Response to Letter Regarding Article, “Cough Cardiopulmonary Resuscitation Revisited”
We are grateful for the opportunity to respond to McLachlan et al, because the brevity of our communication1 precluded anticipating misunderstandings about cough cardiopulmonary resuscitation in ventricular fibrillation (VF). Our response to their statement that “humans cannot physically cough” every 0.42 seconds is that our recordings were consistent with documented episodes of cough cardiopulmonary resuscitation in human and animal studies2,3 in the absence of any other plausible source of the arterial pulsations in VF.
McLachlan’s letter also suggests that coughs merely cause “a static blood column moving to and fro” to explain “why patients are only able to maintain consciousness for up to 90 seconds.” In prior investigations, VF occurred unexpectedly, and coughs were induced while external defibrillator paddles were applied, programmed, and activated. The duration was limited not by patients’ failure to continue coughing but by the time to defibrillate.2,3 Unconsciousness usually occurs within 15 seconds of cessation of cerebral perfusion4; thus, maintenance of consciousness for 3 to 6 times longer2,3 is compelling evidence of cerebral perfusion.
Ethical constraints on prolonging human observations impelled us to develop an animal model. Cineangiographic sequences were provided in conjunction with our report1 that demonstrated forward flow during cough cardiopulmonary resuscitation in VF by a unique mechanism, which has been described previously.3
Untreated VF is tantamount to sudden death because oxygenated flow to the brain and myocardium cease. There are 2 acknowledged methods of inducing artificial circulation until defibrillation: open-chest cardiac massage, and external chest compression. In our opinion, cough cardiopulmonary resuscitation is an effective third method that may be advantageous because it is performed by the victim, it can be effectively taught to high-risk patients,5 and it could buy time to summon help.