Improved ventilation efficiency due to continuous gas flow compared to decelerating gas flow in mechanical ventilation: results of a porcine trial.

In pressure-controlled ventilation (PCV), a decelerating gas flow pattern occurs during inspiration and expiration. In contrast, flow-controlled ventilation (FCV) guarantees a continuous gas flow throughout the entire ventilation cycle where the inspiration and expiration phases are simply performed by a change of gas flow direction. The aim of this trial was to highlight the effects of different flow patterns on respiratory variables and gas exchange. Anesthetized pigs were ventilated with either FCV or PCV for 1 h and thereafter for 30 min each in a crossover comparison. Both ventilation modes were set with a peak pressure of 15 cmH2O, positive end-expiratory pressure of 5 cmH2O, a respiratory rate of 20/min, and a fraction of inspired oxygen at 0.3. All respiratory variables were collected every 15 min. Tidal volume and respiratory minute volume were significantly lower in FCV (n = 5) compared with PCV (n = 5) animals [4.6 vs. 6.6, MD -2.0 (95% CI -2.6 to -1.4) mL/kg; P < 0.001 and 7.3 vs. 9.5, MD -2.2 (95% CI -3.3 to -1.0) L/min; P = 0.006]. Notwithstanding these differences, CO2-removal as well as oxygenation was not inferior in FCV compared with PCV. Mechanical ventilation with identical ventilator settings resulted in lower tidal volumes and consecutive minute volume in FCV compared with PCV. This finding can be explained physically by the continuous gas flow pattern in FCV that necessitates a lower alveolar pressure amplitude. Interestingly, gas exchange was comparable in both groups, which is suggestive of improved ventilation efficiency at a continuous gas flow pattern.NEW & NOTEWORTHY This study examined the effects of a continuous (flow-controlled ventilation, FCV) vs. decelerating (pressure-controlled ventilation, PCV) gas flow pattern during mechanical ventilation. It was shown that FCV necessitates a lower alveolar pressure amplitude leading to reduced applied tidal volumes and consequently minute volume. Notwithstanding these differences, CO2-removal as well as oxygenation was not inferior in FCV compared with PCV, which is suggestive of improved gas exchange efficiency at a continuous gas flow pattern.

COVID-19 Pandemic Did not Influence Number of Oncologic and Emergency Surgeries: A Retrospective Cohort Study from a Tertiary Hospital in Austria.

BACKGROUND: Many articles described a massive decline in surgical procedures during the COVID-19 pandemic waves. Especially the reduction in oncologic and emergency procedures led to the concern that delays and cancelling surgical activity might lead to a substantial increase in preventable deaths. METHODS: Overall numbers and types of surgery were analysed in a tertiary hospital in Austria during the winter period (October-April) from 2015/16 to 2021/22. The half-years 2019/20, 2020/21 and 2021/22 were defined as pandemic half-years and were compared with the mean results of the previous, four, pre-pandemic half-years. RESULTS: A reduction was found for overall numbers and elective surgeries during 2019/20 (4.62%; p < 0.0001 and 12.14; p < 0.0001 respectively) and 2021/22 (14.94%; p < 0.0001 and 34.27; p < 0.0001 respectively). Oncologic surgery increased during 2021/22 (- 12.59%; p < 0.0001) and remained unchanged during the other periods. Emergency surgeries increased during 2019/20 (- 6.97%; p < 0.0001) and during 2021/22 (- 9.44%; p < 0.0001) and remained unchanged during 2020/21. CONCLUSIONS: The concern that the pandemic led to a decrease in oncologic and emergency surgeries cannot be supported with the data from our hospital. A flexible, day-by-day, resource allocation programme with central coordination adhering to hospital resilience recommendations may have helped to adapt to the impact of the COVID-19 pandemic during the first three pandemic half-years.

Individualised flow-controlled versus pressure-controlled ventilation in a porcine oleic acid-induced acute respiratory distress syndrome model.

