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Preliminary observations on the colibri CO2-indicator
Clinical Notes
Preliminary Observations on the Colibri CO2-1ndicator GEORG A. PETROIANU, MD,* WOLFGANG H. MALECK,* WOLFGANG F. BERG.LER, MD,t STEFAN ALTMANNSBERGER, MD,* RODERICH RUFER, MD* The performance of a new colorimetric CO2-indicator (Colibri) was assessed in mini-pigs. It performed well during 8-hour procedures. Neither nitrous oxide, nor halothane, nor carbon monoxide, nor intratracheal application of drugs (epinephrine, atropine, lidocaine, and naloxone) interfered with its function. It gave a distinct color change at high ventilation frequencies up to 120/min. The only problem observed was difficulty in matching the colors displayed with the comparison color chart provided. The Colibri's performance seems at least equal to that of the EasyCAP detector, although both devices share some disadvantages (no alarms, semiquantitative, difficult reading in the dark). After initial control of endotracheal tube position by an esophageal detector device, both the Colibri and the EasyCAP seem suited for monitoring of ventilation and circulation if quantitative capnometry is unavailable. (Am J Emerg aed 1998;16:677-680. Copyright © 1998 by W.B. $aunders Comparty) Capnography has become a standard procedure in the operating room. Its ability to detect an esophageal tube malposition, first described by Ionescu in 1981,1 as well as other ventilatory or circulatory problems make it an important monitor. Undetected esophageal intubation is fairly common in (prehospital) emergency medicine. 2-13 Use of capnometry in emergency medicine to detect esophageal tube malposition was studied as early as 1986 by Mickelson et al. 14 Most capnography devices, however, are costly, bulky, and delicate (eg, requiring a temperature of -> 10°C). Therefore, although prehospital use of capnography has been described, 15-19most emergency medicine studies used the disposable chemical CO2-indicator EasyCAP or small
From the *Institute for Pharmacology and 1-Department of Otorhinolaryngology, University of Heidelberg at Mannheim, Mannheim, Germany. Manuscript received March 26, 1996; revision received March 20, 1997, accepted April 27, 1997. Colorimetric detectors for testing were provided by ICOR (Bromma, Sweden) and Nellcor (Idstein, Germany). Address reprint requests to Dr Petroianu, Institut ffir Pharmakologie und Toxikologie, Fakult,~t fer Klinische Medizin Mannheim der Universitfit Heidelberg, Maybachstr 14-16, D-68169 Mannheim, Germany. Key Words: Colorimetric capnometry, semiquantitative capnometry, intratracheal drug application, prehospital equipment, intratracheal intubation, esophageal tube malposition, mini-pig. Copyright © 1998 by W.B. Saunders Company 0735-6757/98/1607-001658.00/0
infrared CO2-indicators like the MiniCAP or the StatCAR 2°-41 Portable quantitative capnometers have now been introduced. 42-46 Recently, a swedish group presented a new disposable chemical CO2-indicator: the Colibri. 47 Like the EasyCAR it is a mainstream device with a pH-sensitive colorimetric indicator. The initial color (no CO2 detected) of the indicators is blue with the Colibri and purple with the EasyCAR Both change to yellow with normal exhaled CO2 levels. According to the inventors, the Colibri is superior to the EasyCAP in several respects. 47 First, it showed quicker color changes, especially from yellow back to blue when CO2 disappears. It worked well with ventilation frequencies up to 60/min, whereas the EasyCAP showed a decline in performance at 20/rain, which is well within the usual clinical range. Second, the Colibri's performance was nearly independent of relative humidity, whereas the EasyCAP's performance declined when humidity increased. Third, the Colibri performed well for more than 9 hours during low-flow anesthetics and up to 24 hours in the intensive care unit, whereas the EasyCAP is intended by the manufacturer for a 2-hour use only and might deteriorate or fail even earlier in a humid environment. 48-5° Fourth, the Colibri contains a standard filter humidifier with a gas sampling port (ie, it could be used as a substitute for a standard filter humidifier). Higgins 51 questioned the value of the Colibri in cardiopulmonary resuscitation with tracheal application of drugs that had been shown to destroy the EasyCAP detector. 27,31,35,5v53 Two groups, however, could not find problems with tracheal epinephrine in canine arrest models. 54,55 We have previously studied the EasyCAP and MiniCAP portable CO2-indicators and the Esophageal Detector Device as proposed by Pollard and Wee. 36,56-6~In this report, we describe our preliminary experience with the Colibri and discuss the usefulness of colorimetric CO2-indicators. METHODS Devices. Colibri detectors were obtained from the manufacturer (ICOR, Bromma, Sweden). For tests 4 and 5 described below, we obtained EasyCAP detectors from the manufacturer (Nellcor, Idstein, Germany). Animal model. The in vivo tests were performed on 3 pregnant mini-pigs (Grttingen breed) of approximately 50 kg body weight. These pigs were primarily used for unrelated research on amniotic fluid embolism with consent of state authority according to federal
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law. After oral premedication with clonidine (5 pg/kg body weight) and sufentanil (20 pg/kg body weight) on sugar cubes, the animals received ketamine (10 mg/kg body weight) and flunitrazepam (0.1 mg/kg body weight) intramuscularly.62 During preoxygenation by mask, an ear vein was cannulated (1 mm internal diameter Teflon cannula) and fentanyl (5 ~g/kg body weight), lidocalne (1 mg/kg body weight), and alcuronium (0.2 mg/kg body weight) were given intravenously. After tracheal intubation (#4 Miller blade, 7 mm internal diameter tube) the animals were ventilated with 50% N20 and 0.4% halothane in 02. Additional opioid was given as needed. Initial ventilator settings were 15 cycles/min and a tidal volume of 10 mL/kg body weight. After cannulation of the left external jugular vein and left carotid artery, tidal volume was adjusted to keep the Paco2 in the range of 32 to 36 mm Hg (normocapnia in pregnancy). Then the main