Capnography: Not just for confirmation

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Deborah Atkinson
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1 Capnography: Not just for confirmation Pennsylvania DOH ALS Protocol 2032-ALS Ernest Yeh, M.D. Division of EMS Department of Emergency Medicine Temple University Hospital and School of Medicine Medical Director, Trihampton Rescue Squad Associate Regional Medical Director, Bucks County EMS What is it? Why use it? How to use it? Capnography Just because it is protocol??? Know why 1

2 Never missed a tube???? Intubation Confirmation DIRECT VISUALIZATION End Tidal CO 2 Pulse Oximetry Breath sounds Lack of epigastric sounds Misting in the endotracheal tube Pulse Oximetry Normal pulse oximetry readings carbon MONOXIDE poisoning potentially high despite true hypoxia similar wavelength absorption Accurate but misleading cyanide poisoning oxygen NOT USABLE Pulse Oximetry Direct monitoring of hemoglobin saturation Little information about peripheral tissue metabolism of oxygen Pulse Oximetry False low methemoglobinemia abnormal wavelength absorption 2

3 Breath sounds confirmation Limitations Noisy environment Indeterminate exam Mistaken sounds from esophageal intubation Capnography Indirect measure of oxygen METABOLISM Information about CO 2 production pulmonary perfusion cardiac output venous return alveolar ventilation minute volume elimination of CO 2 Capnography vs Capnometry Waveform interpretation End tidal value Why use it? Variety of Studies Sanders et al Annals of EM 18(12) Higher mean ET CO 2 in ROSC (pulse and BP) 9 of 35 with ROSC (15 4 mmhg) 26 of 35 without ROSC (7 5 mmhg) Callaham and Barton, Critical Care Med 18(4) ET CO 2 within 5 min of ED arrival ROSC (19 14 mmhg) vs NO ROSC (5 mmhg) 3

Lack of Use Variable PaCO 2 16-86 mmhg Significant hypo and hyperventilation Helm M, et al: Tight control of prehospital ventilation by capnography in major trauma victims.

4 Lack of Use Variable PaCO mmhg Significant hypo and hyperventilation Helm M, et al: Tight control of prehospital ventilation by capnography in major trauma victims. Br J Anaesth 2003; 90: Colorimetric Chemical reaction Reacts to CO 2 in exhaled gas Qualitative Change in color Yellow (YES) Purple (PULL) (may vary with different manufacturers) What is it? End tidal CO 2 monitoring Qualitative Quantitative Quantitative Direct/proportional measure of amount of CO 2 4

II Patient must be > 15 kg Rebreathing CO 2 from device Pediatric version available Mainstream sampler Infrared beam Photodetector

5 Qualitative Mainstream Limitations CO 2 in esophagus Low values (< 4 and 4-15 mmhg) No waveform data Difficult to interpret in low flow states Easy Cap II Patient must be > 15 kg Rebreathing CO 2 from device Pediatric version available Mainstream sampler Infrared beam Photodetector Absorption of beam Amount of CO 2 Intubated patient Quantitative Mainstream Limitations Sensor/Equipment vulnerable to damage Disposable components available Warm up time Condensation in viewing window Bulk to ventilator circuit 5

6 Quantitative Datascope Passport Monitors Sidestream sampler May be adapted to a nasal cannula Datascope Passport Monitors Datascope Passport Monitors 6

7 Zoll CCT Sidestream Handheld Combination Devices Sidestream Limitations Sampling rates ~ cc/min Distort waveforms Especially with lower tidal volumes 7

8 Problems with Monitoring Increase in dead space volume ETT adaptor/connector More important in pediatrics Especially newborns Equipment specific limitations Where else does CO 2 come from? Part of the buffer system HCO H H 2 CO 3 CO 2 +HO 2 which is used to maintain a normal ph Where does CO 2 come from? Final product in aerobic metabolism Where does CO 2 come from? Transported throughout the body in the blood C 6 H 12 O 6 +O 2 CO 2 +HO 2 Metabolism of glucose as well as fatty acids and proteins As dissolved CO 2 As HCO 3-8