BACKGROUND: A continuous gas flow provided by flow-controlled ventilation (FCV) facilitates accurate dynamic compliance measurement and allows the clinician to individually optimise positive end-expiratory and peak pressure settings accordingly. OBJECTIVE: The aim of this study was to compare the efficiency of gas exchange and impact on haemodynamics between individualised FCV and pressure-controlled ventilation (PCV) in a porcine model of oleic acid-induced acute respiratory distress syndrome (ARDS). DESIGN: Randomised controlled interventional trial conducted on 16 pigs. SETTING: Animal operating facility at the Medical University Innsbruck. INTERVENTIONS: ARDS was induced in lung healthy pigs by intravenous infusion of oleic acid until moderate-to-severe ARDS at a stable Horowitz quotient (PaO 2 FiO 2-1 ) of 80 to 120 over a period of 30 min was obtained. Ventilation was then either performed with individualised FCV ( n  = 8) established by compliance-guided pressure titration or PCV ( n  = 8) with compliance-guided titration of the positive end-expiratory pressure and peak pressure set to achieve a tidal volume of 6 ml kg -1 over a period of 2 h. MAIN OUTCOME MEASURES: Gas exchange parameters were assessed by the PaO 2 FiO 2-1 quotient and CO 2 removal by the PaCO 2 value in relation to required respiratory minute volume. Required catecholamine support for haemodynamic stabilisation was measured. RESULTS: The FCV group showed significantly improved oxygenation [149.2 vs. 110.4, median difference (MD) 38.7 (8.0 to 69.5) PaO 2 FiO 2-1 ; P  = 0.027] and CO 2 removal [PaCO 2 7.25 vs. 9.05, MD -1.8 (-2.87 to -0.72) kPa; P  = 0.006] at a significantly lower respiratory minute volume [8.4 vs. 11.9, MD -3.6 (-5.6 to -1.5) l min -1 ; P  = 0.005] compared with PCV. In addition, in FCV-pigs, haemodynamic stabilisation occurred with a significant reduction of required catecholamine support [norepinephrine 0.26 vs. 0.86, MD -0.61 (-1.12 to -0.09) µg kg -1  min -1 ; P  = 0.037] during 2 ventilation hours. CONCLUSION: In this oleic acid-induced porcine ARDS model, individualised FCV significantly improved gas exchange and haemodynamic stability compared with PCV. TRIAL REGISTRATION: Protocol no.: BMBWF-66.011/0105-V/3b/2019).

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

BACKGROUND: 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. OBJECTIVE: 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). DESIGN: Controlled interventional trial conducted on 16 domestic pigs. SETTING: Animal operating facility at the Medical University of Innsbruck. INTERVENTIONS: 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. MAIN OUTCOME MEASURES: 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. RESULTS: 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). CONCLUSIONS: 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.

A case report of individualized ventilation in a COVID-19 patient - new possibilities and caveats to consider with flow-controlled ventilation.

BACKGROUND: Flow-controlled ventilation (FCV) is a novel ventilation method increasingly being used clinically, particularly during the current COVID-19 pandemic. However, the continuous flow pattern in FCV during inspiration and expiration has a significant impact on respiratory parameters and ventilatory settings compared to conventional ventilation modes. In addition, the constant flow combined with direct intratracheal pressure measurement allows determination of dynamic compliance and ventilation settings can be adjusted accordingly, reflecting a personalized ventilation approach. CASE PRESENTATION: A 50-year old women with confirmed SARS-CoV-2 infection suffering from acute respiratory distress syndrome (ARDS) was admitted to a tertiary medical center. Initial ventilation occurred with best standard of care pressure-controlled ventilation (PCV) and was then switched to FCV, by adopting PCV ventilator settings. This led to an increase in oxygenation by 30 %. Subsequently, to reduce invasiveness of mechanical ventilation, FCV was individualized by dynamic compliance guided adjustment of both, positive end-expiratory pressure and peak pressure; this intervention reduced driving pressure from 18 to 12 cm H2O. However, after several hours, compliance further deteriorated which resulted in a tidal volume of only 4.7 ml/kg. CONCLUSIONS: An individualized FCV approach increased oxygenation parameters in a patient suffering from severe COVID-19 related ARDS. Direct intratracheal pressure measurements allow for determination of dynamic compliance and thus optimization of ventilator settings, thereby reducing applied and dissipated energy. However, although desirable, this personalized ventilation strategy may reach its limits when lung function is so severely impaired that patient's oxygenation has to be ensured at the expense of lung protective ventilation concepts.

