End-expiratory Pressure Research Articles

Respiratory system mechanics during noninvasive proportional assist ventilation: A model study

AbstractPurposeTo assess the accuracies of airway resistance (Raw) and compliance (Crs) calculations using the expiratory time constant (RCexp) method as well as the accuracy of Pmus estimation in obstructive lung models.MethodsA Respironics V60 ventilator was connected to an active lung simulator. The driving pressure was maintained at 5–10 cmH2O and positive end-expiration pressure (PEEP) was 5 cmH2O. Maximal Pmus, estimated based on equations of motion and respiratory mechanical properties, was calculated by the RCexp method to derive respiratory system compliance (Crs) and inspiratory (Rinsp) and expiratory (Rexp) resistance.ResultsDuring PAV, the assist proportion was adjusted to 55% and 40% with Pmus of 5 and 10 cmH2O, respectively. Pmus measurement errors were <20% of the preset values in most lung conditions. In the active lung model with PAV, an overestimation of Raw was found in the normal resistance condition, and Rinsp was underestimated in the severe obstructive model (P < 0.01). Crs was overestimated significantly except in the severe obstructive model at a Pmus of 10 cmH2O (all P < 0.01). Using the RCexp method, the target of ≤20% between the calculated and preset values in airway resistance was achieved in most obstructive models at a Pmus of 5 cmH2O.ConclusionsThe RCexp method might provide real-time assessments of respiratory mechanics (elastance and resistance) in the PAV mode. With low inspiratory effort, the estimation error was acceptable (<20%) in most obstructive lung models.

Sedation-Ventilation Interaction in Acute Hypoxemic Respiratory Failure: Secondary Analysis of the Land and Diaphragm-Protective Ventilation by Means of Assessing Respiratory Work (LANDMARK) Trial

BackgroundVentilation and sedation are used for the management of acute hypoxemic respiratory failure (AHRF), but their optimal combination to minimize the risks of ventilation is not well understood. Research questionWhat are the individual effects and interactions of inspiratory and end-expiratory pressure (PEEP), sedation, and venovenous extracorporeal membrane oxygenation (VV-ECMO) on respiratory drive, effort, and lung-distending pressure in patients with AHRF triggering the ventilator? Study designand methods: Secondary exploratory analysis of a trial of lung and diaphragm protection in AHRF. Inspiratory pressure, sedation, PEEP, and VV-ECMO were titrated while respiratory drive (airway pressure in the first 100 milliseconds, P0.1), effort (esophageal pressure swing, |ΔPes|), and lung-distending pressure (dynamic transpulmonary driving pressure, ΔPL,dyn) were recorded. Associations were evaluated using linear mixed effects regression models including pre-specified terms for potential interactions. ResultsThe study included 223 individual measurements of P0.1 and 235 individual measurements of |ΔPes| and ΔPL,dyn from 30 patients. Propofol attenuated P0.1 (–0.4 cm H2O, 95% CI –0.3, –0.1 per 10 mcg/kg/min increase), |ΔPes| (–2.5 cm H2O, 95% CI –3.4, –1.7 per 10 mcg/kg/min increase) and ΔPL,dyn (–1.6 cm H2O, 95% CI –2.3, –0.8 per 10 mcg/kg/min increase). The effect of inspiratory pressure on |ΔPes| varied depending on propofol dose: with higher propofol dose, inspiratory pressure resulted in higher ΔPL,dyn. Under VV-ECMO, patients (n=16) had significantly lower |ΔPes| (–10 cm H2O, 95% CI –17.5, –2.5) and required less sedation to reduce |ΔPes| than without VV-ECMO (n=14). InterpretationMechanical ventilation, sedation, and VV-ECMO exert interdependent effects on respiratory drive, effort, and lung-distending pressure in AHRF. Patients under VV-ECMO require less sedation to control respiratory effort.

Pulmonary inflammation decreases with ultra-protective ventilation in experimental ARDS under VV-ECMO: a positron emission tomography study.

