Efficacy of the COVID-19 vaccination in patients with asymptomatic or mild illness during the Omicron epidemic in Guangzhou: a multi-centre retrospective cohort study.

BACKGROUND: Despite the widespread administration of coronavirus disease 2019 (COVID-19) vaccines, the impact on patients with asymptomatic to mild illness remains unclear. Here, we aimed to assess the efficacy of various vaccine doses and types on the duration of isolation duration and discharge rates, the viral shedding duration, and negative rates in asymptomatic to mild COVID-19 patients. METHODS: We included adult patients at the Fangcang isolation centres in Pazhou or Yongning between November and December 2022. We analysed data on basic demographics, admission details, laboratory indicators and vaccination information. RESULTS: A total of 6560 infected patients were included (3584 from Pazhou and 2976 from Yongning). Of these, 90.6% received inactivated vaccines, 3.66% received recombinant SARS-CoV-2 spike protein subunit vaccines and 0.91% received adenovirus vaccines. Among the 6173 vaccinated individuals, 71.9% received a booster dose. By day 9, the isolation rate reached 50% among vaccinated patients. On day 7.5, the positive rate among vaccinated individuals reached 50%. CONCLUSIONS: Full vaccination was effective, with heterologous vaccines showing greater efficacy than inactivated vaccines alone. However, there was no significant difference in the vaccine protective effect 12 months after vaccination.

Venovenous extracorporeal membrane oxygenation for COVID-19 and influenza H1N1 associated acute respiratory distress syndrome: A comparative cohort study in China.

Background: Venovenous extracorporeal membrane oxygenation (VV-ECMO) has been demonstrated to be effective in treating patients with virus-induced acute respiratory distress syndrome (ARDS). However, whether the management of ECMO is different in treating H1N1 influenza and coronavirus disease 2019 (COVID-19)-associated ARDS patients remains unknown. Methods: This is a retrospective cohort study. We included 12 VV-ECMO-supported COVID-19 patients admitted to The First Affiliated Hospital of Guangzhou Medical University, Guangzhou Eighth People's Hospital, and Wuhan Union Hospital West Campus between January 23 and March 31, 2020. We retrospectively included VV-ECMO-supported patients with COVID-19 and H1N1 influenza-associated ARDS. Clinical characteristics, respiratory mechanics including plateau pressure, driving pressure, mechanical power, ventilatory ratio (VR) and lung compliance, and outcomes were compared. Results: Data from 25 patients with COVID-19 (n=12) and H1N1 (n=13) associated ARDS who had received ECMO support were analyzed. COVID-19 patients were older than H1N1 influenza patients (P=0.004). The partial pressure of arterial carbon dioxide (PaCO2) and VR before ECMO initiation were significantly higher in COVID-19 patients than in H1N1 influenza patients (P <0.001 and P=0.004, respectively). COVID-19 patients showed increased plateau and driving pressure compared with H1N1 subjects (P=0.013 and P=0.018, respectively). Patients with COVID-19 remained longer on ECMO support than did H1N1 influenza patients (P=0.015). COVID-19 patients who required ECMO support also had fewer intensive care unit and ventilator-free days than H1N1. Conclusions: Compared with H1N1 influenza patients, COVID-19 patients were older and presented with increased PaCO2 and VR values before ECMO initiation. The differences between ARDS patients with COVID-19 and influenza on VV-ECMO detailed herein could be helpful for obtaining a better understanding of COVID-19 and for better clinical management.

The accuracy of simplified calculation of mechanical power: a simulation study.

Background: Mechanical ventilation (MV) is an important life-saving method in the intensive care unit (ICU). A lower mechanical power (MP) is associated with a better MV strategy. However, traditional MP calculating methods are complicated, and algebraic formulas seem to be rather practical. The aim of the present study was to compare the accuracy and application of different algebraic formulas calculating MP. Methods: A lung simulator, TestChest, was used to simulate pulmonary compliance variations. Using the TestChest system software, the parameters, including compliance and airway resistance, were set to simulate various acute respiratory distress syndrome (ARDS) lungs. Ventilator was also set to volume- and pressure-controlled modes with various parameter values (respiratory rate, RR, time of inspiration, Tinsp, positive end-expiratory pressure, PEEP) to ventilate the simulated lung of ARDS (with various respiratory system compliance, Crs). For the lung simulator, resistance of airway (Raw) was fixed to 5 cmH2O/L/s. Crs below lower inflation point (LIP) or above upper inflation point (UIP) was set to 10 mL/cmH2O. The reference standard geometric method was calculated offline with a customized software. Three algebraic formulas for volume-controlled and three for pressure-controlled were used to calculate MP. Results: The performances of the formulas were different, although the derived MP were significantly correlated with that derived from the reference method (R2>0.80, P<0.001). Under volume-controlled ventilation, medians of MP calculated with one equation was significantly lower than that with the reference method (P<0.001). Under pressure-controlled ventilation, median of MP calculated with two equations were significantly higher (P<0.001). The maximum difference was over 70% of the MP value calculated with the reference method. Conclusions: The algebraic formulas may introduce considerably large bias under the presented lung conditions, especially in moderate to severe ARDS. Cautious is required when selecting adequate algebraic formulas to calculate MP based on the formula's premises, ventilation mode, and patients' status. In clinical practice, the trend rather than the value of MP calculated by formulas should require more attention.