The Endothelial Glycocalyx and Organ Preservation-From Physiology to Possible Clinical Implications for Solid Organ Transplantation.

The endothelial glycocalyx is a thin layer consisting of proteoglycans, glycoproteins and glycosaminoglycans that lines the luminal side of vascular endothelial cells. It acts as a barrier and contributes to the maintenance of vascular homeostasis and microperfusion. During solid organ transplantation, the endothelial glycocalyx of the graft is damaged as part of Ischemia Reperfusion Injury (IRI), which is associated with impaired organ function. Although several substances are known to mitigate glycocalyx damage, it has not been possible to use these substances during graft storage on ice. Normothermic machine perfusion (NMP) emerges as an alternative technology for organ preservation and allows for organ evaluation, but also offers the possibility to treat and thus improve organ quality during storage. This review highlights the current knowledge on glycocalyx injury during organ transplantation, presents ways to protect the endothelial glycocalyx and discusses potential glycocalyx protection strategies during normothermic machine perfusion.

Individualized flow-controlled ventilation compared to best clinical practice pressure-controlled ventilation: a prospective randomized porcine study.

BACKGROUND: Flow-controlled ventilation is a novel ventilation method which allows to individualize ventilation according to dynamic lung mechanic limits based on direct tracheal pressure measurement at a stable constant gas flow during inspiration and expiration. The aim of this porcine study was to compare individualized flow-controlled ventilation (FCV) and current guideline-conform pressure-controlled ventilation (PCV) in long-term ventilation. METHODS: Anesthetized pigs were ventilated with either FCV or PCV over a period of 10 h with a fixed FiO2 of 0.3. FCV settings were individualized by compliance-guided positive end-expiratory pressure (PEEP) and peak pressure (Ppeak) titration. Flow was adjusted to maintain normocapnia and the inspiration to expiration ratio (I:E ratio) was set at 1:1. PCV was performed with a PEEP of 5 cm H2O and Ppeak was set to achieve a tidal volume (VT) of 7 ml/kg. The respiratory rate was adjusted to maintain normocapnia and the I:E ratio was set at 1:1.5. Repeated measurements during observation period were assessed by linear mixed-effects model. RESULTS: In FCV (n = 6), respiratory minute volume was significantly reduced (6.0 vs 12.7, MD - 6.8 (- 8.2 to - 5.4) l/min; p < 0.001) as compared to PCV (n = 6). Oxygenation was improved in the FCV group (paO2 119.8 vs 96.6, MD 23.2 (9.0 to 37.5) Torr; 15.97 vs 12.87, MD 3.10 (1.19 to 5.00) kPa; p = 0.010) and CO2 removal was more efficient (paCO2 40.1 vs 44.9, MD - 4.7 (- 7.4 to - 2.0) Torr; 5.35 vs 5.98, MD - 0.63 (- 0.99 to - 0.27) kPa; p = 0.006). Ppeak and driving pressure were comparable in both groups, whereas PEEP was significantly lower in FCV (p = 0.002). Computed tomography revealed a significant reduction in non-aerated lung tissue in individualized FCV (p = 0.026) and no significant difference in overdistended lung tissue, although a significantly higher VT was applied (8.2 vs 7.6, MD 0.7 (0.2 to 1.2) ml/kg; p = 0.025). CONCLUSION: Our long-term ventilation study demonstrates the applicability of a compliance-guided individualization of FCV settings, which resulted in significantly improved gas exchange and lung tissue aeration without signs of overinflation as compared to best clinical practice PCV.

Manual versus Mechanical Chest Compressions on Surfaces of Varying Softness with or without Backboards: A Randomized, Crossover Manikin Study.