procedure was performed (Cesarean section, preparation of amniotic fluid, intravenous infusion of anmiotic fluid, and 150 minutes of observation). By appropriate interventions with cardiocirculatory drugs (eg, atropine, magnesium, dopamine) mean arterial pressure was kept between 60 and 100 mm Hg and pulse rate was kept between 60 and 100 beats/min. During and after the amniotic fluid experiment, the experiments with the Colibri were done. The animals were ultimately killed with intravenous potassium chloride (1 mL/kg body weight of saturated solution). Test 1. In all three pigs a Colibri was connected to the breathing circuit before intubation and used between tracheal tube and the circuit throughout the 8 + hours of experiments on amniotic fluid embolism. Two animals were ventilated with a semi-open circuit, one animal with a semi-closed minimal-flow circuit (fresh gas flow 0A L/min). The durability of the devices was assessed subjectively (ie, visible deterioration of performance). Test 2. In one pig at the end of the main procedure, a new Colibri was connected to the endotracheal tube. The animal was then ventilated with different ventilator settings to evaluate the color change of the Colibri at different end-tidal CO2 values. End-tidal CO2 was measured with a Sirecust 734G (Siemens, Erlangen, Germany) capnograph connected to the gas sampling port of the Colibri. Ten observers (6 women, 4 men), blinded to the end-tidal CO2 values, compared the colors displayed with the 4 colors at the margin of the device (blue, dark green, light green, yellow). This animal was additionally intubated esophageally to test the ability of the Colibri to detect esophageal tube malposition. Further, the color change was assessed when the heart was falling at death. During this experiment, the dominant lighting in the laboratory was natural daylight via northern windows supplemented by fluorescent light. Test 3. To test the device at high respiratory frequencies, one pig was ventilated for a short time at 120 cycles/rain to look for the presence or absence of cyclic color changes at very high respiratory frequencies. Test 4. Four drugs commonly used for resuscitation and treatment of opioid overdose were instilled into the tracheal tube of one pig after disconnecting the tube from the Colibri: (1) 2 mg epinephrine in 10 mL NaC10.9%; (2) 2 mg atropine in 10 mL NaC1 0.9%; (3) 10 mL lidocaine 2%; (4) 0.8 mg naloxone in 10 mL NaC1 0.9%. Before application of naloxone, the halothane concentration was increased to 1% to avoid awakening the animal. After application of each drug the Colibri was reconnected and the pig was ventilated for 3 minutes. The Colibri was observed for possible malfunction (ie, permanent discoloration). Next, 2 mg epinephrine in 10 mL NaC1 0.9% were applied from the tracheal connector side directly onto the filter of the Colibri and the device connected again, observing for malfunction. The animals were not in cardiac arrest during this experiment. The experiment was repeated with the EasyCAP. Test 5. Two Colibri and EasyCAP detectors were taken from their packages and exposed for 1 week to the atmospheric air in the
home of one of the investigators to observe for spontaneous color change. After 1 week, the investigator breathed through the devices to observe breath-dependent color change. Test 6. A heated (37°C) 2.3-L reservoir bag one third full of water was machine-ventilated (tidal volume 450 mL, frequency 15min) with three gas mixtures for 3 minutes each: (1) 95% O2, 5% CO; (2) 45% O2, 5% CO, 50% N20; (3) 44% O2, 5% CO, 50% N20, 1% halothane. The presence of end-tidal CO2 was monitored with the Colibri. This experiment has been performed previously with the EasyCAP and the MiniCAP.58
RESULTS Test 1. In all three pigs, the Colibri detectors showed a cyclic color change from blue to yellow throughout the procedure without any visible deterioration. The humidity in the minimal-flow experiment was so high that it was condensing on the animal side in the Colibri humidifier and in parts of the circle system, but this did not adversely influence the Colibri display. Test 2. The results are given in Table 1. Test 3. With a frequency of 120, a tidal volume of 200 mL, and an end-tidal CO2 of 1.4 Vol %, the device showed a marked decline in its performance (ie, did not cycle between blue and yellow, but rather between dark green and light green), but still gave a distinct color change. Test 4. No disturbance of the Colibri was noted with any of the four tracheally instilled drugs. Even when we applied epinephrine from the patient connector side directly onto the filter of the Colihri, the device performed as before. Only epinephrine applied from the ventilator connector side, reaching the colorimetfic strip directly, destroyed the indicator. With the E a s y C A P we also found no disturbance with tracheally applied drugs. Epinephrine instilled directly onto the filter o f the E a s y C A P reached the colorimetric strip and destroyed it, causing permanent yellow-orange discoloration. Test 5. The Colibri showed no spontaneous color change after 1 week and still performed well. The E a s y C A P began to discolor within 24 hours and changed completely to yellow within 5 days. W h e n we breathed through it after 1 week, it showed no breath-dependent color change at all. Test 6. Presence of CO2 was not signaled with any of the mixtures by any discoloration of the Colibri. Further observations. During test 2, several observers complained that the colors displayed by the detector did not match the comparison colors at the margin o f the Colibri device. Performing tests 4 and 5 with both devices, we found TABLE 1. Color Change of the Colibri With Different End-Tidal 002 Colors Matched by Observers (n) Tidal Capnograph Respiratory Volume 002 Range Light Dark Rate(/min) (mL) (Vol%) Yellow Green Green Blue 15 20 30 30 30 Dying Esophageal
350 350 350 500 700
4.3-4.9 3.4-3.9 2.5-2,6 1.6-1.8 0.9-1.3 0.3-0.5 0
9 9 6 1 0 0 0
1 1 4 9 7 0 0
0 0 0 0 3 8 0
0 0 0 0 0 2 10
PETROIANU ET AL • COLIBRI 002 INDICATOR
the quicker color change of the Colibri easier to observe than the delayed color change of the EasyCAR although we cannot quantify the difference.
