Early detection of inadvertent oesophageal intubation: pulse oximetry vs. capnography

The aim of our retrospective study was to evaluate the efficacy of routine pulse oximetry and capnometry for detection of oesophageal tube misplacement. Patients undergoing ENT interventions at our hospital are routinely monitored by ECG, arterial blood pressure by cuff, capnography, and pulse oximetry. Beat-to-beat values of Sao2 and CO2 waveform were recorded by a graphic printer connected to a microcomputer, ASA I patients were routinely preventilated with FIO2 = 0.3, and ASA II-III patients with FIO2 = 1.0. Anaesthesia was performed by junior anaesthesiologists under the close supervision of a resident. During a 16-month period, 1372 patients were anaesthetized. The records of 21 patients with accidental oesophageal tube misplacement were available for retrospective evaluation. Nine patients were preventilated with FIO2 = 0.3 (ASA I), 12 patients with FIO2 = 1.0 (ASA II-III). Rapid detection of oesophageal tube position as early as the first ventilation is possible by capnometry, because of the highly significant difference in end-tidal CO2 (0.2 +/- 0.2 vol%; tracheal intubation: 3.7 +/- 0.9 vol.%; P less than 0.0001). The present advanced pulse oximetry method does not permit differentiation between oesophageal and tracheal tube position within 30 s in patients preventilated with FIO2 = 1.0. Oesophageal misplacement was detectable within 7.5 +/- 0.9 s in patients preventilated with FIO2 = 0.3 due to a 2.1 +/- 0.8% decrease in Sao2 (P less than 0.001). Our results underscore the significance of capnometry for rapid detection of inadvertent oesophageal intubation. High-resolution pulse oximetry is a valuable supplement but not a substitute for capnometry.     

Capnography does not reliably detect double-lumen endotracheal tube malplacement

Two patients are described in whom double-lumen endotracheal tube malplacement and its ventilatory consequences were not detected by infrared capnography. Problems were suspected on auscultation, and the malplacement was diagnosed by means of bronchospirometry. We conclude that bronchospirometry helps detect problems with endotracheal intubation.     

Continuous end-tidal CO2 sampling within the proximal endotracheal tube estimates arterial CO2 tension in infants

End-tidal CO2 (ETCO2) sampled using a 22-gauge needle inserted through the wall of the proximal endotracheal tube was compared with ETCO2 obtained from the standard proximal connector to determine which was the more accurate sampling site for estimation of arterial CO2 tension (PaCO2). Fourteen infants were anaesthetized and their lungs ventilated using a Drager ventilator and a paediatric circle system. Blood gas determination of PaCO2 was obtained from an arterial catheter and compared with continuous sampling of ETCO2 analyzed by raman spectroscopy. The PaCO2 (35.3 +/- 4.9 mmHg, x +/- SD) was not different from the ETCO2 sampled within the proximal endotracheal tube (34.7 +/- 3.8 mmHg), but was greater (P less than 0.05) than the ETCO2 at the proximal connector (31.6 +/- 4.0 mmHg). We conclude that in infants during ventilation with a circle system, the PaCO2 can be accurately assessed by continuous sampling of ETCO2 from the proximal endotracheal tube.     

Preliminary observations on the colibri CO2-indicator

The performance of a new colorimetric CO₂-indicator (Colibri) was assessed in mini-pigs. It performed well during 8-hour procedures. Neither nitrous oxide, nor halothane, nor carbon monoxide, nor intratracheal application of drugs (epinephrine, atropine, lidocaine, and naloxone) interfered with its function. It gave a distinct color change at high ventilation frequencies up to 120/min. The only problem observed was difficulty in matching the colors displayed with the comparison color chart provided. The Colibri's performance seems at least equal to that of the EasyCAP detector, although both devices share some disadvantages (no alarms, semiquantitative, difficult reading in the dark). After initial control of endotracheal tube position by an esophageal detector device, both the Colibri and the EasyCAP seem suited for monitoring of ventilation and circulation if quantitative capnometry is unavailable.     