BACKGROUND: Chest compression quality is decisive for overall outcome after cardiac arrest. Chest compression depth may decrease when cardiopulmonary resuscitation (CPR) is performed on a mattress, and the use of a backboard does not necessarily improve compression depth. Mechanical chest compression devices may overcome this problem. OBJECTIVES: We sought to investigate the effectiveness of manual chest compressions both with and without a backboard compared to mechanical CPR performed on surfaces of different softness. METHODS: Twenty-four advanced life support (ALS)-certified rescuers were enrolled. LUCAS2 (Physio-Control, Redmond, WA) delivers 52 ± 2 mm deep chest compressions and active decompressions back to the neutral position (frequency 102 min(-1); duty cycle, 50%). This simulated CPR scenario was performed on a Resusci-Anne manikin (Laerdal, Stavanger, Norway) that was lying on 3 different surfaces: 1) a concrete floor, 2) a firm standard mattress, and 3) a pressure-relieving mattress. Data were recorded by the Laerdal Skill Reporting System. RESULTS: Manual chest compression with or without a backboard were performed correctly less often than mechanical chest compressions (floor: 33% [interquartile range {IQR}, 27-48%] vs. 90% [IQR, 86-94%], p < 0.001; standard mattress: 32% [IQR, 20-45%] vs. 27% [IQR, 14-46%] vs. 91% [IQR, 51-94%], p < 0.001; and pressure-relieving mattress 29% [IQR, 17-49%] vs. 30% [IQR, 17-52%] vs. 91% [IQR, 87-95%], p < 0.001). The mean compression depth on both mattresses was deeper with mechanical chest compressions (floor: 53 mm [range, 47-57 mm] vs. 56 mm [range, 54-57 mm], p = 0.003; standard mattress: 50 mm [range, 44-55 mm] vs. 51 mm [range, 47-55 mm] vs. 55 mm [range, 54-58 mm], p < 0.001; and pressure-relieving mattress: 49 mm [range, 44-55 mm] vs. 50 mm [range, 44-53 mm] vs. 55 mm [range, 55-56 mm], p < 0.001). In this ∼6-min scenario, the mean hands-off time was ∼15 to 20 s shorter in the manual CPR scenarios. CONCLUSIONS: In this experimental study, only ∼30% of manual chest compressions were performed correctly compared to ∼90% of mechanical chest compressions, regardless of the underlying surface. Backboard use did not influence the mean compression depth during manual CPR. Chest compressions were deeper with mechanical CPR. The mean hands-off time was shorter with manual CPR.

Normothermic Machine Perfusion Reduces Transfusion Requirements Even After Static Cold Storage: A 1 y Retrospective Single-center Analysis.

Background: Normothermic machine perfusion (NMP) of liver grafts has been shown to reduce intraoperative catecholamine consumption and the need for allogenic blood products after reperfusion compared with organs undergoing classical static cold storage (SCS). This study aimed to investigate the effects of an NMP phase after SCS (NMP after SCS) of liver grafts in terms of postreperfusion hemodynamics and transfusion requirements. Methods: Eighteen recipients of NMP after SCS grafts were matched according to recipient age, donor age, and model for end-stage liver disease score in a 1:2 ratio with recipients of an SCS graft. Postreperfusion hemodynamics and the need for catecholamines, blood products, and clotting factors were compared. Results: After reperfusion of the organ, patients in the NMP after SCS group showed significantly reduced transfusion requirements for packed red blood cells and platelet concentrates compared with patients of the SCS group (P < 0.001 and P = 0.018, respectively). In addition, patients in the NMP after SCS group received less fibrinogen concentrate (NMP after SCS group 0 [0-1.5] g versus SCS group 2 [0-4] g; P = 0.0163). No differences in postreperfusion hemodynamics could be detected between groups. Conclusions: This retrospective analysis shows that NMP reduces postreperfusion requirements of red blood cells, platelet concentrates, and fibrinogen concentrate even if installed after a phase of organ SCS, because it may be practiced on most centers where NMP is available.

Individualised flow-controlled ventilation reduces applied mechanical power and improves ventilation efficiency in a porcine intra-abdominal hypertension model.

