Capnography in the Emergency Department
Emergency Medicine: Open Access

Emergency Medicine: Open Access
Open Access

ISSN: 2165-7548

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Editorial - (2012) Volume 2, Issue 9

Capnography in the Emergency Department

Hassan Soleimanpour1*, Changiz Gholipouri1, Samad EJ Golzari2,3, Farzad Rahmani1 and Majid Sabahi4,5
1Emergency Medicine Department, Tabriz University of Medical Sciences, Daneshgah Street, Tabriz 51664, I.R, Iran
2Cardiovascular Research Center, Tabriz University of Medical Sciences, Daneshgah Street, Tabriz 51664, I.R, Iran
3Students Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran
4Heart and Stroke Foundation of Canada (HSFO), Toronto, Canada
5Sunny brook hospital, University of Toronto, Toronto, Canada
*Corresponding Author: Hassan Soleimanpour, Associate Professor of Anesthesiology and Critical Care, Fellowship in Trauma Critical Care and CPR, Department of Emergency Medicine, Tabriz University of Medical Sciences, Tabriz, Iran Email:


COPD: Chronic Obstructive Pulmonary Disease; ETCO2: End Tidal CO2; ETT: Endo Tracheal Tube; PaCO2: Arterial Pressure of CO2; AHA: American Heart Association; ROSC: Return of Spontaneous Circulation; CPR: Cardiopulmonary Resuscitation

Laudation to the God of majesty and glory! Obedience to him is a cause of approach and gratitude in increase of benefits. Every inhalation of the breath prolongs life and every expiration of it gladdens our nature; wherefore every breath confers two benefits and for every breath gratitude is due.”1

Saadi Shirazi, the prominent Persian-Iranian poet living in the 12th- 13th century whose aphorism “Bani Adam” or the Children of Adam ornaments the entrance of the United Nations, in the introduction section of the Golestan, has elaborately described the importance of the two sections of respiration.

Capnography is one of the non-invasive methods used for the measurement of End-tidal CO2 values (ETCO2). Values for ETCO2 alter based on the CO2 concentrations in each respiratory cycle [1]. Ancient Greeks believed that human body is equipped with a kind of “combustion engine” producing smoke, i.e. breathing; hence, the termcapnography is derived from the Greek word “Capnos” meaning smoke [1,2].

The mechanism of respiration includes two stages of oxygenation and ventilation with are considered as the natural physiological functions of the body that should be taken into consideration in the evaluation of the intubated patients and non-intubated patients with normal respiration. Oxygenation can normally be monitored using pulse oxymetry whereas capnography can provide more accurate information on each respiration cycle regarding ventilation, perfusion, cardiac output, pulmonary blood flow and metabolic status [1].

Carbon dioxide is produced a human body following glucose metabolism which is later delivered to pulmonary blood circulation transferred to the exhaled air through the alveoli. In expiration phase, primarily the air in the upper airways is exhaled; the process is followed by the expiration of the air content of the lower airways. Capnogram demonstrates CO2 content of the expired air throughout the whole expiration phase. Most technologies used in the capnography are based on infrared wave; as CO2 absorbs infrared waves in the specific wavelength of 4.26 nm. Therefore, the amount of the absorbed waves is in close relation with the CO2 content of the expired air [1-3].

In patients with normal pulmonary function, apart from their age, the difference between ETCO2 and arterial carbon dioxide pressure (PaCO2) is a constant figure (2-5 mmHg) [2,3]. This difference originates from the dead alveolar spaces in a normal lung which is ineffective in the ventilation process. Capnography device demonstrates ETCO2 Values and its related curves [2]. A normal capnogram has been illustrated in figure 1 in which the blue line is indicative of PaCO2. The distance between the blue line and section III (C-D distance) is the normal befriends between ETCO2 and PaCO2.


Figure 1: Normal capnography.

In this figure, A is the start point of inspiration; D is the end point of expiration from which the new inspiration cycle starts. The height of the curve is related to ETCO2 whereas its width is related to expiration time [1,3]. The changes in the shape of the curve could be suggestive of the underlying diseases and the alterations in the ETCO2 values could be utilized for the assessment of the severity of the diseases and response to treatment [1]. An Emerg Med (Los Angel) physician should be aware of abnormal curves caused by technical problems of the device and also the contributing physiological and pathological conditions in order to monitor the patients more accurately and to increase his or her diagnostic abilities.

Indications for capnography in the emergency department:

1. Confirmation of the proper placement of the endotracheal tubes: in patients without cardiac arrest, capnography is of a 100% sensitivity and specificity for the confirmation of the proper placement of the endotracheal tubes [4-6].

2. Diagnosis of acidosis: in patients with acidosis, metabolic acidosis is compensated by hyperventilation leading to decrease in PaCO2 and consequently in ETCO2. In similar cases, e.g. ketoacidosis and renal failure, capnography could be used for the diagnosis of acidosis without using ABG. In many studies carried out on children with specious diabetic ketoacidosis, ETCO2 values less than 29 mmHg has been associated with sensitivity 83% and specificity of 100% [7,8].

3. Throughout CPR: according to the guidelines of the CPR published by AHA 2010, capnography is a compulsory monitoring throughout the resuscitation of the patients [9].