An investigation on the respiratory mechanics of mechanically ventilated patients during spontaneous breathing trials with enhanced low-level pressure support ventilation.

INTRODUCTION: Low-level pressure support ventilation (PSV) is most commonly adopted in spontaneous breathing trials (SBTs), and some have proposed setting the positive end-expiratory pressure (PEEP) to 0 cmH2 O in order to shorten the observation time of SBTs. This study aims to investigate the effects of two PSV protocols on the patients' respiratory mechanics. MATERIAL AND METHOD: A prospective randomized self-controlled crossover design was adopted in this study, which involved enrolling 30 difficult-to-wean patients who were admitted to the intensive care unit of the First Affiliated Hospital of Guangzhou Medical University between July 2019 and September 2021. Patients were subjected to the S group (pressure support: 8 cmH2 O, PEEP: 5 cmH2 O) and S1 group (PS: 8 cmH2 O, PEEP: 0 cmH2 O) for 30 min in a random order, and respiratory mechanics indices were dynamically monitored via a four-lumen multi-functional catheter with an integrated gastric tube. Among the 30 enrolled patients, 27 were successfully weaned. RESULT: The S group showed higher airway pressure (Paw), intragastric pressure (Pga) and airway pressure-time product (PTP) than the S1 group. The S group also showed a shorter inspiratory trigger delay, (93.80 ± 47.85) versus (137.33 ± 85.66) ms (P = 0.004); and fewer abnormal triggers, (0.97 ± 2.65) versus (2.67 ± 4.48) (P = 0.042) compared with the S1 group. Stratification based on the causes of mechanical ventilation revealed that under the S1 protocol, patients with chronic obstructive pulmonary disease (COPD) had a longer inspiratory trigger delay compared to both post-thoracic surgery (PTS) patients and patients with acute respiratory distress syndrome. Despite providing greater respiratory support, S group led to significant reductions in inspiratory trigger delay and less abnormal triggers compared to S1 group, especially among patients with chronic obstructive pulmonary disease. CONCLUSION: These findings suggest that the zero PEEP group was more likely to induce a higher number of patient-ventilator asynchronies in difficult-to-wean patients.

Changes of blood gas analysis in moderate-to-severe acute respiratory distress syndrome patients during long-term prone position ventilation: a retrospective cohort study.

Background: Prone position ventilation (PPV) has been recommended for patients with acute respiratory distress syndrome (ARDS) to improve oxygenation. However, whether prolonged prone ventilation will aggravate hyperoxia and whether abdominal compression will aggravate permissive hypercapnia acidosis are topics of concern. We carried out a retrospective analysis to investigate the issues above. Methods: Clinical data were collected from 97 moderate-to-severe ARDS patients who received PPV as part of their treatment in the intensive care unit (ICU) of the First Affiliated Hospital of Guangzhou Medical University from November 2015 to May 2021. We collected arterial blood gas of patients according to the 3 periods: supine position ventilation (SPV), PPV early stage (within 4 hours), and PPV middle and late stage (6 hours or later). We established a linear mixed-effects models with "body position changes, times of PPV, gender, age, baseline SOFA, and baseline APACHE II" as fixed effects, and individual and the number of prone positions as random intercept and random slope to investigate the effect of body position changes on blood gas analysis. Results: Among the 97 patients received PPV included, 51 were ICU survivors. Arterial partial pressure of oxygen (PaO2) and PaO2/fraction of inspired oxygen (FiO2) ratio were significantly higher at the early, middle and late stages of PPV than those in SPV [PFR (mmHg): 158 (118.00, 203.00) vs. 161 (129.00, 202.75) vs. 123 (91.75, 163.00), P<0.05]. Despite the synchronized reduction of FiO2, the incidence of hyperoxia in the prone position was still significantly higher than that in the supine position [hyperoxia (%):33.33 vs. 33.56 vs. 12.42, P<0.05]; there was no significant change in arterial carbon dioxide partial pressure (PaCO2) at each stage of PPV, but there was a significant increase in PH at PPV middle and late stages than those at early stage [PH: 7.39 (7.34, 7.42) vs. 7.37 (7.31, 7.41), P<0.05]. Conclusions: Although PPV improves the patients' oxygenation, the associated incidence of hyperoxia exceeds 33%. Down-regulate FiO2 more sharply after PPV is necessary, if oxygenation conditions permit. PPV may alleviate the acidosis associated with permissive hypercapnia in ARDS patients treated with lung protective ventilation strategy (LPVS).

