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The measurement of rock resistivity currently mainly adopts the method of reducing saturation, which requires the rock sample to reach complete saturation during measurement. In response to the accuracy issue of measuring rock electrical parameters using desaturation methods for unsaturated or incompletely saturated rock samples, the influence of saturation degree on the measurement results of rock electrical parameters and the root causes of the influence were analyzed, and a feasible correction method was established. The results indicate that the saturation degree of rock samples first affects the measurement of porosity, calculation of water saturation, and initial resistivity measurement of saturated saline rock samples, and further transmits to geological factors, cementation index, and lithology coefficient, while the saturation index is not affected by them. After correcting the porosity, water saturation, initial water saturation, and initial resistivity of the rock sample using saturation degree values, a one-to-one correspondence between water saturation and resistivity data was achieved. The base value for calculating the resistivity increase rate is more in line with reality, and the final rock electrical parameters obtained are more reasonable.

SiC MOSFETs have been a game-changer in the domain of power electronics, thanks to their exceptional electrical traits. They are endowed with a high breakdown voltage, reduced on-resistance, and superior thermal conductivity, which make them supremely suitable for high-power and resilient applications across aviation, automotive, and renewable energy sectors. Despite their intrinsic advantages, SiC MOSFETs also necessitate advanced safeguarding mechanisms to counteract the vulnerability to short-circuit conditions due to their lower short-circuit robustness. This review paper offers an in-depth analysis of the array of short-circuit protection (SCP) methods applied to SiC MOSFETs. This paper scrutinizes techniques such as desaturation detection, di/dt detection, gate charge characteristics monitoring, two-dimensional monitoring, Rogowski coil-based detection, and two-stage turn-off strategies. The paper meticulously explores the operational principles, merits, and limitations of each method, with an emphasis on their adaptability to various fault types, including hard switching faults and load-induced faults. This review acts as a thorough compendium, guiding the choice of pertinent SCP strategies, ensuring the secure and efficient functioning of SiC MOSFETs in demanding applications.

The air injection method serves as a liquefaction mitigation technique to improve the liquefaction resistance of the foundations by decreasing the degree of saturation. To investigate the desaturation effect of this technique in various soil strata of the foundation, thin plate model tests were conducted, considering the impacts of gradation and relative density, to visualize the air migration process and distribution. The findings reveal the following: (1) The air migration process, delineated by air injection parameters, comprises four distinct phases, with stages II and III notably influenced by the pore structure; (2) air migration is governed by the pore throat dimensions, particle arrangement, and connectivity within the pore structure, exhibiting two predominant patterns: channel flow, primarily driven by inertial forces, and chamber flow, predominantly influenced by viscous and capillary forces; (3) referring to the air injection port, the gas phase distribution within the sand samples is consistent in the horizontal direction but not in the vertical direction. The concentration area and uniformity of the gas phase distribution are controlled by the pore structure. These results suggest potential enhancements in the positioning of air injection ports within complex soil layers, as well as improvements in the construction process, both aimed at optimizing the desaturation effect.

