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  Table of Contents 
Year : 2022  |  Volume : 23  |  Issue : 2  |  Page : 150-152

An unusual appearance of capnograph - dilemma for an anesthesiologist!

Department of Anaesthesia, Atal Bihari Vajpayee Institute of Medical Sciences and Dr. Ram Manohar Lohia Hospital, New Delhi, India

Date of Submission19-Jun-2022
Date of Decision30-Jul-2022
Date of Acceptance31-Jul-2022
Date of Web Publication29-Oct-2022

Correspondence Address:
Dr. Ruchi Ohri
Department of Anaesthesia, Atal Bihari Vajpayee Institute of Medical Sciences and Dr. Ram Manohar Lohia Hospital, Baba Kharak Singh Marg, New Delhi - 110 001
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/TheIAForum.TheIAForum_66_22

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How to cite this article:
Ohri R, Noufiya S S. An unusual appearance of capnograph - dilemma for an anesthesiologist!. Indian Anaesth Forum 2022;23:150-2

How to cite this URL:
Ohri R, Noufiya S S. An unusual appearance of capnograph - dilemma for an anesthesiologist!. Indian Anaesth Forum [serial online] 2022 [cited 2023 Mar 28];23:150-2. Available from: http://www.theiaforum.org/text.asp?2022/23/2/150/359854


Capnography is an important monitoring tool to assess the respiratory status of a patient. One of the major applications of capnography is the confirmation of the correct positioning of the endotracheal tube.[1],[2] Any abnormal wave pattern in capnography should grab immediate attention of an anesthetist, and it should be promptly dealt with.

A 46-year-old male patient was posted for left intercondylar fracture fixation in our hospital. Preoperative history-taking revealed no other comorbidities. All preoperative investigations were within normal limits. Operation theater was prepared, and the anesthesia workstation self-test showed normal working condition with minimal circuit leak. He was induced using intravenous propofol 2 mg/kg and inhalational agent sevoflurane 2%–4%, and intravenous vecuronium 0.1 mg/kg was used as a relaxant. Airway was secured using a cuffed endotracheal tube 8 mm ID and fixed at 21 cm mark at the right angle of the mouth. Anesthesia was maintained on O2:N2O (50:50), sevoflurane, and intravenous vecuronium. Postinduction, when the patient was put on the right lateral surgical position from supine, the abnormal pattern in capnography was seen as multiple humps in the expiratory plateau phase [Figure 1]a and [Figure 1]b. EtCO2 peak values were maintained between 33 and 37 mmHg. Some moisture in the water trap and EtCO2 line was noticed. Hence, the entire gas sample line and water trap were changed. Still, the humps were persisting. Then, we checked for circuit leakage or any moisture in corrugated tubing. Leakage was ruled out as tidal volume was getting adequately delivered, airway pressure was normal, and endotracheal tube cuff pressure was also in normal range. Circuit tubing did not have any moisture condensation. Then, the dilemma was regarding cardiac oscillations. However, we could not identify any synchrony between heart rate in electrocardiography (ECG) and the humps in EtCO2. Despite the issue regarding capnogram, the intraoperative period went uneventful. After the procedure, the patient was taken back to the supine position for extubation. Then, the wave pattern in the plateau phase decreased considerably, and when the patient was put on spontaneous ventilation, capnogram showed normal waveform [Figure 2]a and [Figure 2]b. The patient was extubated smoothly and shifted to the postoperative recovery room.
Figure 1: (a) Capnogram showing time on X-axis and EtCO2 concentration on Y-axis with abnormal phase III, showing multiple hump appearance. (b) Capnogram showing multiple hump appearance in the plateau limb of expiratory phase. Note – The patient was in the lateral position

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Figure 2: (a) Capnogram showing time on X.axis and EtCO2 concentration on Y.axis with normal phase III. (b) Example of a normal

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Very few reports are available explaining the reasons for what is called as Dromedary hump sign.[3] Loose connections between EtCO2 sample line and gas analyzer, moisture in the corrugated tubes/gas sample line/water trap, leak in the breathing system, damaged water trap, lateral positioning during surgery, associated lung disease, sudden hypotension, and mismatch ventilation were found to be some of the reasons for abnormal plateau phase in capnogram.[3],[4],[5] Lateral positioning during mechanical ventilation results in dependent lung being compressed more by the mediastinal and abdominal contents. Thus, the dependent lung will be poorly ventilated but highly perfused compared to nondependent lung. This causes a significant ventilation perfusion mismatch during lateral decubitus positioning and can result in EtCO2 value to raise when the patient is shifted from supine position to lateral. In our patient, though the capnography tracings were not exactly similar to dromedary sign, the exaggeration of the wavy pattern in the plateau phase of capnography during lateral positioning may be due to the alterations in ventilation-perfusion mismatch. One problem we faced during the surgery was difficulty in appreciating curare cleft in EtCO2 tracings at the earliest because of this unusual appearance of capnograph. This bears a potential risk of unnecessary relaxant administration during the intraoperative period. EtCO2 monitoring has to be done with the utmost care during the intraoperative period. Humps in the plateau phase of capnogram should grab our attention to look for all the above-mentioned reasons. However, this can be an uneventful finding as well.

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  References Top

Turle S, Sherren PB, Nicholson S, Callaghan T, Shepherd SJ. Availability and use of capnography for in-hospital cardiac arrests in the United Kingdom. Resuscitation 2015;94:80-4.  Back to cited text no. 1
Grmec S. Comparison of three different methods to confirm tracheal tube placement in emergency intubation. Intensive Care Med 2002;28:701-4.  Back to cited text no. 2
Jaffe R, Talavera J, Hah J, Brock-Utne J. The dromedary sign-An unusual capnograph tracing. Anesthesiology 2008;109:149-50.  Back to cited text no. 3
Healzer JM, Spiegelman WG, Jaffe RA. Internal gas analyzer leak resulting in an abnormal capnogram and incorrect calibration. Anesth Analg 1995;81:202-3.  Back to cited text no. 4
Body SC, Taylor K, Philip JH. Dual-plateau capnogram caused by cracked sample filter. Anesth Analg 2000;90:233-4.  Back to cited text no. 5


  [Figure 1], [Figure 2]


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