Dynamic evaluation of the pulmonary protective effects of prone position ventilation via respiratory mechanics for patients with moderate to severe acute respiratory distress syndrome.

Background: Patients with moderate to severe acute respiratory distress syndrome (ARDS) have been recommended to receive prone position ventilation (PPV). However, the dynamic changes in respiratory mechanics during PPV and their relationship with the prognosis have not been sufficiently evaluated. In addition, the impact of using neuromuscular blocking agents (NMBAs) during PPV on respiratory mechanics is not clear enough. Thus, the study aims to investigate the above-mentioned issues. Methods: A prospective cohort study was conducted on 22 patients with moderate to severe ARDS who received PPV in the intensive care unit (ICU) of the First Affiliated Hospital of Guangzhou Medical University. A multifunctional gastric tube was used to measure the patients' respiratory mechanics during supine position ventilation (SPV), early PPV (PPV within 4 h of initiation), and middle/late PPV (more than 6 h after the initiation of PPV). Longitudinal data were analyzed with generalized estimating equations (GEE). Results: Compared with SPV, the esophageal pressure swings (ΔPes) measured during the PPV was significantly higher (SPV 7.46 vs. early PPV 8.00 vs. middle/late PPV 8.30 cmH2O respectively; PSPV vs. middle/late PPV =0.025<0.05). A stratified analysis by patients' outcome showed that the peak airway pressure (Ppeak), ΔPes and respiration rate (RR) in the death group were significantly higher than survival group. On the contrary, the tidal volume (Vt), diaphragmatic electromyogram (EMGdi) and PaO2/FiO2 ratio (PFR) in the death group were significantly lower than survival group. Notably, the ΔPes and transpulmonary driving pressure (DPL) were significantly lower in the patients treated with NMBAs (7.08 vs. 8.76 cmH2O ΔPes; P<0.01), (14.82 vs. 18.08 cmH2O DPL; P<0.001). Conclusions: During the transition from SPV to early PPV and then to middle/late PPV, the ΔPes in the PPV were greater than SPV and it fluctuated within a normal range while oxygenation improved significantly in all patients. The Ppeak, ΔPes and RR in the death group were significantly higher than survival group. When NMBAs were used, the ΔPes, inspiratory transpulmonary pressure (PLei), driving pressure (DP) and DPL were significantly decreased, suggesting that the rational combination of NMBAs and PPV may exert a synergistic protective effect on the lungs.

Patients with infectious diseases undergoing mechanical ventilation in the intensive care unit have better prognosis after receiving metagenomic next-generation sequencing assay.

OBJECTIVES: To evaluate the relation between metagenomic next-generation sequencing (mNGS) and the prognosis of patients with infectious diseases undergoing mechanical ventilation in the intensive care unit (ICU). METHODS: This is a single-center observational study, comparing nonrandomly assigned diagnostic approaches. We analyzed the medical records of 228 patients with suspected infectious diseases undergoing mechanical ventilation in the ICU from March 2018 to May 2020. The concordance of pathogen results was also assessed for the results of mNGS, culture, and polymerase chain reaction assays. RESULTS: The 28-day mortality of the patients in the mNGS group was lower after the baseline difference correction (19.23% (20/104) vs 29.03% (36/124) , P = 0.039). Subgroup analysis showed that mNGS assay was associated with improved 28-day mortality of patients who are not immunosuppressed (14.06% vs 29.82%, P = 0.018). Not performing mNGS assay, higher acute physiology and chronic health evaluation II score, and hypertension are independent risk factors for 28-day mortality. The mNGS assay presented an advantage in pathogen positivity (69.8% double-positive and 25.0% mNGS-positive only), and the concordance between these two assays was 79.0%. CONCLUSION: mNGS survey may be associated with a better prognosis by reducing 28-day mortality of patients with infectious diseases on mechanical ventilation in the ICU. This technique presented an advantage in pathogen positivity over traditional methods.

Effect of IFN-α and other commonly used nebulization drugs in different nebulization methods on the resistance of breathing circuit filters under invasive mechanical ventilation.

