Death by
hyperventilation: A common and life-threatening problem during cardiopulmonary
resuscitation.
Scientific Reviews
Critical
Care Medicine. 32(9) Supplement:S345-S351, September 2004.
Aufderheide, Tom P. MD; Lurie, Keith
G. MD
Abstract:
Context: This translational research initiative focused on the physiology of
cardiopulmonary resuscitation (CPR) initiated by a clinical observation of
consistent hyperventilation by professional rescuers in out-of-hospital cardiac
arrest. This observation generated scientific hypotheses that could only
ethically be tested in the animal laboratory.
Objective: To examine the hypothesis that
excessive ventilation rates during performance of CPR by overzealous but
well-trained rescue personnel causes a significant decrease in coronary
perfusion pressure and an increased likelihood of death.
Design and Setting: In the in vivo human
aspect of the study, we set out to objectively and electronically record rate
and duration of ventilation during performance of CPR by trained professional
rescue personnel in a prospective clinical trial in intubated,
adult patients with out-of-hospital cardiac arrest. In the in vivo animal
aspect of the study, to simulate the clinically observed hyperventilation, nine
pigs in cardiac arrest were ventilated in a random order with 12, 20, or 30 breaths/min, and physiologic variables were assessed.
Next, three groups of seven pigs in cardiac arrest were ventilated at 12
breaths/min with 100% oxygen, 30 breaths/min with 100% oxygen, or 30 breaths/min
with 5% Co2/95% oxygen, and survival was assessed.
Main Outcome Measures: Ventilation rate and
duration in humans; mean intratracheal pressure,
coronary perfusion pressure, and survival rates in animals.
Results: In 13 consecutive adults (average age,
63 +/- 5.8 yrs) receiving CPR (seven men) the average ventilation rate was 30
+/- 3.2 breaths/min (range, 15 to 49 breaths/min) and the average duration of
each breath was 1.0 +/- 0.07 sec. The average percentage of time in which a
positive pressure was recorded in the lungs was 47.3 +/- 4.3%. No patient
survived. In animals treated with 12, 20, and 30 breaths/min, the mean intratracheal pressures and coronary perfusion pressures
were 7.1 +/- 0.7, 11.6 +/- 0.7, 17.5 +/- 1.0 mm Hg/min (p < .0001) and 23.4
+/- 1.0, 19.5 +/- 1.8, 16.9 +/- 1.8 mm Hg (p = .03) with each of the different
ventilation rates, respectively (p = comparison of 12 breaths/min vs. 30
breaths/min for mean intratracheal pressure and
coronary perfusion pressure). Survival rates were six of seven, one of seven,
and one of seven with 12, 30, and 30 + Co2 breaths/min, respectively (p =
.006).
Conclusions: Despite seemingly adequate
training, professional rescuers consistently hyperventilated patients during
out-of-hospital CPR. Subsequent hemodynamic and
survival studies in pigs demonstrated that excessive ventilation rates
significantly decreased coronary perfusion pressures and survival rates,
despite supplemental Co2 to prevent hypocapnia. This
translational research initiative demonstrates an inversely proportional
relationship between mean intratracheal pressure and
coronary perfusion pressure during CPR. Additional education of CPR providers
is urgently needed to reduce these newly identified and deadly consequences of
hyperventilation during CPR. These findings also have significant implications
for interpretation and design of resuscitation research, CPR guidelines,
education, the development of biomedical devices,
emergency medical services quality assurance, and clinical practice.
(C) 2004 Lippincott
Williams & Wilkins, Inc.