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similar conditions can occur "out of hospital." The colors and the numeric values at the margin of the strip might need revision and further testing with different CO2 concentrations, frequencies, and tidal volumes in different light conditions, and including colorblind observers.
DISCUSSION We could confirm the claim of the inventors 47 that the Colibri has a quicker response to the appearance and disappearance of CO2 than the EasyCAR The Colibri showed no decline in its performance at 30 respiratory cycles/min. It functioned suboptimally at 120 cycles/rain, but such high ventilation frequencies are unusual in humans. With frequencies up to 30/min, the Colibri showed a perfect change of color back to blue when CO2 disappeared in inspiration. The EasyCAP did not change back completely to purple even at 15 cycles/min. Thus, the display of the Colibri is easier to read at "adult" ventilation frequencies. We could confirm further that the Colibri works well for at least 8 hours regardless of high or low humidity in the breathing circuit. Concerning the question of Higgins, 5J we saw surprisingly no influence of tracheally applied drugs on the performance of either the Colibri or the EasyCAR which is in contradiction to the majority of the literature. 27,3~,35,51-55 This might be due to the fact that our animals were not in cardiac arrest, and therefore the drugs were absorbed rapidly. Two groups, however, like us, could not confirm the "epinephrine complication," using canine arrest models. When we simulated the worst case instilling epinephrine directly from the patient side connectors into the devices-the Colibri still functioned normally, whereas the EasyCAP was destroyed. This result was probably caused by the different capacity of the filters. We conclude that the "epinephrine complication" is unlikely with the Colibri unless the drugs are applied into the ventilator side connector of the device, thus reaching the detector strip directly and destroying it. However, this could happen "in the heat of fire" during cardiopulmonary resuscitation and it must be stressed that only a cyclic color change, not a permanent color change, indicates CO2 exhalation. The fact that the Colibri was not affected by 1-week storage outside its package in normal room air, whereas the EasyCAP completely discolored to yellow within 1 week, points to a possibly longer shelf life for the Colibri than for the EasyCAP if a package is damaged. The fact that the Colibri does not cross-react to carbon monoxide, nitrous oxide, and halothane is not surprising, because these gases are not acidic. However, because similar experiments had been done with the EasyCAP by us and others, we wanted to repeat them with the Colibri. 48,58 The only problem occurred with the color matching process. First, it was noted that the colors at the margin of the device did not match well with the colors displayed by the detector in response to CO2. Second, according to the manufacturer the device should change from blue to dark green at 0.5% CO2, from dark green to light green at 1.5% CO2, and from light green to yellow at 4% CO2. According to our results (Table 1) the device changes to dark green at about 0.3%, to light green at about 1%, and to yellow at about 2.5% CO2. These results might be caused in part by the nonstandard light conditions in our laboratory. However,
CONCLUSIONS Except for the problems with the color chart, the device performed properly and seems at least equal in performance to the EasyCAP detector. Both devices are useful as substitutes for quantitative capnometry in settings where quantitative capnometers are not yet available and as backup monitors if the electronic capnometer fails during a critical phase of a rescue, transport, or operation. Both devices share three important disadvantages. They have no alarms, are only semiquantitative, and are difficult to read in low light conditions in the "out-of-hospital" setting. Therefore, electronic capnometers should be used if funds permit. However, capnometry of any kind is not ideal for initial control of tube position in emergencies for two reasons. First, there is a high failure rate in confirmation of tracheal intubation during cardiopulmonary resuscitation due to insufficient exhalation of COz. 57 Second, the patient should be ventilated six times before a capnometric decision on tube position is made. 63 These six breaths are time consuming and risk stomach inflation and regurgitation if the tube position is actually esophageal. Therefore we recommend that an esophageal detector device should always be used for initial control of tube position, followed by continuous monitoring with capnometry.57,64