Background: Interferon (IFN) is widely used in clinical practice and nebulization inhalation is one of the commonly used routes of administration. However, nebulization drugs such as interferon-α (IFN-α) with large molecular weights may deposit in the membrane of the breathing filters, causing its resistance to gradually increase. Thus, our study explores the effect of IFN-α and other nebulization drugs on the resistance of breathing circuit filters under invasive mechanical ventilation. Methods: We divided 96 breathing filters into eight groups. The baseline group was not treated while the blank group was installed but were not nebulized. The remaining groups received jet nebulized or vibrating nebulized with either normal saline, Combivent, Amphotericin B, or IFN-α at a frequency of once every 12 hours separately and were removed from the breathing circuit after 24 hours. The resistance of the filter of each group was then measured and statistical comparisons were made. Results: Filter resistance of the IFN-α jet nebulization group was greater than that of the other groups, and there were statistical differences except for the Amphotericin B jet nebulization group. Comparison of the resistance [cmH2O/(L·s)] of the IFN-α jet nebulization group vs. the baseline group showed 2.56 (2.40, 2.68) vs. 2.26 (2.03, 2.40), P=0.037; of the IFN-α jet nebulization group vs. the blank group showed 2.56 (2.40, 2.68) vs. 2.11 (1.98, 2.27), P=0.003; of the IFN-α jet nebulization group vs. the normal saline group: 2.56 (2.40, 2.68) vs. 2.16 (2.08, 2.32), P=0.023; of the IFN-α jet nebulization group vs. the Combivent jet nebulization group: 2.56 (2.40, 2.68) vs. 2.18 (2.14, 2.27), P=0.018; and of the IFN-α jet nebulization group vs. the Amphotericin B jet nebulization group: 2.56 (2.40, 2.68) vs. 2.33 (2.05, 2.45), P=0.221. The effect of jet nebulization and vibrating mesh nebulization on the resistance of breathing filters showed no significant statistical difference. Conclusions: Jet nebulization with IFN-α significantly increased the resistance of the breathing filter within 24 hours and there was no significant difference in filter resistance between jet nebulization and vibrating mesh nebulization of IFN-α or Amphotericin B.

Weaning critically ill patients from mechanical ventilation: a protocol from a multicenter retrospective cohort study.

BACKGROUND: Mechanical ventilation (MV) is an important lifesaving method in intensive care unit (ICU). Prolonged MV is associated with ventilator associated pneumonia (VAP) and other complications. However, premature weaning from MV may lead to higher risk of reintubation or mortality. Therefore, timely and safe weaning from MV is important. In addition, identification of the right patient and performing a suitable weaning process is necessary. Although several guidelines about weaning have been reported, compliance with these guidelines is unknown. Therefore, the aim of this study is to explore the variation of weaning in China, associations between initial MV reason and clinical outcomes, and factors associated with weaning strategies using a multicenter cohort. METHODS: This multicenter retrospective cohort study will be conducted at 17 adult ICUs in China, that included patients who were admitted in this 17 ICUs between October 2020 and February 2021. Patients under 18 years of age and patients without the possibility for weaning will be excluded. The questionnaire information will be registered by a specific clinician in each center who has been evaluated and qualified to carry out the study. DISCUSSION: In a previous observational study of weaning in 17 ICUs in China, weaning practices varies nationally. Therefore, a multicenter retrospective cohort study is necessary to be conducted to explore the present weaning methods used in China. TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR) (No. ChiCTR2100044634).

Artificial intelligence for stepwise diagnosis and monitoring of COVID-19.

BACKGROUND: Main challenges for COVID-19 include the lack of a rapid diagnostic test, a suitable tool to monitor and predict a patient's clinical course and an efficient way for data sharing among multicenters. We thus developed a novel artificial intelligence system based on deep learning (DL) and federated learning (FL) for the diagnosis, monitoring, and prediction of a patient's clinical course. METHODS: CT imaging derived from 6 different multicenter cohorts were used for stepwise diagnostic algorithm to diagnose COVID-19, with or without clinical data. Patients with more than 3 consecutive CT images were trained for the monitoring algorithm. FL has been applied for decentralized refinement of independently built DL models. RESULTS: A total of 1,552,988 CT slices from 4804 patients were used. The model can diagnose COVID-19 based on CT alone with the AUC being 0.98 (95% CI 0.97-0.99), and outperforms the radiologist's assessment. We have also successfully tested the incorporation of the DL diagnostic model with the FL framework. Its auto-segmentation analyses co-related well with those by radiologists and achieved a high Dice's coefficient of 0.77. It can produce a predictive curve of a patient's clinical course if serial CT assessments are available. INTERPRETATION: The system has high consistency in diagnosing COVID-19 based on CT, with or without clinical data. Alternatively, it can be implemented on a FL platform, which would potentially encourage the data sharing in the future. It also can produce an objective predictive curve of a patient's clinical course for visualization. KEY POINTS: • CoviDet could diagnose COVID-19 based on chest CT with high consistency; this outperformed the radiologist's assessment. Its auto-segmentation analyses co-related well with those by radiologists and could potentially monitor and predict a patient's clinical course if serial CT assessments are available. It can be integrated into the federated learning framework. • CoviDet can be used as an adjunct to aid clinicians with the CT diagnosis of COVID-19 and can potentially be used for disease monitoring; federated learning can potentially open opportunities for global collaboration.

