Conventional Mechanical Ventilation Research Articles

Extracorporeal carbon dioxide removal for acute hypercapnic respiratory failure in a child with cystic fibrosis

Background. Acute respiratory failure is a prevalent condition in childhood with a high rate of mortality. Invasive mechanical ventilation support may be required for the management of these patients. Extracorporeal membrane oxygenation (ECMO) is a method used when ventilation support is insufficient. However, the less invasive extracorporeal carbon dioxide removal method can be used as an alternative in cases of hypercapnic respiratory failure. Case. A 9-year-old patient with cystic fibrosis presented to the hospital with acute respiratory failure due to pneumonia. Bilateral patchy areas of consolidation were evident in the chest x-ray. Invasive mechanical ventilation support was consequently provided to treat severe hypercapnia. Although peak and plateau pressure levels exceeded 32 cmH₂O (49 cmH₂O) and 28 cmH₂O (35 cmH₂O), respectively, the patient continued to have severe respiratory acidosis. Therefore extracorporeal carbon dioxide removal support was initiated to provide lung-protective ventilation. By Day 10, venovenous ECMO support was initiated due to deteriorating oxygenation. Conclusion. In cases where conventional invasive mechanical ventilation support is insufficient due to acute hypercapnic respiratory failure, extracorporeal carbon dioxide removal support, which is less invasive compared to ECMO, should be considered as an effective and reliable alternative method. However, it should be noted that extracorporeal carbon dioxide removal support does not affect oxygenation; it functions solely as a carbon dioxide removal system.

Early pathophysiology-driven airway pressure release ventilation versus low tidal volume ventilation strategy for patients with moderate-severe ARDS: study protocol for a randomized, multicenter, controlled trial

BackgroundConventional Mechanical ventilation modes used for individuals suffering from acute respiratory distress syndrome have the potential to exacerbate lung injury through regional alveolar overinflation and/or repetitive alveolar collapse with shearing, known as atelectrauma. Animal studies have demonstrated that airway pressure release ventilation (APRV) offers distinct advantages over conventional mechanical ventilation modes. However, the methodologies for implementing APRV vary widely, and the findings from clinical studies remain controversial. This study (APRVplus trial), aims to assess the impact of an early pathophysiology-driven APRV ventilation approach compared to a low tidal volume ventilation (LTV) strategy on the prognosis of patients with moderate to severe ARDS.MethodsThe APRVplus trial is a prospective, multicenter, randomized clinical trial, building upon our prior single-center study, to enroll 840 patients from at least 35 hospitals in China. This investigation plans to compare the early pathophysiology-driven APRV ventilation approach with the control intervention of LTV lung-protective ventilation.The primary outcome measure will be all-cause mortality at 28 days after randomization in the intensive care units (ICU). Secondary outcome measures will include assessments of oxygenation, and physiology parameters at baseline, as well as on days 1, 2, and 3. Additionally, clinical outcomes such as ventilator-free days at 28 days, duration of ICU and hospital stay, ICU and hospital mortality, and the occurrence of adverse events will be evaluated.Trial ethics and disseminationThe research project has obtained approval from the Ethics Committee of West China Hospital of Sichuan University (2019-337). Informed consent is required. The results will be submitted for publication in a peer-reviewed journal and presented at one or more scientific conferences.Trial registrationThe study was registered at Clinical Trials.gov (NCT03549910) on June 8, 2018.

Indications and Short-Term Outcomes of Conventional Mechanical Ventilation in a Neonatal Intensive Care Unit of a Tertiary Care Hospital in a Developing Country

