Comparison of two techniques of administering the Valsalva manoeuvre in patients under general anaesthesia: A randomised controlled study.

Background and Aims: Surgeons often request a Valsalva manoeuvre (VM) at the end of surgery (head-neck surgery, craniotomy) to check haemostasis and to unmask covert venous bleeders. We aimed to compare an anaesthesia machine-generated objective technique for delivering VM under pressure-control (PC) mode with the traditional subjective technique of delivering VM in manual mode. Methods: This randomised controlled study included 60 adult patients randomised to manual (Group M) and controlled ventilation (Group C) groups. Our primary outcome measure was internal jugular vein (IJV) diameter at pre-determined time points (T0 = baseline, T1 = VM initiation, T2 = 20 s after VM initiation, T3 = immediately after VM release, and T4 = 1 min, T5 = 2 min and T6 = 5 min post-VM release). Secondary outcome measures included mean arterial pressure (MAP), heart rate, time to desired plateau airway pressure, number of patients with bleeders unmasked and surgeon satisfaction. Independent/paired sample t-tests were applied. Results are expressed as mean (standard deviation), mean difference (95% confidence interval), dotted box-whisker plots and trendlines. P <0.05 is considered statistically significant. Results: Mean differences in diameter changes in IJV (in centimetres) in the mediolateral and anteroposterior directions between Group C and Group M were -0.136 (-0.227, -0.044) and -0.073 (-0.143, -0.002), respectively. VM in the PC mode produced more significant IJV dilatation (P = 0.004, P = 0.044). MAP at T0 and T1 was comparable. At T2 and T3, there was a more significant fall in MAP in Group C versus Group M (P = 0.018 and P = 0.021, respectively). At T4, T5 and T6, MAP was comparable. Conclusion: Performing VM in PC mode is a better technique based on IJV diameter, haemodynamics, bleeder unmasking and surgeon satisfaction.

Management of severe acute respiratory distress syndrome in Australia and New Zealand (SAGE-ANZ): An observational study.

Objective: Acute respiratory distress syndrome (ARDS) is associated with significant mortality, morbidity, and cost. We aimed to describe characteristics and management of adult patients admitted to intensive care units (ICUs) in Australia and New Zealand with moderate-severe ARDS, to better understand contemporary practice. Design: Bi-national, prospective, observational, multi-centre study. Setting: 19 ICUs in Australia and New Zealand. Participants: Mechanically ventilated patients with moderate-severe ARDS. Main outcome measures: Baseline demographic characteristics, ventilation characteristics, use of adjunctive support therapy and all-cause mortality to day 28. Data were summarised using descriptive statistics. Results: 200 participants were enrolled, mean (±SD) age 55.5 (±15.9) years, 40% (n = 80) female. Around half (51.5%) had no baseline comorbidities and 45 (31%) tested positive for COVID-19. On day 1, mean SOFA score was 9 ± 3; median (IQR) PaO2/FiO2 ratio 119 (89, 142), median (IQR) FiO2 70% (50%, 99%) and mean (±SD) positive end expiratory pressure (PEEP) 11 (±3) cmH2O. On day one, 10.5% (n = 21) received lung protective ventilation (LPV) (tidal volume ≤6.5 mL/kg predicted body weight and plateau pressure or peak pressure ≤30 cm H2O). Adjunctive therapies were received by 86% (n = 172) of patients at some stage from enrolment to day 28. Systemic steroids were most used (n = 127) followed by neuromuscular blockers (n = 122) and prone positioning (n = 27). Median ventilator-free days (IQR) to day 28 was 5 (0, 20). In-hospital mortality, censored at day 28, was 30.5% (n = 61). Conclusions: In Australia and New Zealand, compliance with evidence-based practices including LPV and prone positioning was low in this cohort. Therapies with proven benefit in the treatment of patients with moderate-severe ARDS, such as lung protective ventilation and prone positioning, were not routinely employed.

Prospective Evaluation of Extubation Failure in Neonates and Infants After Cardiac Surgery.