Experimentally, ultra-protective ventilation (UPV, tidal volumes [VT] < 4 mL.kg-1) strategies in conjunction with veno-venous extracorporeal membrane oxygenation (VV-ECMO) are associated with lesser ventilator-induced lung injuries (VILI) during acute respiratory distress syndrome (ARDS). However, whether these strategies reduce lung inflammation more effectively than protective ventilation (PV) remains unclear. We aimed to demonstrate that a UPV strategy decreases acute lung inflammation in comparison with PV in an experimental swine model of ARDS. ARDS was induced by tracheal instillation of chlorhydric acid in sedated and paralyzed animals under mechanical ventilation. Animals were randomized to receive either UPV (VT 1 mL.kg-1, positive end-expiration pressure [PEEP] set to obtain plateau pressure between 20 and 25 cmH2O and respiratory rate [RR] at 5 min-1 under VV-ECMO) or PV (VT 6 mL.kg-1, PEEP set to obtain plateau pressure between 28 and 30 cmH2O and RR at 25 min-1) during 4 h. After 4 h, a positron emission tomography with [11C](R)-PK11195 (ligand to TSPO-bearing macrophages) injection was realized, coupled with quantitative computerized tomography (CT). Pharmacokinetic multicompartment models were used to quantify regional [11C](R)-PK11195 lung uptake. [11C](R)-PK11195 lung uptake and CT-derived respiratory variables were studied regionally across eight lung regions distributed along the antero-posterior axis. Five pigs were randomized to each study group. Arterial O2 partial pressure to inspired O2 fraction were not significantly different between study groups after experimental ARDS induction (75 [68-80] mmHg in a PV group vs. 87 [69-133] mmHg in a UPV group, p = 0.20). Compared to PV animals, UPV animals exhibited a significant decrease in the regional non-aerated compartment in the posterior lung levels, in mechanical power, and in regional dynamic strain and no statistical difference in tidal hyperinflation after 4 h. UPV animals had a significantly lower [11C](R)-PK11195 uptake, compared to PV animals (non-displaceable binding potential 0.35 [IQR, 0.20-0.59] in UPV animals and 1.01 [IQR, 0.75-1.59] in PV animals, p = 0.01). Regional [11C](R)-PK11195 uptake was independently associated with the interaction of regional tidal hyperinflation and regional lung compliance. In an experimental model of ARDS, 4 h of UPV strategy significantly decreased lung inflammation, in relation to the control of VT-derived determinants of VILI.

Association between (ΔPaO2/FiO2)/PEEP and in-hospital mortality in patients with COVID-19 pneumonia: A secondary analysis.

The arterial pressure of oxygen (PaO2)/inspiratory fraction of oxygen (FiO2) is associated with in-hospital mortality in patients with Coronavirus Disease 2019 (COVID-19) pneumonia. ΔPaO2/FiO2 [the difference between PaO2/FiO2 after 24 h of invasive mechanical ventilation (IMV) and PaO2/FiO2 before IMV] is associated with in-hospital mortality. However, the value of PaO2 can be influenced by the end-expiratory pressure (PEEP). To the best of our knowledge, the relationship between the ratio of (ΔPaO2/FiO2)/PEEP and in-hospital mortality remains unclear. This study aimed to evaluate their association. The study was conducted in southern Peru from April 2020 to April 2021. A total of 200 patients with COVID-19 pneumonia requiring IMV were included in the present study. We analyzed the association between (ΔPaO2/FiO2)/PEEP and in-hospital mortality by Cox proportional hazards regression models. The median (ΔPaO2/FiO2)/PEEP was 11.78 mmHg/cmH2O [interquartile range (IQR) 8.79-16.08 mmHg/cmH2O], with a range of 1 to 44.36 mmHg/cmH2O. Patients were divided equally into two groups [low group (< 11.80 mmHg/cmH2O), and high group (≥ 11.80 mmHg/cmH2O)] according to the (ΔPaO2/FiO2)/PEEP ratio. In-hospital mortality was lower in the high (ΔPaO2/FiO2)/PEEP group than in the low (ΔPaO2/FiO2)/PEEP group [18 (13%) vs. 38 (38%)]; hazard ratio (HR), 0.33 [95% confidence intervals (CI), 0.17-0.61, P < 0.001], adjusted HR, 0.32 (95% CI, 0.11-0.94, P = 0.038). The finding that the high (ΔPaO2/FiO2)/PEEP group exhibited a lower risk of in-hospital mortality compared to the low (ΔPaO2/FiO2)/PEEP group was consistent with the results from the sensitivity analysis. After adjusting for confounding variables, we found that each unit increase in (ΔPaO2/FiO2)/PEEP was associated with a 12% reduction in the risk of in-hospital mortality (HR, 0.88, 95%CI, 0.80-0.97, P = 0.013). The (ΔPaO2/FiO2)/PEEP ratio was associated with in-hospital mortality in patients with COVID-19 pneumonia. (ΔPaO2/FiO2)/PEEP might be a marker of disease severity in COVID-19 patients.

Modifiable Mechanical Ventilation Targets Are Associated With Improved Survival in Ventilated VA-ECLS Patients

