Capnography for Monitoring Response to Care After Out-Of-Hospital Cardiac Arrest

ORIGINAL ARTICLE Capnography for monitoring response to care after out-of-hospital cardiac arrest

LUIS DÍAZ DÍEZ-PICAZO, SANTIAGO BARROSO MATILLA, RICARDO CHICO CÓRDOBA, ÁNGELES GÓMEZ MUÑOZ Grupo de Investigación sobre Capnografía. Servicio de Urgencia Médica de Madrid (SUMMA 112). Madrid, Spain.

CORRESPONDENCIA: Objective: To analyze the usefulness of capnography to monitor patients after out-of- Dr. Luis Díaz Díez-Picazo hospital cardiorespiratory arrest, in terms of the ability of capnography to confirm Madrid, Spain tracheal intubation and the ability of capnometry to promptly detect return of E-mail: [email protected] spontaneous circulation and predict patient recovery. Methods: Preliminary description of the first 30 cases in a prospective study of out-of- FECHA DE RECEPCIÓN: hospital cardiorespiratory arrest in elderly non-trauma patients attended by the 7 19-5-2010 ambulance units of the SUMMA 112 emergency service in Madrid, Spain, in 2008. FECHA DE ACEPTACIÓN: Clinical, evolutive and capnographic data were recorded. 7-7-2010 Results: Seventy percent of the 30 patients were men. The mean (SD) age was 64.5 (16.3) years. A capnogram was observed after the first intubation attempt in 28 cases. In CONFLICTO DE INTERESES: the remaining 2 cases, the absence of a capnogram indicated esophageal intubation; None. correct intubation was accomplished and confirmed on the second try (positive and Prize for best oral presentation negative predictive values, 100%). However, no differences were observed between end- at the XXI Congress of the tidal carbon dioxide partial pressure (PETCO2) in the absence or presence of a Spanish Society of Emergency capnogram with the first and second attempts at intubation. Eight patients recovered. In Medicine (Benidorm, 2009). 5 of them (62.5%), a significant increase in PETCO2 was observed before the change in the electrocardiographic signal and before detection of a carotid pulse (P<.05). Finally, ACKNOWLEDGEMENTS The authors wish to thank Dr. PETCO2 values after cardiopulmonary resuscitation (CPR) were significantly higher in the Alonso Mateos for help with the patients who recovered (33.5 [12.7] mm Hg) than in those who died (15.3 [11.1] mm study design and Dr. Nelva Hg) (P<.01). After 20 minutes of CPR, PETCO2 was more than 20 mm Hg in all patients Mata for invaluable help in who recovered. statistical analysis and Conclusions: Capnography monitoring in responding to out-of-hospital preparation of the manuscript. cardiorespiratory arrest is useful for confirming correct placement of the endotracheal tube, as indicated by the presence of a capnogram. Capnometry offers the first sign of return of spontaneous circulation in some cases and can be used to predict the success of prolonged CPR. [Emergencias 2010;22:345-348]

Key words: Capnography. Cardiac arrest. Emergency medical services.

Introduction CO2 (ETCO2). Recording ETCO2 without a capnogram is known as capnometry7. Capnography is non-invasive monitoring of The 2005 European Resuscitation Council ventilation, introduced in medical emergency (ERC) Guidelines on cardiopulmonary resuscitation services in our country during recent years1. Its (CPR) recommended the routine use of capnogra- main application is for confirmation of correct en- phy during cardiopulmonary arrest (CPA) intuba- dotracheal tube placement2, and its routine use in tion to verify correct intubation and clearly stipu- intubated patients in the hospital setting is rec- lates that the non-detection of CO2 may be due ommended by relevant medical societies3-6. It is to esophageal intubation or failure of detection usually presented as a graph of expiratory CO2 due to low pulmonary perfusion in the CPR situa- concentration during the breathing cycle, known tion8. It also recommends capnography monitor- as a capnogram, and also shows the maximum ing as a reliable indicator of heart output during value of CO2 for each exhalation, i.e. end-tidal CPA and suggests that ETCO2 may behave as an

Emergencias 2010; 22: 345-348 345 L. Díaz Díez-Picazo et al.