ObjectiveLombardy (Italy) was the epicentre of the COVID-19 pandemic in March 2020. The healthcare system suffered from a shortage of ICU beds and oxygenation support devices. In our Institution, most patients received chest CT at admission, only interpreted visually. Given the proven value of quantitative CT analysis (QCT) in the setting of ARDS, we tested QCT as an outcome predictor for COVID-19.MethodsWe performed a single-centre retrospective study on COVID-19 patients hospitalised from January 25, 2020, to April 28, 2020, who received CT at admission prompted by respiratory symptoms such as dyspnea or desaturation. QCT was performed using a semi-automated method (3D Slicer). Lungs were divided by Hounsfield unit intervals. Compromised lung (%CL) volume was the sum of poorly and non-aerated volumes (− 500, 100 HU). We collected patient’s clinical data including oxygenation support throughout hospitalisation.ResultsTwo hundred twenty-two patients (163 males, median age 66, IQR 54–6) were included; 75% received oxygenation support (20% intubation rate). Compromised lung volume was the most accurate outcome predictor (logistic regression, p < 0.001). %CL values in the 6–23% range increased risk of oxygenation support; values above 23% were at risk for intubation. %CL showed a negative correlation with PaO2/FiO2 ratio (p < 0.001) and was a risk factor for in-hospital mortality (p < 0.001).ConclusionsQCT provides new metrics of COVID-19. The compromised lung volume is accurate in predicting the need for oxygenation support and intubation and is a significant risk factor for in-hospital death. QCT may serve as a tool for the triaging process of COVID-19.Key Points• Quantitative computer-aided analysis of chest CT (QCT) provides new metrics of COVID-19.• The compromised lung volume measured in the − 500, 100 HU interval predicts oxygenation support and intubation and is a risk factor for in-hospital death.• Compromised lung values in the 6–23% range prompt oxygenation therapy; values above 23% increase the need for intubation.

Background Oxygen desaturation during exercise is mainly observed in severe cases of chronic obstructive pulmonary disease (COPD) and is associated with a worse prognosis, but little is known about the type of desaturation that causes the greatest risk of mortality. Material and Methods We studied all of the 6-min walk tests performed periodically at a tertiary hospital over a period of 12 years in patients with moderate or severe COPD. We classified patients as non-desaturators if they did not suffer a drop in oxygen saturation (SpO2 < 88%) during the test, early desaturators if the time until desaturation was < 1 min, and non-early desaturators if it was longer than 1 min. The average length of follow-up per patient was 5.6 years. Results Of the 319 patients analyzed, 126 non-desaturators, 91 non-early desaturators and 102 early desaturators were identified. The mortality analysis showed that early desaturators had a mortality of 73%, while it was 38% for non-early desaturators and 28% for non-desaturators, with a survival of 5.9 years compared to 7.5 years and 9.6 years, respectively (hazard ratio of 3.50; 95% CI 2.3–5.3; p  < 0.0001). Conclusions The early desaturation seen in patients with chronic obstructive pulmonary disease is associated with greater mortality and is likely responsible for the poor prognosis shown globally in patients who desaturate. The survival of patients with early desaturation is almost 4 years less with respect to non-desaturators, and they, thus, require closer observation.

Background Sleep-related hypoventilation, particularly during rapid eye movement (REM) sleep, has been linked to pulmonary hypertension and recurrent exacerbations in individuals with advanced chronic respiratory or neuromuscular diseases. Overnight pulse oximetry (OPO) serves as a valuable screening tool to depict episodic oxygen desaturation resulting from sleep-related hypoventilation. However, differentiating nocturnal desaturation caused by physical activity from that attributable to sleep-related hypoventilation remains clinically challenging. This study aimed to determine whether the integration of accelerometer data with OPO readings can assist in distinguishing exertional nocturnal desaturation from desaturation due to sleep-related hypoventilation. Methods Between July 2021 and December 2022, a prospective enrollment was conducted among consecutive individuals with stable chronic respiratory disorders who reported worsening exertional dyspnea. Participants underwent overnight monitoring involving transcutaneous carbon dioxide pressure (PtcCO₂) and pulse oximetry integrated with accelerometer sensors. The number of exertion-associated desaturation events was compared between participant self-reports and acceleration-derived data. Additionally, the diagnostic accuracy of accelerometer-integrated pulse oximetry for detecting episodic nocturnal hypercapnia was assessed using PtcCO₂ monitoring as the reference standard. The primary endpoint was the patient-level diagnostic accuracy of accelerometer-integrated pulse oximetry in detecting episodic nocturnal hypercapnia. Results Thirty-six individuals were enrolled, with a median age of 78.0 (IQR: 72.0–82.0) years and a mean daytime arterial carbon dioxide pressure (PaCO₂) of 42.4 ± 6.9 mmHg. Of the 89 desaturation events observed, 56 (62.9%) were identified as exertion-related using accelerometer data, including 19 events (21.3%) that were not self-reported. The device demonstrated a sensitivity of 100% (95% CI: 79.6–100%) and a specificity of 75.7% (95% CI: 64.8–84.0%) in identifying episodic nocturnal hypoxia associated with hypercapnia. At the patient level, sensitivity and specificity were 100% (95% CI: 100–100%) and 73.1% (95% CI: 53.9–86.3%), respectively. At the event level, sensitivity and specificity were 100% (95% CI: 79.6–100%) and 75.7% (95% CI: 64.8–84.2%), respectively. Conclusion Among individuals with suspected sleep-related breathing disorders, accelerometer-integrated pulse oximetry may serve as a valuable tool to distinguish nocturnal desaturation episodes caused by exertion from those due to sleep-related hypoventilation. These findings suggest that accelerometer-integrated pulse oximetry could offer a feasible screening method for detecting sleep-related hypoventilation in outpatient settings lacking access to PtcCO 2 monitoring.