Background: Extubation failure and its associated complications are not uncommon after pediatric cardiac surgery, especially in neonates and young infants. We aimed to identify the frequency, etiologies, and clinical characteristics associated with extubation failure after cardiac surgery in neonates and young infants. Methods: We conducted a single center prospective observational study of patients ≤180 days undergoing cardiac surgery between June 2022 and May 2023 with at least one extubation attempt. Patients who failed extubation, defined as reintubation within 72 h of first extubation attempt, were compared with patients extubated successfully using χ2, Fisher exact, or Wilcoxon rank-sum tests as appropriate. Results: We prospectively enrolled 132 patients who met inclusion criteria, of which 11 (8.3%) failed extubation. Median time to reintubation was 25.5 h (range 0.4-55.8). Extubation failures occurring within 12 h (n = 4) were attributed to upper airway obstruction or apnea, whereas extubation failures occurring between 12 and 72 h (n = 7) were more likely to be due to intrinsic lung disease or cardiac dysfunction. Underlying genetic anomalies, greater weight relative to baseline at extubation, or receiving positive end expiratory pressure (PEEP) > 5 cmH2O at extubation were significantly associated with extubation failure. Conclusions: In this study of neonates and young infants recovering from cardiac surgery, etiologies of early versus later extubation failure involved different pathophysiology. We also identified weight relative to baseline and PEEP at extubation as possible modifiable targets for future investigations of extubation failure in this patient population.

Management of analgosedation during noninvasive respiratory support: an expert Delphi consensus document developed by the Italian Society of Anesthesia, Analgesia, Resuscitation and Intensive Care (SIAARTI).

BACKGROUND: Discomfort can be the cause of noninvasive respiratory support (NRS) failure in up to 50% of treated patients. Several studies have shown how analgosedation during NRS can reduce the rate of delirium, endotracheal intubation, and hospital length of stay in patients with acute respiratory failure. The purpose of this project was to explore consensus on which medications are currently available as analgosedatives during NRS, which types of patients may benefit from analgosedation while on NRS, and which clinical settings might be appropriate for the implementation of analgosedation during NRS. METHODS: The Italian Society of Anesthesia, Analgesia, Resuscitation and Intensive Care (SIAARTI) selected a panel of experts and asked them to define key aspects of the use of analgesics and sedatives during NRS treatment. The methodology applied is in line with the principles of the modified Delphi and RAND-UCLA methods. The experts developed statements and supportive rationales which were then subjected to blind votes for consensus. RESULTS: The use of an analgosedation strategy in adult patients with acute respiratory failure of different origins may be useful where there is a need to manage discomfort. This strategy should be considered after careful assessment of other potential factors associated with respiratory failure or inappropriate noninvasive respiratory support settings, which may, in turn, be responsible for NRS failure. Several drugs can be used, each of them specifically targeted to the main component of discomfort to treat. In addition, analgosedation during NRS treatment should always be combined with close cardiorespiratory monitoring in an appropriate clinical setting. CONCLUSIONS: The use of analgosedation during NRS has been studied in several clinical trials. However, its successful application relies on a thorough understanding of the pharmacological aspects of the sedative drugs used, the clinical conditions for which NRS is applied, and a careful selection of the appropriate clinical setting.

[Clinical-demographic characteristics of tracheostomized patients with chronic obstructive pulmonary disease] / Características clínico-demográficas de pacientes traqueostomizados con enfermedad pulmonar obstructiva crónica.

Tracheostomy (TQT) has emerged as a valuable alternative for patients with orotracheal intubation, especially those under prolonged mechanical ventilation (VMP), as in the case of chronic obstructive pulmonary disease (COPD). This population presents additional challenges, and the available information regarding their progression in specialized centers is limited in Argentina.A descriptive, retrospective, and cross-sectional study was conducted at Santa Catalina Neurorehabilitation Clinic between August 2015 and December 2018. Patients with COPD referred to the Intensive Care Unit (ICU), tracheostomized, and subsequently referred to the Center for Ventilation Disconnection and Rehabilitation (CDVMR) were included. Cases with missing data or derived from other CDVMRs were excluded. Clinical records and interviews were employed to collect demographic and progression data.Out of the 27 COPD patients included (4.9% of 555), the majority were males (63%) with an average age of 68.1 years. Most were admitted with AVMi, and 11 (45.8%) were successfully disconnected, while 11 (40.7%) were decannulated. Survival and home discharge were more frequent in decannulated patients (81.8% were discharged) compared to non-decannulated ones (50% deceased, and none were discharged).COPD patients undergoing TQT and VMP, who succeed in being decannulated, seem to have better prospects for survival and home discharge compared to those who do not have the cannula removed. There is a suggestion for the need for additional analytical studies to confirm these findings and improve the understanding of this specific population.