Optimal Positive End Expiratory Pressure Levels in Ventilated Patients Without Acute Respiratory Distress Syndrome: A Bayesian Network Meta-Analysis and Systematic Review of Randomized Controlled Trials.

Background: To find the optimal positive end expiratory pressure (PEEP) in mechanical ventilated patients without Acute Respiratory Distress Syndrome (ARDS), we conducted a Bayesian network meta-analysis and systematic review of randomized controlled trials (RCTs) comparing different level of PEEP based on a novel classification of PEEP level: ZEEP group (PEEP = 0 cm H2O); lower PEEP group (PEEP = 1-6 cm H2O); intermediate PEEP group (PEEP = 7-10 cm H2O); higher PEEP group (PEEP > 10 cm H2O). Result: Twenty eight eligible studies with 2,712 patients were included. There were no significant differences in the duration of mechanical ventilation between higher and intermediate PEEP (MD: 0.020, 95% CI: -0.14, 0.28), higher and lower PEEP (MD: -0.010, 95% CI: -0.23, 0.22), higher PEEP and ZEEP (MD: 0.010, 95% CI: -0.40, 0.22), intermediate and lower PEEP (MD: -0.040, 95% CI: -0.18, 0.040), intermediate PEEP and ZEEP (MD: -0.010, 95% CI: -0.42, 0.10), lower PEEP and ZEEP (MD: 0.020, 95% CI: -0.32, 0.13), respectively. Higher PEEP was associated with significantly higher PaO2/FiO2 ratio(PFR) when compared to ZEEP (MD: 73.24, 95% CI: 11.03, 130.7), and higher incidence of pneumothorax when compared to intermediate PEEP, lower PEEP and ZEEP (OR: 2.91e + 12, 95% CI: 40.3, 1.76e + 39; OR: 1.85e + 12, 95% CI: 29.2, 1.18e + 39; and OR: 1.44e + 12, 95% CI: 16.9, 8.70e + 38, respectively). There was no association between PEEP levels and other secondary outcomes. Conclusion: We identified higher PEEP was associated with significantly higher PFR and higher incidence of pneumothorax. Nonetheless, in terms of other outcomes, no significant differences were detected among four levels of PEEP. Systematic Review Registration: The study had registered on an international prospective register of systematic reviews, PROSPERO, on 09 April 2021, identifier: [CRD42021241745].

Effect of sequential high-flow nasal cannula oxygen therapy and non-invasive positive-pressure ventilation in patients with difficult weaning from mechanical ventilation after extubation on respiratory mechanics.

BACKGROUND: Patients with difficult weaning who undergo mechanical ventilation are more likely to be at risk of reintubation and the sequential use of oxygen therapy after extubation is a concern for clinicians. Therefore, the aim of the present study was to compare the effects of transnasal high-flow nasal cannula (HFNC) oxygen therapy and non-invasive positive-pressure ventilation (NIV) on respiratory mechanics in patients with difficult weaning. METHODS: The present study was a single-center, retrospective, observational study. Twenty-nine patients with difficult weaning off invasive mechanical ventilation from the Department of Critical Care Medicine, The First Affiliated Hospital of Guangzhou Medical University, from December 2018 to April 2021, were included. Within 48 h after extubation, alternate respiratory support with HFNC and NIV was provided. Relevant indicators were recorded after each support mode had been maintained for at least 60 min. These included esophageal pressure (Pes), gastric pressure (Pga), transdiaphragmatic pressure (Pdi), pressure-time product of Pes (PTPes), pressure-time product of Pga (PTPga), pressure-time product of Pdi (PTPdi), ratio of the PTPdi to the PTPes (PTPdi/PTPes), and ratio of the Pes to the Pdi (Pes/Pdi), diaphragmatic electromyogram (EMGdi), percentage of esophageal pressure coefficient of variation (CVes%),diaphragmatic electromyogram coefficient of variation (CVEMG),inspiratory time (Ti), expiratory time (Te) and respiratory cycle time (Ttot). RESULTS: Of the 29 patients included, 22 were males and 7 were females [age: 63.97±15.34 years, Acute Physiological and Chronic Health Estimation II (APACHE II) score: 18.00±5.63]. The CVes% and the Pes/Pdi were significantly higher in patients with NIV than HFNC using 40 L/min, CVes%: 9 (-6, 20) vs. -7 (-23, 6) and Pes/Pdi: 0.17 (-0.1, 0.53), vs. -0.12 (-0.43, 0.08) (P<0.05). The remaining indicators were not statistically different. CONCLUSIONS: The sequential NIV and HFNC can be tolerated in patients with such difficult weaning off mechanical ventilation after extubation, and more patients tend to choose HFNC subjectively. Compared with HFNC, NIV reduces the work of adjunctive respiratory muscle, but the patient's Pes dispersion is high when NIV is used, and it is necessary to pay attention to patient-ventilator coordination in clinical practice. We recommend alternating HFNC and NIV during the sequential respiratory therapy after extubation.