REFERENCES 1. Ionescu 7-."Signs of endotracheal intubation. Anaesthesia 1981 ; 36:422-423 2. Aijian O, Tsai A, Knopp R, Kallsen GW: Endotracheal intubation of pediatric patients by paramedics. Ann Emerg Med 1989;18:489494 3. Goldenberg IF, Campion BC, Siebold CM, McBride JW, Long LA: Esophageal gastric tube airway vs. endotracheal tube in prehospital cardiopulmonary arrest. Chest 1986;90:90-96 4. Guss DA, Posluszny M: Paramedic orotracheal intubation. Am J Emerg Med 1984;2:399-401 5. Hankins DG, Carruthers N, Frascone RK, et al: Complication rates for the esophageal obturator airway and endotracheal tube in the prehospital setting. Prehosp Disaster Med 1993;8:117-122 6. Kuchinski J, Tikoff G, Rhodes M, Becher JW: Emergency intubation for paralysis of the uncooperative trauma patient. J Emerg Med 1991 ;9:9-12 7. Nakayama DK, Gardner MJ, Rowe Mi: Emergency endotracheal intubation in pediatric trauma. Ann Surg 1990;211:218-223 8. O'Brien DJ, Danzl DF, Hooker EA, et al: Prehospital blind nasotracheal intubation by paramedics. Ann Emerg Med 1989; 18:612617 9. Pointer JE: Clinical characteristics of paramedics performance of pediatric endotracheal intubation. Am J Emerg Med 1989;7:364366 10. Schou J: Prehospital Emergency Medicine (ed t). Kopenhagen Cambridge L6rrach, Alix, 1992 11. Shea SR, MacDonald JR, Gruzinski G: Prehospital endotracheal tube airway or esophageal gastric tube airway. Ann Emerg Med 1985;14:102-112 12. Stewart R, Paris PM, Winter PM, et al: Field endotracheal intubation by paramedic personnel--Success rates and complications. Chest 1984;85:341-345
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13. Stratton SJ, Kane G, Gunter CS, et al: Prospective study of manikin-only versus manikin and human subject endotracheal intubation training of paramedics. An n Emerg Med 1991;20:1314-1318 14. Mickelson KS, Sterner SP, Ruiz E: Exhaled pCO2as a predictor of endotrachealtube placement.Ann Emerg Med 1986;15:657 (abstr) 15. Cantineau JP, Merckx P, Lambert Y, et al: Effect of epinephrine on end-tidal carbon dioxide pressure during prehospital resuscitation. Am J Emerg Med 1994;12:267-270 16. Ellinger K, Luiz TH, Denz C, van Ackern K: Randomisierte Anwendung der aktiven Kompressions-Dekompressions-Technik (ACD) im Rahmen der pr&klinischen Reanimation. An&sthesiol Intensivmed Notfallmed Schmerzther 1994;29:492-500 17. Entholzner E, FelberA, Mielke L, et al: Wertigkeit der endexspiratorischen CO2-Messung bei der Reanimation. An&sthesiol Intensivmed Notfallmed Schmerzther 1992;27:473-476 18. Orliaguet GA, Carli PA, Rozenberg A, et al: End-tidal carbon dioxide during out-of-hospital cardiac arrest resuscitation: Comparison of active compression-decompression and standard CPR. Ann Emerg Med 1995;25:48-51 19. White RD, Asplin BR: Out-of-hospital quantitative monitoring of end-tidal carbon dioxide pressure during CPR. Ann Emerg Med 1994;23:25-30 20. Anton WR, Gordon RW, Jordan TM, et al: A disposable end-tidal CO2 detector to verify endotracheal intubation. Ann Emerg Med 1991 ;20:271-275 21. Bhende MS, Thompson AE, Cook DR, Saville AL: Validity of a disposable end-tidal CO2 detector in verifying endotracheal tube placement in infants and children. Ann Emerg Med 1992;21:142-145 22. Bhende MS, Thompson AE, Orr RA: Utility of an end-tidal carbon dioxide detector during stabilization and transport of critically ill children. Pediatrics 1992;89:1042-1044 23. Bhende MS, Thompson AE: Evaluation of an end-tidal CO2 detector during pediatric cardiopulmonary resuscitation. Pediatrics 1995;95:395-399 24. Bozeman WP, Hexter D, Liang HK, Kelen GD: Esophageal detector device versus detection of end-tidal carbon dioxide level in emergency intubation. Ann Emerg Med 1996;27:595-599 25. Campbell RC, Boyd CR, Shields RO, et al: Evaluation of an end-tidal carbon dioxide detector in the aeromedical setting. J Air Medical Transport 1990;9:13-15 26. Deem S, Kasper C, Benson M: Confirmation of endotracheal tube placement after emergency intubation. Anesthesiology 1996;85: A232 (abstr) 27. Eitel DR, Hess D, Drawbaugh R, et al: Use of the Fenem end-tidal CO2 detector in patients in cardiac arrest. Respir Care 1991 ;36:1289 (abstr) 28. Gerard J, MacLeod GJ, Heller MB, Yealy DM: Verification of endotracheal intubation using a disposable end-tidal CO2-detector. Prehosp Disaster Med 1989;4:74 (abstr) 29. Hayden SR, Sciammarella J, Viccellio P, et al: Colorimetric end-tidal CO2 detector for verification of endotracheal tube placement in out-of-hospitalcardiac arrest.Acad Emerg Med 1995;2:499-502 30. Helm M, Lampl L, Mutzbauer T, Bock KH: Semiquantitative Kapnometrie--hiffreich bei der Verifizierung der Tubuslage bei Traumapatienten? Unfallchirurg 1996;99:11-16 31. Higgins D, Hayes M, Denman W, Wilkinson DJ: Effectiveness of using end tidal carbon dioxide concentration to monitor cardiopulmonary resuscitation. BMJ 1990;300:581 32. MacLeod BA, Heller MB, Gerard J, et al: Verification of endotracheal tube placement with colorimetric end-tidal CO2 detection. Ann Emerg Med 1991 ;20:267-270 33. McCabe L, Heller MB: Confirmation of prehospital endotracheal intubation using an infrared end-tidal CO2-detector. Prehosp Disaster Med 1991 ;6:379 34. Merckx P, Cantineau JP, Reynaud P, et al: Evaluation of maximal PETCO2 values detected by a portable electronic ETCO2 sensor to predict return of spontaneous circulation. Anesthesiology 1994;81 :A588 (abstr) 35. Ornato JP, Shipley JB, Racht EM, et al: Multicenter study of a portable, hand-size, colorimetric end-tidal carbon dioxide detection device. Ann Emerg .M.ed1992;21:518-523 36. Petroianu G: Uberpr0fung der Tubuslage mit einem nichtquantitativen CO2-Detektor. Anaesthesist 1993;42:324-325 37. RSper A, Milz HP, Lauven PM: Erste Erfahrungen mitder semiquantitativen Kapnometrie als Monitoring der prAklinischen Beatmung. Intensivmed 1995;32:1 (suppl, abstr)