La traqueostomía (TQT) es una una alternativa valiosa para pacientes con intubación orotraqueal, especialmente aquellos bajo ventilación mecánica prolongada (VMP), como en el caso de la enfermedad pulmonar obstructiva crónica (EPOC). Esta población presenta desafíos adicionales,  la información disponible sobre su evolución en centros especializados es limitada en Argentina.Se realizó un estudio descriptivo, retrospectivo y transversal en  Santa Catalina Neurorehabilitación Clínica entre agosto de 2015 y diciembre de 2018. Se incluyeron pacientes EPOC derivados a la unidad de terapia intensiva (UTI), traqueostomizados y posteriormente remitidos al Centro de Desvinculación de Ventilación Mecánica y Rehabilitación (CDVMR). Se excluyeron casos con datos faltantes o derivados de otros CDVMR. Se emplearon registros clínicos y entrevistas para recolectar datos demográficos y de evolución.De los 27 pacientes con EPOC incluidos (4.9% de 555), la mayoría eran hombres (63%) con una edad promedio de 68.1 años. La mayoría ingresó con AVMi, y se logró desvincular a 11 (45.8%) y decanular a 11 (40.7%) pacientes. La sobrevida y el alta domiciliaria fueron más frecuentes en pacientes decanulados (81.8% recibieron el alta) en comparación con los no decanulados (50% fallecieron y ninguno recibió el alta).Los pacientes EPOC sometidos a TQT y VMP, que logran ser decanulados, parecerían tener mejores perspectivas de sobrevida y alta domiciliaria en comparación con aquellos que no se les retira la cánula. Se sugiere la necesidad de estudios analíticos adicionales para confirmar estos hallazgos y mejorar la comprensión de esta población específica.

Towards an improved wind effect assessment for asbestos abatement: A methodology for reduced-scale experiments.

During building renovation or demolition, asbestos fibers can be released which can contaminate the environment, leading to potential occupational health and public health concerns. Strict asbestos abatement procedures and regulations are in place to mitigate this risk, which involve sealing the worksite and depressurizing it relative to the outdoor environment (i.e., indoor pressure lower than the outdoor pressure) using mechanical ventilation. However, the depressurization of the containment can be breached by the effects of the wind. Hence, it is essential to identify which wind conditions are problematic and how to prevent their effects. To conduct corresponding laboratory measurements, it is first required to scale down the building and its containment zone including a working mechanical ventilation system. This paper presents an innovative methodology for conducting reduced-scale experiments on buildings equipped with mechanical ventilation systems for contaminant containment. The methodology, here explained in the context of asbestos abatement, could also be applied to any other type of particulate pollutant. The methodology of this research study includes the design of a mechanical ventilation system for depressurization; a method to scale down the building and the ventilation system for testing in a wind tunnel; and 3D steady Reynolds averaged Navier-Stokes (RANS) simulations for optimizing the positioning of the ventilation components. The methodology is applied for a single-zone building including its ventilation system, which is found to achieve the targeted indoor depressurization of -40 Pa, making it ready for wind tunnel tests.

The relationship between positive end-expiratory pressure (PEEP) and intra-abdominal pressure (IAP) in mechanically ventilated patients: A prospective observational study.