9 Amount of CO 2 Pulmonary capillaries: 40 mmhg Alveoli: ~38 mmhg Difference allows for diffusion from capillaries to alveoli NOT ACTIVE TRANSPORT Alveolar Ventilation Dead space Unused for ventilation Tidal volume Fills only to terminal bronchioles Last portion of airway Diffusion Individual gas molecules moving at high velocity How does this help us? CO 2 is produced in the tissues transported through the venous system back to the right side of the heart into the pulmonary arteries to the pulmonary capillaries to the alveoli Alveolar Ventilation Dead space First portion of gas exhaled (last portion of gas inhaled) Contains no CO 2 Not involved in actual ventilation 9

10 Alveolar Ventilation First part of mixed gas Rapid riseof CO 2 level Last part of mixed gas Plateau of CO 2 level So what does all this mean? Good waveform implies Adequate circulation to deliver O 2 to tissues Aerobic metabolism Using O 2 and producing CO 2 Adequate circulation to return CO 2 to lungs Adequate ventilation to expire CO 2 Cardiopulmonary Resuscitation Goals Restore Circulation Restore Ventilation Restore Oxygenation Why not just use pulse oximetry? Preoxygenation may give up to 4 minutes of reserve Requires peripheral pulses Frequently vasoconstricted Vasopressors Clamped extremities 10

11 Why not just use pulse oximetry? Normal Waveform Detects inadvertent esophageal intubation faster than pulse oximetry especially in the preoxygenated patient before deteriorating physiological parameters Guggenberger H., Lenz G., Federle R., Early detection of inadvertent oesophageal intubation: pulse oximetry vs. capnography. Acta Anaesthesiol Scand (1989) 33 : pp Vaghadia H., Jenkins L.C., Ford R.W., Comparison of end-tidal carbon-dioxide, oxygen saturation and clinical signs for the detection of oesophageal intubation. Can J Anaesth (1989) 36 : pp Poirier M.P., Gonzalez del Ray J.A., McAneney C.M., et al. Utility of monitoring capnography, pulse oximetry and vital signs in detecting airway mishaps: a hyperoxemic animal model. Am J Emerg Med (1998) 16 : pp Not just for confirmation Waveforms Interpreting the waveform Following the trends Changes in the patient Changes in tube placement FIGURE 1 Example of normal capnogram (A), alveolar hypoventilation (B), and apnea (C) Lightdale, J. R. et al. Pediatrics 2006;117:e1170-e

edu/sah/nura833/new833/.../end%20tidal%20co2.

12 Esophageal Intubation False positive with qualitative Must interpret the waveform Partial obstruction Kinked tube Bronchospasm No Plateau classes.kumc.edu/sah/nura833/new833/.../end%20tidal%20co2.ppt Drop to Zero Asthma Extubated Before After beta agonist Totally obstructed tube Sampler disconnect Ventilator failure 12

13 Hyperventilation Blowing down CO 2 Failing perfusion Decreased venous return Gradual Decrease Sudden Drop (not to zero) ETT leak Sampler leak Mild obstruction Mucous plug Condensation Hypoventilation Sudden increase in perfusion Bicarbonate infusion Gradual Increase End Tidal CO 2 Goal measurement (majority of patients) 35 mmhg COPD with chronic hypercapnia Baseline elevated May target higher than 40 No reliable estimate without knowing actual levels 13

14 Guide Resuscitation Efforts Improving ET CO2 Adequate perfusion/ventilation/oxygenation Lower values = lower rate or survival Sanders AB, Karen KB, Otto CW, Milander MM, Ewy GA. End-tidal carbon dioxide monitoring during cardiopulmonary resuscitation. A prognostic indicator for survival JAMA 1989;262: Endotracheal Tube Placement Monitor/document Quality assurance Medical legal Any patient movement Transfer from stretcher Movement of stretcher Transfer of care Guide Resuscitation Efforts Early termination of efforts < 10 mmhg after 20 minutes of ALS NO SURVIVORS Levine RL, Wayne MA, Miller CC. End-tidal carbon dioxide and outcome of out-ofhospital cardiac arrest. N Engl J Med 1997;337(5): Not just because you have to.. Because you know why and how it helps your patients 14

15 Questions??? 15

June 2011 Bill Streett-Training Section Chief

Capnography 102 June 2011 Bill Streett-Training Section Chief Terminology Capnography: the measurement and numerical display of end-tidal CO2 concentration, at the patient s airway, during a respiratory