38. Sanders KC, Clum WB, Nguyen SS, Balasubramaniam S: End-tidal carbon dioxide detection in emergency intubation in four groups of patients. J Emerg Med 1994;12:771-777 39. Schaller R, Huff JS, Zahn A: Comparison of an Esophageal Detector Device to a Colorimetric End-Tidal CO2 Detector in the Prehospital Setting. South Med J 1994;87:$30 (abstr) 40. Vukmir RB, Heller MB, Stein KL: Confirmation of endotracheal tube placement: A miniaturized infrared qualitative CO2 detector. Ann Emerg Med 1991;20:726-729 41. Varon AJ, Morinna J, Civetta JM: Clinical utility of a colorimetric end-tidal CO2 detector in cardiopulmonary resuscitation and emergency intubation. J Clin Mon 1991;7:289-293 42. Biedler A, Wilhelm W, GrL~nel3 V, et al: 0berprLifung von CO2-Mer~genauigkeit und CO2-BereichsprAzision zweier fur den potentiellen Einsatz im Rettungsdienst konzipierter Kapnometer. Anaesthesist 1996;45:957-964 43. BSbel M, Domres B: Kapnometrieger&te for den Rettungsdienst. Rettungsdienst 1996; 19:990-993 44. Koch A, Schneider 7"."Kapnometrie im Notarztwagen. Notfallmedizin 1996;22:234-238 45. Petroianu GA, Junker HM, Maleck WH, R0fer R: A portable quantitative capnometer in test. Am J Emerg Med 1996;14:586-587 46. Tobias JD, Higgins M: Capnography during transtracheal needle cricothyrotomy. Anesth Analg 1995;81:1077-1078 47. Gedeon A, Krill P, Mebius C: A new colorimetric breath indicator (Colibri). A comparison of two CO2 indicators. Anaesthesia 1994;49:798-803 48. ECRI: Fenem FEF ETCO2 Detector. Health Devices 1991;20: 37-42 49. Feinstein R, White PF, Westerfield SZ: Intraoperative evaluation of a disposable end-tidal CO2 detector. Anesthesiology 1989;71: A461 (abstr) 50. Ponitz AL, Gravenstein N, Banner MJ: Humidity affecting a chemically based monitor of exhaled carbon dioxide. Anesthesiology 1990;73:A515 (abstr) 51. Higgins D: A new colorimetric breath indicator. Anaesthesia 1995;50:88 (letter) 52. Hayes M, Higgins D, Yau EHS, et al: End tidal carbon dioxide detector for monitoring cardiopulmonary resuscitation. BMJ 1990; 301:42 (letter) 53. Muir JD, Randalls PB, Smith GB: End tidal carbon dioxide detector for monitoring cardiopulmonary resuscitation. BMJ 1990;301: 41-42 (letter) 54. Bhende MS, Karasic DG, Menegazzi JJ: Evaluation of an end-tidal CO2 detector during cardiopulmonary resuscitation in a canine model for pediatric cardiac arrest. Pediatr Emerg Care 1995;11:365-368 55. Wright RE, Smith KW, Hayes JK, et al: Evaluation of the Fenem FEF end-tidal CO2 detector in a dog model of cardiopulmonary resuscitation. Anesth Analg 1990;70:$443 (abstr) 56. Petroianu G, Widjaja B, Bergler WF: Detection of oesophageal intubation: Can the "cola complication" be potentially lethal? Anaesthesia 1992;47:70-71 (letter) 57. Petroianu G, Maleck W, Bergler WF, et al: Pr&klinischeKontrolle von Tubuslage und Beatmung.Anaesthesist 1995;44:613-623 58. Petroianu G, Bergler WF, Schulte S, Rufer R: Carbon Monoxide and Non-Quantitative CO2 Detection. J Emerg Med Serv 1995; 20(3): 107 (abstract) 59. Pollard BJ: A test to verify accurate placement of an endotracheal tube. World Congress of Anaesthesiology 1980 Hamburg; Abstract 1112.Amsterdam, Excerpta medica, ICS 533 60. Pollard BJ: Oesophageal detector device. Anaesthesia 1988; 43:713-714 61. Wee MYK: The oesophageal detector device. Anaesthesia
1988;43:27-29 62. Petroianu G, R0fer R: Zero-stress-anaesthesia-induction (ZESTRANI) in mini-pigs: A five year experience in 200 (plus) pigs. Fifth International Congress of Veterinary Anesthesia University of Guelph, Canada, 1994 (abstr) 63. Clyburn P, Rosen M: Accidental oesophageal intubation. Br J Anaesth 1994;73:55-63 64. Petroianu G, Maleck W: Detection of an oesophageal intubation: "State-of-the-art." Anaesth Intens Care 1994;22:744-746 (letter)
Preliminary Observations on the Colibri CO2-1ndicator GEORG A. PETROIANU, MD,* WOLFGANG H. MALECK,* WOLFGANG F. BERG.LER, MD,t STEFAN ALTMANNSBERGER, MD,* RODERICH RUFER, MD* The performance of a new colorimetric CO2-indicator (Colibri) was assessed in mini-pigs. It performed well during 8-hour procedures. Neither nitrous oxide, nor halothane, nor carbon monoxide, nor intratracheal application of drugs (epinephrine, atropine, lidocaine, and naloxone) interfered with its function. It gave a distinct color change at high ventilation frequencies up to 120/min. The only problem observed was difficulty in matching the colors displayed with the comparison color chart provided. The Colibri's performance seems at least equal to that of the EasyCAP detector, although both devices share some disadvantages (no alarms, semiquantitative, difficult reading in the dark). After initial control of endotracheal tube position by an esophageal detector device, both the Colibri and the EasyCAP seem suited for monitoring of ventilation and circulation if quantitative capnometry is unavailable. (Am J Emerg aed 1998;16:677-680. Copyright © 1998 by W.B. $aunders Comparty) Capnography has become a standard procedure in the operating room. Its ability to detect an esophageal tube malposition, first described by Ionescu in 1981,1 as well as other ventilatory or circulatory problems make it an important monitor. Undetected esophageal intubation is fairly common in (prehospital) emergency medicine. 2-13 Use of capnometry in emergency medicine to detect esophageal tube malposition was studied as early as 1986 by Mickelson et al. 14 Most capnography devices, however, are costly, bulky, and delicate (eg, requiring a temperature of -> 10°C). Therefore, although prehospital use of capnography has been described, 15-19most emergency medicine studies used the disposable chemical CO2-indicator EasyCAP or small
