Evidence-based medicine requires a critical appraisal of the literature based upon study methodology and number of subjects. Not all references are equally robust. The findings of a large, prospective, randomized, and blinded trial should carry more weight than a case report.

To help the reader judge the strength of each reference, pertinent information about the study, such as the type of study and the number of patients in the study, are included in bold type following the reference, where available.

1. Kline JA, Israel EG, Michelson EA, et al. Diagnostic accuracy of a bedside D-dimer assay and alveolar dead-space measurement for rapid exclusion of pulmonary embolism: a multicenter study. JAMA. 2001;285(6):761-768. (Prospective, observational; 380 patients)
2. Verschuren, F, et al. Volumetric capnography as a screening test for pulmonary embolism in the emergency department. Chest. 2004;125(3):841-850. (Prospective, observational; 45 patients)
3. Nunn JF, Hill DW. Respiratory dead space and arterial to end-tidal carbon dioxide tension difference in anesthetized man. J Appl Physiol. 1960;15:383-389. (Prospective, observational; 12 patients)
4. Wahba RW, Tessler MJ. Misleading end-tidal CO2 tensions. Can J Anaesth. 1996;43(8):862-866. (Review)
5. Ornato JP, Shipley JB, Racht EM, et al. Multicenter study of a portable, hand-size, colorimetric end-tidal carbon dioxide detection device. Ann Emerg Med. 1992;21(5):518-523. (Prospective, observational; 227 patients)
6. Goldberg JS, Rawle PR, Zehnder JL, et al. Colorimetric end-tidal carbon dioxide monitoring for tracheal intubation. Anesth Analg. 1990;70(2):191-194. (Prospective, observational; 62 intubations)
7. Yamanaka MK, Sue DY. Comparison of arterial-end-tidal PaCO2 difference and dead space/tidal volume ratio in respiratory failure. Chest. 1987;92(5):832-835. (Prospective, observational; 17 patients)
8. Yosefy C, Hay E, Nasri Y, et al. End tidal carbon dioxide as a predictor of the arterial PaCO2 in the emergency department setting. Emerg Med J. 2004;21(5):557-559. (Prospective, observational; 73 patients)
9. Russell GB, Graybeal JM. The arterial to end-tidal carbon dioxide difference in neurosurgical patients during craniotomy. Anesth Analg. 1995;81(4):806-810. (Prospective, observational; 35 patients)
10. Curley FJ. In: Irwin RRJ, ed. Routine Monitoring of Critically Ill Patients, in Intensive Care Medicine. Philadelphia: Lippincott Williams and Wilkins; 2003:226-246. (Review, text)
11. Kerr ME, Zempsky J, Sereika S, et al. Relationship between arterial carbon dioxide and end-tidal carbon dioxide in mechanically ventilated adults with severe head trauma. Crit Care Med. 1996;24(5):785-790. (Prospective, observational; 35 patients)
12. AARC clinical practice guideline. Capnography/capnometry during mechanical ventilation--2003 revision & update. Respir Care. 2003;48(5):534-539. (Review, practice guidelines)
13. Prause G, Hetz H, Lauda P, et al. A comparison of the endtidal- CO2 documented by capnometry and the arterial PaCO2 in emergency patients. Resuscitation. 1997;35(2):145-148. (Prospective, observational; 27 subjects)
14. Russell GB, Graybeal JM. Reliability of the arterial to endtidal carbon dioxide gradient in mechanically ventilated patients with multisystem trauma. J Trauma. 1994;36(3):317-322. (Prospective, observational; 9 patients, 171 measurements)
15. Kodali BS. Physiology of capnography: components of a time capnogram. 2007;3/07. [cited 4/21/07]; 7th:Available from: www.capnography.com. (Review)
16. Adrogué HJ, Rashad MN, Gorin AB, et al. Assessing acid-base status in circulatory failure. N Engl J Med. 1989;320(20):1312-1316. (Prospective; 105 patients)
17. Kelly AM, Kyle E, McAlpine R. Venous pCO(2) and pH can be used to screen for significant hypercarbia in emergency patients with acute respiratory disease. J Emerg Med. 2002;22(1):15-19. (Prospective; 112 patients)