Purpose Preoxygenation with high-flow therapy by nasal cannulae (HFNC) is now widespread in the intensive care unit (ICU). However, no large randomized study has assessed its relevance in non-severely hypoxemic patients. In a randomized controlled trial (PROTRACH study), we aimed to evaluate preoxygenation with HFNC vs. standard bag-valve mask oxygenation (SMO) in non-severely hypoxemic patients during rapid sequence intubation (RSI) in the ICU. Methods Randomized controlled trial including non-severely hypoxemic patients requiring intubation in the ICU. Patients received preoxygenation by HFNC or SMO during RSI. HFNC was maintained throughout the intubation procedure whereas SMO was removed to perform laryngoscopy. The primary outcome was the lowest pulse oximetry (SpO 2 ) throughout the intubation procedure. Secondary outcomes included drop in SpO 2 , adverse events related to intubation, and outcome in the ICU. Results A total of 192 patients were randomized. In the intent-to-treat analysis, 184 patients (HFNC n  = 95; SMO n  = 89), the median [IQR] lowest SpO 2 was 100% [97; 100] for HFNC and 99% [95; 100] for the SMO group ( P  = 0.30). Mild desaturation below 95% was more frequent with SMO (23%) than with HFNC (12%) (RR 0.51, 95% CI 0.26–0.99, P  = 0.045). There were fewer adverse events in the HFNC group (6%) than in the SMO group (19%) (RR 0.31, 95% CI 0.13–0.76, P  = 0.007), including fewer severe adverse events, respectively 6 (6%) and 14 (16%) with HFNC and SMO (RR 0.38, 95% CI 0.15–0.95, P  = 0.03). Conclusions Compared with SMO, preoxygenation with HFNC in the ICU did not improve the lowest SpO 2 during intubation in the non-severely hypoxemic patients but led to a reduction in intubation-related adverse events. Trial registration Clinical trial Submission: 7 March 2016. Registry name: Benefits of high-flow nasal cannulae oxygen for preoxygenation during intubation in non-severely hypoxemic patients: the PROTRACH study. Clinicaltrials.gov identifier: NCT02700321. Eudra CT: 2015-A00145-44. CPP: 15/13-975 (Comité de protection des personnes de Rennes). URL registry: https://clinicaltrials.gov/ct2/show/record/NCT02700321 .

During flexible fiberoptic bronchoscopy (FOB) the arterial partial pressure of oxygen can drop, increasing the risk for respiratory failure. To avoid desaturation episodes during the procedure several oxygenation strategies have been proposed, including conventional oxygen therapy (COT), high flow nasal cannula (HFNC), continuous positive airway pressure (CPAP) and non-invasive ventilation (NIV). By a review of the current literature, we merely describe the clinical practice of oxygen therapies during FOB. We also conducted a pooled data analysis with respect to oxygenation outcomes, comparing HFNC with COT and NIV, separately. COT showed its benefits in patients undergoing FOB for broncho-alveolar lavage (BAL) or brushing for cytology, in those with peripheral arterial oxyhemoglobin saturation < 93% prior to the procedure or affected by obstructive disorder. HFNC is preferable over COT in patients with mild to moderate acute respiratory failure (ARF) undergoing FOB, by improving oxygen saturation and decreasing the episodes of desaturation. On the opposite, CPAP and NIV guarantee improved oxygenation outcomes as compared to HFNC, and they should be preferred in patients with more severe hypoxemic ARF during FOB.