From the *Institute for Pharmacology and 1-Department of Otorhinolaryngology, University of Heidelberg at Mannheim, Mannheim, Germany. Manuscript received March 26, 1996; revision received March 20, 1997, accepted April 27, 1997. Colorimetric detectors for testing were provided by ICOR (Bromma, Sweden) and Nellcor (Idstein, Germany). Address reprint requests to Dr Petroianu, Institut ffir Pharmakologie und Toxikologie, Fakult,~t fer Klinische Medizin Mannheim der Universitfit Heidelberg, Maybachstr 14-16, D-68169 Mannheim, Germany. Key Words: Colorimetric capnometry, semiquantitative capnometry, intratracheal drug application, prehospital equipment, intratracheal intubation, esophageal tube malposition, mini-pig. Copyright © 1998 by W.B. Saunders Company 0735-6757/98/1607-001658.00/0
infrared CO2-indicators like the MiniCAP or the StatCAR 2°-41 Portable quantitative capnometers have now been introduced. 42-46 Recently, a swedish group presented a new disposable chemical CO2-indicator: the Colibri. 47 Like the EasyCAR it is a mainstream device with a pH-sensitive colorimetric indicator. The initial color (no CO2 detected) of the indicators is blue with the Colibri and purple with the EasyCAR Both change to yellow with normal exhaled CO2 levels. According to the inventors, the Colibri is superior to the EasyCAP in several respects. 47 First, it showed quicker color changes, especially from yellow back to blue when CO2 disappears. It worked well with ventilation frequencies up to 60/min, whereas the EasyCAP showed a decline in performance at 20/rain, which is well within the usual clinical range. Second, the Colibri's performance was nearly independent of relative humidity, whereas the EasyCAP's performance declined when humidity increased. Third, the Colibri performed well for more than 9 hours during low-flow anesthetics and up to 24 hours in the intensive care unit, whereas the EasyCAP is intended by the manufacturer for a 2-hour use only and might deteriorate or fail even earlier in a humid environment. 48-5° Fourth, the Colibri contains a standard filter humidifier with a gas sampling port (ie, it could be used as a substitute for a standard filter humidifier). Higgins 51 questioned the value of the Colibri in cardiopulmonary resuscitation with tracheal application of drugs that had been shown to destroy the EasyCAP detector. 27,31,35,5v53 Two groups, however, could not find problems with tracheal epinephrine in canine arrest models. 54,55 We have previously studied the EasyCAP and MiniCAP portable CO2-indicators and the Esophageal Detector Device as proposed by Pollard and Wee. 36,56-6~In this report, we describe our preliminary experience with the Colibri and discuss the usefulness of colorimetric CO2-indicators. METHODS Devices. Colibri detectors were obtained from the manufacturer (ICOR, Bromma, Sweden). For tests 4 and 5 described below, we obtained EasyCAP detectors from the manufacturer (Nellcor, Idstein, Germany). Animal model. The in vivo tests were performed on 3 pregnant mini-pigs (Grttingen breed) of approximately 50 kg body weight. These pigs were primarily used for unrelated research on amniotic fluid embolism with consent of state authority according to federal
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law. After oral premedication with clonidine (5 pg/kg body weight) and sufentanil (20 pg/kg body weight) on sugar cubes, the animals received ketamine (10 mg/kg body weight) and flunitrazepam (0.1 mg/kg body weight) intramuscularly.62 During preoxygenation by mask, an ear vein was cannulated (1 mm internal diameter Teflon cannula) and fentanyl (5 ~g/kg body weight), lidocalne (1 mg/kg body weight), and alcuronium (0.2 mg/kg body weight) were given intravenously. After tracheal intubation (#4 Miller blade, 7 mm internal diameter tube) the animals were ventilated with 50% N20 and 0.4% halothane in 02. Additional opioid was given as needed. Initial ventilator settings were 15 cycles/min and a tidal volume of 10 mL/kg body weight. After cannulation of the left external jugular vein and left carotid artery, tidal volume was adjusted to keep the Paco2 in the range of 32 to 36 mm Hg (normocapnia in pregnancy). Then the main procedure was performed (Cesarean section, preparation of amniotic fluid, intravenous infusion of anmiotic fluid, and 150 minutes of observation). By appropriate interventions with cardiocirculatory drugs (eg, atropine, magnesium, dopamine) mean arterial pressure was kept between 60 and 100 mm Hg and pulse rate was kept between 60 and 100 beats/min. During and after the amniotic fluid experiment, the experiments with the Colibri were done. The animals were ultimately killed with intravenous potassium chloride (1 mL/kg body weight of saturated solution). Test 1. In all three pigs a Colibri was connected to the breathing circuit before intubation and used between tracheal tube and the circuit throughout the 8 + hours of experiments on amniotic fluid embolism. Two animals were ventilated with a semi-open circuit, one animal with a semi-closed minimal-flow circuit (fresh gas flow 