High-flow nasal cannula oxygen reduced hypoxemia in patients undergoing gastroscopy under general anesthesia at ultra-high altitude: a randomized controlled trial.

BACKGROUND: Hypoxemia can occur in people at ultra-high altitude (above 3500 m) even at rest, and patients undergoing gastroscopy under general anesthesia have higher risk of hypoxemia. Supplementary oxygen via standard nasal cannula (SNC) is the standard of care for most patients who undergo gastroscopy under general anesthesia, which provides oxygen flow up to 15 L/min. High-flow nasal cannula (HFNC) could deliver oxygen at a rate up to 60 L/min, which is recommended by the American Society of Anesthesiologists Practice Guidelines. We speculated that the benefit with HFNC is more prominent in high-altitude areas, and aimed to compare the incidence of hypoxemia during gastroscopy under general anesthesia at ultra-high altitude with oxygen supply via either HFNC or SNC. METHODS: The trial was registered at at Chinese Clinical Trial Registry (ChiCTR2100045513; date of registration on 18/04/2021). Adult patients undergoing gastroscopy with anesthesia (estimated duration of anesthesia at ≥ 15 min) were randomized at a 1:1 ratio to receive HFNC oxygen or SNC oxygen. The primary outcome was hypoxemia (SpO2 < 90% for any duration). Secondary outcomes included severe hypoxemia (SpO2 < 75% for any duration or SpO2 < 90% but ≥ 75% for ≥ 60 s) and hypotension, as defined by reduction of mean arterial blood pressure by ≥ 25% from the baseline. RESULTS: A total of 262 patients were enrolled: 129 in the HFNC group and 133 in the SNC group. All patients received the designated intervention. Student's t-test, Mann-Whitney U test and χ2 test were employed in the study. The rate of hypoxemia was 9.3% (12/129) in the HFNC group versus 36.8% (49/133) in the SNC group [risk ratio (95% confidence interval): 0.25(0.14-0.45); P < 0.001). The HFNC group also had lower rate of severe hypoxemia [0.0% (0/129) versus 11.3% (15/133); risk ratio (95% confidence interval): 0.03(0.00-0.55); P < 0.001, respectively]. The rate of hypotension did not differ between the 2 groups [22.5% (29/129) in HFNC group versus 21.1% (28/133) in SNC group; risk ratio (95% confidence interval): 1.07(0.67-1.69) ; P = 0.779]. CONCLUSION: HFNC oxygen reduced the incidence of hypoxemia during anesthesia in adult patients undergoing gastroscopy at ultra-high altitude.

Supraglottic jet oxygenation and ventilation decreased hypoxemia during gastrointestinal endoscopy under deep sedation at high altitudes: a randomized clinical trial.

BACKGROUND: Hypobaric hypoxia is common at high altitudes. Whether this exacerbates hypoxia during procedural sedation and whether hypoxia can be alleviated by the use of supraglottic jet oxygenation and ventilation (SJOV) are unknown. This study aimed to compare the incidence of hypoxia during gastrointestinal endoscopy under deep sedation at high altitudes with oxygen supply techniques using either a nasal cannula or SJOV. METHODS: This study was conducted from April 2022 to July 2022 in a tertiary hospital located 3650 m above sea level. Adult patients scheduled for routine gastrointestinal endoscopy under sedation were enrolled and randomized 1:1 to receive SJOV or a nasal cannula during sedation. Moderate hypoxia was the primary outcome, defined as an SPO2 of 75-89% for < 60 s. The secondary outcomes were respiratory-, cardiovascular-, and SJOV-related complications. The influence of characteristics regarding acclimatization to high altitudes (Tibetan ethnic group and erythrocytosis) on the occurrence of hypoxia was analyzed. RESULTS: None of the patients were lost to follow-up. A total of 72 patients were included in the analysis (36 patients in each group). There were 20 (27.8%) patients who experienced moderate hypoxia events. Significantly fewer hypoxic events occurred in the SJOV group than in the nasal cannula group [3 (8.3%) vs. 17 (47.2%), absolute risk difference (95% CI): - 38.9 (- 57.5, - 20.2) %, risk ratio (RR, 95% CI): 0.18 (0.06, 0.55), P < 0.001]. Significantly fewer patients in the SJOV group experienced mild hypoxia (P < 0.001) and severe hypoxia (P = 0.002). No serious adverse events occurred in either of the groups. The Tibetan ethnic group (P = 0.086) and erythrocytosis (P = 0.287) were not associated with the occurrence of hypoxia events. CONCLUSIONS: The incidence of hypoxia was lower with SJOV than with nasal cannula in patients undergoing gastrointestinal endoscopy under deep sedation at high altitudes. The Tibetan ethnic group and erythrocytosis did not influence the occurrence of hypoxia. TRIAL REGISTRATION: This study was registered at ClinicalTrials.gov (NCT05304923) before enrollment by Dr. Yi Feng on 31/03/2022.

Associations between long-term exposure to ambient air pollution and renal function in Southwest China: The China Multi-Ethnic Cohort (CMEC) study.

BACKGROUND: Limited studies have examined associations between air pollutants exposure and renal function, especially in China, with the most extensive chronic kidney disease (CKD) disease burden worldwide. OBJECTIVES: This study examines associations between long-term exposure to ambient PM2.5, NO2, CO, O3, SO2 and renal function. METHODS: We included 80,225 participants aged 30-79 years from the baseline data of the China Multi-Ethnic Cohort (CMEC) study. Three-year average concentrations of PM2.5, NO2, CO, O3, and SO2 were estimated using satellite-based spatiotemporal models. Renal function is determined by the estimated glomerular filtration rate (eGFR) using Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. After adjusting for covariates, generalized propensity scores (GPS) weighting regression was used to estimate associations between ambient air pollutants and renal function. RESULTS: An increase of 0.1 mg/m3 CO (OR [odds ratio] =1.20 95% CI [confidence interval], 1.05-1.37) was positively associated with CKD. An increase of 1 µg/m3 in SO2 (1.07, 1.00-1.14) concentration was positively associated with CKD. An increase of 10 µg/m3 in PM2.5 (1.17, 0.99-1.38), NO2 (1.12, 0.83-1.51) and O3 (1.10, 0.81-1.50) concentration was not associated with CKD. These effects are stronger in those younger than 65, smoking and with low BMI. CONCLUSIONS: In this study, we found that long-term exposure to ambient CO and SO2 were positively associated with CKD. Gaseous pollutants should also arouse the concern of relevant departments.