Rapid sequence induction intubation (RSII) is commonly used in emergency surgeries for patients at high risk of aspiration. However, these patients are more susceptible to hypoxemia during the RSII process. High-flow nasal cannula (HFNC) oxygen therapy has emerged as a potential alternative to traditional face mask (FM) ventilation pre- and apneic oxygenation. This meta-analysis aimed to evaluate the efficacy of HFNC compared to FM during RSII in emergency surgeries. We conducted a comprehensive literature search across PubMed-MEDLINE, EMBASE-OVID, Scopus, and Web of Science databases up to July 20, 2024. Randomized controlled trials comparing HFNC with FM during RSII for emergency surgery patients were included. The primary outcomes were post-intubation arterial partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2). Secondary outcomes included post-intubation end-tidal carbon dioxide concentration (EtCO2), incidence of desaturation, apnea time, lowest peripheral oxygen saturation (Lowest SpO2), and occurrence of regurgitant aspiration. We used the GRADE approach to assess the certainty of evidence and the Cochrane Risk of Bias 2 (RoB 2) tool to evaluate risk of bias. This meta-analysis encompassed six studies, involving a total of 703 patients. HFNC oxygen therapy demonstrated a significant increase in post-intubation arterial PaO2 compared to FM (mean difference = 63.02 mmHg, 95% CI: 8.99 to 117.05, p = 0.02), while no significant difference was observed in arterial PaCO2. Moreover, HFNC substantially prolonged apnea time (mean difference = 19.25 seconds, 95% CI: 1.69 to 36.82, p = 0.03). No statistically significant differences were found between HFNC and FM regarding EtCO2, incidence of desaturation, Lowest SpO2, or regurgitant aspiration. This systematic review and meta-analysis indicates that HFNC may be superior to FM for pre-oxygenation and apneic oxygenation during RSII in emergency surgeries, particularly in improving oxygenation. While these findings are promising, further high-quality research is necessary to establish definitive guidelines for HFNC use in this context.

Continuous positive airway pressure (CPAP) therapy is an efficacious treatment for patients diagnosed with obstructive sleep apnea (OSA). However, there are only few data on long-term adherence. The aim of this study is to quantify the extent of non-adherence and describe the clinical characteristics. A retrospective study including 695 patients with newly diagnosed OSA and prescribed CPAP therapy within an inclusion period of 14 months. All patients were offered free of charge individually adjusted CPAP therapy. Data on comorbidity, medication, BMI and Epworth Sleepiness Score (ESS) were obtained by questionnaires and consultation with an otorhinolaryngeal specialist. The median follow-up time after initiating CPAP therapy was 3.0 (range 2.4-3.6) years. An adherence rate of 89% was found for severe OSA, 71% for moderate OSA and 55% for mild OSA. 18% initiated humidification. Patients adherent to CPAP had a significantly higher Body Mass Index (BMI), Apnea Hypopnea Index (AHI), Oxygen Desaturation Index (ODI) and ESS compared to non-adherent patients. Furthermore, adherence was associated with a higher frequency of observed interrupted breathing, a less frequent use of hypnotic drugs, fewer smokers, and they were more often offered humidification. Age, gender and comorbidity were not significantly associated with adherence. In a Cox model only AHI (Hazard Ratio (HR) 0.963, p < 0.001), ESS (HR 0.939, p = 0.001) and smoking (HR 1.576, p = 0.022) were independently associated with CPAP non-adherence. The severity of OSA, subjective daytime sleepiness and smoking status are independently related to adherence to CPAP therapy.