Expired carbon dioxide: a noninvasive monitor of cardiopulmonary resuscitation.

Abstract

End-tidal CO2 concentration (ETCO2) may serve as a simple noninvasive measurement of the blood flow generated by precordial compression during cardiopulmonary resuscitation (CPR). In a mechanically ventilated porcine preparation of ventricular fibrillation, onset of fibrillation was associated with a rapid decrease in ETCO2 from 4.0 + 0.2% to less than 0.7 + 0.2%. With precordial compression, it increased to 1.9 + 0.3%. Animals that were successfully defibrillated after 12 min of CPR demonstrated an immediate increase in ETCO2. The ETCO2 increased from 1.9 + 0.3% to 4.9 + 0.3% over an interval of between 30 and 60 sec. These changes in ETCO2 were closely related to proportionally similar decreases and increases in cardiac output (CO), and a close correlation between ETCO2 and CO was demonstrated (r = .92). A similar highly significant correlation between ETCO2 and CO was also demonstrated during open-chest cardiac massage (r = .95). ETCO2 therefore serves as a noninvasive measure of pulmonary blood flow and therefore CO. In 17 successfully resuscitated animals, ETCO2 during precordial compression averaged 1.7 + 0.2%, whereas it was only 0.5 ± 0. 1% in five animals in whom resuscitation procedures were unsuccessful (p<.001). Accordingly, ETCO2 prognosticates outcome during CPR and immediately identifies restoration of spontaneous circulation. Circulation 77, No. 1, 234-239, 1988. PRIMARY INTERVENTIONS during cardiopulmonary resuscitation (CPR) include external ventilation after establishing airway patency, and precordial compression.t It is precordial compression that maintains forward flow of blood in amounts that temporarily sustain the viability of major organs and especially the heart and the brain. The cardiac output measured during experimental closed-chest cardiac massage has ranged between 17% and 27% of prearrest values.2-5 Except for arterial or intracardiac pressure measurements, there are currently no reliable options for continuously monitoring the efficacy of precordial compression in terms of the blood flow that is generated. We therefore searched for practical, and preferably noninvasive, options with which the efficacy of precordial compression could be quantitatively monitored. Received Aug. 12, 1987; accepted Sept. 24, 1987. 234 In prior studies in a porcine preparation of cardiac arrest and subsequently on human patients, measurements of arterial blood gases demonstrated hypercarbia in mixed venous blood and hypocarbia in arterial blood during CPR.6-9 There was venous acidemia and arterial alkalemia. A large venoarterial Pco2 gradient was associated with decreases in end-tidal CO2 concentration (ETCO2). We hypothesized that this was related to a critical reduction in pulmonary blood flow during CPR accounting for a critical curtailment of CO2 excretion.10 11 In the present study, we observed a close relationship between ETCO2 and cardiac output. We further demonstrated the potential usefulness of ETCO2 as a prognosticator of resuscitability. Moreover, ETCO2 was an immediate in...

Patient-Centric Blood Pressure–targeted Cardiopulmonary Resuscitation Improves Survival from Cardiac Arrest

“…This apparent discrepancy should not be surprising. ETCO 2 correlates better with pulmonary blood flow than with CPP or myocardial blood flow (44)(45)(46)(47)(48)(49). Our data support that among the patient physiologic variables during CPR, CPP is a better predictor of outcome than ETCO 2 measurements, and in line with the American Heart Association recommendation to use arterial blood pressure first tier and ETCO 2 second tier to monitor CPR effect (11).…”

NHE-1 Inhibitors and Erythropoietin for Maintaining Myocardial Function during Cardiopulmonary Resuscitation

“…The presence of a "firm" myocardium was associated with reduced hemodynamic efficacy of cardiac compression as evidenced by a lower endtidal CO 2 tension (PETCO2) ĉ which is a well documented surrogate measurement of systemic and regional blood flow during cardiac resuscitation. (4,(25)(26)(27) Hearts with "very firm" myocardium never regained spontaneous contractions. Hearts with "less firm" myocardium showed some, albeit insufficient, spontaneous contractions.…”

“…As discussed earlier, PETCO2 is a good surrogate measurement of forward blood flow during chest compression. (4,(25)(26)(27) In the study, rescuers were trained and retrained to provide consistent depth and rate of compression and the values of PETCO2 in both control groups were already indicative of high quality chest compression. If ĉ as hypothesized ĉ erythropoietin preserved myocardial distensibility, for a given compression depth, one would expect higher forward blood flow in the presence of erythropoietin and therefore higher P ET CO 2 .…”

A Knowledge-Based Diagnosis and Treatment Display Unit

“…Under conditions of constant ventilation, end-tidal Pco2 re A ects me status of the circulatory system [e.g., Gudipati et al, 1988;Falk et al, 1988]. When cardiac output is critically reduced, end-tidal Pccb * s linearly correlated with pulmonary blood flow.…”