0A L/min). The durability of the devices was assessed subjectively (ie, visible deterioration of performance). Test 2. In one pig at the end of the main procedure, a new Colibri was connected to the endotracheal tube. The animal was then ventilated with different ventilator settings to evaluate the color change of the Colibri at different end-tidal CO2 values. End-tidal CO2 was measured with a Sirecust 734G (Siemens, Erlangen, Germany) capnograph connected to the gas sampling port of the Colibri. Ten observers (6 women, 4 men), blinded to the end-tidal CO2 values, compared the colors displayed with the 4 colors at the margin of the device (blue, dark green, light green, yellow). This animal was additionally intubated esophageally to test the ability of the Colibri to detect esophageal tube malposition. Further, the color change was assessed when the heart was falling at death. During this experiment, the dominant lighting in the laboratory was natural daylight via northern windows supplemented by fluorescent light. Test 3. To test the device at high respiratory frequencies, one pig was ventilated for a short time at 120 cycles/rain to look for the presence or absence of cyclic color changes at very high respiratory frequencies. Test 4. Four drugs commonly used for resuscitation and treatment of opioid overdose were instilled into the tracheal tube of one pig after disconnecting the tube from the Colibri: (1) 2 mg epinephrine in 10 mL NaC10.9%; (2) 2 mg atropine in 10 mL NaC1 0.9%; (3) 10 mL lidocaine 2%; (4) 0.8 mg naloxone in 10 mL NaC1 0.9%. Before application of naloxone, the halothane concentration was increased to 1% to avoid awakening the animal. After application of each drug the Colibri was reconnected and the pig was ventilated for 3 minutes. The Colibri was observed for possible malfunction (ie, permanent discoloration). Next, 2 mg epinephrine in 10 mL NaC1 0.9% were applied from the tracheal connector side directly onto the filter of the Colibri and the device connected again, observing for malfunction. The animals were not in cardiac arrest during this experiment. The experiment was repeated with the EasyCAP. Test 5. Two Colibri and EasyCAP detectors were taken from their packages and exposed for 1 week to the atmospheric air in the
home of one of the investigators to observe for spontaneous color change. After 1 week, the investigator breathed through the devices to observe breath-dependent color change. Test 6. A heated (37°C) 2.3-L reservoir bag one third full of water was machine-ventilated (tidal volume 450 mL, frequency 15min) with three gas mixtures for 3 minutes each: (1) 95% O2, 5% CO; (2) 45% O2, 5% CO, 50% N20; (3) 44% O2, 5% CO, 50% N20, 1% halothane. The presence of end-tidal CO2 was monitored with the Colibri. This experiment has been performed previously with the EasyCAP and the MiniCAP.58
RESULTS Test 1. In all three pigs, the Colibri detectors showed a cyclic color change from blue to yellow throughout the procedure without any visible deterioration. The humidity in the minimal-flow experiment was so high that it was condensing on the animal side in the Colibri humidifier and in parts of the circle system, but this did not adversely influence the Colibri display. Test 2. The results are given in Table 1. Test 3. With a frequency of 120, a tidal volume of 200 mL, and an end-tidal CO2 of 1.4 Vol %, the device showed a marked decline in its performance (ie, did not cycle between blue and yellow, but rather between dark green and light green), but still gave a distinct color change. Test 4. No disturbance of the Colibri was noted with any of the four tracheally instilled drugs. Even when we applied epinephrine from the patient connector side directly onto the filter of the Colihri, the device performed as before. Only epinephrine applied from the ventilator connector side, reaching the colorimetfic strip directly, destroyed the indicator. With the E a s y C A P we also found no disturbance with tracheally applied drugs. Epinephrine instilled directly onto the filter o f the E a s y C A P reached the colorimetric strip and destroyed it, causing permanent yellow-orange discoloration. Test 5. The Colibri showed no spontaneous color change after 1 week and still performed well. The E a s y C A P began to discolor within 24 hours and changed completely to yellow within 5 days. W h e n we breathed through it after 1 week, it showed no breath-dependent color change at all. Test 6. Presence of CO2 was not signaled with any of the mixtures by any discoloration of the Colibri. Further observations. During test 2, several observers complained that the colors displayed by the detector did not match the comparison colors at the margin o f the Colibri device. Performing tests 4 and 5 with both devices, we found TABLE 1. Color Change of the Colibri With Different End-Tidal 002 Colors Matched by Observers (n) Tidal Capnograph Respiratory Volume 002 Range Light Dark Rate(/min) (mL) (Vol%) Yellow Green Green Blue 15 20 30 30 30 Dying Esophageal
350 350 350 500 700
4.3-4.9 3.4-3.9 2.5-2,6 1.6-1.8 0.9-1.3 0.3-0.5 0
9 9 6 1 0 0 0
1 1 4 9 7 0 0
0 0 0 0 3 8 0
0 0 0 0 0 2 10
PETROIANU ET AL • COLIBRI 002 INDICATOR
the quicker color change of the Colibri easier to observe than the delayed color change of the EasyCAR although we cannot quantify the difference.