Background: Mechanical ventilation is an advanced intervention employed in neonatal intensive care units (NICUs) to assist neonates who require external ventilation for adequate gas exchange, while minimizing associated complications. Understanding the indications and short-term outcomes of mechanical ventilation is crucial for improving neonatal care, especially in developing countries with limited resources. Objective: To examine the indications and short-term outcomes of conventional mechanical ventilation in a neonatal intensive care unit of a tertiary care hospital in a developing country. Methods: This descriptive cross-sectional study was conducted from July 2022 to February 2023 in the Department of Paediatrics at Combined Military Hospital, Kharian. The study included 227 pediatric patients admitted to the NICU for mechanical ventilation, selected via consecutive non-probability sampling. Written informed consent was obtained from parents or guardians. Data collected included neonatal and pregnancy parameters, primary indication for mechanical ventilation, duration of mechanical ventilation, and length of hospital stay. Patients were monitored for complications such as pneumothorax, sepsis, and ventilator-associated pneumonia. Statistical analysis was performed using IBM SPSS Statistics for Windows, version 26.0. Quantitative variables were expressed as mean ± standard deviation or median and interquartile range, while qualitative variables were presented as frequencies and percentages. Comparisons were made using the Chi-square test, Fisher's exact test, independent samples t-test, or Mann-Whitney U test as appropriate, with a p-value of ≤0.05 considered significant. Results: The study included 128 males (56.4%) and 99 females (43.6%). The mean gestational age at birth was 36.4 ± 1.5 weeks, and the mean birth weight was 2994.1 ± 450.1 grams. Common indications for mechanical ventilation included pneumonia (26.4%), respiratory distress syndrome (24.7%), and sepsis (18.5%). The mean duration of mechanical ventilation was 7.1 ± 2.5 days, and the mean length of hospital stay was 13.4 ± 6.0 days. Complications were observed in 29.5% of patients, with ventilator-associated pneumonia (18.1%) being the most common, followed by sepsis (9.7%) and pneumothorax (5.3%). The overall mortality rate was 18.5%. Significant associations were found between mortality and duration of mechanical ventilation (p<0.001), occurrence of complications (p<0.001), and requirement for re-intubation (p<0.001). Conclusion: The study highlights the significant association between prolonged mechanical ventilation, the development of complications, and increased mortality in neonates. Effective strategies to prevent and manage complications, as well as to limit the duration of mechanical ventilation, are essential to improve neonatal outcomes in resource-limited settings.

Apnea Testing on Conventional Mechanical Ventilation During Brain Death Evaluation.

The use of continuous positive airway pressure has been shown to improve the tolerance of the apnea test, a critical component of brain death evaluation. The ability to deactivate the apnea backup setting has made apnea testing possible using several conventional mechanical ventilators. Our goal was to evaluate the safety and efficacy of apnea testing performed on mechanical ventilation, compared with the oxygen insufflation technique, for the determination of brain death. This was a retrospective study. In 2016, our institution approved a change in policy to permit apnea testing on conventional mechanical ventilation. We examined the records of consecutive adults who underwent apnea testing as part of the brain death evaluation process between 2016 and 2022. Using an apnea test technique was decided at the discretion of the attending physician. Outcomes were successful apnea test and the occurrence of patient instability during the test. This included oxygen desaturation (SpO2) < 90%, hypotension (mean arterial pressure < 65mm Hg despite titration of vasopressor), cardiac arrhythmia, pneumothorax, and cardiac arrest. Ninety-two adult patients underwent apnea testing during the study period: 58 (63%) with mechanical ventilation, 32 (35%) with oxygen insufflation, and 2 (2%) lacked documentation of technique. Apnea tests could not be completed successfully in 3 of 92 (3%) patients-two patients undergoing the oxygen insufflation technique (one patient with hypoxemia and one patient with hypotension) and one patient on mechanical ventilation (aborted for hemodynamic instability). Hypoxemia occurred in 4 of 32 (12.5%) patients with oxygen insufflation and in zero patients on mechanical ventilation (p = 0.01). Hypotension occurred during 3 of 58 (5%) tests with mechanical ventilation and 4 of 32 (12.5%) tests with oxygen insufflation (p = 0.24). In multivariate analysis, the use of oxygen insufflation was an independent predictor of patient instability during the apnea test (odds ratio 37.74, 95% confidence interval 2.74-520.14). Apnea testing on conventional mechanical ventilation is feasible and offers several potential advantages over other techniques.

Lung behavior during a staircase high-frequency oscillatory ventilation recruitment maneuver

BackgroundLung volume optimization maneuvers (LVOM) are necessary to make physiologic use of high-frequency oscillatory ventilation (HFOV), but lung behavior during such maneuvers has not been studied to determine lung volume changes after initiation of HFOV, to quantify recruitment versus derecruitment during the LVOM and to calculate the time to stabilization after a pressure change.MethodsWe performed a secondary analysis of prospectively collected data in subjects < 18 years on HFOV. Uncalibrated respiratory inductance plethysmography (RIP) tracings were used to quantify lung recruitment and derecruitment during the LVOM inflation and deflation. The time constant was calculated according to the Niemann model.ResultsRIP data of 51 subjects (median age 3.5 [1.7–13.3] months) with moderate-to-severe pediatric acute respiratory distress syndrome (PARDS) in 85.4% were analyzed. Lung recruitment and derecruitment occurred during the LVOM inflation phase upon start of HFOV and between and within pressure changes. At 90% of maximum inflation pressure, lung derecruitment already started during the deflation phase. Time to stable lung volume (time constant) could only be calculated in 26.2% of all pressure changes during the inflation and in 21.4% during the deflation phase, independent of continuous distending pressure (CDP). Inability to calculate the time constant was due to lack of stabilization of the RIP signal or no change in any direction.ConclusionsSignificant heterogeneity in lung behavior during a staircase incremental–decremental LVOM occurred, underscoring the need for higher initial inflation pressures when transitioning from conventional mechanical ventilation (CMV) and a longer time between pressure changes to allow for equilibration.