BACKGROUND: Positive end-expiratory pressure is a crucial mechanical breathing parameter. Intra-abdominal hypertension is well defined as a sustained increase in the intra-abdominal pressure ≥12 mmHg. There are still controversies about mechanical ventilation's effect and use of positive end-expiratory pressure on intra-abdominal pressure. AIMS: We aimed to delineate the relationship between positive end-expiratory pressure and intra-abdominal pressure in mechanically ventilated patients admitted to the intensive care units of a large tertiary hospital in Upper Egypt. STUDY DESIGN: This study was a prospective observational study. The study was conducted at a university hospital from October 2023 to February 2024. The enrolled adult patients were allocated into two groups based on their positive end-expiratory pressure: group I, low pressure (<8 cm H2O) and group II, high pressure (8-10 cm H2O). RESULTS: A total of 120 patients were enrolled, 60 patients in each group. The most commonly encountered diagnoses were pneumonia (32/120, 26.7%) and acute respiratory distress syndrome (ARDS) (31/120, 25.8%), respectively. There was a significant difference between the intra-abdominal pressure mean values of the two patient groups, 18.9 ± 3.3 versus 24.4 ± 5.9 mmHg in the group of low versus high pressure (correlation value of .454, p < .001), respectively. There were highly significant correlations between intra-abdominal pressure categories and the patient groups (correlation value of .495, p < .001). There were 24 (40%) versus 0 (0%) patients of high pressure versus low pressure within the category IV group of intra-abdominal hypertension (>25 mmHg). CONCLUSIONS: We observed a significant relationship between positive end-expiratory pressure and intra-abdominal pressure in mechanically ventilated patients. The patient group with high pressure had higher mean values compared with the group with low pressure. The study highlights the importance of closely monitoring intra-abdominal pressure in mechanically ventilated patients who receive positive end-expiratory pressure. Further studies are warranted. RELEVANCE TO CLINICAL PRACTICE: The relationship between positive end-expiratory pressure and intra-abdominal pressure is an essential issue in daily critical care nursing clinical practice. Considering the occurrence of multiple organ dysfunction as a result of a non-detected increase in intra-abdominal pressure, critical care nurses should pay attention to measuring this pressure to maintain intra-abdominal pressures that are safe for mechanically ventilated and critically ill intensive care unit patients, thereby preventing these undue effects.

Independent Risk Factors and Economic Burden Associated With Delayed Extubation Following Pediatric Liver Transplantation.

BACKGROUND: Successful early extubation (EE) after liver transplant (LT) has been shown to reduce intensive care unit (ICU) and hospital length of stay and infectious, vascular, and sedation-related complications in adults. EE may not always be feasible in children, and many may require prolonged mechanical ventilation. Limited data exists regarding the candidacy of EE, risk factors, consequences, and hospital costs of delayed extubation (DE) in pediatric LT. METHODS: We conducted a retrospective review to investigate predictive factors and associated costs of EE and DE in infants and children after orthotopic LT at our institution between 2011 and 2021. RESULTS: Of 338 LT (median age 39 months, 54% females), 246 (73%) had EE (within 24 h of LT), while 27% had DE. Age < 1 year (p = 0.0019), diagnosis of biliary atresia (0.02), abnormal pre-LT echocardiogram (0.02), and patients with ongoing hospital admission before LT (0.0001) were independently associated with DE. Hospital costs were significantly (∼3-fold) higher (p < 0.0001) in the DE group. In addition, factors associated with increased total hospital costs were age < 1 year and hospitalization before LT. CONCLUSION: EE post-LT is feasible and merits a trial. The prevalence of DE though modest is associated with increased resource utilization and hospital costs. Children who can be extubated early and those at risk for DE can be identified pre-operatively for optimal planning and allocation of resources.

Evaluation of lung homogeneity in neonates and small infants during general anaesthesia using electrical impedance tomography: a prospective observational study.

Background: Prolonged mechanical ventilation can create heterogeneous ventilation patterns, which increase the risk of lung injury in infants. However, little is understood about the risk of brief exposure to mechanical ventilation during anaesthesia. The aim of this prospective observational study was to describe the regional pattern of lung ventilation during general anaesthesia in healthy neonates and infants, using electrical impedance tomography. Methods: Twenty infants (age 3 days to 12 months), without known lung disease and receiving general anaesthesia with endotracheal intubation for supine positioned surgery, were included in the study. Anaesthesia and ventilation management was at the discretion of the treating clinician. Standardised lung imaging using electrical impedance tomography was made at six time points during anaesthesia from induction to post-extubation. At each time point, the gravity-dependent and right-left lung centre of ventilation was calculated. Results: Tidal ventilation favoured the dorsal lung regions at induction, with a median (inter-quartile range) centre of ventilation (CoV) of 58.2 (53.9-59.3)%. After intubation, there was a redistribution of ventilation to the ventral lung, with the greatest change occurring early in surgery: CoV of 53.8 (52.3-55.2)%. After extubation, CoV returned to pre-intubation values: 56.5 (54.7-58)%. Across all time points, the pattern of ventilation favoured the right lung. Conclusions: General anaesthesia creates heterogenous patterns of ventilation similar to those reported during prolonged mechanical ventilation. This potentially poses a risk for lung injury that may not be recognised clinically. These results suggest the need to better understand the impact of general anaesthesia on the developing lung. Clinical trial registration: Australian New Zealand Clinical Trials Registry (ACTRN 12616000818437, 22 June 2016).