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similar conditions can occur "out of hospital." The colors and the numeric values at the margin of the strip might need revision and further testing with different CO2 concentrations, frequencies, and tidal volumes in different light conditions, and including colorblind observers.
DISCUSSION We could confirm the claim of the inventors 47 that the Colibri has a quicker response to the appearance and disappearance of CO2 than the EasyCAR The Colibri showed no decline in its performance at 30 respiratory cycles/min. It functioned suboptimally at 120 cycles/rain, but such high ventilation frequencies are unusual in humans. With frequencies up to 30/min, the Colibri showed a perfect change of color back to blue when CO2 disappeared in inspiration. The EasyCAP did not change back completely to purple even at 15 cycles/min. Thus, the display of the Colibri is easier to read at "adult" ventilation frequencies. We could confirm further that the Colibri works well for at least 8 hours regardless of high or low humidity in the breathing circuit. Concerning the question of Higgins, 5J we saw surprisingly no influence of tracheally applied drugs on the performance of either the Colibri or the EasyCAR which is in contradiction to the majority of the literature. 27,3~,35,51-55 This might be due to the fact that our animals were not in cardiac arrest, and therefore the drugs were absorbed rapidly. Two groups, however, like us, could not confirm the "epinephrine complication," using canine arrest models. When we simulated the worst case instilling epinephrine directly from the patient side connectors into the devices-the Colibri still functioned normally, whereas the EasyCAP was destroyed. This result was probably caused by the different capacity of the filters. We conclude that the "epinephrine complication" is unlikely with the Colibri unless the drugs are applied into the ventilator side connector of the device, thus reaching the detector strip directly and destroying it. However, this could happen "in the heat of fire" during cardiopulmonary resuscitation and it must be stressed that only a cyclic color change, not a permanent color change, indicates CO2 exhalation. The fact that the Colibri was not affected by 1-week storage outside its package in normal room air, whereas the EasyCAP completely discolored to yellow within 1 week, points to a possibly longer shelf life for the Colibri than for the EasyCAP if a package is damaged. The fact that the Colibri does not cross-react to carbon monoxide, nitrous oxide, and halothane is not surprising, because these gases are not acidic. However, because similar experiments had been done with the EasyCAP by us and others, we wanted to repeat them with the Colibri. 48,58 The only problem occurred with the color matching process. First, it was noted that the colors at the margin of the device did not match well with the colors displayed by the detector in response to CO2. Second, according to the manufacturer the device should change from blue to dark green at 0.5% CO2, from dark green to light green at 1.5% CO2, and from light green to yellow at 4% CO2. According to our results (Table 1) the device changes to dark green at about 0.3%, to light green at about 1%, and to yellow at about 2.5% CO2. These results might be caused in part by the nonstandard light conditions in our laboratory. However,
CONCLUSIONS Except for the problems with the color chart, the device performed properly and seems at least equal in performance to the EasyCAP detector. Both devices are useful as substitutes for quantitative capnometry in settings where quantitative capnometers are not yet available and as backup monitors if the electronic capnometer fails during a critical phase of a rescue, transport, or operation. Both devices share three important disadvantages. They have no alarms, are only semiquantitative, and are difficult to read in low light conditions in the "out-of-hospital" setting. Therefore, electronic capnometers should be used if funds permit. However, capnometry of any kind is not ideal for initial control of tube position in emergencies for two reasons. First, there is a high failure rate in confirmation of tracheal intubation during cardiopulmonary resuscitation due to insufficient exhalation of COz. 57 Second, the patient should be ventilated six times before a capnometric decision on tube position is made. 63 These six breaths are time consuming and risk stomach inflation and regurgitation if the tube position is actually esophageal. Therefore we recommend that an esophageal detector device should always be used for initial control of tube position, followed by continuous monitoring with capnometry.57,64
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1988;43:27-29 62. Petroianu G, R0fer R: Zero-stress-anaesthesia-induction (ZESTRANI) in mini-pigs: A five year experience in 200 (plus) pigs. Fifth International Congress of Veterinary Anesthesia University of Guelph, Canada, 1994 (abstr) 63. Clyburn P, Rosen M: Accidental oesophageal intubation. Br J Anaesth 1994;73:55-63 64. Petroianu G, Maleck W: Detection of an oesophageal intubation: "State-of-the-art." Anaesth Intens Care 1994;22:744-746 (letter)