Weaning strategies for children on home invasive mechanical ventilation.

Children who require home mechanical ventilation (HMV) with an artificial airway or invasive mechanical ventilation (HMV) have a possibility of successful weaning due to the potential of compensatory lung growth. Internationally accepted guidelines on how to wean from HMV in children is not available, we summarize the weaning strategies from the literature reviews combined with our 27-year experience in the Pediatric Home Respiratory Care program at the tertiary care center in Thailand. The readiness to wean is considered in patients with hemodynamic stability, having effective cough measured by maximal inspiratory pressure, requiring a fraction of inspired oxygen (FiO2) < 40%, positive end expiratory pressure <5 cmH2O, and acceptable arterial blood gases. The strategies of weaning is start weaning during the daytime while the child is awake and close monitoring is feasible. Disconnect time is gradually increased through naps and sleeping hours. Weaning from the conventional mechanical ventilator to Bilevel PAP or CPAP are optional. Factors affected the successful weaning are mainly the underlying diseases, complications, growth and development, caregivers, and resources. Weaning should be stopped during acute illness or increased work of breathing. The readiness for decannulation could be determined by using the speaking devices, tracheostomy capping, and measurement of end-expiratory pressure. Polysomnography and airway evaluation by bronchoscopy are recommended before decannulation.Weaning when the child is ready is crucial because living with HMV can be challenging and stressful. Failure to remove a tracheostomy when indicated can result in delayed speech, social problems as well as risk for infection.

Albuterol delivery via in-line intrapulmonary percussive ventilation superimposed on conventional mechanical ventilation in an adult lung model.

Background: Intrapulmonary percussive ventilation (IPV) is frequently used for airway clearance, together with delivery of aerosols containing medications. Drug delivery via IPV alone increases with decreasing percussion frequency and correlates with tidal volume (VT) while drug delivery via IPV during conventional mechanical ventilation (IPV/CMV) is not well characterized. We hypothesized that drug delivery via IPV/CMV would take place differently from that via IPV alone due to control of ventilation by CMV. Methods: An adult ventilator circuit was used for IPV/CMV. A normal or diseased lung model was configured to airway resistance (Raw) 5 cm H2O/L/s and lung compliance (CL) 100 mL/cm H2O or Raw 20 cm H2O/L/s and CL 50 mL/cm H2O, respectively. The ventilator settings were: pressure control continuous mandatory ventilation mode, 10 breaths/min, PEEP 5 cm H2O, FIO2 0.21, inspiratory time 1 s, no bias flow, and inspiratory pressure 10 or 15 cm H2O for the normal or diseased lung model, respectively, to reach VT 500 mL with IPV off. Albuterol nebulized from Phasitron 5 was captured in a filter placed before the lung model and quantitated by spectrophotometry. Results: The maximal efficiency of albuterol delivery via IPV/CMV was not different from that via IPV alone (3.7 ± 0.2% vs 4.2 ± 0.3%, mean ± SD of loading dose, P= .12). Albuterol delivery efficiency with IPV/CMV was lower for the diseased lung model than for the normal model (1.6 ± 0.3% vs 3.2 ± 0.5%, mean ± SD, P < .001), which increased with decreasing percussion frequency. In contrast, VT was lower for the normal lung model than for the diseased model (401 ± 14 mL vs 470 ± 11 mL, mean ± SD, P < .001). Conclusions: Albuterol delivery via IPV/CMV was modulated by percussion frequency but not increased with increasing VT The delivery efficiency was not sufficiently high for clinical use, in part due to nebulizer retention and extrapulmonary deposition.

Noninvasive respiratory support in the emergency department: Controversies and state-of-the-art recommendations.

Acute respiratory failure is a common reason for emergency department visits and hospital admissions. Diverse underlying physiologic abnormalities lead to unique aspects about the most common causes of acute respiratory failure: acute decompensated heart failure, acute exacerbation of chronic obstructive pulmonary disease, and acute de novo hypoxemic respiratory failure. Noninvasive respiratory support strategies are increasingly used methods to support work of breathing and improve gas exchange abnormalities to improve outcomes relative to conventional oxygen therapy or invasive mechanical ventilation. Noninvasive respiratory support includes noninvasive positive pressure ventilation and nasal high flow, each with unique physiologic mechanisms. This paper will review the physiology of respiratory failure and noninvasive respiratory support modalities and offer data and guideline-driven recommendations in the context of key clinical controversies.