4. ETCO2 more than 10 mmHg has been recommended for a successful resuscitation and any dramatic increase in capnography throughout CPR could be considered as an early indicative of ROSC. As capnography is in close relation with cardiac output and a minimum of 30% of the normal cardiac output is required to maintain the activity of vital organs including the heart and brain, ETCO2 should be about 30% or 10-15 mmHg in each chest compression [9]. This is of great importance in emergency situations and natural disasters (earth quake, flood and etc.) in which physicians are overwhelmed by the magnitude of the event and the number of the ones in need of medical care [10].

5. Procedural sedation: In procedural sedation, capnography is a required monitoring device (especially in the procedures requiring moderate to deep sedation) as it is able to reveal the ventilation problems prior to any alterations in the clinical status of the patients [3,11].

Considering the different associated patterns of the capnography curves, the findings of their related pathologies are as follows (Figure 2) [12,13]:


Figure 2: Different capnography patterns.

1. Rebreathing: In this pattern, the descending part of the curve (phase IV) does not reach the zero line. The common causes would include low pressure oxygen stream into the mask or problem in the valve section of the non-breather mask.

2. Bronchoconstriction: In this condition, the slope of the ascending section of the curve (phase II) decreases resembling shark fin. This pattern is mostly seen in asthma or COPD patients.

3. Prolonged phase IV: In intubated patients, whenever the cuff is deflated or a smaller size tube has been selected (especially in children), air leakage would occur causing this pattern.

4. Curare cleft: In intubated patients under mechanical ventilation, when the effect of the muscle relaxants wears off, this pattern emerges due to the return of the diaphragm constrictions indicating the requirement for further muscle relaxation.

5. Severe kyphoscoliosis: A bi-phasic pattern could be observed in the plateau section (phase III) of the curve.

6. Ripple effect: This effect, Cardiogenic Oscillations, is a normal variant mostly seen while inspiration due to the expansion of the lungs and their contact with the heart throughout the phase IV of the curve.

7. Stair step alveolar plateau: In this pattern, the ending half of the alveolar or III phase resembles stairs or steps, especially in intubated patients under mechanical ventilation whenever the oxygen pressure decreases in the ventilator.

8. Hypoventilation: The range of the curve increase due to the increased arterial CO2 content.

9. Hyperventilation: The range of the curve decrease due to the decreased arterial CO2 content caused by increased minute ventilation.

10. Apnea or dislodged ETT: No curve could be detected in the monitor.

11. Pneumothorax: In patients with tension pneumothorax, due to decrease in cardiac output caused by the pressure effect of the pneumothorax on the heart, ETCO2 values decrease leading to a decreased range of the curve. In patients with small non-tension pneumothorax, if under mechanical ventilation and in volume modes, intra-pulmonary pressure increases and cardiac output decreases as in each inspiration a constant volume enters the lungs; consequently, the ETCO2 values decrease. However, on the other hand in the pressure modes, smaller volumes enter the lungs due to the existing pneumothorax leading to a hypoventilation state associated with increased ETCO2 values.

1From The Golestan of Saadi, by Sheikh Mosleh al-Din Saadi Shirazi, Translated by Richard Francis Burton, 1821-1890 CE.


  1. Baruch K, Philip EM (2010) Clinical Procedure in Emerg Med (Los Angel) . In: Robert, Hedges (eds). Devices for Assessing Oxygenation and Ventilation.
  2. Louis M, Guzzi (2011) Mechanical ventilation Types techniques pitfalls. Florida Hospital Orlando, Florida
  3. John SR (2011) Procedural Sedation and Analgesia. Emerg Med (Los Angel) Board Review Manual.
  4. Soleimanpour H, Sarahrudi K, Hadju S, Golzari SEJ (2012) How to Overcome Difficult-Bag-Mask-Ventilation: Recents Approaches. Emerg Med (Los Angel) 2: e116.
  5. Soleimanpour H, Gholipouri C, Panahi JR, Afhami MR, Ghafouri RR, et al. (2011) Role of anesthesiology curriculum in improving bag-mask ventilation and intubation success rates of Emerg Med (Los Angel) residents: a prospective descriptive study. BMC Emerg Med 11: 8.
  6. Soleimanpour H, Rahimi Panahi J, Mahmoodpoor A, Rajaei Ghafouri R (2011) Digital intubation training in residency program, as an alternative method in airway management. Pak J Med Sci .
  7. Mutlu K, , Oktay E, Stephan R, Erkan G, Firat B et al. (2011) ETCO2: a predictive tool for excluding metabolic disturbances in nonintubated patients. American Journal of Emergency Medicine 29: 65-69.
  8. Fearon DM, Steele DW (2002) End-tidal Carbon Dioxide Predicts the Presence and Severity of Acidosis in Children with Diabetes. Acad Emerg Med 9: 1373-1378 .
  9. Neumar RW, Otto CW, Link MS, Kronick SL, Shuster M, et al. (2010) 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science. Circulation 122: 729-767.
  10. Golzari SE, Ghabili K (2012) Twin earthquakes in northwest Iran. Lancet 380: 1384.
  11. Krauss B, Hess DR (2007) Capnography for Procedural Sedation and Analgesia in the Emergency Department. Ann Emerg Med 50: 172-181 .
Citation: Soleimanpour H, Gholipouri C, Golzari SEJ, Rahmani F, Sabahi M (2012) Capnography in the Emergency Department. Emergency Med 2:e123.

Copyright: © 2012 Soleimanpour H. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.