early indicator of return to spontaneous circula- calculated predictive values of the presence of a tion and be useful in prognosis regarding recov- capnogram after intubation, and analyzed ETCO2 ery capacity8. values obtained after intubation, using the non- In the literature supporting these recommen- parametric Mann-Whitney test since these vari- dations, the few studies on capnography in pre- ables were not normal. hospital CPR9-13 agree on the need for more solid 2. To determine the ability of capnometry to evidence. We therefore designed the present detect early recovery of circulation after successful study aimed primarily at analyzing the effective- CPR, we analyzed the relationship between the ness of capnographic monitoring in out-of-hospi- dependent variable (reason for CPR) and the inde- tal CPA. The specific objectives were: to determine pendent variable (capnographic event prior to re- the ability of capnography and capnometry to covery) using chi-square test. confirm correct intubation in CPA, to assess 3. To determine the prognostic value of cap- whether capnometry detected early restoration of nometry regarding spontaneous recovery, we ana- spontaneous circulation following successful CPR, lyzed the relationship between the dependent and study the prognostic value of capnometry for variable (reason for CPR) and each independent patient recovery capacity. variable (initial, 20-minute and final ETCO2) using Mann Whitney test. In all cases, a p value of less than 0.05 was Method considered statistically significant and the strength of association was estimated by OR using a confi- We performed a preliminary study from January dence interval of 95% (CI 95%). All statistical 2008 to January 2009 for seven mobile units be- analyses were performed using SPSS v 14.0. longing to the Medical Emergencies Service of Madrid (SUMMA 112). We included 30 adult patients with non-traumatic CPA who received ad- Results vanced CPR according to ERC recommendations8. For capnographic monitoring we used a low flow Of the 30 patients treated, 21 (70%) were side current method (Microstream, OridionTM) in- men, and mean age was 64.5 ± 16.3 years. The tegrated into a LifePack 12 defibrillator monitor most common initial rhythm was asystole (22 cas- (Physiocontrol, Medtronic Ibérica®). After intuba- es, 73%), followed by pulseless electrical activity tion, we recorded the presence of a capnogram af- (5 cases, 17%) and ventricular fibrillation (3 cases, ter six similar capnograms, and the value of initial 10%). Table 1 shows the main patient characteris-

ETCO2. Then we recorded ETCO2 every 5 minutes tics according to final evolution. until the end of CPR. In addition, the researchers Regarding the ability of capnography and cap- noted any capnographic events observed, defined nometry to confirm proper intubation, 28 of the Ն as variations in ETCO2 10 mmHg maintained for 30 cases showed the presence of a capnogram af- Ն 1 minute or a persistent change in the capno- ter the first intubation attempt. In the remaining gram. At the end of the intervention, we request- two cases, the absence of capnogram was due to ed informed consent from a member of the family esophageal intubation; the capnogram appeared and completed a data collection sheet, including on the second attempt and confirmed proper in- date and call-out number, sex, age, initial heart tubation, which meant positive predictive and rate, initial monitoring capnography (presence of a negative values of 100% (Table 2). capnogram and ETCO2 value) and capnographic Regarding capnometry, ETCO2 values obtained events observed. This investigation was approved after the first attempt at intubation were 25 ± 17.7 by the Research Committee of SUMMA 112. mmHg when the capnogram was present, and The variables analyzed were: sex, age, initial 14.5 ± 6.4 mmHg in its absence (p = 0.18). In re- heart rate, capnogram after intubation, initial, 20- lation to the capacity of capnometry to detect the minute and final ETCO2 values, capnographic early recovery of circulation after successful CPR, events, and reason for cessation of CPR. Qualita- eight patients (26%) recovered and were admitted tive variables were expressed as the number of alive to the hospital. Five of these patients (62.5%) cases and percentages and quantitative variables showed an increase of ETCO2 > 10 mmHg prior to as mean ± standard deviation. Subsequently, spe- the change in the electrocardiogram and pulse de- cific analysis was performed for each objective: tection; this relationship between the increase in

1. To determine the ability of capnography ETCO2 and recovery of circulation was statistically and capnometry to confirm correct intubation, we significant (p < 0.05).

346 Emergencias 2010; 22: 345-348 CAPNOGRAPHY FOR MONITORING RESPONSE TO CARE AFTER OUT-OF-HOSPITAL CARDIAC ARREST

Table 1. Description of patients included in the study Recovered Deaths p N = 8 N = 22 Sex (male/female) 6/2 15/7 1.00 Age (years) (mean ± SD) 70 ± 16.3 62.5 ± 16.2 0.23 Initial rhythm (VF/asystole, PEA) 1/7 2/20 1.00 Initial ETCO2 (mmHg) (mean ± SD) 27.1 ± 22.1 23.3 ± 15.7 0.66 20 min ETCO2 (mmHg) (mean ± SD) 38.7 ± 8.4 25.8 ± 22.8 0.11 Final ETCO2 (mmHg) (mean ± SD) 33.5 ± 12.7 15.3 ± 11.1 < 0.01 Capnographic events (RSC/OTI) 5/1 3/1 1.00

VF: ventricular fibrillation; PEA: pulseless electrical activity; ETCO2: End-tidal CO2; RSC: Recovery of spontaneous circulation; OTI: Orotracheal intubation: capnographic event after intubation (no capnogram).