Pulmonary Shunt in Critical Care: A Comprehensive Review of Pathophysiology, Diagnosis, and Management Strategies.

Pulmonary shunt, an abnormal passage of blood through the pulmonary circulation without adequate gas exchange, poses significant challenges in critical care. This comprehensive review explores the pathophysiology, diagnostic approaches, and management strategies associated with pulmonary shunt. Pulmonary shunts are classified into anatomical and physiological types, each with distinct mechanisms and implications for gas exchange. Anatomical shunts result from structural heart defects, while physiological shunts arise from ventilation-perfusion (V/Q) mismatches. Both conditions can significantly impair oxygenation and contribute to multi-organ dysfunction. This review delves into various diagnostic modalities, including clinical assessment, imaging techniques such as chest X-ray and CT scans, and advanced diagnostic methods such as V/Q scanning and echocardiography. Challenges in diagnosing pulmonary shunt are discussed, emphasizing the limitations of current tools and the need for accurate differentiation of shunt types. Management strategies are examined, covering pharmacological interventions, non-pharmacological treatments such as mechanical ventilation and prone positioning, and surgical options. Emerging therapies and innovations in treatment are also highlighted. Special considerations are given to different patient populations, including pediatric and elderly patients and those with multiple comorbidities. This review concludes with an analysis of the prognosis and outcomes associated with pulmonary shunt, focusing on short-term and long-term impacts on survival and quality of life. This review aims to enhance understanding and guide effective management practices for pulmonary shunt in critical care settings by synthesizing current knowledge and identifying areas for further research.

Influence of echo time on pulmonary ventilation and perfusion derived by phase-resolved functional lung (PREFUL) MRI using multi-echo ultrashort echo time acquisition.

Non-contrast enhanced 1H magnetic resonance imaging (MRI) is promising for ventilation/perfusion (V/Q) assessment of the lung but the influence of the echo time (TE) on V/Q parameters is lacking. Therefore, the purpose of this study was to investigate the influence of different TEs on pulmonary V/Q parameters derived by phase-resolved functional lung (PREFUL) MRI using a multi-echo ultrashort TE (UTE) acquisition. A 2D multi-echo UTE sequence with radial center out readout and tiny golden angle increment was developed. Forty-eight participants were enrolled in this study: 25 healthy subjects, six patients with asthma, and 17 patients with pulmonary fibrosis. Participants underwent two acquisitions of 2D multi-echo UTE MRI with three TEs per acquisition (TE1-6: 0.07, 0.82, 1.72, 2.47, 3.37, and 4.12 ms). Regional ventilation (RVent), flow-volume loop cross-correlation metric (FVL-CM), and normalized perfusion-weighted signal (QN) maps were calculated. V/Q defect percentages (VDP/QDP) were determined. To assess repeatability, the measurement was repeated in healthy subjects. Median and interquartile range of RVent, FVL-CM, QN, VDP, and QDP were calculated. To assess significant differences between parameters obtained at different TEs, Friedman's test and Dunnett's test were performed. Pearson correlation coefficients between RVent derived at TE1 and the difference in RVent between TE2,3 and TE1 were calculated. For repeatability assessment, coefficient of variation (CoV) and intraclass correlation coefficient (ICC) were determined. Significant differences were found comparing V/Q parameters obtained at TE3-6 compared to TE1. CoV increased with TE. For ICC, values between 0.35 (QDP at TE1) and 0.83 (VDPRVent at TE2) were obtained for T1,2. Statistically significant differences for ventilation and perfusion parameters derived by PREFUL were found for TE3-6 compared to TE1. All V/Q parameters were well repeatable for TE1-2. With increasing TE and respiratory volume, RVent shows a T2*-dependency leading to biased ventilation assessment compared to TE1.

Emergency Knowledge Translation, COVID-19 and indoor air: evaluating a virtual ventilation and filtration consultation program for community spaces in Ontario.