A Retrospective Cohort Study of the Impact of Implementing Volume-Targeted Compared to Pressure-Limited Ventilation in a Single-Center, Level III Neonatal Intensive Care Unit in Oman.

Background The use of volume-targeted ventilation (VTV) in neonatology has been introduced in the last decade. This study was performed to determine the impact of clinical implementation of volume-targeted conventional mechanical ventilation using the volume guarantee mode in mechanical ventilation of all neonates needing mechanical ventilation compared to pressure-limited ventilation (PLV) modes. The mortality rate, duration of mechanical ventilation, and bronchopulmonary dysplasia were the primary outcomes of the study. Methodology This retrospective cohort study was conducted at a level III-VI neonatal intensive care unit (NICU) within a tertiary academic hospital in Oman. All intubated neonates admitted to the NICU within two time periods, i.e., the PLV cohort: January 2011 to December 2013 (three years), and the VTV cohort: January 2017 to December 2019 (three years), were eligible for inclusion in the study. Neonates were excluded if they had multiple congenital anomalies, tracheostomy, and those with a Do Not Resuscitate status. A predetermined data set was collected retrospectively from electronic records. The PLV and VTV cohorts were compared, and SPSS version 25 (IBM Corp., Armonk, NY, USA) was used for data analysis. Results A total of 290 neonates were included (PLV: n = 138, and VTV: n = 152). The two cohorts were statistically similar in their baseline characteristics, including gestational age, birth weight, Apgar scores, indications for mechanical ventilation, age at intubation, need for surfactant therapy, and age at extubation. The VTV cohort had a significantly lower mortality rate (n (%) = 10 (6.6%) vs. 21 (15.3%), p = 0.02). An insignificant trend of lower duration of ventilation was observed in the VTV cohort (34.5 vs. 50.5 hours, p = 0.24). There was no significant difference in bronchopulmonary dysplasia (16 (21.3%) vs. 12 (17.8%), p = 0.18). VTV was associated with a significant reduction in pulmonary hemorrhage (1 (0.7%) vs. 8 (5.7%), p = 0.04), episodes of hypocapnia (2 vs. 3/patient, p = 0.04), and episodes of hypercapnia (0 vs 1/patient, p = 0.04). Conclusions The implementation of VTV in clinical practice in our level III-VI NICU was associated withsignificant advantages, including reduction in mortality, pulmonary hemorrhage, and episodes of hypercapnia and hypocapnia. A large prospective, randomized, and multicenter trial is recommended to confirm these findings.

Benefits of intratracheal and extrathoracic high-frequency percussive ventilation in a model of capnoperitoneum.

Abdominal inflation with CO2 is used to facilitate laparoscopic surgeries, however, providing adequate mechanical ventilation in this scenario is of major importance during anesthesia management. We characterized high-frequency percussive ventilation (HFPV) in protecting from the gas exchange and respiratory mechanical impairments during capnoperitoneum. In addition, we aimed to assess the difference between conventional pressure-controlled mechanical ventilation (CMV) and HFPV modalities generating the high-frequency signal intratracheally (HFPVi) or extrathoracally (HFPVe). Anesthetized rabbits (n = 16) were mechanically ventilated by random sequences of CMV, HFPVi, and HFPVe. The ventilator superimposed the conventional waveform with two high-frequency signals (5 Hz and 10 Hz) during intratracheal HFPV (HFPVi) and HFPV with extrathoracic application of oscillatory signals through a sealed chest cuirass (HFPVe). Lung oxygenation index ([Formula: see text]/[Formula: see text]), arterial partial pressure of carbon dioxide ([Formula: see text]), intrapulmonary shunt (Qs/Qt), and respiratory mechanics were assessed before abdominal inflation, during capnoperitoneum, and after abdominal deflation. Compared with CMV, HFPVi with additional 5-Hz oscillations during capnoperitoneum resulted in higher [Formula: see text]/[Formula: see text], lower [Formula: see text], and decreased Qs/Qt. These improvements were smaller but remained significant during HFPVi with 10 Hz and HFPVe with either 5 or 10 Hz. The ventilation modes did not protect against capnoperitoneum-induced deteriorations in respiratory tissue mechanics. These findings suggest that high-frequency oscillations combined with conventional pressure-controlled ventilation improved lung oxygenation and CO2 removal in a model of capnoperitoneum. Compared with extrathoracic pressure oscillations, intratracheal generation of oscillatory pressure bursts appeared more effective. These findings may contribute to the optimization of mechanical ventilation during laparoscopic surgery.NEW & NOTEWORTHY The present study examines an alternative and innovative mechanical ventilation modality in improving oxygen delivery, CO2 clearance, and respiratory mechanical abnormalities in a clinically relevant experimental model of capnoperitoneum. Our data reveal that high-frequency oscillations combined with conventional ventilation improve gas exchange, with intratracheal oscillations being more effective than extrathoracic oscillations in this clinically relevant translational model.

