Abstract
Objective: During intravenous sedation, end-tidal carbon dioxide (ETCO2) is usually measured with a nasal cannula or mouth-nose cannula. We compared the measurement accuracy of ETCO2 between these two devices and TC-CO2 and assessed which device is more useful during intravenous sedation in volunteers. Methods: Eight male volunteers aged 25 to 35 years were evaluated in this single-institution blinded observational trial. After they lay quietly for 5 min without supplemental oxygen, the volunteers received supplemental oxygen by means of each device at a flow rate of 3 L/min for 15 min. Next, midazolam (0.05 mg/kg) was intravenously injected, flumazenil (20 mg) was injected 30 min later, and the ETCO2 and TC-CO2 waveform were recorded. Results: The differences between ETCO2 and TC-CO2 significantly increased after midazolam injection and decreased after flumazenil injection. The difference between ETCO2 and TC-CO2 using the nasal cannula was greater than that using the mouth-nose cannula. The mean difference between TC-CO2 and ETCO2 ranged from 3 to 9 mmHg after midazolam injection using a nasal mask, and the mean difference ranged from 3 to 6 mmHg after midazolam injection using a mouth-nose cannula. Conclusions: The difference between ETCO2 and TC-CO2 against TC-CO2 was within the clinically acceptable range. Both the nasal and mouth-nose cannula were useful for ETCO2 measurement with supplemental oxygen by means of each device at flow rate of 3 L/min during intravenous sedation in volunteers.
Highlights
Current clinical guidelines recommend capnography as one of the best noninvasive methods with which to assess the adequacy of ventilation in nonintubated patients
The TCCO2 increased after midazolam injection and tended to decrease after flumazenil injection, and there were significant differences between the values 5 to 16 min after injection and the value before injection (P
The ETCO2 using the nasal cannula tended to decrease after injection, and that uses the mouth-nose cannula intended to increase immediately after injection
Summary
Current clinical guidelines recommend capnography as one of the best noninvasive methods with which to assess the adequacy of ventilation in nonintubated patients. The need for capnographic monitoring has dramatically increased with the large number of procedures performed on sedated patients outside the operating room [1]. End-tidal carbon dioxide (ETCO2) waveforms on a capnograph can provide vital information about CO2 retention and respiratory depression [2]. The absence of ETCO2 waveforms indicates a possible state of apnea [3]. ETCO2 measurement is important for identification of intraoperative ventilatory problems in patients undergoing general anesthesia with tracheal intubation [4]. ETCO2 monitoring in nonintubated patients under sedation is frequently necessary in both the intraoperative and postoperative periods. Sedation for medical and dental procedures is a common practice, but it is associated with the risk of excessive respiratory depression [3]
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