Regarding the prognostic value of capnometry correct tube placement since both predictive val- for recovery, the final ETCO2 values at the end of ues were 100%. In contrast, the use of capnome- the CPR were significantly higher in patients who ters for this could lead to misinterpretation. recovered than in those who died (p < 0.01) With respect to the use of capnometry to de- (Table 1), but not for initial or 20-minute values. tect early recovery of spontaneous circulation, the

All patients who recovered had ETCO2 values over results presented here are consistent with those of 20 mmHg both after 20 minutes and at the end previous studies12,13 indicating that a capnographic of CPR. event could be the first sign of such recovery and serves to alert the emergency team about inter- rupting cardiac massage some time before elec- Discussion trocardiogram and carotid pulse signs. Furthermore, in line with several published This work is the first to study the effectiveness studies9-12, our results indicate that higher ETCO2 of capnography in out-of-hospital CPA in Spain. values during CPR suggest greater chance of re- Being a pilot study, it presented the limitations in- covery and that, after 20 minutes of CPR without herent in its design including non-randomization, success, ETCO2 values < 20 mm Hg are an indica- lack of specific software for data collection and a tor of poor prognosis for recovery. low number of patients included. Moreover, since These results indicate that capnography can it is not currently possible to follow recovered CPR aid clinical decision-making in out-of-hospital CPA, patients in Madrid hospitals, the endpoint result but they must be interpreted with caution and had to be the recovery of circulation and live hos- checked against other results of research conduct- pital admission, without including the patient's ed with a greater number of patients. However, subsequent recovery. Despite these limitations, we conclude that capnographic monitoring in the present study provides novel initial evidence out-of-hospital CPA effectively confirms correct of great clinical relevance on the usefulness of positioning of the endotracheal tube by the pres- capnography in out-of-hospital CPA. ence of a capnogram, and that capnometry may First, there is abundant literature on the use of serve to detect the first signs of recovery of spon- capnography to confirm correct endotracheal in- taneous circulation and be used as a prognostic tubation14,15 in the hospital setting, but doubts ex- indicator in prolonged CPR. isted in the CPR situation, given the low pulmonary perfusion due to reduced cardiac output, about its ability to confirm successful intubation, References as warned by the ERC8. Our results highlight the 1 Díez-Picazo LD, Barrado-Muñoz L, Blanco-Hermo P, Barroso-Matilla clinical significance of the presence of a capno- S, Espinosa-Ramírez S. La capnografía en los servicios de emergencia gram after intubation, which effectively confirmed médica. SEMERGEN. 2009;35:138-43.

Table 2. Calculation of predictive values of the presence of a capnogram as confirmation test of orotracheal intubation (OTI) Capnogram after OTI Tube in airway Tube in the esophagus Present TP = 28 FP = 0 Absent FN = 0 TN = 2 NPV = TN/(TN + FN) = 2/(2 +0) = 1 PPV = TP/(TP + FN) = 28 / (28 + 0) = 1 TP: True positive; FP: False positive; FN: False negative; TN: True negative; PPV: positive predictive value; NPV: negative predictive value.