BACKGROUND: An October, 2021 review of Public Health Ontario's COVID-19 guidance for congregate settings such as shelters and long-term care homes demonstrated that this guidance did not include references to ventilation or filtration. In April 2022, an interdisciplinary team with expertise in indoor air quality (IAQ), engineering, epidemiology, community programming and knowledge translation launched a virtual ventilation and filtration consultation program for community spaces in Toronto, Ontario. The program gives people working in community spaces direct access to IAQ experts through 25-min online appointments. The program aims to help reduce the risk of COVID-19 transmission in community spaces, and was designed to help compensate for gaps in public health guidance and action. METHODS: Representatives from participating organizations (n. 27) received a link to an online survey via email in April 2023. Survey questions explored the impacts of the program on topics such as: purchase and use of portable air filters; maintenance and use of bathroom fans; and, maintenance and modification of HVAC systems. Survey participation was anonymous, and no demographic information was collected from participants. RESULTS: Representatives from 11 organizations completed the survey (40%). Of those who responded, nine (82%) made changes as a result of the program, with eight (73%) making two or more changes such as purchasing portable air filters and increasing routine maintenance of HVAC systems. CONCLUSIONS: When presented with brief access to expert support and tailored plain language guidance, people working in community spaces increased their use of ventilation and filtration strategies for COVID-19 infection prevention and control.

Adaptive non-invasive ventilation treatment for sleep apnea.

The purpose of this study was to investigate the effectiveness of two non-invasive mechanical ventilation (NIV) modalities to treat sleep apnea: (1) Average Volume Assured Pressure Support (AVAPS) NIV, and (2) Pressure Support (PS) NIV with Continuously Calculated Average Required Ventilation (CCARV). Two detailed (previously developed and tested) simulation models were used to assess the effectiveness of the NIV modalities. One simulated subjects without chronic obstructive pulmonary disease (COPD), and the other simulated patients with COPD. Sleep apnea was simulated in each model (COPD and Non-COPD), and the ability of each NIV modality to normalize breathing was measured. In both NIV modalities, a low level continuous positive airway pressure was used and a backup respiratory rate was added to the algorithm in order to minimize the respiratory work rate. Both modalities could help normalize breathing in response to an episode of sleep apnea within about 5 min (during which time blood gases were within safe limits). AVAPS NIV and PS NIV with CCARV have potential value to be used for treatment of sleep apnea. Clinical evaluations are needed to fully assess the effectiveness of these NIV modalities.

Comparison of Modified ROX Index Score and ROX Index Score for Early Prediction of High Flow Nasal Oxygen Therapy Outcome in Patients with Acute Respiratory Failure: A Prospective Observational Cohort Study.

Background: We compared the modified ROX index and ROX index scores in earlier predictions of high-flow nasal oxygen (HFNO) therapy outcomes in patients with acute respiratory failure. Methods: We conducted a prospective observational study on 151 acute respiratory failure patients initiated on HFNO therapy. The primary objective of this research was to compare the modified ROX index and ROX index to investigate which score predicted HFNO treatment outcome earlier. Results: The modified ROX index score had better predictive power than the ROX score at different time points, especially one hour following the start of HFNO therapy (AUC 0.790; 95% CI: 0.717-0.863; p < 0.001). For the ROX Index at 1 hour, the ideal cut-off value for HFNO outcome was 4.36 (sensitivity: 72.6%, specificity: 53.9%), and for the modified ROX index at 1 hour, it was 4.63 (sensitivity: 74.2%, specificity: 69.7%). The presence of various comorbidities didn't show any change in ROX-HR cut-off values. Conclusion: The modified ROX index is a better predictor of the success of HFNO therapy than the ROX index. Furthermore, the presence of any comorbidities did not affect modified ROX index cut-off values or the outcome of HFNO therapy. How to cite this article: Sarkar AG, Sharma A, Kothari N, Goyal S, Meshram T, Kumari K, et al. Comparison of Modified ROX Index Score and ROX Index Score for Early Prediction of High Flow Nasal Oxygen Therapy Outcome in Patients with Acute Respiratory Failure: A Prospective Observational Cohort Study. Indian J Crit Care Med 2024;28(9):842-846.

Ventilation does not affect close-range transmission of influenza virus in a ferret playpen setup.

