Prehospital management of a non-intubated inhalation injury patient using transcutaneous monitoring of carbon dioxide

Abstract

A 46-year-old man experienced facial burns due to a fire in his house. In the prehospital setting, suspecting inhalation injury and carbon monoxide poisoning, an emergency physician decided to bring him to the hospital for carbon dioxide (CO₂) monitoring without endotracheal intubation for approximately 20 min because of less severe respiratory distress. On the way to the hospital, the patient’s end-tidal CO₂ monitoring ranged from 19 to 30 mm Hg, and transcutaneous carbon dioxide (TcPCO₂) remained between 50 and 55 mm Hg. On arrival at the hospital, PaCO₂ showed 51.6 mm Hg. Endotracheal intubation using a bronchoscope was performed in the emergency room, and inhalation injury was observed. He was extubated on day 5 and discharged on day 10. In the prehospital setting, TcPCO₂ monitoring is useful for initial management of non-intubated inhalation injury patients even with high concentration oxygen.

Background

Transcutaneous carbon dioxide (TcPCO₂) monitoring has been reported to be beneficial since the 1980s. However, the research fields were restricted to perinatal, paediatric, anaesthetic, intensive care, and so on.^1–4 Although a few articles reported interhospital transport,^{5 6} to the best of our knowledge, no studies have investigated TcPCO₂ monitoring in the prehospital emergency setting.

Theoretically, TcPCO₂ could be independent of inhaled high concentration oxygen and could be more reliable than end-tidal carbon dioxide (EtCO₂) according to a previous report.⁷ In case of inhalation injury, discontinuing or reducing high concentration oxygen is difficult, because not only respiratory insufficiency but also carbon monoxide (CO) poisoning is treated by high oxygen flow and concentration. Therefore, the initial management of inhalation injury seemed to be a good target for the TcPCO₂ monitoring.

We report herein the first non-intubated inhalation injury case demonstrating the high accuracy of TcPCO₂ to simultaneously monitor transcutaneous and transnasal CO₂ under high concentration oxygen in the prehospital setting.

Case presentation

A 46-year-old man, who was a never-smoker experienced facial burns due to a fire in his house, which he escaped from by himself after 5 min. Emergency medical technicians (EMT) arrived at the scene, and then a doctor-stuffed ambulance was dispatched because of the possibility of inhalation injury. In the prehospital setting, the emergency physician (EP) observed nose and ear redness, burned vibrissae and head hair, soot in the nasal and oral cavities, hoarseness, slight stridor and severe abnormal crackles in the lungs. On examination, his vital signs were as follows: Glasgow Coma Scale, 15 (E4V5M6); blood pressure, 96/71 mm Hg; heart rate, 87 beats/min; respiratory rate, 40 breaths/min; and oxygen saturation, 96% with 15 L/min oxygen. His respiratory distress slightly improved compared with that at first presentation to the EMT. As per the EP’s discretion, inhalation injury in the peripheral airways played a major role in the patient’s pathology compared with upper airway swelling. Therefore, as per the EP’s expertise, the patient did not need to be intubated immediately. With regards to CO poisoning and administering high concentration oxygen, the EP decided to bring him to the hospital for further CO₂ monitoring without endotracheal intubation for approximately 20 min, with standby surgical airway management. Transnasal CO₂ was measured using BSM-4103 (NIHON KODEN; Tokyo), and TcPCO₂ was monitored using TCM5 (RADIOMETER; Tokyo) (figure 1). On the way to the hospital, the patient’s end-tidal CO₂ (EtCO₂) monitoring ranged from 19 to 30 mm Hg, and TcPCO₂ remained between 50 and 55 mm Hg (figure 1). Finally, EtCO₂ and TcPCO₂ on arrival were 22 mm Hg and 51 mm Hg, respectively. On arrival, initial arterial blood gas analysis showed PaCO₂ of 51.6 mm Hg; therefore, the TcPCO₂ value was more approximate. His carboxyhaemoglobin (Hb-CO) value was 6.0%. Endotracheal intubation using a bronchoscope was performed in the emergency room and inhalation injury was observed. Swelling was observed at the arytenoid region, and a large amount of soot was found in his trachea and bilateral and distal parts of the main bronchus (figure 2). He was admitted to the intensive care unit after clearance of the soot.