A Scalable Graph Neural Network Method for Developing an Accurate Force Field of Large Flexible Organic Molecules.

An accurate force field is the key to the success of all molecular mechanics simulations on organic polymers and biomolecules. Accurate correlated wave function (CW) methods scale poorly with system size, so this poses a great challenge to the development of an extendible ab initio force field for large flexible organic molecules at the CW level of accuracy. In this work, we combine the physics-driven nonbonding potential with a data-driven subgraph neural network bonding model (named sGNN). Tests on polyethylene glycol, polyethene, and their block polymers show that our strategy is highly accurate and robust for molecules of different sizes and chemical compositions. Therefore, one can develop a parameter library of small molecular fragments (with sizes easily accessible to CW methods) and assemble them to predict the energy of large polymers, thus opening a new path to next-generation organic force fields.

Reverse Trigger in Ventilated Non-ARDS Patients: A Phenomenon Can Not Be Ignored!

INTRODUCTION: The role of reverse trigger (RT) was unknown in ventilated non-acute respiratory distress syndrome (ARDS) patients. So we conducted a retrospective study to evaluate the incidence, characteristics and physiologic consequence of RT in such population. METHOD: Six ventilated non-ARDS patients were included, the esophageal balloon catheter were placed for measurements of respiratory mechanics in all patients. And the data were analyzed to identified the occurrence of RT, duration of the entrainment, the entrainment pattern or ratio, the phase difference (dP) and the phase angle (θ), phenotypes, Effects and clinical correlations of RT. RESULT: RT was detected in four patients of our series (66.7%), and the occurrence of RT varying from 19 to 88.6% of their recording time in these 4 patients. One patient (No.2) showed a stable 1:1 ratio and Mid-cycle RT was the most common phenotype. However, the remained patients showed a mixed ratios, and Late RT was the most common phenotype, followed by RT with breath stacking. The average values of mean phase delay and phase angles were 0.39s (0.32, 0.98) and 60.52° (49.66, 102.24). Mean phase delay and phase angles were shorter in early reverse triggering with early and delayed relaxation, and longer in mid, late RT and RT with breath stacking. Pmus was variable between patients and phenotypes, and larger Pmus was generated in Early RT, Delayed Relaxation and mid cycle RT. When the RT occurred, the Peso increased 17.27 (4.91, 19.71) cmH2O compared to the controlled breathing, and the average value of incremental ΔPeso varied widely inter and intra patients (Table 3B and Figure 1). Larger ΔPeso was always generated in Early RT, Delayed Relaxation and mid cycle RT, accompanied by an significant increase of PL with 19.12 (0.75) cmH2O and 16.10 (6.23) cmH2O. CONCLUSION: RT could also be observed in ventilated non-ARDS patients. The characteristics of pattern and phenotype was similar to RT in ARDS patients to a large extent. And RT appeared to alter lung stress and delivered volumes.

Secondary infection in severe and critical COVID-19 patients in China: a multicenter retrospective study.