Sustained community spread of influenza viruses relies on efficient person-to-person transmission. Current experimental transmission systems do not mimic environmental conditions (e.g., air exchange rates, flow patterns), host behaviors, or exposure durations relevant to real-world settings. Therefore, results from these traditional systems may not be representative of influenza virus transmission in humans. To address this pitfall, we developed a close-range transmission setup that implements a play-based scenario and used it to investigate the impact of ventilation rates on transmission. In this setup, four immunologically naive recipient ferrets were exposed to a donor ferret infected with a genetically barcoded 2009 H1N1 virus (H1N1pdm09) for 4 h. The ferrets interacted in a shared space that included toys, similar to a childcare setting. Transmission efficiency was assessed under low and high ventilation, with air exchange rates of ~1.3 h-1 and 23 h-1, respectively. Transmission efficiencies observed in three independent replicate studies were similar between ventilation conditions. The presence of infectious virus or viral RNA on surfaces and in air throughout the exposure area was also not impacted by the ventilation rate. While high viral genetic diversity in donor ferret nasal washes was maintained during infection, recipient ferret nasal washes displayed low diversity, revealing a narrow transmission bottleneck regardless of ventilation rate. Examining the frequency and duration of ferret physical touches revealed no link between these interactions and a successful transmission event. Our findings indicate that exposures characterized by frequent, close-range interactions and the presence of fomites can overcome the benefits of increased ventilation.

Optimization of ventilation efficiency in tunnel-type underground spaces using response surface methodology: a case study of Yunlong Mountain civil defense in Xuzhou.

Civil defense projects, designed as wartime underground spaces, often lack effective natural ventilation and have considerable depth, which complicates their use as public spaces in peacetime. However, the application of passive ventilation technologies can create effective airflow channels within these structures, significantly enhancing ventilation efficiency and thus improving the overall thermal comfort level. For this study, air age, along with average wind speed, temperature, and relative humidity as stipulated by the "Requirements for Environmental Sanitation of Civil Air Defense Works during Peacetime Use" (GBT 17216-2012), were selected as evaluation metrics. This paper compares the ventilation effectiveness between single ventilation shafts and multiple ventilation shafts under positive and negative pressure conditions in underground civil defense structures. The results indicate that negative pressure ventilation in multiple shaft configurations performs optimally across various ventilation approaches. Subsequently, the Response Surface Methodology (RSM) was utilized to further optimize the positioning of multiple ventilation shafts. The study examined the impact of three ventilation shaft locations on average wind speed, temperature, relative humidity, and air age, leading to an optimized design. Specifically, the optimal positions are 54.76 m for Shaft A, 51.45 m for Shaft B, and 79.85 m for Shaft C, achieving an average wind speed of 0.222 m/s, a temperature of 26 °C, a relative humidity reduction to 85.47%, and an average air age of 10.57 s. This research provides practical insights for the optimization of ventilation in underground civil defense facilities.

Sedation Vacations in Neurocritical Care: Friend or Foe?

PURPOSE OF REVIEW: To evaluate the role of sedation vacations in optimizing patient outcomes and enhancing the quality of care in neurological intensive care units (ICUs). We discuss the importance of sedation management in neurocritical care, considering recent research findings and clinical guidelines. RECENT FINDINGS: Recent studies have highlighted the significance of sedation interruption protocols in improving patient outcomes in the ICU setting. Evidence suggests that daily sedation interruptions can reduce the duration of mechanical ventilation, ICU length of stay, and mortality rates. However, the implementation of these protocols requires careful consideration of patient-specific factors and a multidisciplinary approach. Sedation vacations play a critical role in neurocritical care by reducing mechanical ventilation duration, ICU stay length, and mortality rates. Despite the benefits, the presence of complications must be addressed to avoid adverse outcomes. Continued research is necessary to refine these strategies and improve guideline quality, ensuring safe and effective sedation management in critically ill neurological patients.

Phenotypes based on respiratory drive and effort to identify the risk factors when P0.1 fails to estimate ∆PES in ventilated children.