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2 Walls RM. Chapter 1: Airway. In: Marx JA, editor. Rosen’s Emergency come of out of hospital cardiac arrest. N Eng J Med. 1997;337:301- Medicine: Concepts and Clinical Practice, 7th edition. Filadelfia: Else- 6. vier; 2010. pp. 3-22. 10 Wayne MA, Levine RL, Miller CC. Use of end-tidal carbon dioxide to 3 American College of Emergency Physicians. Expired carbon dioxide predict outcome in prehospital cardiac arrest. Ann Emerg Med. monitoring. Ann Emerg Med. 1995;25:441. 1995;25:762-7. 4 The American Heart Association. Guidelines 2000 for Cardiopulmo- 11 Grmec S, Klemen P. Does the end-tidal carbon dioxide (EtCO2)con- nary and Emergency Cardiovascular Care. Part 6: Advanced cardio- centration have prognostic value during out-of-hospital cardiac vascular life support. Section 3: Adjuncts for oxygenation, ventilation arrest? Eur J Emerg Med. 2001;8:263-9. and airway control. Circulation. 2000;102(Supl 8):I95-I104. 12 Grmec S, Krizmaric M, Mally, Kozelj A, Spindler M, Lesnik B. Utstein 5 The Intensive Care Society. Guidelines for the transport of the criti- analysis of out-of-hospital cardiac arres- Bystander CPR and end ex- cally ill adult; 20002. (Consultado 3 Mayo 2010). Disponible en pired carbon dioxide. Resuscitation. 2007;72:404-14. http://www.ics.ac.uk/downloads/icstransport2002mem.pdf 13 Kolar M, Krizmaric M, Klemen P, Grmec S. Partial pressure of end-tidal 6 European Standard EN 1789:2007 (E). Medical vehicles and their carbon dioxide successful predicts cardiopulmonary resuscitation in the equipment – Road ambulances. CEN European Committee for Stan- field: a prospective observational study. Critical Care. 2008;12:R115. dardization, Brussels, Belgium, aprobado el 27 Febrero 2007. 14 Silvestri S, Ralls GA, Krauss B, Thundiyil J, Rothrock SG, Senn A, et al. 7 Murphy MF, Krauss B. Chapter 3: Monitoring the emergency patient. The effectiveness of prehospital use of continuous end-tidal carbon In: Marx JA, editor. Rosen’s Emergency Medicine: Concepts and Clini- dioxide monitoring on the rate of unrecognized misplaced intuba- cal Practice, 7th edition. Filadelfia: Elsevier; 2010. pp. 29-33. tion within a regional emergency medical services system. Ann 8 Nolan JP, Deakin CD, Soar J, Böttiger BW, Smith G, European Resus- Emerg Med. 2005;45:497-503. citation Council. European Resuscitation Council Guidelines for Re- 15 Timmermann A, Russo SG, Eich C, Roessler M, Braun U, Rosenblatt suscitation 2005. Section 4. Adult advanced life support. Resuscita- WH, et al. The out-of-hospital esophageal and endobronchial intubation. 2005;67(Supl. 1):S39-S86. tions performed by emergency physicians. Anesth Analg. 9 Levine RL, Wayne MA, Miller CL. End-tidal carbon dioxide and out- 2007;104:619-23.

La monitorización capnográfica en la parada cardiaca extrahospitalaria

Díaz Díez-Picazo L, Barroso Matilla S, Chico Córdoba R, Gómez Muñoz A Objetivo: Analizar la eficacia de la monitorización capnográfica en la parada cardiorrespiratoria (PCR) extrahospitalaria, mediante la determinación de la capacidad de la capnografía y la capnometría para confirmar la intubación endotraqueal, la detección precoz de la recuperación de circulación espontánea mediante capnometría y el valor pronóstico de la capnometría sobre la capacidad de recuperación del paciente. Método: Estudio descriptivo preliminar del estudio prospectivo en curso realizado con los 30 primeros casos de PCR no traumática en pacientes mayores de edad atendidos por siete unidades móviles de emergencia del SUMMA 112 durante el año 2008. Se recogieron datos clínicos evolutivos y de la monitorización capnográfica. Resultados: De los 30 pacientes (70% varones, 64,5 ± 16,3 años), en 28 casos se observó capnograma tras el primer intento de intubación y en los dos restantes, la ausencia de capnograma se debió a la intubación esofágica. En ambos se obtuvo capnograma al segundo intento, y confirmó así la correcta intubación (valores predictivos positivo y negativo del 100%). No se observó diferencia en los valores de end-tidal CO2 (ETCO2) obtenidos tras el primer intento de intubación en presencia o ausencia de capnograma. De los ocho pacientes recuperados, en cinco de ellos (62,5%) se observó un incremento significativo del ETCO2 anterior al cambio en la monitorización electrocardiográfica y a la detección de pulso carotídeo (p < 0,05). Final- mente, se observó que los valores de ETCO2 al final de la reanimación cardiopulmonar (RCP) fueron significativamente mayores en los pacientes recuperados (33,5 ± 12,7 mmHg) que en los fallecidos (15,3 ± 11,1 mmHg; p < 0,01), y fueron mayores de 20 mmHg en todos los pacientes recuperados, tanto a los 20 minutos como al final de la RCP. Conclusiones: La monitorización capnográfica en la PCR extrahospitalaria confirma eficazmente la posición del tubo endotraqueal mediante la presencia de capnograma y la capnometría puede, en algunos casos, ser el primer signo de recuperación de la circulación espontánea y emplearse como indicador pronóstico en la RCP prolongada. [Emergencias 2010;22:345-348]

Palabras clave: Capnografía. Parada cardiaca. Servicios de emergencia médica.

348 Emergencias 2010; 22: 345-348