BACKGROUND: Since 2020 COVID-19 pandemic became an emergent public sanitary incident. The epidemiology data and the impact on prognosis of secondary infection in severe and critical COVID-19 patients in China remained largely unclear. METHODS: We retrospectively reviewed medical records of all adult patients with laboratory-confirmed COVID-19 who were admitted to ICUs from January 18th 2020 to April 26th 2020 at two hospitals in Wuhan, China and one hospital in Guangzhou, China. We measured the frequency of bacteria and fungi cultured from respiratory tract, blood and other body fluid specimens. The risk factors for and impact of secondary infection on clinical outcomes were also assessed. RESULTS: Secondary infections were very common (86.6%) when patients were admitted to ICU for >72 hours. The majority of infections were respiratory, with the most common organisms being Klebsiella pneumoniae (24.5%), Acinetobacter baumannii (21.8%), Stenotrophomonas maltophilia (9.9%), Candida albicans (6.8%), and Pseudomonas spp. (4.8%). Furthermore, the proportions of multidrug resistant (MDR) bacteria and carbapenem resistant Enterobacteriaceae (CRE) were high. We also found that age ≥60 years and mechanical ventilation ≥13 days independently increased the likelihood of secondary infection. Finally, patients with positive cultures had reduced ventilator free days in 28 days and patients with CRE and/or MDR bacteria positivity showed lower 28-day survival rate. CONCLUSIONS: In a retrospective cohort of severe and critical COVID-19 patients admitted to ICUs in China, the prevalence of secondary infection was high, especially with CRE and MDR bacteria, resulting in poor clinical outcomes.

[Comparison of the effects between low-level assisted ventilation and T-piece method on respiratory mechanics during weaning of mechanically ventilated patients].

OBJECTIVE: To compare the difference of low-level assisted ventilation and T-piece method on respiratory mechanics of patients with invasive mechanical ventilation during spontaneous breathing trial (SBT) within 3 days before extubation. METHODS: A retrospective observational study was conducted. Twenty-five patients with difficulty in weaning or delayed weaning from invasive mechanical ventilation who were admitted to department of critical care medicine of the First Affiliated Hospital of Guangzhou Medical University from December 2018 to June 2020, and were in stable condition and entered the weaning stage after more than 72 hours of invasive mechanical ventilation were studied. A total of 119 cases of respiratory mechanical indexes were collected, which were divided into the low-level assisted ventilation group and the T-piece group according to the ventilator method and parameters used during the data collection. The different ventilation modes related respiratory mechanics indexes such as the esophageal pressure (Pes), the gastric pressure (Pga), the transdiaphragmatic pressure (Pdi), the maximum Pdi (Pdimax), Pdi/Pdimax ratio, the esophageal pressure-time product (PTPes), the gastric pressure-time product (PTPga), the transdiaphragmatic pressure-time product (PTPdi), the diaphragmatic electromyography (EMGdi), the maximum diaphragmatic electromyography (EMGdimax), PTPdi/PTPes ratio, Pes/Pdi ratio, the inspiratory time (Ti), the expiratory time (Te) and the total time respiratory cycle (Ttot) at the end of monitoring were recorded and compared between the two groups. RESULTS: Compared with the T-piece group, Pes, PTPes, PTPdi/PTPes ratio, Pes/Pdi ratio and Te were higher in low-level assisted ventilation group [Pes (cmH2O, 1 cmH2O = 0.098 kPa): 2.84 (-1.80, 5.83) vs. -0.94 (-8.50, 2.06), PTPes (cmH2O×s×min-1): 1.87 (-2.50, 5.93) vs. -0.95 (-9.71, 2.56), PTPdi/PTPes ratio: 0.07 (-1.74, 1.65) vs. -1.82 (-4.15, -1.25), Pes/Pdi ratio: 0.17 (-0.43, 0.64) vs. -0.47 (-0.65, -0.11), Te (s): 1.65 (1.36, 2.18) vs. 1.33 (1.05, 1.75), all P < 0.05], there were no significant differences in Pga, Pdi, Pdimax, Pdi/Pdimax ratio, PTPga, PTPdi, EMGdi, EMGdimax, Ti and Ttot between the T-piece group and the low-level assisted pressure ventilation group [Pga (cmH2O): 6.96 (3.54,7.60) vs. 7.74 (4.37, 11.30), Pdi (cmH2O): 9.24 (4.58, 17.31) vs. 6.18 (2.98, 11.96), Pdimax (cmH2O): 47.20 (20.60, 52.30) vs. 29.95 (21.50, 47.20), Pdi/Pdimax ratio: 0.25 (0.01, 0.34) vs. 0.25 (0.12, 0.41), PTPga (cmH2O×s×min-1): 7.20 (2.54, 9.97) vs. 7.97 (5.74, 13.07), PTPdi (cmH2O×s×min-1): 12.15 (2.95, 19.86) vs. 6.87 (2.50, 12.63), EMGdi (µV): 0.05 (0.03, 0.07) vs. 0.04 (0.02, 0.06), EMGdimax (µV): 0.07 (0.05, 0.09) vs. 0.07 (0.04, 0.09), Ti (s): 1.20 (0.95, 1.33) vs. 1.07 (0.95, 1.33), Ttot (s): 2.59 (2.22, 3.09) vs. 2.77 (2.35, 3.24), all P > 0.05]. CONCLUSIONS: When mechanically ventilated patients undergo SBT, the use of T-piece method increases the work of breathing compared with low-level assisted ventilation method. Therefore, long-term use of T-piece should be avoided during SBT.

