Although clinical studies of the high-flow nasal cannula (HFNC) and its effect on positive end-expiratory pressure (PEEP) have been done, the washout effect has not been well evaluated. Therefore, we made an experimental respiratory model to evaluate the respiratory physiological effect of HFNC. An airway model was made by a 3D printer using the craniocervical 3D-CT data of a healthy 32-year-old male. CO2 was infused into four respiratory lung models (normal-lung, open- and closed-mouth models; restrictive- and obstructive-lung, open-mouth models) to maintain the partial pressure of end-tidal CO2 (PETCO2) at 40 mmHg. HFNC flow was changed from 10 to 60 L/min. Capnograms were recorded at the upper pharynx, oral cavity, subglottic, and inlet sites of each lung model. With the normal-lung, open-mouth model, 10 L/min of HFNC flow decreased the subglottic PETCO2 to 30 mmHg. Increasing the HFNC flow did not further decrease the subglottic PETCO2. With the normal-lung, closed-mouth model, HFNC flow of 40 L/min was required to decrease the PETCO2 at all sites. Subglottic PETCO2 reached 30 mmHg with an HFNC flow of 60 L/min. In the obstructive-lung, open-mouth model, PETCO2 at all sites had the same trend as in the normal-lung, open-mouth model. In the restrictive-lung, open-mouth model, 20 L/min of HFNC flow decreased the subglottic PETCO2 to 25 mmHg, and it did not decrease further. As HFNC flow was increased, PEEP up to 7 cmH2O was gradually generated in the open-mouth models and up to 17 cmH2O in the normal-lung, closed-mouth model. The washout effect of the HFNC was effective with relatively low flow in the open-mouth models. The closed-mouth model needed more flow to generate a washout effect. Therefore, HFNC flow should be considered based on the need for the washout effect or PEEP.

Dexmedetomidine (Dex) provides sedation and analgesia by acting on central alpha-2 receptors and is suitable for use after extubation because it has little respiratory depression. Considering the sympathoinhibitory and anxiolytic action of Dex, there is the possibility that Dex might reduce the incidence of atrial fibrillation (AF), which is recognized as a common complication after cardiovascular surgery. We investigated whether the postoperative incidence of AF decreased in patients who received Dex only during the nighttime in the intensive care unit (ICU). We retrospectively reviewed ICU charts to determine the incidence of AF and associated factors during the 2-day period after tracheal extubation in patients who underwent cardiovascular surgery from November 2009 to November 2010. The patients were divided into a Dex group (n = 16) and a non-Dex group (n = 29). There were no differences in AF risk factors except for diabetes between the two groups. The average rate of Dex administration was 0.3 ± 0.2 μg/kg/h. There were also no differences between the groups in heart rate during the daytime, central venous pressure, body temperature, white blood cell count, serum level of C-reactive protein, catecholamine use, beta-blocker use, and amount of fentanyl. AF developed in one patient in the Dex group (6.3 %) and ten patients in the non-Dex group (34.5 %) during the observation period, and the difference was significant (p = 0.035). None of the risk factors for AF was significantly associated with AF in univariate analysis; however, multivariate logistic regression analysis using age, Dex use, and beta-blocker use, extracted because their p values in univariate analysis were not exceeding 0.15, showed that Dex use was the only factor associated with the development of AF (p = 0.045, odds ratio 9.75 [1.05–90.8]). The results suggest that adequate sedation with Dex during the nighttime can reduce the incidence of AF in cardiovascular surgery patients after extubation.

Onodera Y, et al. Korean J Anesthesiol. 2017 Feb;70(1):105-106. https://doi.org/10.4097/kjae.2017.70.1.105

Aims: While Japan's bathing culture contributes to better health, it has also become a social problem due to the high number of medical care emergencies arising from bathing‐related adverse events. In particular, bathing in hot springs may pose unique risks. This study aimed to examine the relationship between bathing‐related adverse events, including drowning, and the location of bathing, specifically hot springs and other bathing sites. Methods: This single‐center, retrospective cohort study included 125 participants who had bathing‐related adverse events from March 1, 2012 to February 29, 2024. Participants were classified into two groups according to the bathing location: hot spring (Group H; n = 24) and other bathing (Group B; n = 101) groups. Logistic regression analysis was conducted using drowning as the objective variable and bathing in hot springs and age as explanatory variables. Results: Only the incidence of drowning showed a significant difference between the two groups (Group H: 9/24 [37%] vs. Group B: 18/95 [18%]). Logistic regression analysis showed that bathing in hot springs was an independent factor associated with drowning, with no significant difference by age. Conclusion: The results of this study suggest that drowning is more frequent among individuals who bathe in hot springs. Larger scale studies are needed to explore the causes of drowning during hot spring bathing and the relationship between hot spring bathing and bathing‐related adverse events.