18. Davis DP, Dunford JV, Poste JC, et al. The impact of hypoxia and hyperventilation on outcome after paramedic rapid sequence intubation of severely head-injured patients. J Trauma. 2004;57(1):1-8; discussion 8-10. (Retrospective; 426 patients)
19. Stewart RD, Paris PM, Pelton GH, et al. Effect of varied training techniques on field endotracheal intubation success rates. Ann Emerg Med. 1984;13(11):1032-1036. (Prospective, observational; 779 patients)
20. Pelucio M, Halligan L, Dhindsa H. Out-of-hospital experience with the syringe esophageal detector device. Acad Emerg Med. 1997;4(6):563-568. (Prospective, observational; 168 patients)
21. Katz SH, Falk JL. Misplaced endotracheal tubes by paramedics in an urban emergency medical services system. Ann Emerg Med. 2001;37(1):32-37. (Prospective, observational; 108 patients)
22. Silvestri S, Ralls GA, Krauss B, et al. The effectiveness of out-of-hospital use of continuous end-tidal carbon dioxide monitoring on the rate of unrecognized misplaced intubation within a regional emergency medical services system. Ann Emerg Med. 2005;45(5):497-503. (Prospective, observational; 153 patients)
23. Grmec S, Mally S. Prehospital determination of tracheal tube placement in severe head injury. Emerg Med J. 2004;21(4):518- 520. (Prospective, observational; 81 patients)
24. Grmec S. Comparison of three different methods to confirm tracheal tube placement in emergency intubation. Intensive Care Med. 2002;28(6):701-704. (Prospective, observational; 345 patients)
25. American College of Emergency Physicians policy statement: verification of endotracheal tube placement. 2001;10/2001. [cited 2/6/07]; Available from: http://www. acep.org/webportal/PracticeResources/PolicyStatements/pracmgt/VerificationofEndotrachealTubePlacement.htm. (Review, practice guidelines)
26. American Society of Anesthesiologists: Standards for basic anesthetic monitoring. 2005;10/2005. [cited 2/6/2007]; Available from: http://www.asahq.org/publicationsAnd- Services/standards/02.pdf. (Review, practice guidelines)
27. Krauss B, Hess DR. Capnography for procedural sedation and analgesia in the emergency department. Ann Emerg Med. 2007;50(2):172-181. (Review)
28. Burton JH, Harrah JD, Germann CA, et al. Does end-tidal carbon dioxide monitoring detect respiratory events prior to current sedation monitoring practices? Acad Emerg Med. 2006;13(5):500-504. (Prospective, observational; 59 patients)
29. Deitch K, Miner J, Chudnofsky CR, et al. Does end tidal CO2 monitoring during emergency department procedural sedation and analgesia with propofol decrease the incidence of hypoxic events? A randomized, controlled trial. Ann Emerg Med. 2010;55(3):258-264. (Randomized controlled trial; 132 patients)
30. Witting MD, Lueck CH. The ability of pulse oximetry to screen for hypoxemia and hypercapnia in patients breathing room air. J Emerg Med. 2001;20(4):341-348. (Retrospective; 513 arterial blood gas results)
31. Muizelaar JP, Marmarou A, Ward JD, et al. Adverse effects of prolonged hyperventilation in patients with severe head injury: a randomized clinical trial. J Neurosurg. 1991;75(5):731- 739. (Prospective, randomized; 103 patients)
32. Lee SW, Hong YS, Han C, et al. Concordance of end-tidal carbon dioxide and arterial carbon dioxide in severe traumatic brain injury. J Trauma. 2009;67(3):526-530. (Prospective; 77 patients)
33. Ornato JP, Garnett AR, Glauser FL. Relationship between cardiac output and the end-tidal carbon dioxide tension. Ann Emerg Med. 1990;19(10):1104-1106. (Animal model)
34. Levine RL, Wayne MA, Miller CC. End-tidal carbon dioxide and outcome of out-of-hospital cardiac arrest. N Engl J Med. 1997;337(5):301-306. (Prospective, observational; 150 patients)
35. Wayne MA, Levine RL, Miller CC. Use of end-tidal carbon dioxide to predict outcome in prehospital cardiac arrest. Ann Emerg Med. 1995;25(6):762-767. (Prospective, observational; 90 patients)