Numerical analysis and improvement strategy of particulate matter concentration in underground subway stations

Particulate matter (PM) is an important air pollutant in subway systems. Exposure to high PM concentrations poses a threat to human health and raises concerns. Piston effect can provide the outdoor fresh air to subway stations through station exits, but it also brings PM from tunnels to platforms when the train enters the station. In this paper, a transient numerical model is developed according to an actual subway station and validated by field tests. The model is used to investigate PM10 concentration at platform induced by train movement. The cumulative PM10 concentration at platform in one day is calculated according to the train schedule. Platform screen door (PSD) with adjustable vents is studied to control the PM10 level at platform and energy saving in 27 cities of five climatic zones in China are discussed. The results show that adjustable vent height should be less than 0.70 m to ensure that PM10 concentrations at platform can be maintained at an acceptable level and the requirement of fresh air can be met. Moreover, energy consumption can be reduced by more than 70 % in different cities compared with the conventional mechanical ventilation system. The optimized adjustable vent can provide an important reference for improving indoor air quality (IAQ) and saving energy consumption of ventilation systems in underground facilities.

Successful application of airway pressure release ventilation in a child with severe acute respiratory distress syndrome induced by trauma: a case report

BackgroundTrauma has been identified as one of the risk factors for acute respiratory distress syndrome. Respiratory support can be further complicated by comorbidities of trauma such as primary or secondary lung injury. Conventional ventilation strategies may not be suitable for all trauma-related acute respiratory distress syndrome. Airway pressure release ventilation has emerged as a potential rescue method for patients with acute respiratory distress syndrome and hypoxemia refractory to conventional mechanical ventilation. However, there is a lack of research on the use of airway pressure release ventilation in children with trauma-related acute respiratory distress syndrome. We report a case of airway pressure release ventilation applied to a child with falling injury, severe acute respiratory distress syndrome, hemorrhagic shock, and bilateral hemopneumothorax. We hope this case report presents a potential option for trauma-related acute respiratory distress syndrome and serves as a basis for future research.Case presentationA 15-year-old female with falling injury who developed severe acute respiratory distress syndrome, hemorrhagic shock, and bilateral hemopneumothorax was admitted to the surgical intensive care unit. She presented refractory hypoxemia despite the treatment of conventional ventilation with deep analgesia, sedation, and muscular relaxation. Lung recruitment was ineffective and prone positioning was contraindicated. Her oxygenation significantly improved after the use of airway pressure release ventilation. She was eventually extubated after 12 days of admission and discharged after 42 days of hospitalization.ConclusionAirway pressure release ventilation may be considered early in the management of trauma patients with severe acute respiratory distress syndrome when prone position ventilation cannot be performed and refractory hypoxemia persists despite conventional ventilation and lung recruitment maneuvers.

Detection and quantitative analysis of patient-ventilator interactions in ventilated infants by deep learning networks.

The study of patient-ventilator interactions (PVI) in mechanically ventilated neonates is limited by the lack of unified PVI definitions and tools to perform large scale analyses. An observational study was conducted in 23 babies randomly selected from 170 neonates who were ventilated with SIPPV-VG, SIMV-VG or PSV-VG mode for at least 12 h. 500 breaths were randomly selected and manually annotated from each recording to train convolutional neural network (CNN) models for PVI classification. The average asynchrony index (AI) over all recordings was 52.5%. The most frequently occurring PVIs included expiratory work (median: 28.4%, interquartile range: 23.2-40.2%), late cycling (7.6%, 2.8-10.2%), failed triggering (4.6%, 1.2-6.2%) and late triggering (4.4%, 2.8-7.4%). Approximately 25% of breaths with a PVI had two or more PVIs occurring simultaneously. Binary CNN classifiers were developed for PVIs affecting ≥1% of all breaths (n = 7) and they achieved F1 scores of >0.9 on the test set except for early triggering where it was 0.809. PVIs occur frequently in neonates undergoing conventional mechanical ventilation with a significant proportion of breaths containing multiple PVIs. We have developed computational models for seven different PVIs to facilitate automated detection and further evaluation of their clinical significance in neonates. The study of patient-ventilator interactions (PVI) in mechanically ventilated neonates is limited by the lack of unified PVI definitions and tools to perform large scale analyses. By adapting a recent taxonomy of PVI definitions in adults, we have manually annotated neonatal ventilator waveforms to determine prevalence and co-occurrence of neonatal PVIs. We have also developed binary deep learning classifiers for common PVIs to facilitate their automatic detection and quantification.