BACKGROUND: Aim of this study was to evaluate feasibility and effects of individualised flow-controlled ventilation (FCV), based on compliance guided pressure settings, compared to standard of pressure-controlled ventilation (PCV) in a porcine intra-abdominal hypertension (IAH) model. The primary aim of this study was to investigate oxygenation. Secondary aims were to assess respiratory and metabolic variables and lung tissue aeration. METHODS: Pigs were randomly assigned to FCV (n = 9) and PCV (n = 9). IAH was induced by insufflation of air into the abdomen to induce IAH grades ranging from 0 to 3. At each IAH grade FCV was undertaken using compliance guided pressure settings, or PCV (n = 9) was undertaken with the positive end-expiratory pressure titrated for maximum compliance and the peak pressure set to achieve a tidal volume of 7 ml/kg. Gas exchange, ventilator settings and derived formulas were recorded at two timepoints for each grade of IAH. Lung aeration was assessed by a computed tomography scan at IAH grade 3. RESULTS: All 18 pigs (median weight 54 kg [IQR 51-67]) completed the observation period of 4 h. Oxygenation was comparable at each IAH grade, but a significantly lower minute volume was required to secure normocapnia in FCV at all IAH grades (7.6 vs. 14.4, MD - 6.8 (95% CI - 8.5 to - 5.2) l/min; p < 0.001). There was also a significant reduction of applied mechanical power being most evident at IAH grade 3 (25.9 vs. 57.6, MD - 31.7 (95% CI - 39.7 to - 23.7) J/min; p < 0.001). Analysis of Hounsfield unit distribution of the computed tomography scans revealed a significant reduction in non- (5 vs. 8, MD - 3 (95% CI - 6 to 0) %; p = 0.032) and poorly-aerated lung tissue (7 vs. 15, MD - 6 (95% CI - 13 to - 3) %, p = 0.002) for FCV. Concomitantly, normally-aerated lung tissue was significantly increased (84 vs. 76, MD 8 (95% CI 2 to 15) %; p = 0.011). CONCLUSIONS: Individualised FCV showed similar oxygenation but required a significantly lower minute volume for CO2-removal, which led to a remarkable reduction of applied mechanical power. Additionally, there was a shift from non- and poorly-aerated lung tissue to normally-aerated lung tissue in FCV compared to PCV.

LUCAS compared to manual cardiopulmonary resuscitation is more effective during helicopter rescue-a prospective, randomized, cross-over manikin study.

OBJECTIVE: High-quality chest-compressions are of paramount importance for survival and good neurological outcome after cardiac arrest. However, even healthcare professionals have difficulty performing effective chest-compressions, and quality may be further reduced during transport. We compared a mechanical chest-compression device (Lund University Cardiac Assist System [LUCAS]; Jolife, Lund, Sweden) and manual chest-compressions in a simulated cardiopulmonary resuscitation scenario during helicopter rescue. METHODS: Twenty-five advanced life support-certified paramedics were enrolled for this prospective, randomized, crossover study. A modified Resusci Anne manikin was employed. Thirty minutes of training was allotted to both LUCAS and manual cardiopulmonary resuscitation (CPR). Thereafter, every candidate performed the same scenario twice, once with LUCAS and once with manual CPR. The primary outcome measure was the percentage of correct chest-compressions relative to total chest-compressions. RESULTS: LUCAS compared to manual chest-compressions were more frequently correct (99% vs 59%, P < .001) and were more often performed correctly regarding depth (99% vs 79%, P < .001), pressure point (100% vs 79%, P < .001) and pressure release (100% vs 97%, P = .001). Hands-off time was shorter in the LUCAS than in the manual group (46 vs 130 seconds, P < .001). Time until first defibrillation was longer in the LUCAS group (112 vs 49 seconds, P < .001). CONCLUSIONS: During this simulated cardiac arrest scenario in helicopter rescue LUCAS compared to manual chest-compressions increased CPR quality and reduced hands-off time, but prolonged the time interval to the first defibrillation. Further clinical trials are warranted to confirm potential benefits of LUCAS CPR in helicopter rescue.

