association.
“EMS personnel of helicopters operating in mountainous areas are highly exposed to HH [hypobaric hypoxia] due to the rapid rise in altitude of the helicopter. Acute exposure to HH results in short-term physiological responses involving the cardiovascular and respiratory systems, such as increased heart rate, cardiac output, blood pressure and respiratory rate, ”explained the authors of the ‘study.
The group suggested the use of mechanical CPR devices in helicopter EMS missions and a reassessment of CPR guidelines for rescuers practicing at altitude.
“Mechanical compression itself has advantages and disadvantages. They can link people to other interventions that may be clinically beneficial in certain scenarios. However, these machines can migrate and compress in suboptimal locations if not properly monitored, ”commented emergency physician Stephen Sanko, MD, of the Keck School of Medicine at the University of Southern California at Los Angeles.
“In addition, their application can be time consuming – and we know that patient outcomes (especially neuro-intact survival) are very sensitive to both the frequency of pauses as well as the longest pause of a. resuscitation, “he said. MedPage today in an email.
Ultimately, the study is a reminder that performing high-quality CPR is a physical activity and somewhat exhausting, according to cardiologist Lorrel Toft, MD, of the University of Nevada, Reno.
“It’s no surprise that this physical activity becomes more difficult with rapid ascent to high altitudes, just like other strenuous physical activities. But while performing CPR can be physically demanding (if you do it right), it can be physically demanding. shouldn’t stop spectators from doing their best if they come across someone who has suffered cardiac arrest, ”she said.
The study participants were 48 helicopter EMS personnel recruited from Austria, Germany, Italy and Switzerland. They were on average 40 years old and 77% of them were men.
The trial had a randomized crossover design such that people tested their compression skills for 5 minutes at a time at two of the three simulated altitudes, the highest being 5,000 meters.
By comparison, the world’s tallest city, La Paz, Bolivia, rises 3,869 meters above sea level; the highest city in the United States, Denver, rises to 1,609 meters.
Temperature, humidity and carbon dioxide levels were held constant at typical indoor levels. The ascent and descent rates of the hypobaric chamber were set to a typical helicopter climb rate of 4 m / s.
The mannequins were connected to a tablet to measure the quality of CPR. Participants also subjectively rated their performance on a visual analog scale.
Their perceived performance and effort did not correlate with objective measures of performance.
“This is consistent with other research which tells us that even professionals are not very good at assessing their own CPR skills. your chest compressions are good (or bad), ”Toft noted.
The deleterious effects of altitude on CPR were more pronounced in female providers and people weighing less than 70 kg (154 lbs). However, Strapazzon and her colleagues admitted that their study was not designed to study gender differences.
Additionally, the simulations failed to recreate the increased sympathetic activity and alertness associated with a true EMS rescue operation.
“This study highlights how we are just beginning to appreciate the role of characteristics and behavior of resuscitators themselves – not just patients who are resuscitated. In the future, these types of studies will also be important to perform in the future. units, ”Sanko noted.
“Any information that we can gather about modifiers of chest compressor performance in any setting will inevitably have implications beyond the specific setting studied. everyday life, ”he said.
Strapazzon’s group has had no disclosure.