Figure 1.

Prehospital carbon monoxide monitoring. (A) Transcutaneous carbon dioxide (TcPCO₂) (white arrow) and end-tidal carbon dioxide (black arrow-head) monitoring sensor on the patient. (B) Monitor screen revealed TcPCO₂: 55 mm Hg (white arrow), and EtCO₂: 19 mm Hg (black arrow-head).

Figure 2.

Bronchoscopy findings on admission. (A) Swelling of the arytenoid region (black arrow head). (B, C) Soot was detected in the trachea and bilateral parts of the main bronchus.

Outcome and follow-up

After admission, laryngeal oedema was examined using a bronchoscope daily. When laryngeal oedema was resolved and endotracheal cuff leakage was identified, the patient was extubated without any neurological sequelae on day 5. He was transferred to the department of internal medicine and dermatology on day 10.

Discussion

In the initial management of burn injury, inhalation injury should be considered. Abnormal respiratory sounds and contractions of respiratory accessory muscles have been reported as intubation predictors.⁸ In this case, several findings have been found to be related to upper and lower airway abnormality; thus, inhalation injury and necessity of intubation were suspected early. However, prehospital intubation is a high-risk procedure for patients suspected with laryngeal oedema by only one EP.⁹ In addition, in case of a difficult airway, there were only few alternative approaches, such as bronchoscope-assisted intubation except for surgical interventions. Therefore, the EP decided to bring the patient to the hospital without intubation and to monitor CO₂. In the prehospital setting, capnometry is an important tool for early detection of circulatory and/or respiratory failure, including airway obstruction or breathing abnormalities by means of monitoring sudden changes of EtCO₂.^10–12 For this reason, our doctor-stuffed ambulance has been equipped with EtCO₂ monitor for intubated and non-intubated patients. However, in non-intubated patients, EtCO₂ monitoring might be inaccurate when a measuring site is exposed to high concentration oxygen¹³ to prevent hypoxia and/or hypercapnia or to hasten the dissociation of CO from CO-Hb. Considering these reasons, TcPCO₂ has been recently available on trial in our hospital. In fact, the gap between EtCO₂ and TcPCO₂ values is high immediately after arrival because of two reasons: the measuring methodology of EtCO₂, that is, CO₂ diluted by high oxygen flow and the dead space increased due to hyperventilation. Lastly, the high TcPCO₂ value was consistent with inhalation injury, as confirmed by bronchoscopy, indicating that TcPCO₂ could be a useful predictor for prehospital diagnosis of inhalation injury.

In general, the earlobe is the region for TcPCO₂ measurement⁴; however, an intact precordial region could be an alternative location in case of facial epidermal burn including the bilateral earlobes, such as present case. The duration of TcPCO₂ monitoring is limited to 8 hours.⁴ Because monitoring probes may heat up moderately, its overuse sometimes causes thermal injury on the contacting skin. In Japan, it might not be a serious problem because a routine prehospital medical practice can be completed within an hour. Hinkelbein et al demonstrated that TcPCO₂ provided an accuracy equivalent to arterial blood gas analysis during inter-hospital ground transport of critically ill adult patients.⁶ During the trial, TcPCO₂ values were also stable in other trauma patients despite variation of temperature or ambulance vibration. A majority of monitored patients had TcPCO₂ that was practically approximate to PaCO₂ on arrival.

There are some problems for this device. The electrochemical method requires 10 min or so to heat a sensor probe and to calibrate and equilibrate the device for an accurate and reliable measurement.¹ Furthermore, an effect of CO or cyanide poisoning on TcPCO₂ monitoring is unknown.

Learning points.

• This is the first reported case of prehospital emergency management using transcutaneous carbon dioxide (TcPCO₂) monitoring.

• TcPCO₂ monitoring is a reliable method for patients without intubation under high concentration oxygen in estimating PaCO₂.

• From the viewpoint of not only monitoring but also diagnosis, TcPCO₂ monitoring is found to be reasonable in the initial management of non-intubated inhalation injury patients.

Ethics statements

Patient consent for publication

Obtained.