Where P ♾CO 2 is the mixed expired PCO 2. VD phy/VT = (PaCO 2 - P ♾CO 2)/PaCO 2 (2) Expired VT is composed of alveolar VT and total physiologic dead space (VD phy). ♵A is the product of respiratory frequency and expired tidal volume (VT). ![]() Note that pulmonary shunt will add mixed venous blood with high PCO 2 (PVCO 2) to arterial blood and slightly increase PaCO 2. If one assumes no diffusion defect for carbon dioxide, then the partial carbon dioxide tension (PCO 2) of arterial blood (PaCO 2) leaving the lung is the perfusion-weighted average alveolar PCO 2 (PACO 2). Where ♵CO 2,ti is the tissue carbon dioxide production, ♵A is alveolar ventilation, and FICO 2 is the inspired FCO 2. In this model the lung is a simple mixing chamber and the alveolar fractional carbon dioxide (FACO 2) is given by 1a), transported in blood to the lung by venous return (essentially equal to cardiac output ), and eliminated from the lung by minute ventilation (VE). xliii, 2128 pages p.Carbon dioxide is produced in the tissues by aerobic plus/minus anaerobic metabolism (Fig. Tintinalli’s emergency medicine : a comprehensive study guide. Tintinalli JE, Stapczynski JS, Ma OJ, Cline D, Meckler GD, Yealy DM. Comparison of end-tidal carbon dioxide and arterial blood bicarbonate levels in patients with metabolic acidosis referred to emergency medicine. Taghizadieh A, Pouraghaei M, Moharamzadeh P, Ala A, Rahmani F, Basiri Sofiani K. Philadelphia, PA: Elsevier/Saunders 2014. Rosen’s emergency medicine : concepts and clinical practice. Capnography in the Emergency Department: A Review of Uses, Waveforms, and Limitations. End-tidal carbon dioxide and outcome of out-of-hospital cardiac arrest. Capnography during cardiopulmonary resuscitation: Current evidence and future directions. Comparison of three different methods to confirm tracheal tube placement in emergency intubation. Does end tidal CO2 monitoring during emergency department procedural sedation and analgesia with propofol decrease the incidence of hypoxic events? A randomized, controlled trial. An early indicator of reperfusion from ROSC is sudden rise in EtCO 2 and thereby may help to decrease deleterious pauses in chest compressions for pulse checksĭeitch K, Miner J, Chudnofsky CR, Dominici P, Latta D.Prognostic factor of ROSC if Can provide a quantitative measure of chest compression effectiveness.The gold standard for confirmation of tracheal placement ( Grmec 2002).Pattern also seen in leaks in breathing system (endotracheal tube leaks).Upsloping of alveolar plateau due to alveolar leak of CO 2.Metabolic acidosis → decreased HCO 3 → compensatory hyperventilation → increased minute ventilation and decreased ETCO 2.May also detect other adverse effects, such as bronchospasm, laryngospasm, or upper airway obstruction.Median time to difference in detection = 60 seconds. ![]() Earlier recognition of respiratory depression when compared to pulse-oximetry ( Deitch 2010).Unlike pulse-oximetry, not prone to motion artifact. ![]() Sedated patients (Opioid Abuse, EtOH intoxication, procedural sedation, etc.).Purple ( 50 mmHg or increase greater than 10 mmHg from baselineĬlinical Applications in the Emergency Department.Colorimetric – qualitative measure (color change) of expired CO 2 covering a wide range of values, therefore use is limited primarily to verify correct ETT placement.Can be placed in parallel and can be used in non-intubated patients (e.g.Side Stream detector – takes sample of expired gas.In series with endotracheal intubation tube.Mainstream – must be attached to the ventilator circuit.Definition: Noninvasive measurement of the concentration (partial pressure) of expired carbon dioxide over time.
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