BACKGROUND: Monitoring respiratory effort and drive during mechanical ventilation is needed to deliver lung and diaphragm protection. Esophageal pressure (∆PES) is the gold standard measure of respiratory effort but is not routinely available. Airway occlusion pressure in the first 100 ms of the breath (P0.1) is a readily available surrogate for both respiratory effort and drive but is only modestly correlated with ∆PES in children. We sought to identify risk factors for P0.1 over or underestimating ∆PES in ventilated children. METHODS: Secondary analysis of physiological data from children and young adults enrolled in a randomized controlled trial testing lung and diaphragm protective ventilation in pediatric acute respiratory distress syndrome (PARDS) (NCT03266016). ∆PES (∆PES-REAL), P0.1 and predicted ∆PES (∆PES-PRED = 5.91*P0.1) were measured daily to identify phenotypes based upon the level of respiratory effort and drive: one passive (no spontaneous breathing), three where ∆PES-REAL and ∆PES-PRED were aligned (low, normal, and high effort and drive), two where ∆PES-REAL and ∆PES-PRED were mismatched (high underestimated effort, and overestimated effort). Logistic regression models were used to identify factors associated with each mismatch phenotype (High underestimated effort, or overestimated effort) as compared to all other spontaneous breathing phenotypes. RESULTS: We analyzed 953 patient days (222 patients). ∆PES-REAL and ∆PES-PRED were aligned in 536 (77%) of the active patient days. High underestimated effort (n = 119 (12%)) was associated with higher airway resistance (adjusted OR 5.62 (95%CI 2.58, 12.26) per log unit increase, p < 0.001), higher tidal volume (adjusted OR 1.53 (95%CI 1.04, 2.24) per cubic unit increase, p = 0.03), higher opioid use (adjusted OR 2.4 (95%CI 1.12, 5.13, p = 0.024), and lower set ventilator rate (adjusted OR 0.96 (95%CI 0.93, 0.99), p = 0.005). Overestimated effort was rare (n = 37 (4%)) and associated with higher alveolar dead space (adjusted OR 1.05 (95%CI 1.01, 1.09), p = 0.007) and lower respiratory resistance (adjusted OR 0.32 (95%CI 0.13, 0.81), p = 0.017). CONCLUSIONS: In patients with PARDS, P0.1 commonly underestimated high respiratory effort particularly with high airway resistance, high tidal volume, and high doses of opioids. Future studies are needed to investigate the impact of measures of respiratory effort, drive, and the presence of a mismatch phenotype on clinical outcome. TRIAL REGISTRATION: NCT03266016; August 23, 2017.

Heterogeneous impact of Sighs on mortality in patients with acute hypoxemic respiratory failure: insights from the PROTECTION study.

BACKGROUND: Sigh breaths may impact outcomes in acute hypoxemic respiratory failure (AHRF) during assisted mechanical ventilation. We investigated whether sigh breaths may impact mortality in predefined subgroups of patients enrolled in the PROTECTION multicenter clinical trial according to: 1.the physiological response in oxygenation to Sigh (responders versus non-responders) and 2.the set levels of positive end-expiratory pressure (PEEP) (High vs. Low-PEEP). If mortality differed between Sigh and No Sigh, we explored physiological daily differences at 7-days. RESULTS: Patients were randomized to pressure support ventilation (PSV) with Sigh (Sigh group) versus PSV with no sigh (No Sigh group). (1) Sighs were not associated with differences in 28-day mortality in responders to baseline sigh-test. Contrarily-in non-responders-56 patients were randomized to Sigh (55%) and 28-day mortality was lower with sighs (17%vs.36%, log-rank p = 0.031). (2) In patients with PEEP > 8cmH2O no difference in mortality was observed with sighs. With Low-PEEP, 54 patients were randomized to Sigh (48%). Mortality at 28-day was reduced in patients randomised to sighs (13%vs.31%, log-rank p = 0.021). These findings were robust to multivariable adjustments. Tidal volume, respiratory rate and ventilatory ratio decreased with Sigh as compared with No Sigh at 7-days. Ventilatory ratio was associated with mortality and successful extubation in both non-responders and Low-PEEP. CONCLUSIONS: Addition of Sigh to PSV could reduce mortality in AHRF non-responder to Sigh and exposed to Low-PEEP. Results in non-responders were not expected. Findings in the low PEEP group may indicate that insufficient PEEP was used or that Low PEEP may be used with Sigh. Sigh may reduce mortality by decreasing physiologic dead space and ventilation intensity and/or optimizing ventilation/perfusion mismatch. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; Identifier: NCT03201263.