BackgroundIn acute respiratory distress syndrome (ARDS), lung protective ventilation (LPV) improves patient outcomes by minimizing ventilator-induced lung injury. The value of LPV in ventilated patients with cardiogenic shock (CS) requiring venoarterial extracorporeal life support (VA-ECLS) is not known, but the extracorporeal circuit provides a unique opportunity to modify ventilatory parameters to improve outcomes. ObjectivesThe authors hypothesized that CS patients on VA-ECLS who require mechanical ventilation (MV) may benefit from low intrapulmonary pressure ventilation (LPPV), which has the same end goals as LPV. MethodsThe authors queried the ELSO (Extracorporeal Life Support Organization) registry for hospital admissions between 2009 and 2019 for CS patients on VA-ECLS and MV. They defined LPPV as peak inspiratory pressure at 24 hours on ECLS of <30 cm H2O. Positive end-expiration pressure and dynamic driving pressure (DDP) at 24 hours were also studied as continuous variables. Their primary outcome was survival to discharge. Multivariable analyses were performed that adjusted for baseline Survival After Venoarterial Extracorporeal Membrane Oxygenation score, chronic lung conditions, and center extracorporeal membrane oxygenation volume. ResultsA total of 2,226 CS patients on VA-ECLS were included: 1,904 received LPPV. The primary outcome was higher in the LPPV group vs the no-LPPV group (47.4% vs 32.6%; P < 0.001). Median peak inspiratory pressure (22 vs 24 cm H2O; P < 0.001) as well as DDP (14.5 vs 16 cm H2O; P < 0.001) were also significantly lower in those surviving to discharge. The adjusted OR for the primary outcome with LPPV was 1.69 (95% CI: 1.21-2.37; P = 0.0021). ConclusionsLPPV is associated with improved outcomes in CS patients on VA-ECLS requiring MV.

Performance of helmet CPAP using different configurations: Turbine-driven ventilators vs Venturi devices

BackgroundTraditionally, Venturi-based flow generators have been preferred over mechanical ventilators to provide continuous positive airway pressure (CPAP) through the helmet (h-CPAP). Recently, modern turbine-driven ventilators (TDVs) showed to be safe and effective in delivering h-CPAP. We aimed to compare the pressure stability during h-CPAP delivered by Venturi devices and TDVs and assess the impact of High Efficiency Particulate Air (HEPA) filters on their performance. MethodsWe performed a bench study using an artificial lung simulator set in a restrictive respiratory condition, simulating two different levels of patient effort (high and low) with and without the interposition of the HEPA filter. We calculated the average of minimal (Pmin), maximal (Pmax) and mean (Pmean) airway pressure and the time product measured on the airway pressure curve (PTPinsp). We defined the pressure swing (Pswing) as Pmax - Pmin and pressure drop (Pdrop) as End Expiratory Pressure - Pmin. ResultsPswing across CPAP levels varied widely among all the tested devices. During “low effort”, no difference in Pswing and Pdrop was found between Venturi devices and TDVs; during high effort, Pswing (p<0.001) and Pdrop (p<0.001) were significantly higher in TDVs compared to Venturi devices, but the PTPinsp was lower (1.50 SD 0.54 vs 1.67 SD 0.55, p<0.001). HEPA filter addition almost doubled Pswing and PTPinsp (p<0.001) but left unaltered the differences among Venturi and TDVs systems in favor of the latter (p<0.001). ConclusionsTDVs performed better than Venturi systems in delivering a stable positive pressure level during h-CPAP in a bench setting.

Adaptive servo-ventilation and mortality in patients with systolic heart failure and central sleep apnea: a single-center experience

BackgroundCentral sleep apnea (CSA) is associated with increased mortality and morbidity in patients with heart failure with reduced ejection fraction (HFrEF). Treatment of CSA with a certain type of adaptive servo-ventilation (ASV) device that targets minute ventilation (ASVmv) was found to be harmful in these patients. A newer generation of ASV devices that target peak flow (ASVpf) is presumed to have different effects on ventilation and airway patency. We analyzed our registry of patients with HFrEF-CSA to examine the effect of exposure to ASV and role of each type of ASV device on mortality.MethodsThis is a retrospective cohort study in patients with HFrEF and CSA who were treated with ASV devices between 2008 and 2015 at a single institution. Mortality data were collected through the institutional data honest broker. Usage data were obtained from vendors’ and manufacturers’ servers. Median follow-up was 64 months.ResultsThe registry included 90 patients with HFrEF-CSA who were prescribed ASV devices. Applying a 3-h-per-night usage cutoff, we found a survival advantage at 64 months for those who used the ASV device above the cutoff (n = 59; survival 76%) compared to those who did not (n = 31; survival 49%; hazard ratio 0.44; CI 95%, 0.20 to 0.97; P = 0.04). The majority (n = 77) of patients received ASVpf devices with automatically adjusting end-expiratory pressure (EPAP) and the remainder (n = 13) received ASVmv devices mostly with fixed EPAP (n = 12). There was a trend towards a negative correlation between ASVmv with fixed EPAP and survival.ConclusionIn this population of patients with HFrEF and CSA, there was no evidence that usage of ASV devices was associated with increased mortality. However, there was evidence of differential effects of type of ASV technology on mortality.

Individualised flow-controlled ventilation versus pressure-controlled ventilation in a porcine model of thoracic surgery requiring one-lung ventilation: A laboratory study.