36. Grmec S, Kupnik D. Does the Mainz Emergency Evaluation Scoring (MEES) in combination with capnometry (MEESc) help in the prognosis of outcome from cardiopulmonary resuscitation in a prehospital setting? Resuscitation. 2003;58(1):89-96. (Prospective; 246 patients)
37. Grmec S, Klemen P. Does the end-tidal carbon dioxide (EtCO2) concentration have prognostic value during out-ofhospital cardiac arrest? Eur J Emerg Med. 2001;8(4):263-269. (Prospective; 139 patients)
38. Kolar M, Krizmaric M, Klemen P, et al. Partial pressure of end-tidal carbon dioxide successful predicts cardiopulmonary resuscitation in the field: a prospective observational study. Crit Care. 2008;12(5):R115. (Prospective, observational; 737 cases of out-of-hospital cardiac arrest)
39. Sanders AB, Kern KB, Otto CW, et al. End-tidal carbon dioxide monitoring during cardiopulmonary resuscitation. A prognostic indicator for survival. JAMA. 1989;262(10):1347- 1351. (Prospective, observational; 34 patients)
40. Callaham M, Barton C. Prediction of outcome of cardiopulmonary resuscitation from end-tidal carbon dioxide concentration. Crit Care Med. 1990;18(4):358-362. (Prospective, observational; 55 patients)
41. Neumar RW, Otto CW, Link MS, et al. Part 8: adult advanced cardiovascular life support: 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2010;122(18 Suppl 3):S729-S767. (Guideline)
42. Nakatani K, Yukioka H, Fujimori M, et al. Utility of colorimetric end-tidal carbon dioxide detector for monitoring during prehospital cardiopulmonary resuscitation. Am J Emerg Med. 1999;17(2):203-206. (Prospective; 121 patients)
43. Bhende MS, Thompson AE. Evaluation of an end-tidal CO2 detector during pediatric cardiopulmonary resuscitation. Pediatrics. 1995;95(3):395-399. (Prospective, observational; 40 patients)
44. Pokorná M, Necas E, Kratochvíl J, et al. A sudden increase in partial pressure end-tidal carbon dioxide (P(ET)CO(2)) at the moment of return of spontaneous circulation. J Emerg Med. 2010;38(5):614-621. (Prospective; 108 patients)
45. Sehra R, Underwood K, Checchia P. End tidal CO2 is a quantitative measure of cardiac arrest. Pacing Clin Electrophysiol. 2003;26(1 Pt 2):515-517. (Prospective; 31 cardiac arrest/VF episodes)
46. Entholzner E, Felber A, Mielke L, et al. Assessment of endtidal CO2 measurement in reanimation. Anasthesiol Intensivmed Notfallmed Schmerzther. 1992;27:473–476.
47. Garnett AR, Ornato JP, Gonzalez ER, et al. End-tidal carbon dioxide monitoring during cardiopulmonary resuscitation. JAMA. 1987;257(4):512-515. (Prospective; 23 patients)
48. Bhende MS, Karasic DG, Karasic RB. End-tidal carbon dioxide changes during cardiopulmonary resuscitation after experimental asphyxial cardiac arrest. Am J Emerg Med. 1996;14(4):349-350. (Prospective; 11 animals)
49. Falk JL, Rackow EC, Weil MH. End-tidal carbon dioxide concentration during cardiopulmonary resuscitation. N Engl J Med. 1988;318(10): 607-611. (Prospective; 10 patients)
50. Tremper KK, Barker SJ. Pulse oximetry. Anesthesiology. 1989;70(1):98-108. (Review)
51. Reich DL, Timcenko A, Bodian CA, et al. Predictors of pulse oximetry data failure. Anesthesiology. 1996;84(4):859-864. (Retrospective; 9203 patients)
52. Palve H, Vuori A. Accuracy of three pulse oximeters at low cardiac index and peripheral temperature. Crit Care Med. 1991;19(4):560-562. (Prospective, observational; 33 patients)
53. Jay GD, Hughes L, Renzi FP. Pulse oximetry is accurate in acute anemia from hemorrhage. Ann Emerg Med. 1994;24(1):32-35. (Prospective, observational; 17 patients)
54. Perkins GD, McAuley DF, Giles S, et al. Do changes in pulse oximeter oxygen saturation predict equivalent changes in arterial oxygen saturation? Crit Care. 2003;7(4):R67. (Prospective, observational; 41 patients, 1085 measurements)