[Emergency missions in Tyrol in spring 2020 : Influence of COVID-19-A retrospective observational study focusing on air rescue]. / Notärztliche Einsätze in Tirol im Frühjahr 2020 : Der Einfluss von COVID-19 ­ eine retrospektive Beobachtungsstudie mit Fokus Luftrettung.

BACKGROUND: Tyrol, a province of Austria with about 760,000 inhabitants, was one of the first regions in Europe, along with northern Italy, to be affected by the pandemic spread of the coronavirus in spring 2020. A lockdown with far-reaching restrictions in all areas of life occurred from 16 March 2020. Restrictions were imposed in the areas of gastronomy, trade and free mobility as well as in recreational sports. The ski resorts were closed and due to the strong winter tourism in Tyrol, this meant that about 340,000 people left the region. In the province of Tyrol comprehensive emergency medical care is provided by 13 ground-based emergency medical systems (NEF) in combination with air rescue (16 emergency medical helicopters, some of which are seasonal). Normally, this system provides emergency medical care for approx. 1 million people; however, in spring 2020 during the first lockdown, the number of people to be cared for was approx. 30% less. In order to protect the emergency medical teams as best as possible from infections and thus the system from failures, the Integrated Control Center Tyrol (Landesleitstelle Tirol GmbH) adapted the release order for emergency medical resources. The aim of the study is to describe the influence of the pandemic in spring 2020 on the emergency medical services in Tyrol in comparison to the three preceding years. METHODS: A retrospective survey of all emergency helicopter missions and ground-based emergency physician missions in Tyrol in the period 15 March 2020-15 May 2020, as well as in the same period of the previous years 2017-2019, was conducted. Detailed figures on medical procedures and patient-related data were collected from 6 ÖAMTC helicopter bases. In addition, all ground-based emergency physician missions from all 13 physician systems including appeal mission diagnoses were collected in the same period. RESULTS: The total number of emergency helicopter missions and ground-based emergency physician missions showed a significant decrease during the observational period (67.3% and 39.8%, respectively). In the area of ground-based emergency medical resources, there was a significant increase in respiratory and CNS diseases during the observational period. The range of emergency helicopter missions showed a significant shift from sports and leisure missions to internal medicine and neurological emergencies and the duration of missions was significantly longer. The NACA score was higher with a significant decrease in NACA 3 scores in favor of NACA 4 and 5. The circulatory status of patients during the observational period was significantly more often documented as unstable. Hypertension, impending shock and circulatory arrest occurred more frequently in the trend. Cardiac massage, oxygen administration, circulatory drugs and specific monitoring were used more frequently in 2020. Analgesics were administered less frequently. In air rescue, there was no infection of rescue workers in the field. CONCLUSION: The first pandemic wave in Tyrol and the consecutive lockdown from 16 March 2020 had a massive impact on emergency medical care in Tyrol, both quantitatively and in terms of the spectrum of operations and emergency medical interventions. The decline in patient numbers was highly relevant, especially in air rescue and can be explained in part by the discontinuation of tourism, the general exit restrictions and the restrictive disengagement order. This decline primarily affected patients in the NACA 3 category and the analgesic administration measure. The patients treated had a higher NACA score and the emergency procedures were more extensive during the observational period. The measures to protect the emergency helicopter team from infections were presumably successful as no infections occurred.

Flow-controlled versus pressure-controlled ventilation in cardiac surgery with cardiopulmonary bypass - A single-center, prospective, randomized, controlled trial.