Flow-controlled ventilation (FCV) enables precise determination of dynamic compliance due to a continuous flow coupled with direct tracheal pressure measurement. Thus, pressure settings can be adjusted accordingly in an individualised approach. The aim of this study was to compare gas exchange of individualised FCV to pressure-controlled ventilation (PCV) in a porcine model of simulated thoracic surgery requiring one-lung ventilation (OLV). Controlled interventional trial conducted on 16 domestic pigs. Animal operating facility at the Medical University of Innsbruck. Thoracic surgery was simulated with left-sided thoracotomy and subsequent collapse of the lung over a period of three hours. When using FCV, ventilation was performed with compliance-guided pressure settings. When using PCV, end-expiratory pressure was adapted to achieve best compliance with peak pressure adjusted to achieve a tidal volume of 6 ml kg -1 during OLV. Gas exchange was assessed by the Horowitz index (= P aO 2 /FIO 2 ) and CO 2 removal by the P aCO 2 value in relation to required respiratory minute volume. In the FCV group ( n = 8) normocapnia could be maintained throughout the OLV trial despite a significantly lower respiratory minute volume compared to the PCV group ( n = 8) (8.0 vs. 11.6, 95% confidence interval, CI -4.5 to -2.7 l min -1 ; P < 0.001), whereas permissive hypercapnia had to be accepted in PCV ( P aCO 2 5.68 vs. 6.89, 95% CI -1.7 to -0.7 kPa; P < 0.001). The Horowitz index was comparable in both groups but calculated mechanical power was significantly lower in FCV (7.5 vs. 22.0, 95% CI -17.2 to -11.8 J min -1 ; P < 0.001). In this porcine study FCV maintained normocapnia during OLV, whereas permissive hypercapnia had to be accepted in PCV despite a substantially higher minute volume. Reducing exposure of the lungs to mechanical power applied by the ventilator in FCV offers a possible advantage for this mode of ventilation in terms of lung protection.

Fluid dynamic assessment of positive end-expiratory pressure in a tracheostomy tube connector during respiration.

High-flow oxygen therapy using a tracheostomy tube is a promising clinical approach to reduce the work of breathing in tracheostomized patients. Positive end-expiratory pressure (PEEP) is usually applied during oxygen inflow to improve oxygenation by preventing end-expiratory lung collapse. However, much is still unknown about the geometrical effects of PEEP, especially regarding tracheostomy tube connectors (or adapters). Quantifying the degree of end-expiratory pressure (EEP) that takes patient-specific spirometry into account would be useful in this regard, but no such framework has been established yet. Thus, a platform to assess PEEP under respiration was developed, wherein three-dimensional simulation of airflow in a tracheostomy tube connector is coupled with a lumped lung model. The numerical model successfully reflected the magnitude of EEP measured experimentally using a lung phantom. Numerical simulations were further performed to quantify the effects of geometrical parameters on PEEP, such as inlet angles and rate of stenosis in the connector. Although sharp inlet angles increased the magnitude of EEP, they cannot be expected to achieve clinically reasonable PEEP. On the other hand, geometrical constriction in the connector can potentially result in PEEP as obtained with conventional nasal cannulae.Graphical abstract

Breath-dependent pressure fluctuations in various constant- and variable-flow neonatal CPAP devices.

In continuous positive airway pressure(CPAP) devices, pressure can be generated by two different mechanisms: either via an expiratory valve or by one or more jets. Valved CPAP devices are referred to as constant-flow devices, and jet devices are called variable-flow devices. Constant-flow CPAP devices are said to reduce the imposed work of breathing due to lower breath-dependent pressure fluctuations. The present study investigates the performance of various constant-and variable-flow CPAP devices in relation to breath-dependent pressure fluctuations. Experimental study comparing the pressure fluctuations incurred by seven neonatal CPAP devices attached to an active neonatal lung model. Spontaneous breathing was simulated using a tidal volume of 6 ml at pressure levels of 5, 7, and 9 mbar. The main outcomes were respiratory pressure fluctuations, tidal volume, and end-expiratory pressure. All CPAP devices tested showed respiratory pressure fluctuations, varying from 0.631to 3.466 mbar. The generated tidal volume correlated significantly with the pressure fluctuations (r = -0.947; p = 0.001) and varied between 5.550and 6.316 ml. CPAP devices with jets showed no advantage over CPAP devices with expiratory valves. End-expiratory pressure in the nose deviated from the set pressure between -1.305and 0.644 mbar and varied depending on whether the pressure was measured in the device or in the tube extending to the nose. During standard spontaneous breathing, breath-dependent pressure fluctuations in constant-and variable-flow devices are comparable. Pressure measurements taken in the tubing system can lead to a considerable deviation of the applied pressure.

Safety and efficacy of vacuum bottle plus catheter for drainage of iatrogenic pneumothorax