55. MacLeod DB, Cortinez LI, Keifer JC, et al. The desaturation response time of finger pulse oximeters during mild hypothermia. Anaesthesia. 2005;60(1):65-71. (Prospective; 10 patients)
56. Shelley KH, Tamai D, Jablonka D, et al. The effect of venous pulsation on the forehead pulse oximeter wave form as a possible source of error in SpO2 calculation. Anesth Analg. 2005;100(3):743-747. (Prospective, observational; 25 patients)
57. Barker SJ, Tremper KK, Hyatt J. Effects of methemoglobinemia on pulse oximetry and mixed venous oximetry. Anesthesiology. 1989;70(1):112-117. (Animal model)
58. Barker SJ, Tremper KK. The effect of carbon monoxide inhalation on pulse oximetry and transcutaneous PO2. Anesthesiology. 1987;66(5):677-679. (Animal model)
59. Barker SJ, Curry J, Redford D, et al. Measurement of carboxyhemoglobin and methemoglobin by pulse oximetry: a human volunteer study. Anesthesiology. 2006;105(5):892-897. (Prospective, observational; 10 patients)
60. Fluck RR Jr, Schroeder C, Frani G, et al. Does ambient light affect the accuracy of pulse oximetry? Respir Care. 2003;48(7):677-680. (Prospective, observational; 54 patients)
61. Coté CJ, Goldstein EA, Fuchsman WH, et al. The effect of nail polish on pulse oximetry. Anesth Analg. 1988;67(7):683- 686. (Prospective, randomized, single-blind; 14 patients)
62. Hinkelbein J, Genzwuerker HV, Sogl R, et al. Effect of nail polish on oxygen saturation determined by pulse oximetry in critically ill patients. Resuscitation. 2007;72(1):82-91. (Prospective, observational; 50 patients)
63. Adler JN, Hughes LA, Vivilecchia R, et al. Effect of skin pigmentation on pulse oximetry accuracy in the emergency department. Acad Emerg Med. 1998;5(10):965-970. (Prospective, observational; 284 patients)
64. Barker SJ. “Motion-resistant” pulse oximetry: a comparison of new and old models. Anesth Analg. 2002;95(4):967-972. (Prospective, observational; 70 patients)
65. Tobias JD. Cerebral oximetry monitoring with near infrared spectroscopy detects alterations in oxygenation before pulse oximetry. J Intensive Care Med. 2008;23(6):384-388. (Prospective; 10 patients)
66. Foo JY, Wilson SJ, Dakin C, et al. Variability in time delay between two models of pulse oximeters for deriving the photoplethysmographic signals. Physiol Meas. 2005;26(4):531- 544. (Prospective; 9 healthy adults)
67. Xue FS, Liao X, Tong SY, et al. Effect of epidural block on the lag time of pulse oximeter response. Anaesthesia. 1996;51(12):1102-1105. (Prospective; 36 patients)
68. Soltani HA, Hashemi SJ, Tavakkol K. Effect of digital block on SpO2, lag time and height of plethysmographic wave of pulse oximeter in presence of shock simulation. European Journal of Anaesthesiology. 2004;21:23.
69. Murphy MF. In: Walls RM, ed. Manual of Emergency Airway Management. Philadelphia, PA: Lippincott Williams & Wilkins; 2004:333-335. (Review, text)
70. Mateer JR, Olson DW, Stueven HA, et al. Continuous pulse oximetry during emergency endotracheal intubation. Ann Emerg Med. 1993;22(4):675-679. (Prospective, observational; 284 patients)
71. Pedersen T, Moller AM, Pedersen BD. Pulse oximetry for perioperative monitoring: systematic review of randomized, controlled trials. Anesth Analg. 2003;96(2):426-431. (Metaanalysis of 4 studies; 21,773 patients)
72. Guggenberger H, Lenz G, Federle R. Early detection of inadvertent oesophageal intubation: pulse oximetry vs. capnography. Acta Anaesthesiol Scand. 1989;33(2):112-115. (Retrospective, observational; 21 patients)
73. Kellerman AL, Cofer CA, Joseph S, et al. Impact of portable pulse oximetry on arterial blood gas test ordering in an urban emergency department. Ann Emerg Med. 1991;20(2):130- 134. (Prospective, observational; 20,120 patient visits)
74. Rotello LC, Warren J, Jastremski MS, et al. A nurse-directed protocol using pulse oximetry to wean mechanically ventilated patients from toxic oxygen concentrations. Chest. 1992;102(6):1833-1835. (Prospective; 13 patients)