Transcutaneous carbon dioxide monitoring during rigid bronchoscopy-again!
Myron Yaster MD, Francis Veyckemans MD, Melissa Brooks Peterson, and Britta S von Ungern-Sternberg MD, PhD
I have no idea how or why this happens, but very frequently, a topic gets “hot” and is “discovered” and published in several journals almost simultaneously. Over the last few months, several journals and investigators have rediscovered transcutaneous carbon dioxide monitoring during anesthesia for rigid bronchoscopy, micro laryngoscopy, and during intubation for difficult airways. We recently reviewed an article by Bordini et al1 on this topic (PAAD (04/25/2025 https://ronlitman.substack.com/p/transcutaneous-carbon-dioxide-monitoring ) which generated an enormous amount of interest from the PAAD’s readers. So, when I saw this article by van Wijk et al.2 I thought many of you might want another bite of the apple even though the results are similar to Bodini’s. Myron Yaster MD
Original article
van Wijk JJ, Gangaram-Panday NH, van Weteringen W, Pullens B, Bernard SE, Hoeks SE, Reiss IKM, Stolker RJ, Staals LM. The clinical application of transcutaneous carbon dioxide monitoring during rigid bronchoscopy or microlaryngeal surgery in children. J Clin Anesth. 2025 Jan;100:111692. doi: 10.1016/j.jclinane.2024.111692. Epub 2024 Nov 23. PMID: 39581128
During rigid and flexible bronchoscopies, direct and indirect laryngoscopies, and microlaryngeal surgery (MLS), end tidal CO2 monitoring is often impossible because these procedures preclude the use of a secured airway, which would block the view of the procedure area. “As a consequence, end-tidal measurements of oxygen, volatile anesthetic agents and, most importantly, carbon dioxide (CO2) are not reliable or possible. Ventilation strategies are therefore commonly based on the experience, knowledge and skills of the anesthesiologist.”2 “For airway management and gas exchange of the so-called ‘open airway’ several ventilation strategies can be applied, such as spontaneous ventilation and manual ventilation through a rigid bronchoscope, supraglottic or even infraglottic high-frequency jet ventilation (HFJV) or high flow nasal oxygen (HFNO) can be applied during MLS. Unfortunately, all these methods are used without ‘closed-loop’ ventilation, and provide no information on CO2 elimination.”2 In today’s PAAD, van Wijk et al found, just like Bordini et al., that transcutaneous carbon dioxide (TcCO2) monitoring could be used in these patients, and that not surprisingly, most patients were hypercapnic during these procedures.
As a quick review, transcutaneous carbon-dioxide (tcPCO2) monitors use heated skin sensors that increase skin blood flow through the cutaneous capillary system. The locally produced PCO2 is then measured electrochemically and adjusted to provide an output reflective of the arterial blood PCO2.3 TcPCO2 measured carbon dioxide is routinely used in NICUs and PICUs with good agreement with PaCO2.4 It has also been used in the ORs5,6 but hasn’t really caught on as a standard or commonly used monitor in all institutions.
In their prospective observational study, van Wijk et al. “hypothesized that monitoring of tcPCO2 levels can impact ventilation strategies, resulting in a lower CO2 load during the procedure. This study aimed to evaluate the effects of the clinical implementation of tcPCO2 monitoring on the cumulative tcPCO2 load during rigid bronchoscopies or MLS.”2 “TcPCO2 monitoring was performed in two groups; blinded before clinical implementation (control group) and visible for ventilation management after clinical implementation (tcPCO2 group).”2 Of note, no clinical targets for TcPCO2 were given in the study group. Mild to moderate hypercapnia was present in all patients. When the anesthesiologist knew that hypercapnia was present by rising TcPCO2, a change in ventilation was only performed in 60% of the cases. However, these changes in ventilation strategies were applied without much success, begging the question “why bother” to use this monitor?
Again, as discussed in the article and in several recent PAADs, hypercarbia isn’t something that should be feared and often can be used therapeutically to increase HR, BP, cardiac output, cerebral blood flow, and oxygen delivery through the shifting of the oxygen dissociation curve to the right. Further, by increasing cerebral blood flow anesthetic agents are more rapidly delivered to the brain, speeding the induction of anesthesia. On the other hand, hypoxemia is always to be avoided regardless of the ventilation strategy employed. Although hypercarbia should physiologically stimulate ventilation, I (FV) sometimes observed patients (generally tiny ones) who remained apneic after receiving almost no opiates and with no measurable end-tidal sevoflurane on board, but an EtCO2 higher than 60 mmHg. It was necessary to apply gentle hand ventilation during a few minutes to decrease their EtCO2 down to 50 mmHg before they started breathing and woke up quickly. A sort of carbonarcosis? On the other hand, I (MY) often took advantage of hypercarbia, particularly at the end of a case to stimulate and accelerate spontaneous ventilation and wake up.
Are any of you using transcutaneous CO2 monitoring in your practice? If you are send Myron a “consumer report” of your experience and we will post in a Friday reader response.
References
1. Bordini M, Olsen JM, Siu JM, et al. Transcutaneous carbon dioxide monitoring in children undergoing rigid bronchoscopy: a prospective blinded observational study. Canadian journal of anaesthesia = Journal canadien d'anesthesie 2025;72(2):273-284. (In eng). DOI: 10.1007/s12630-024-02862-7.
2. van Wijk JJ, Gangaram-Panday NH, van Weteringen W, et al. The clinical application of transcutaneous carbon dioxide monitoring during rigid bronchoscopy or microlaryngeal surgery in children. Journal of clinical anesthesia 2025;100:111692. (In eng). DOI: 10.1016/j.jclinane.2024.111692.
3. Mukhopadhyay S, Maurer R, Puopolo KM. Neonatal Transcutaneous Carbon Dioxide Monitoring--Effect on Clinical Management and Outcomes. Respiratory care 2016;61(1):90-7. (In eng). DOI: 10.4187/respcare.04212.
4. Setar L, Lee JG, Sanchez-Pinto LN, Coates BM. Accuracy and Interpretation of Transcutaneous Carbon Dioxide Monitoring in Critically Ill Children. Pediatric critical care medicine : a journal of the Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies 2024;25(9):e372-e379. (In eng). DOI: 10.1097/pcc.0000000000003564.
5. Humphreys S, von Ungern-Sternberg BS, Taverner F, et al. High-flow nasal oxygen for children's airway surgery to reduce hypoxaemic events: a randomised controlled trial. Lancet Respir Med 2024;12(7):535-543. (In eng). DOI: 10.1016/s2213-2600(24)00115-2.
6. Humphreys S, Schibler A, von Ungern-Sternberg BS. Carbon dioxide monitoring in children-A narrative review of physiology, value, and pitfalls in clinical practice. Paediatric anaesthesia 2021;31(8):839-845. (In eng). DOI: 10.1111/pan.14208.