BackgroundIatrogenic pneumothorax is common after thoracic procedures. For patients with pneumothorax larger than 15%, simple aspiration is suggested. Although vacuum bottle plus non-tunneled catheter drainage has been performed in many institutions, its safety and efficacy remain to be assessed.MethodsThrough this prospective cohort study (NCT03724721), we evaluated the safety and efficacy of vacuum bottle plus non-tunneled catheter drainage. Patients older than 20 years old who developed post-procedural pneumothorax were enrolled. A non-tunneled catheter was placed at the intersection of the midclavicular line and the second intercostal space. A 3-way stopcock, a drainage set, and a digital pressure gauge were connected. The stopcock was manipulated to connect the pleural space to the pressure gauge for measurement of end-expiration intrapleural pressure or to the vacuum bottle for air drainage. The rate of successful drainage, the end-expiration intrapleural pressure before, during, and after the procedure and the duration of hospitalization were recorded.ResultsFrom August 2018 to February 2020, 21 patients underwent vacuum bottle plus catheter drainage (intervention group) and 31 patients received conservative treatment (control group). The end-expiration intrapleural pressure of all patients remained less than − 20 cmH2O during drainage. No procedure related complication was observed. Large pneumothorax (≥ 15%) was associated with higher risk of persistent air leak (Odds ratio 12, 95% CI 1.2–569.7). Vacuum bottle assisted air drainage yielded shorter event-free duration than that of conservative treatment (2 days vs 5 days [interquartile range 1–4 days vs 3–7 days], p < .05). Vacuum bottle assisted air drainage also help identifying patients with persistent pneumothorax and necessitate the subsequent management. The event-free duration of persistent air leak in the intervention group was also comparable with that of conservative treatment (5 days vs 5 days [interquartile range 5–8 days vs 3–7 days], p = .45).ConclusionsVacuum bottle plus catheter drainage of iatrogenic pneumothorax is a safe and efficient procedure. It may be considered as an alternative management of stable post-procedural pneumothorax with size larger than 15%.Trial registration The study protocol was approved by the Research Ethics Committee of National Taiwan University Hospital (No. 201805105DINA) on 6th August, 2018. The first participant was enrolled on 23rd August, 2018 after Research Ethics Committee approval. This clinical trial complete registration at U.S. National Library of Medicine clinicaltrials.gov with identifier NCT03724721 and URL: https://clinicaltrials.gov/ct2/show/NCT03724721 on 30th October, 2018.

ARTERIAL BLOOD GAS ANALYSIS PROFILE IN EXTREMELY PREMATURE NEONATES ADMITTED IN A TERTIARY CARE NEONATAL INTENSIVE CARE UNIT

Early studies suggest an association of abnormal carbon dioxide (PCO2) or oxygen (PO2) levels with adverse inpatient outcomes in very preterm babies. Recent resuscitation practice changes, such as targeted oxygen therapy, end-expiratory pressure, and rescue surfactant may influence these associations. The aim of this study is to assess the range of the initial partial pressures of PCO2 and PO2 in extremely preterm neonates (&lt;1 kg) after birth and their correlation to inpatient neonatal outcomes.

Comparison of the effectiveness of high-flow nasal oxygen vs. standard facemask oxygenation for pre- and apneic oxygenation during anesthesia induction: a systematic review and meta-analysis

BackgroundIn recent years, high flow nasal oxygen (HFNO) has been widely used in clinic, especially in perioperative period. Many studies have discussed the role of HFNO in pre- and apneic oxygenation, but their results are controversial. Our study aimed to examine the effectiveness of HFNO in pre- and apneic oxygenation by a meta-analysis of RCTs.MethodsEMBASE, PUBMED, and COCHRANE LIBRARY databases were searched from inception to July 2021 for relevant randomized controlled trails (RCTs) on the effectiveness of HFNO versus standard facemask ventilation (FMV) in pre- and apenic oxygenation. Studies involving one of the following six indicators: (1) Arterial oxygen partial pressure (PaO2), (2) End expiratory oxygen concentration (EtO2), (3) Safe apnoea time, (4) Minimum pulse oxygen saturation (SpO2min), (5) Oxygenation (O2) desaturation, (6) End expiratory carbon dioxide (EtCO2) or Arterial carbon dioxide partial pressure(PaCO2) were included. Due to the source of clinical heterogeneity in the observed indicators in this study, we adopt random-effects model for analysis, and express it as the mean difference (MD) or risk ratio (RR) with a confidence interval of 95% (95%CI). We conducted a risk assessment of bias for eligible studies and assessed the overall quality of evidence for each outcome.ResultsFourteen RCTs and 1012 participants were finally included. We found the PaO2 was higher in HFNO group than FMV group with a MD (95% CI) of 57.38 mmHg (25.65 to 89.10; p = 0.0004) after preoxygenation and the safe apnoea time was significantly longer with a MD (95% CI) of 86.93 s (44.35 to 129.51; p < 0.0001) during anesthesia induction. There were no significant statistical difference in the minimum SpO2, CO2 accumulation, EtO2 and O2 desaturation rate during anesthesia induction between the two groups.ConclusionsThis systematic review and meta-analysis suggests that HFNO should be considered as an oxygenation tool for patients during anesthesia induction. Compared with FMV, continuous use of HFNO during anesthesia induction can significantly improve oxygenation and prolong safe apnoea time in surgical patients.

Computed Tomography Assessment of Tidal Lung Overinflation in Domestic Cats Undergoing Pressure-Controlled Mechanical Ventilation During General Anesthesia.