Relationship between the Pre-ECMO and ECMO Time and Survival of Severe COVID-19 Patients: A Systematic Review and Meta-Analysis

Background: Coronavirus disease 2019 (COVID-19) is the etiology of acute respiratory distress syndrome (ARDS). Extracorporeal membrane oxygenation (ECMO) is used to support gas exchange in patients who have failed conventional mechanical ventilation. However, there is no clear consensus on the timing of ECMO use in severe COVID-19 patients. Objective: The aim of this study is to compare the differences in pre-ECMO time and ECMO duration between COVID-19 survivors and non-survivors and to explore the association between them. Methods: PubMed, the Cochrane Library, Embase, and other sources were searched until 21 October 2022. Studies reporting the relationship between ECMO-related time and COVID-19 survival were included. All available data were pooled using random-effects methods. Linear regression analysis was used to determine the correlation between pre-ECMO time and ECMO duration. The meta-analysis was registered with PROSPERO under registration number CRD42023403236. Results: Out of the initial 2473 citations, we analyzed 318 full-text articles, and 54 studies were included, involving 13,691 patients. There were significant differences between survivors and non-survivors in the time from COVID-19 diagnosis (standardized mean difference (SMD) = −0.41, 95% confidence interval (CI): [−0.53, −0.29], p &lt; 0.00001), hospital (SMD = −0.53, 95% CI: [−0.97, −0.09], p = 0.02) and intensive care unit (ICU) admission (SMD = −0.28, 95% CI: [−0.49, −0.08], p = 0.007), intubation or mechanical ventilation to ECMO (SMD = −0.21, 95% CI: [−0.32, −0.09], p = 0.0003) and ECMO duration (SMD = −0.18, 95% CI: [−0.30, −0.06], p = 0.003). There was no statistical association between a longer time from symptom onset to ECMO (hazard ratio (HR) = 1.05, 95% CI: [0.99, 1.12], p = 0.11) or time from intubation or mechanical ventilation (MV) and the risk of mortality (highest vs. lowest time groups odds ratio (OR) = 1.18, 95% CI: [0.78, 1.78], p = 0.42; per one-day increase OR = 1.14, 95% CI: [0.86, 1.52], p = 0.36; HR = 0.99, 95% CI: [0.95, 1.02], p = 0.39). There was no linear relationship between pre-ECMO time and ECMO duration. Conclusion: There are differences in pre-ECMO time between COVID-19 survivors and non-survivors, and there is insufficient evidence to conclude that longer pre-ECMO time is responsible for reduced survival in COVID-19 patients. ECMO duration differed between survivors and non-survivors, and the timing of pre-ECMO does not have an impact on ECMO duration. Further studies are needed to explore the association between pre-ECMO and ECMO time in the survival of COVID-19 patients.

Effects of driving pressure-guided ventilation on postoperative pulmonary complications in patients with COVID-19 undergoing abdominal surgery: A post-hoc propensity score-matched analysis

BackgroundApplication of individualized positive end-expiratory pressure (PEEP) based on minimum driving pressure facilitates to prevent from postoperative pulmonary complications (PPCs). Whether lung protective ventilation strategy can reduce the risk of PPCs in COVID-19 patients remains unclear. In this study, we compared the effects of driving pressure-guided ventilation with conventional mechanical ventilation on PPCs in patients with COVID-19. MethodsPatients infected COVID-19 within 30-day before surgery were retrospectively enrolled consecutively. Patients were divided into two group: driving pressure-guided lung protective ventilation strategy group (LPVS group) and conventional mechanical ventilation group (Control group). Propensity score matching for variables selected was used by logistic regression with the nearest-neighbor method. The outcomes were the incidence of PPCs and hypoxemia in post-anesthesia care unit. ResultsThere was no significant difference in the baseline data between both groups (P > 0.05). The incidence of PPCs (12.73 % vs 36.36 %, χ2 = 7.068, P = 0.008) and hypoxemia [18.18 % vs 38.18 %, χ2 = 4.492, P = 0.034], and lung ultrasound scores [4.68 ± 1.60 vs 8.39 ± 1.87, t = 8.383, P < 0.001] in LPVS group were lower than control group. The PEEP, airway pressure and plateau pressure in LPVS group were higher than control group, but driving pressure and tidal volume was lower than control group, the difference was statistically significant (P < 0.05). ConclusionIndividualized PEEP ventilation strategy guided by minimum driving pressure could improve oxygenation and reduce the incidence of PPCs in surgical patients with COVID-19.

