• Users Online: 363
  • Print this page
  • Email this page

 Table of Contents  
Year : 2023  |  Volume : 6  |  Issue : 1  |  Page : 34-35

Regularly irregular 'missed mandatory breath' leading to abnormal capnographic waveform

Department of Anaesthesiology and Critical Care, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India

Date of Submission10-Nov-2022
Date of Acceptance24-Dec-2022
Date of Web Publication20-Apr-2023

Correspondence Address:
Dr. Muthapillai Senthilnathan
Department of Anaesthesiology and Critical Care, Second Floor, Institute Block, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry - 605 006
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/arwy.arwy_44_22

Rights and Permissions

How to cite this article:
Elakkumanan LB, Kumar MR, Senthilnathan M. Regularly irregular 'missed mandatory breath' leading to abnormal capnographic waveform. Airway 2023;6:34-5

How to cite this URL:
Elakkumanan LB, Kumar MR, Senthilnathan M. Regularly irregular 'missed mandatory breath' leading to abnormal capnographic waveform. Airway [serial online] 2023 [cited 2023 Sep 21];6:34-5. Available from: https://www.arwy.org/text.asp?2023/6/1/34/374368

Preuse checklist of anaesthesia workstations has become mandatory in the practice of anaesthesiologists to ensure patient safety. While this would avoid many common issues, problems can still occur even after successful checklist tests.[1] Knowledge of the working principle of anaesthesia workstation and constant, eternal vigilance during the perioperative period is essential to avoid unexpected complications due to malfunction of the anaesthesia workstation. Here, we report an unusual complication related to the anaesthesia workstation.

A 60-year-old female with carcinoma of the oesophagus was scheduled for feeding jejunostomy. The patient had given written consent to submit this incident as a case report. Preoperative assessment was unremarkable. The anaesthetic plan was general anaesthesia with endotracheal tube (ETT) placement and positive pressure ventilation. The anaesthesia Workstation (Datex Aestiva 7100, GE Healthcare) was checked as per the machine check protocol, and there was no leak in the machine. Routine monitoring was established. The patient's trachea was intubated following rapid sequence intubation. After ruling out endobronchial intubation, the ETT was connected to the ventilator. The set ventilator parameters included tidal volume (VT) of 325 ml, respiratory rate of 12/min, I: E of 1:2. The baseline peak airway pressure (Paw) was 11 cmH2O.

One minute later, we observed an abnormal capnography waveform with a low expired VT alarm. The abnormal capnogram led us to look for common causes, such as surgical manipulation and spontaneous breathing efforts. Even though there was no curare cleft, it was assumed to be due to the patient's spontaneous effort; hence, atracurium was administered. However, the abnormal capnogram and alarm persisted [Figure 1]. We noted that the breath corresponding with the alarm had a tidal volume of around 40 ml with abnormal capnogram (end-tidal CO2 of 28 mmHg) with Paw 4 cmH2O and occurred every third breath during which there was no movement in bellow assembly [Video 1] [Additional file 1]. While we analysed the root cause, the patient's lungs were ventilated manually. As we could not find any possible causes, mechanical ventilation was attempted again, and the missed breath persisted. Hence, for the rest of the surgical procedure, manual ventilation was continued. At the end of the surgery, the patient's residual neuromuscular blockade was antagonised, and the trachea was extubated. The postoperative course was uneventful.
Figure 1: This image shows the abnormal capnogram (1–3) followed by the two normal capnogram

Click here to view

We assumed moisture condensation over the flow sensor to be the cause. Hence, all components were cleaned and assembled again. The machine was rechecked, and there was no leak. However, the missed breath persisted when we checked the ventilator using a test lung with a similar ventilator settings. After the discussion with service engineers from the manufacturers, they suggested that this might due to problems with flow sensor calibration, pressure sensitivity calibration, defective check valves, kinking in the pneumatic line between the flow sensor or any defect in the monitor interface assembly board.[2] In our case, the flow sensor calibration was done, after which the problem did not recur. Although there was less VT delivered during inspiration without movement of the bellow assembly during missed breath, the passive recoil of the chest during exhalation would have resulted in an abnormal capnogram in this patient. Flow sensor calibration should be performed during regular intervals to prevent this malfunction. The same anaesthesia workstation was used for mechanical ventilation without any missed breath in the subsequent days. We want to report this incident to make all anaesthesiologists aware of this problem. Despite having so many safety features, any machine can fail at any point, so a vigilant anaesthesiologist is necessary to prevent untoward complications.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Miller RD, Cohen NH, editors. Miller's Anesthesia. 8th ed. Philadelphia: Elsevier, Saunders; 2015.  Back to cited text no. 1
Datex-Ohmeda. Aestiva Anesthesia Machine: Technical Manual. Wisconsin; 2006.  Back to cited text no. 2


  [Figure 1]


Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

  In this article
Article Figures

 Article Access Statistics
    PDF Downloaded16    
    Comments [Add]    

Recommend this journal