ObjectiveThis study aimed to evaluate lung overinflation at different airway inspiratory pressure levels using computed tomography in cats undergoing general anesthesia.Study DesignProspective laboratory study.AnimalsA group of 17 healthy male cats, aged 1.9–4.5 years and weighing 3.5 ± 0.5 kg.MethodsSeventeen adult male cats were ventilated in pressure-controlled mode with airway pressure stepwise increased from 5 to 15 cmH2O in 2 cmH2O steps every 5 min and then stepwise decreased. The respiratory rate was set at 15 movements per min and end-expiratory pressure at zero (ZEEP). After 5 min in each inspiratory pressure step, a 4 s inspiratory pause was performed to obtain a thoracic juxta-diaphragmatic single slice helical CT image and to collect respiratory mechanics data and an arterial blood sample. Lung parenchyma aeration was defined as overinflated, normally-aerated, poorly-aerated, and non-aerated according to the CT attenuation number (−1,000 to −900 HU, −900 to −500 HU, −500 to −100 HU, and −100 to +100 HU, respectively).ResultAt 5 cmH2O airway pressure, tidal volume was 6.7± 2.2 ml kg−1, 2.1% (0.3–6.3%) of the pulmonary parenchyma was overinflated and 84.9% (77.6%−87.6%) was normally inflated. Increases in airway pressure were associated with progressive distention of the lung parenchyma. At 15 cmH2O airway pressure, tidal volume increased to 31.5± 9.9 ml kg−1 (p < 0.001), overinflated pulmonary parenchyma increased to 28.4% (21.2–30.6%) (p < 0.001), while normally inflated parenchyma decreased 57.9% (53.4–62.8%) (p < 0.001). Tidal volume and overinflated lung fraction returned to baseline when airway pressure was decreased. A progressive decrease was observed in arterial carbon dioxide partial pressure (PaCO2) and end-tidal carbon dioxide (ETCO2) when the airway pressures were increased above 9 cmH2O (p < 0.001). The increase in airway pressure promoted an elevation in pH (p < 0.001).Conclusions and Clinical RelevanceVentilation with 5 and 7 cmH2O of airway pressure prevents overinflation in healthy cats with highly compliant chest walls, despite presenting acidemia by respiratory acidosis. This fact can be controlled by increasing or decreasing respiratory rate and inspiratory time.

The role of mechanical ventilation in primary graft dysfunction in the postoperative lung transplant recipient: A single center study and literature review.

BackgroundPrimary graft dysfunction (PGD) is still a major complication in patients undergoing lung transplantation (LTx). Much is unknown about the effect of postoperative mechanical ventilation on outcomes, with debate on the best approach to ventilation.Aim/PurposeThe goal of this study was to generate hypotheses on the association between postoperative mechanical ventilation settings and allograft size matching in PGD development.MethodThis is a retrospective study of LTx patients between September 2011 and September 2018 (n = 116). PGD was assessed according to the International Society of Heart and Lung Transplantation (ISHLT) criteria. Data were collected from medical records, including chest x‐ray assessments, blood gas analysis, mechanical ventilator parameters and spirometry.ResultsPositive end‐expiratory pressures (PEEP) of 5 cm H2O were correlated with lower rates of grade 3 PGD. Graft size was important as tidal volumes calculated according to the recipient yielded greater rates of PGD when low volumes were used, a correlation that was lost when donor metrics were used.ConclusionOur results highlight a need for greater investigation of the role donor characteristics play in determining post‐operative ventilation of a lung transplant recipient. The mechanical ventilation settings on postoperative LTx recipients may have an implication for the development of acute graft dysfunction. Severe PGD was associated with the use of a PEEP higher than 5 and lower tidal volumes and oversized lungs were associated with lower long‐term mortality. Lack of association between ventilatory settings and survival may point to the importance of other variables than ventilation in the development of PGD.

Pressure Ramp Testing for Optimization of End-Expiratory Pressure Settings in Adaptive Servo-Ventilation Therapy.

Background: Clinical outcomes of adaptive servo-ventilation (ASV) therapy have not been rigorously assessed. Optimal device settings ascertained by a pressure ramp test may increase the utility of ASV therapy. Methods and Results: Patients with congestive heart failure (CHF) who underwent ASV therapy were prospectively included in the study. Patients in the ramp test group underwent a pressure ramp test, during which the end-expiratory pressure was optimized to maximize cardiac output (assessed using the AESCLONE mini). The control group consisted of age-matched patients who received ASV therapy with a default pressure 5 cmH2O. The primary endpoint was a composite of all-cause death and heart failure recurrence, and was compared between the 2 groups. Of a total of 37 patients, 11 each were included in the ramp test and control groups. Median patient age was 73 years (interquartile range 59–75 years) and 16 were men. There were no significant differences in baseline characteristics between the 2 groups. In the ramp test group, end-expiratory pressure was optimized between 2 and 5 cmH2O in each patient. The 2-year incidence of the primary endpoint tended to be lower in the ramp test than control group (0% vs. 59%; P=0.080). Conclusions: Pressure ramp testing may be a promising strategy to optimize device pressure settings in patients with CHF undergoing ASV therapy. Larger-scale trials are needed to validate our findings.