Respiratory function testing for guiding ventilator mode conversion in congenital diaphragmatic hernia.

For patients with a congenital diaphragmatic hernia, conventional mechanical ventilation (CMV) and high-frequency oscillatory ventilation (HFOV) are used in initial ventilatory management. HFOV has recently been recommended as a rescue therapy; however, we use HFOV for initial ventilation management, with a preoperative challenge test for CMV conversion and respiratory function testing at the time of CMV conversion. We aimed to compare patient characteristics between CMV conversion- and HFOV-preferred treatment groups. Ventilator settings and blood gases were retrospectively evaluated pre- and post-CMV conversion, and respiratory function tests for compliance of the respiratory system (Crs) and for resistance of the respiratory system (Rrs) were performed during the trial to CMV conversion. No differences were observed between the CMV conversion- and HFOV-preferred groups regarding gestational age, birth weight, and observed/expected lung area-to-head circumference ratios. The median Crs (ml/cmH2 O/kg) and Rrs (cmH2 O･kg/L/s) in the CMV conversion- and HFOV-preferred groups was 0.42 versus 0.53 (p = .44) and 467 versus 327 (p = .045), respectively. The pre and posttrial amount of change in blood gas levels and ventilator parameters in the CMV conversion- and HFOV-preferred groups were as follows: mean airway pressure, -2.0 versus 0 cmH2 O; partial pressure of carbon dioxide, 6.1 versus 2.9 Torr; alveolar-arterial oxygen difference, -39.5 versus -50 Torr; and oxygenation index, -1.0 versus -0.6; respectively. Respiratory function tests were useful in tailoring ventilator settings. Patients with high Rrs values responded better to CMV conversion.

Long-term outcomes of patients supported with extracorporeal membrane oxygenation for acute respiratory distress syndrome: a systematic review and meta-analysis.

Extracorporeal membrane oxygenation (ECMO) is increasingly used to support patients with severe acute respiratory distress syndrome (ARDS). The impact of ECMO on long-term outcomes of patients with severe ARDS is unclear. We searched electronic databases from inception to January 17th 2023. We selected clinical trials and observational studies reporting on long-term outcomes of patients supported with ECMO for ARDS. Health-related quality of life (HRQoL) was the primary outcome. Secondary outcomes included cognitive function, mental health, functional status, respiratory symptoms, and return to work. Of the 7126 screened citations, 1 randomized clinical trial and 31 observational studies were included, of which 7 compared conventional mechanical ventilation (CMV) and ECMO. Overall quality of studies of the included studies was limited, with the majority being either low (45%) or fair (32%) quality. There was no significant difference in HRQoL measured with the SF-36 score between ECMO and CMV patients (physical component score [PCS]: mean difference 3.91 (- 6.22 to 14.05), mental component score [MCS] mean difference 1.33 (- 3.93 to 6.60)). There was no difference between cognitive function, mental health, functional status, and respiratory symptoms between ECMO and CMV, but data available for comparison were limited. There were high rates of disability for ECMO survivors with 49% of patients returning to work and 23% needing assistance at home on follow-up. Survivors of ECMO for ARDS experience significant disability in multiple domains. Further studies are needed to examine the effect of ECMO on long-term outcomes of patients compared to CMV.

Recovery and safety with prolonged high-frequency jet ventilation for catheter ablation of atrial fibrillation: A hospital registry study from a New England healthcare network