STUDY OBJECTIVE: Multifactorial comparison of flow-controlled ventilation (FCV) to standard of pressure-controlled ventilation (PCV) in terms of oxygenation in cardiac surgery patients after chest closure. DESIGN: Prospective, non-blinded, randomized, controlled trial. SETTING: Operating theatre at an university hospital, Austria. PATIENTS: Patients scheduled for elective, open, on-pump, cardiac surgery. INTERVENTIONS: Participants were randomized to either individualized FCV (compliance guided end-expiratory and peak pressure setting) or control of PCV (compliance guided end-expiratory pressure setting and tidal volume of 6-8 ml/kg) for the duration of surgery. MEASUREMENTS: The primary outcome measure was oxygenation (PaO2/FiO2) 15 min after intraoperative chest closure. Secondary endpoints included CO2-removal assessed as required minute volume to achieve normocapnia and lung tissue aeration assessed by Hounsfield unit distribution in postoperative computed tomography scans. MAIN RESULTS: Between April 2020 and April 2021 56 patients were enrolled and 50 included in the primary analysis (mean age 70 years, 38 (76%) men). Oxygenation, assessed by PaO2/FiO2, was significantly higher in the FCV group (n = 24) compared to the control group (PCV, n = 26) (356 vs. 309, median difference (MD) 46 (95% CI 3 to 90) mmHg; p = 0.038). Additionally, the minute volume required to obtain normocapnia was significantly lower in the FCV group (4.0 vs. 6.1, MD -2.0 (95% CI -2.5 to -1.5) l/min; p < 0.001) and correlated with a significantly lower exposure to mechanical power (5.1 vs. 9.8, MD -5.1 (95% CI -6.2 to -4.0) J/min; p < 0.001). Evaluation of lung tissue aeration revealed a significantly reduced amount of non-aerated lung tissue in FCV compared to PCV (5 vs. 7, MD -3 (95% CI -4 to -1) %; p < 0.001). CONCLUSIONS: In patients undergoing on-pump, cardiac surgery individualized FCV significantly improved oxygenation and lung tissue aeration compared to PCV. In addition, carbon dioxide removal was accomplished at a lower minute volume leading to reduced applied mechanical power.

Short time effects of compliance guided flow-controlled ventilation versus standard of care pressure-controlled ventilation: a prospective porcine trial.

BACKGROUND: Flow-controlled ventilation (FCV) represents a novel ventilation method, which guarantees a continuous gas flow during inspiration and expiration. Long term comparison to volume- and pressure-controlled ventilation (PCV) after five- and ten hours have shown improved gas exchange parameters and lung tissue aeration. Aim of this porcine trial was to compare gas exchange parameters and lung tissue aeration in short time application of FCV compared to PCV to determine effects which will most probably pertain in short lasting procedures under general anesthesia. METHODS: After induction of general anesthesia nine pigs were randomly ventilated either with compliance guided FCV settings or standard of PCV with compliance titrated positive end-expiratory pressure and peak pressure set to achieve a tidal volume of 7 mL/kg. Subsequently an arterial blood gas sample was obtained, and a computed tomography scan was performed. Afterwards, each animal was extubated and on the following day the same protocol was performed again with the alternative ventilation method. RESULTS: Primary analysis of 18 datasets from nine animals (with paired comparison) revealed a significantly improved oxygenation with FCV compared to control (paO2 118 vs. 109, 95% CI 2 to 16 mm Hg; P=0.042). The required respiratory minute volume was significantly lower with FCV (7.4 vs. 10.8, 95% CI -4.0 to -2.9 L/min; P<0.001) to achieve similar levels of normocapnia. However, lung tissue aeration did not significantly differ between ventilation methods. CONCLUSIONS: In this short-term ventilation comparison FCV improved gas exchange parameters without differences in lung tissue aeration compared to PCV.

Interleukin-6 Levels During Normothermic Machine Perfusion Impact Postreperfusion Hemodynamics of Liver Graft Recipients: A Prospective Single-center Observational Study.