Impact of Platelet Transfusion on Pulmonary Function of Hematology Oncology Patients: The Piper Study

Background. Platelet transfusion is a critical therapy for hematology-oncology patients at risk of transfusion-transmitted infection (TTI) and pulmonary injury. Amotosalen-UVA pathogen reduction (PR) treatment of apheresis platelet components (PC) in plasma or additive solution (INTERCEPT Blood System for Platelets, Cerus, Concord, CA) is FDA approved to reduce risk of TTI and transfusion associated graft vs. host disease (TA-GVHD). PRPC meet the FDA bacteria risk reduction guidance, and approximately 50% of U.S. PC are PRPC. Amotosalen-UVA PR replaces bacteria screening, gamma irradiation, and CMV serology. PR is performed within 24 hours of collection enabling early release of PRPC with 5-day storage. We tested the hypothesis that PRPC were not inferior to conventional PC(CPC) for the incidence of pulmonary injury. Methods. An open-label sequential cohort study in platelet transfusion dependent hematology-oncology patients was conducted under routine practice conditions in 15 clinical centers. Each site enrolled a CPC cohort followed by a PRPC cohort using 4 primary therapy strata matched ± 10%: chemotherapy without hematopoietic cell transplant (HCT), HCT with myeloablation, HCT with non-myeloablative conditioning, and HCT with reduced intensity conditioning (RIC). Patients were supported with the assigned PC type for up to 21 days with 7 days of surveillance after the last PC exposure. Patients participated in only one cohort. The primary endpoint was treatment emergent assisted mechanical ventilation (TEAMV) by intubation or tight mask with positive end expiration pressure (5cm H 2O) after initiation of study PC. All endpoint patients were adjudicated by a blinded pulmonary expert panel (PEP) for diagnosis of acute respiratory distress syndrome (ARDS) by the Berlin Criteria. Secondary endpoints included: time to initiation of TEAMV, clinically significant pulmonary adverse events (CSPAE, CTCAE ≥ Grade 2), transfusion reactions, and mortality. The incidence of TEAMV by non-inferiority (margin = 2.3%), and secondary endpoints were analyzed by modified intention to treat (mITT) and per protocol (PP). Sensitivity analyses with propensity score matching for key variables were conducted for the primary endpoint. The associations between PC and categorical variables were tested by stratified Cochran-Mantel-Haenszel and continuous variables by ANOVA for two-sided significance p = 0.05. results. A total of 2291 pediatric and adult patients (1068 PRPC and 1223 CPC) were enrolled in the respective cohorts with transfusion of 5,277 PRPC and 5,491 CPC. PC assignment compliance and study completion were > 94%. For the mITT data set, the cumulative incidence of TEAMV was lower for the PRPC cohort (log rank p = 0.039) than the CPC cohort (2.9% versus 4.6%, HR = 0.633: 95% CI 0.408-0.982). PRPC by mITT were non-inferior to CPC for the incidence of TEAMV due to all indications, and for TEAMV with pulmonary dysfunction (PD) by PEP (Table). PP analyses were consistent with mITT. Relative risk (RR) of TEAMV showed significantly (p<0.05) decreased RR of PRPC respectively for baseline covariates: age < 65 (0.53), male (0.54), non-white (0.32), chemotherapy (0.40), prior pulmonary disease (0.55), and prior cardiac disease (0.58). Least squares (LS) mean days to initiation of TEAMV for patients with PD were longer for PRPC recipients. PEP adjudicated incidence of ARDS was not significantly different between cohorts (Table). Total and serious CSPAE were not different between the cohorts. There were no significant differences between cohorts in Respiratory, Thoracic, and Mediastinal Disorders, the most frequent system organ class event. Mortality was not different between cohorts. Multivariate analysis (mITT) for the probability of CSPAE or transfusion associated cardiac overload (TACO) showed PC type had no effect. The odds ratio (OR) of CSPAE or TACO during PC support was significantly increased (p< 0.05) in both cohorts for history of cardiac disease (1.35), history of pulmonary disease (2.57), diagnosis of Myelodysplasia (1.88), and diagnosis of Myelodysplasia/Myeloproliferative disease (2.27). There was a significant treatment interaction (p= 0.043) between PC type and acute myelogenous leukemia (AML), increased OR = 1.49 for CPC versus PRPC. Conclusions. PRPC did not potentiate pulmonary injury during PC support; and their use may decrease TEAMV risk with benefit of reduced TTI risk. [Display omitted] DisclosuresWheeler: Novo Nordisk A/S: Consultancy; Bayer: Consultancy; BioMarin: Consultancy; HEMA Biologics: Consultancy; Spark: Consultancy; Takeda: Consultancy; UniQure: Consultancy. Nooka: Janssen Oncology: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Sanofi: Consultancy; Oncopeptides: Consultancy; Amgen: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy; Adaptive technologies: Consultancy; GlaxoSmithKline: Consultancy, Other: Travel expenses; Karyopharm Therapeutics: Consultancy. Uhl: UpToDate: Patents & Royalties; Abbott: Consultancy, Speakers Bureau; Grifols: Consultancy, Speakers Bureau. Spinella: Secure Transfusion Services: Current Employment, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company; Cerus Corporation: Consultancy, Research Funding. Liu: Cerus Corporation: Current Employment, Current equity holder in publicly-traded company. Benjamin: Cerus Corporation: Current Employment, Current equity holder in publicly-traded company. Corash: Cerus Corporation: Current Employment, Current equity holder in publicly-traded company.

