In the setting of cardiopulmonary resuscitation (CPR), classical physiological concept about ventilation become challenging. Ventilation may exert detrimental hemodynamic effects that must be balanced with its expected benefits. The risks of hyperventilation have been thoroughly addressed, even questioning the need for ventilation, emphasizing the need to prioritize chest compression quality. However, ventilation is mandatory for adequate gas exchange as soon as CPR is prolonged. Factors affecting the capability of chest compressions to produce alveolar ventilation are poorly understood. In this review, we discuss the conventional interpretation of interactions between ventilation and circulation, from the perspective of novel physiological observations.
Many patients with cardiac arrest exhibit ‘intrathoracic airway closure.’ This phenomenon is associated with lung volume reduction, impedes chest compressions to generate ventilation and overall limits the delivered ventilation. This phenomenon can be reversed by the application of small levels of positive end-expiratory pressure. Also, a novel interpretation of the capnogram can rate the magnitude of this phenomenon, contributing to clarify the physiological meaning of exhaled CO2 and may help assess the real amount of delivered ventilation.
Recent advances in the understanding of ventilatory physiology during CPR shows that capnogram analysis not only provides information on the quality of resuscitation but also on the amount of ventilation produced by chest compressions and on the total amount of ventilation.
aDepartment of Critical Care, Intensive Care Unit, Israelita Hospital Albert Einstein
bDepartment of Critical Care, Intensive Care Unit, Alemao Hospital Oswaldo Cruz Sao Paulo, Sao Paulo, Brazil
cDepartment of Anesthesiology and Intensive Care Medicine, Catholic University of the Sacred Heart, IRCCS Fondazione Policlinico Universitario A. Gemelli, Rome, Italy
dUniversité de Montréal, Montreal, Canada
eLaboratoire d’anatomie, Université du Québec à Trois-Rivières (UQTR)
fSAMU74, Emergency Department, General Hospital of Annecy, Annecy
gINSERM UMR 1066, Creteil, France
Correspondence to Ricardo L. Cordioli, Israelita Hospital Albert Einstein, Adult Intensive Care Unit Av. Albert Einstein, 5th floor, 627 - Jardim Leonor, Sao Paulo, SP 05652-900, Brazil. Tel: +55 11 2151 1500; e-mail: firstname.lastname@example.org