Independent risk factors of hypoxemia in patients after surgery with acute type A aortic dissection.

BACKGROUND: This study aimed to investigate independent risk factors of postoperative hypoxemia in patients with acute type A aortic dissection (ATAAD). METHODS: A single-center retrospective study was conducted with enrolled 75 ATAAD patients following surgery, which were stratified into three groups on the basis of the postoperative PaO2/FiO2 ratio: severe hypoxemia group (PaO2/FiO2 ratio ≤100 mmHg); moderate hypoxemia group (100 mmHg < PaO2/FiO2 ratio ≤200 mmHg); and non-hypoxemia group (PaO2/FiO2 ratio >200 mmHg). The patient's demography, perioperative laboratory results, operative details, clinical outcomes were collected and analyzed. Univariable and multivariable analyses were performed and logistic regression model was established. RESULTS: The incidence of postoperative severe hypoxemia and hypoxemia was 32% and 52%, respectively. Among the three groups, severe hypoxemia group exhibited a high significance of body mass index (BMI) and preoperative white blood cell (WBC) and main distribution of hypertension; meanwhile, Marfan syndrome was mainly distributed in non-hypoxemia group. On intensive care unit (ICU) admission, severe hypoxemia group exhibited a high significance of Acute Physiology and Chronic Health Evaluation (APACHE II) score of postoperative patients, and more patients would present shock. Moreover, severe hypoxemia group patients had a higher incidence of postoperative acute kidney injury (AKI) and usage of renal replacement therapy, longer length of stay (LOS) of ICU, and shorter 28 days ventilator-free days (VFDs). CONCLUSIONS: The incidence of postoperative hypoxemia was high in ATAAD patients owing to comprehensive high-risk factors. Besides, postoperative complications negatively impacted their clinical outcomes.

COVID-19-associated coagulopathy: thromboembolism prophylaxis and poor prognosis in ICU.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is associated with coagulation abnormalities which are indicators of higher mortality especially in severe cases. METHODS: We studied patients with proven COVID-19 disease in the intensive care unit of Jinyintan Hospital, Wuhan, China from 30 to 2019 to 31 March 2020. RESULTS: Of 180 patients, 89 (49.44 %) had died, 85 (47.22 %) had been discharged alive, and 6 (3.33 %) were still hospitalised by the end of data collection. A D-dimer concentration of > 0.5 mg/L on admission was significantly associated with 30 day mortality, and a D-dimer concentration of > 5 mg/L was found in a much higher proportion of non-survivors than survivors. Sepsis-induced coagulopathy (SIC) and disseminated intravascular coagulation (DIC) scoring systems were dichotomised as < 4 or ≥ 4 and < 5 or ≥ 5, respectively, and the mortality rate was significantly different between the two stratifications in both scoring systems. Enoxaparin was administered to 68 (37.78 %) patients for thromboembolic prophylaxis, and stratification by the D-dimer concentration and DIC score confirmed lower mortality in patients who received enoxaparin when the D-dimer concentration was > 2 than < 2 mg/L or DIC score was ≥ 5 than < 5. A low platelet count and low serum calcium concentration were also related to mortality. CONCLUSIONS: A D-dimer concentration of > 0.5 mg/L on admission is a risk factor for severe disease. A SIC score of > 4 and DIC score of > 5 may be used to predict mortality. Thromboembolic prophylaxis can reduce mortality only in patients with a D-dimer concentration of > 2 mg/L or DIC score of ≥ 5.

Critical Care Response to the Outbreak of COVID-19: The Experience From Guangdong Province, China.

In December 2019, human infection with a novel coronavirus, known as SARS-CoV-2, was confirmed in Wuhan, China, and spread rapidly beyond Wuhan and around the world. By 7 May 2020, a total of 84,409 patients were infected in mainland China, with 4,643 deaths, according to a Chinese Center for Disease Control and Prevention report. Recent studies reported that critically ill patients were presented with high mortality. However, the clinical experiences of patients with coronavirus disease 2019 (COVID-19) have not been described in Guangdong Province, where by 7 May 2020, 1,589 people had been confirmed as having COVID-19 but with a very low mortality of 8 death (0.5%). Here, we describe the experience of critical care response to the outbreak of SARS-CoV-2 in Guangdong Province in the following points: Early intervention by the government, Establishment of a Multidisciplinary Working Group, Prompt intensive care interventions, Adequate ICU beds and Human resource in ICU, Infection control practices.