Effect of single-port inflatable mediastinoscopy simultaneous laparoscopic-assisted radical esophagectomy on respiration and circulation

Background and purposeWe previously developed a new surgical method, namely, single-port inflatable mediastinoscopy simultaneous laparoscopic-assisted radical esophagectomy. The purpose of this study was to evaluate the effect of carbon dioxide inflation on respiration and circulation using this approach.MethodsFrom April 2018 to October 2020, 105 patients underwent this novel surgical approach. The changes in respiratory and circulatory functions were reported when the mediastinal pressure and pneumoperitoneum pressure were 10 and 12 mmHg, respectively. Data on blood loss, operative time, and postoperative complications were also collected.Results104 patients completed the operation successfully, except for 1 patient who was converted to thoracotomy because of intraoperative injury. During the operation, respectively, the heart rate, mean arterial pressure, central venous pressure, peak airway pressure, end-expiratory partial pressure of carbon dioxide and partial pressure of carbon dioxide increased in an admissibility range. The pH and oxygenation index decreased 1 h after inflation, but these values were all within a safe and acceptable range and restored to the baseline level after CO2 elimination. Postoperative complications included anastomotic fistula (8.6%), pleural effusion that needed to be treated (8.6%), chylothorax (0.9%), pneumonia (7.6%), arrhythmia (3.8%) and postoperative hoarseness (18.2%). There were no cases of perioperative death.ConclusionsWhen the inflation pressure in the mediastinum and abdomen was 10 mmHg and 12 mmHg, respectively, the inflation of carbon dioxide from single-port inflatable mediastinoscopy simultaneous laparoscopic-assisted radical esophagectomy did not cause serious changes in respiratory and circulatory function or increase perioperative complications.

Electrical Impedance Tomography might be a Practical Tool to Provide Information about COVID-19 Pneumonia Progression

Abstract COVID-19 induced acute respiratory distress syndrome (ARDS) could have two different phenotypes, which might have different response and outcome to the traditional ARDS positive end-expiration pressure (PEEP) treatment. The identification of the different phenotypes in terms of the PEEP recruitment can help improve the patients’ outcome. In this contribution we reported a COVID-19 patient with seven-day electrical impedance tomography monitoring. From the conductivity distribution difference image analysis of the data, a clear course developing trend can be observed in addition to the phenotype identification. This case might suggest that EIT can be a practical tool to identify phenotypes and to provide progressive information of COVID-19 pneumonia.

Heart-Protective Mechanical Ventilation in Postoperative Cardiosurgical Patients.

Background This study compared the hemodynamic effects and gas exchange under several different ventilator settings—with regard to tidal volume, respiratory rate, and end-expiratory pressure—in patients after coronary artery bypass grafting (CABG). Methods Prospective interventional cohort study with a controlled group in a single cardiosurgical ICU involving 119 patients following on-pump CABG surgery. During the 1st postoperative hour, the intervention group patients were ventilated with Vt 10 ml × kg−1, RR 14/min, PEEP 5 cmH2O (“conventional ventilation”). During the 2nd hour, RR was reduced to 8/min (“reduced RR ventilation”). At 3 hrs, Vt was decreased to 6 ml × kg−1, RR returned to 14/min, and PEEP increased to 10 cmH2O (“low Vt-high PEEP ventilation”). Results Patients in the “low Vt-high PEEP” ventilation period showed significantly lower alveolar ventilation and thoraco-pulmonary compliance than during “reduced RR” ventilation. Mean airway pressure and Vds/Vt peaked during low Vt-high PEEP ventilation; however, driving pressure was lower. Vt decrease and PEEP increase did not lead to oxygenation improvement and worsened CO2 elimination. Hemodynamically, the study revealed significant cardiac output decrease during low Vt-high PEEP ventilation. In 23.2% of patients, catecholamine therapy was initiated. Conclusions In postoperative cardiosurgical patients, MV with Vt 6 ml × kg−1 and PEEP 10 cm H2O is characterized by worsened oxygenation and elimination of CO2 and a less favorable hemodynamic profile than ventilation with Vt 10 ml × kg−1 and PEEP 5 cmH2O. New and Noteworthy. (i) Patients after CABG may be especially sensitive to low tidal volume and increased PEEP as it negatively affects hemodynamic profile by means of the right heart preload decrease and afterload increase. (ii) Mechanical ventilation settings aiming to minimize mean airway pressure reduce the negative effects of positive inspiratory pressure and are favorable for hemodynamics.