组织CO2监测进展

组织CO2监测被认为是监测组织灌注的理想指标。舌下张力测定仪是近几年出现的监测组织灌注的新技术，和胃张力测定仪相比，它具有快速简单，临床超前，经济，无血液操作等优点，现综述如下。     

End-tidal Carbon Dioxide Monitoring in Emergency Medicine, Part 2: Clinical Applications

Abstract. End-tidal carbon dioxide (PetCO₂) monitoring is becoming more common in both the ED and the out-of-hospital setting. Its main use has been as an aid when confirming endotracheal intubation. Other uses in the ED include monitoring CPR efforts and monitoring the ventilatory and hemodynamic status of intubated and nonintubated patients. In addition, future uses may include using PetCO₂ as an adjunct when monitoring the status of asthma treatment, when making the diagnosis of pulmonary embolism, and when measuring cardiac output nonin-vasively. This article reviews these specific uses of PetCO₂ monitoring in emergency medicine.     

Tissue capnometry: does the answer lie under the tongue?

Increases in tissue partial pressure of carbon dioxide (PCO₂) can reflect an abnormal oxygen supply to the cells, so that monitoring tissue PCO₂ may help identify circulatory abnormalities and guide their correction. Gastric tonometry aims at monitoring regional PCO₂ in the stomach, an easily accessible organ that becomes ischemic quite early when the circulatory status is jeopardized. Despite substantial initial enthusiasm, this technique has never been widely implemented due to various technical problems and artifacts during measurement. Experimental studies have suggested that sublingual PCO₂ (P_slCO₂) is a reliable marker of tissue perfusion. Clinical studies have demonstrated that high P_slCO₂ values and, especially, high gradients between P_slCO₂ and arterial PCO₂ (P_sl-aCO₂) are associated with impaired microcirculatory blood flow and a worse prognosis in critically ill patients. Although some questions remain to be answered about sublingual capnometry and its utility, this technique could offer new hope for tissue PCO₂ monitoring in clinical practice.     

舌下CO2分压检测在休克救治中的应用

目的应用一种临床新技术——舌下CO2分压检测,通过对局部灌流的检测最终达到对休克以及全身血液灌注状态的了解。方法采用回顾性分析失血性休克患者的休克指数、动脉血乳酸（IAC）和舌下CO2分压。结果通过对正常组（A组）、轻中度休克组（B组）和重度休克组（C组）患者的检测发现,A、B、C三组之间的舌下CO2分压值差异有统计学意义。结论舌下CO2分压具有检测方便,对休克患者能量化组织灌流不足的严重性,从而指导现场急救或临床中对休克的救治工作。     

Noninvasive monitoring of peripheral perfusion

Background Early hemodynamic assessment of global parameters in critically ill patients fails to provide adequate information on tissue perfusion. It requires invasive monitoring and may represent a late intervention initiated mainly in the intensive care unit. Noninvasive monitoring of peripheral perfusion can be a complementary approach that allows very early application throughout the hospital. In addition, as peripheral tissues are sensitive to alterations in perfusion, monitoring of the periphery could be an early marker of tissue hypoperfusion. This review discusses noninvasive methods for monitoring perfusion in peripheral tissues based on clinical signs, body temperature gradient, optical monitoring, transcutaneous oximetry, and sublingual capnometry.Discussion Clinical signs of poor peripheral perfusion consist of a cold, pale, clammy, and mottled skin, associated with an increase in capillary refill time. The temperature gradients peripheral-to-ambient, central-to-peripheral and forearm-to-fingertip skin are validated methods to estimate dynamic variations in skin blood flow. Commonly used optical methods for peripheral monitoring are perfusion index, near-infrared spectroscopy, laser Doppler flowmetry and orthogonal polarization spectroscopy. Continuous noninvasive transcutaneous measurement of oxygen and carbon dioxide tensions can be used to estimate cutaneous blood flow. Sublingual capnometry is a noninvasive alternative for gastric tonometry.This study was in part supported by materials provided by Hutchinson Technology and a grant from Philips USA. Both authors received a grant US $12,000 from Philips USA and $10,000 from Hutchinson Technology.