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Background: Capnometry detects hypoventilation earlier than pulse oximetry while supplemental oxygen is being administered. We compared the end-tidal CO 2 (P ETCO 2 ) measured using a newly developed oxygen nasal cannula with a CO 2 -sampling port and the P aCO 2 in extubated subjects after abdominal surgery. We also investigated whether the difference between P aCO 2 and P ETCO 2 is affected by resting, by spontaneous breathing with the mouth consciously closed, and by deep breathing with the mouth closed., Methods: Adult post-abdominal surgery subjects admitted to the ICU were enrolled. After extubation, oxygen was supplied at 4 L/min using a capnometry-type oxygen cannula. The breathing frequency, P ETCO 2 , and P aCO 2 were measured after 30 min of oxygen supplementation. P ETCO 2 was continuously measured during rest, during breathing with the mouth consciously closed, and during deep breathing with the mouth closed. The difference between P ETCO 2 and P aCO 2 during various breathing patterns was analyzed using the Bland-Altman method., Results: Twenty subjects were included. The bias ± SD (limits of agreement) for breathing frequency measured by capnometry compared with those obtained by direct measurement was 0.4 ± 3.6 (-6.7 to 7.4). In P ETCO 2 compared with P aCO 2 , the biases (limits of agreement) were 14.8 ± 8.2 (-1.3 to 30.9) at rest, 10.2 ± 6.4 (-2.3 to 22.7) with the mouth closed, and 7.7 ± 5.6 (-3.2 to 18.6) for deep breathing with the mouth closed. P ETCO 2 determined using the capnometry device yielded unreliable and widely ranging values under various breathing patterns. However, deep breathing with the mouth closed decreased the difference between P ETCO 2 and P aCO 2 , as compared with other breathing patterns., Conclusions: P ETCO 2 measurements under deep breathing with mouth closed with a capnometry-type oxygen cannula improved the prediction of the absolute value of P aCO 2 in extubated post-abdominal surgical subjects without respiratory dysfunction., (Copyright © 2017 by Daedalus Enterprises.)

Background: During sedation for upper gastrointestinal endoscopy, oxygen delivery via a nasal cannula is often necessary. However, the influences of the oxygen delivery route and breathing pattern on the F(IO2) have not been thoroughly investigated. The aim of this simulation study was to investigate the difference in the F(IO2) with a pharyngeal cannula versus nasal cannula during high- or low-tidal volume (V(T)) ventilation and open- or closed-mouth breathing., Methods: Six healthy volunteers were asked to breathe using 2 patterns of ventilation (high or low V(T)) via a sealed face mask connected to an endotracheal tube that was retrogradely inserted into the trachea of a mannequin. The mannequin also had a pharyngeal or nasal cannula inserted into the pharynx or attached to the nose, through which oxygen (2 or 5 L/min) was delivered. The mouth of the mannequin was kept open or closed by packing. We measured the F(IO2) of every breath for 1 min at each setting., Results: During low- and high-V(T) ventilation, the F(IO2) was highest at a flow of 5 L/min with a pharyngeal cannula. Oxygen delivery was higher with the pharyngeal cannula compared with the nasal cannula at all settings. Differences in flow did not result in significant differences in the F(IO2) with high- and low-V(T) ventilation. At a flow of 5 L/min via a pharyngeal cannula, open-mouth breathing resulted in a significantly higher F(IO2) compared with closed-mouth breathing., Conclusions: A pharyngeal cannula provided a higher F(IO2) compared with a nasal cannula at the same oxygen flow. Open-mouth breathing resulted in a higher F(IO2) compared with closed-mouth breathing when 5 L/min oxygen was delivered via a pharyngeal cannula. The breathing pattern did not affect the F(IO2) in this study., (Copyright © 2015 by Daedalus Enterprises.)