BACKGROUND: Hemodynamic instability after liver graft reperfusion increases recipient morbidity after liver transplantation. The etiologies of hemodynamic disturbances appear to be multifactorial and are poorly understood. Normothermic machine perfusion (NMP) provides an opportunity to analyze graft quality prior to transplantation. In the present study, we aim to investigate the influence of interleukin-6 (IL-6) levels during NMP on postreperfusion hemodynamics of the recipient. METHODS: Consecutive NMP-liver transplants at a single-center were prospectively analyzed. Perfusate samples were collected at the beginning, after 6 h, and at the end of perfusion and analyzed for IL-6 levels. Mean arterial pressure (MAP) and catecholamine consumption during surgery were recorded. IL-6 levels at the end of NMP were correlated to donor and perfusion characteristics as well as changes in MAP and catecholamine requirements during the anhepatic and reperfusion phase. RESULTS: IL-6 perfusate measurements were assessed in 77 livers undergoing NMP and transplantation. Donor age, sex, cold ischemic time, and NMP time did not correlate with IL-6 levels. Perfusates of donation after circulatory death grafts showed higher IL-6 levels at the end of NMP than donation after brain death grafts. However, IL-6 levels at the end of NMP correlated with catecholamine requirements and MAP in the reperfusion phase. Per log10 increase in IL-6 levels, an increase of 42% points in administered catecholamine dose was observed, despite MAP being decreased by 3.6% points compared to baseline values. CONCLUSIONS: IL-6 levels may be a predictor for recipient hemodynamic instability during liver reperfusion. Larger studies are needed to confirm this finding.

Low Ambient Temperature Exposition Impairs the Accuracy of a Non-invasive Heat-Flux Thermometer.

Background: Indirect core body temperature (CBT) monitoring from skin sensors is gaining attention for in-field applications thanks to non-invasivity, portability, and easy probe positioning. Among skin sensors, heat-flux devices, such as the so-called Double Sensor (DS), have demonstrated reliability under various experimental and clinical conditions. Still, their accuracy at low ambient temperatures is unknown. In this randomized cross-over trial, we tested the effects of cold temperature exposition on DS performance in tracking CBT. Methods: Twenty-one participants were exposed to a warm (23.2 ± 0.4°C) and cold (-18.7 ± 1.0°C) room condition for 10 min, following a randomized cross-over design. The accuracy of the DS to estimate CBT in both settings was assessed by quantitative comparison with esophageal (reference) and tympanic (comparator) thermometers, using Bland-Altman and correlation analyses (Pearson's correlation coefficient, r, and Lin's concordance correlation coefficient, CCC). Results: In the warm room setting, the DS showed a moderate agreement with the esophageal sensor [bias = 0.09 (-1.51; 1.69) °C, r = 0.40 (p = 0.069), CCC = 0.22 (-0.006; 0.43)] and tympanic sensor [bias = 2.74 (1.13; 4.35) °C, r = 0.54 (p < 0.05), CCC = 0.09 (0.008; 0.16)]. DS accuracy significantly deteriorated in the cold room setting, where DS temperature overestimated esophageal temperature [bias = 2.16 (-0.89; 5.22) °C, r = 0.02 (0.94), CCC = 0.002 (-0.05; 0.06)]. Previous exposition to the cold influenced temperature values measured by the DS in the warm room setting, where significant differences (p < 0.00001) in DS temperature were observed between randomization groups. Conclusion: DS accuracy is influenced by environmental conditions and previous exposure to cold settings. These results suggest the present inadequacy of the DS device for in-field applications in low-temperature environments and advocate further technological advancements and proper sensor insulation to improve performance in these conditions.

Solid Organ Donation From Brain-dead Donors With Cardiorespiratory Arrest After Snow Avalanche Burial: A Retrospective Single-center Study.

BACKGROUND: Complete snow avalanche burial is associated with high mortality. The aim of this study was to assess the feasibility and incidence of organ retrieval in brain-dead donors following cardiorespiratory arrest due to avalanche burial and to evaluate the function of transplanted organs. METHODS: The transplant registry of the Medical University of Innsbruck was searched for organ donors with a history of avalanche burial, and the function and survival of transplanted organs were assessed. RESULTS: Thirty-three organs were procured from eight donors and 31 organs (13 kidneys, 6 livers, 3 pancreases, 5 hearts, and 4 lungs) were ultimately transplanted. Allograft and recipient 1-y survival were 100% and both initial and long-term graft function were good. Only one-third of all avalanche victims who died in the intensive care unit with signs of irreversible hypoxic brain injury became organ donors. CONCLUSIONS: Initial experience from this retrospective study suggests that organs from brain-dead avalanche victims can be transplanted with good results. Starting a Donation after Circulatory Determination of Death program might be an option for increasing the number of organ donations from avalanche victims with irreversible hypoxic brain injury.