Study objectiveTo investigate post-procedural recovery as well as peri-procedural respiratory and hemodynamic safety parameters with prolonged use of high-frequency jet ventilation (HFJV) versus conventional ventilation in patients undergoing catheter ablation for atrial fibrillation. DesignHospital registry study. SettingTertiary academic teaching hospital in New England. Patients1822 patients aged 18 years and older undergoing catheter ablation between January 2013 and June 2020. InterventionsHFJV versus conventional mechanical ventilation. MeasurementsThe primary outcome was post-anesthesia care unit (PACU) length of stay. In secondary analyses we assessed the effect of HFJV on intra-procedural hypoxemia, defined as the occurrence of peripheral hemoglobin oxygen saturation (SpO2) <90%, post-procedural respiratory complications (PRC) as well as intra-procedural hypocarbia and hypotension. Multivariable negative binomial and logistic regression analyses, adjusted for patient and procedural characteristics, were applied. Main results1157 patients (63%) received HFJV for a median (interquartile range [IQR]) duration of 307 (253–360) minutes. The median (IQR) length of stay in the PACU was 244 (172–370) minutes in patients who underwent ablation with conventional mechanical ventilation and 226 (163–361) minutes in patients receiving HFJV. In adjusted analyses, patients undergoing HFJV had a longer PACU length of stay (adjusted absolute difference: 37.7 min; 95% confidence interval [CI] 9.7–65.8; p = 0.008). There was a higher risk of intra-procedural hypocarbia (adjusted odds ratio [ORadj] 5.90; 95%CI 2.63–13.23; p < 0.001) and hypotension (ORadj 1.88; 95%CI 1.31–2.72; p = 0.001) in patients undergoing HFJV. No association was found between the use of HFJV and intra-procedural hypoxemia or PRC (p = 0.51, and p = 0.97, respectively). ConclusionAfter confounder adjustment, HFJV for catheter ablation procedures for treatment of atrial fibrillation was associated with a longer length of stay in the PACU. It was further associated with an increased risk of intra-procedural abnormalities including abnormal carbon dioxide homeostasis, as well as intra-procedural arterial hypotension.

Changes in respiratory mechanics in response to crystalloid infusions in extremely premature infants.

Extremely premature infants are at a higher risk of developing respiratory distress syndrome and circulatory impairments in the first few weeks of life. Administration of normal saline boluses to manage hypotension is a common practice in preterm infants. As a crystalloid, a substantial proportion might leak into the interstitium; most consequently the lungs in the preterm cohorts, putatively affecting ventilation. We downloaded and analyzed ventilator mechanics data in infants managed by conventional mechanical ventilation and administered normal saline bolus for clinical reasons. Data were downloaded for 30 min prebolus, 60 min during the bolus followed by 30 min postbolus. Sixteen infants (mean gestational age 25.2 ± 1 wk and birth weight 620 ± 60 g) were administered 10 mL/kg normal saline over 60 min. The most common clinical indication for saline was hypotension. No significant increase was noted in mean blood pressure after the saline bolus. A significant reduction in pulmonary compliance (mL/cmH2O/kg) was noted (0.43 ± 0.07 vs. 0.38 ± 0.07 vs. 0.33 ± 0.07, P = 0.003, ANOVA). This was accompanied by an elevation in the required peak inspiratory pressure to deliver set volume-guarantee (19 ± 2 vs. 22 ± 2 vs. 22 ± 3 mmHg, P < 0.0001, ANOVA), resulting in a higher respiratory severity score. Normal saline infusion therapy was associated with adverse pulmonary mechanics. Relevant pathophysiologic mechanisms might include translocation of fluid across pulmonary capillaries affected by low vascular tone and heightened permeability in extremes of prematurity, back-pressure effects from raised left atrial volume due to immature left-ventricular myocardium; complemented by the effect of cytokine release from positive pressure ventilation.NEW & NOTEWORTHY Administration of saline boluses is common in premature infants although hypovolemia is an uncommon underlying cause of hypotension. This crystalloid can redistribute into pulmonary interstitial space. In the presence of an immature myocardium and diastolic dysfunction, excess fluid can also be "edemagenic." This study on extremely premature infants (25 wk gestation) noted adverse influence on respiratory physiology after saline infusion. Clinicians need to choose judiciously and reconsider routine use of saline boluses in premature infants.

Study of temperature distribution and smoke movement by mobile ventilation during emergency rescue in tunnel fires

Mobile ventilation unit (MVU), as a convenient and maneuverable ventilation method, can provide forced airflow for emergency ventilation to reduce tunnel fire risk. Compared with the conventional natural ventilation and mechanical ventilation, this mobile ventilation method plays a crucial role in the current tunnel fire emergency rescue. To explore the effects of MVU on the temperature or smoke spread in tunnel fires, Computational Fluid Dynamics simulation, validated by the previous experimental data, is applied in the current study. A series of tests are conducted with fire heat release rate of 1–30 MW and MVU fan flow being up to 3 × 105 m3/h. The results show the maximum tunnel ceiling temperature presents exponential attenuation with increasing fan flow and its relational expression with fan flow and fire size is proposed. Furthermore, the temperature decay distribution between upstream and downstream area is obviously different and a new coefficient γ is imported to represent the difference by connecting the fan flow and fire size. Moreover, the smoke backflow length theoretical equation in the upstream area is obtained, which can provide effective guidance to tunnel fire emergency rescue with MVU.