First-line treatment of persistent and long-standing persistent atrial fibrillation with single-stage hybrid ablation: a 2-year follow-up study.

AIMS: This study evaluates the efficacy and safety of first-line single-stage hybrid ablation of (long-standing) persistent atrial fibrillation (AF), over a follow-up period of 2 years, and provides additional information on arrhythmia recurrences and electrophysiological findings at repeat ablation. METHODS AND RESULTS: This is a prospective cohort study that included 49 patients (65% persistent AF; 35% long-standing persistent AF) who underwent hybrid ablation as first-line ablation treatment (no previous endocardial ablation). Patients were relatively young (57.0 ± 8.5 years) and predominantly male (89.8%). Median CHA2DS2-VASc score was 1.0 (0.5; 2.0) and mean left atrium volume index was 43.7 ± 10.9 mL/m2. Efficacy was assessed by 12-lead electrocardiography and 72-h Holter monitoring after 3, 6, 12, and 24 months. Recurrence was defined as AF/atrial flutter (AFL)/tachycardia (AT) recorded by electrocardiography or Holter monitoring lasting >30 s during 2-year follow-up. At 2-year follow-up, single and multiple procedure success rates were 67% and 82%, respectively. Two (4%) patients experienced a major complication (bleeding) requiring intervention following hybrid ablation. Among the 16 (33%) patients who experienced an AF/AFL/AT recurrence, 13 (81%) were ATs/AFLs and only 3 (19%) were AF. Repeat ablation was performed in 10 (20%) patients and resulted in sinus rhythm in 7 (70%) at 2-year follow-up. CONCLUSION: First-line single-stage hybrid AF ablation is an effective treatment strategy for patients with persistent and long-standing persistent AF with an acceptable rate of major complications. Recurrences are predominantly AFL/AT that can be successfully ablated percutaneously. Hybrid ablation seems a feasible approach for first-line ablation of (long-standing) persistent AF.

Extracorporeal Chloride Removal by Electrodialysis. A Novel Approach to Correct Acidemia.

Rationale: Acidemia is a severe condition among critically ill patients. Despite lack of evidence, sodium bicarbonate is frequently used to correct pH; however, its administration is burdened by several side effects. We hypothesized that the reduction of plasma chloride concentration could be an alternative strategy to correct acidemia.Objectives: To evaluate feasibility, safety, and effectiveness of a novel strategy to correct acidemia through extracorporeal chloride removal by electrodialysis.Methods: Ten swine (six treated and four control animals) were sedated, mechanically ventilated and connected to an extracorporeal electrodialysis device capable of selectively removing chloride. In random order, an arterial pH of 7.15 was induced either through reduction of ventilation (respiratory acidosis) or through lactic acid infusion (metabolic acidosis). Acidosis was subsequently sustained for 12-14 hours. In treatment pigs, soon after reaching target acidemia, electrodialysis was started to restore pH.Measurements and Main Results: During respiratory acidosis, electrodialysis reduced plasma chloride concentration by 26 ± 5 mEq/L within 6 hours (final pH = 7.36 ± 0.04). Control animals exhibited incomplete and slower compensatory response to respiratory acidosis (final pH = 7.29 ± 0.03; P < 0.001). During metabolic acidosis, electrodialysis reduced plasma chloride concentration by 15 ± 3 mEq/L within 4 hours (final pH = 7.34 ± 0.07). No effective compensatory response occurred in control animals (final pH = 7.11 ± 0.08; P < 0.001). No complications occurred.Conclusions: We described the first in vivo application of an extracorporeal system targeted to correct severe acidemia by lowering plasma chloride concentration. Extracorporeal chloride removal by electrodialysis proved to be feasible, safe, and effective. Further studies are warranted to assess its performance in the presence of impaired respiratory and renal functions.

Transpulmonary Pressure Describes Lung Morphology During Decremental Positive End-Expiratory Pressure Trials in Obesity.

OBJECTIVES: Atelectasis develops in critically ill obese patients when undergoing mechanical ventilation due to increased pleural pressure. The current study aimed to determine the relationship between transpulmonary pressure, lung mechanics, and lung morphology and to quantify the benefits of a decremental positive end-expiratory pressure trial preceded by a recruitment maneuver. DESIGN: Prospective, crossover, nonrandomized interventional study. SETTING: Medical and Surgical Intensive Care Units at Massachusetts General Hospital (Boston, MA) and University Animal Research Laboratory (São Paulo, Brazil). PATIENTS/SUBJECTS: Critically ill obese patients with acute respiratory failure and anesthetized swine. INTERVENTIONS: Clinical data from 16 mechanically ventilated critically ill obese patients were analyzed. An animal model of obesity with reversible atelectasis was developed by placing fluid filled bags on the abdomen to describe changes of lung mechanics, lung morphology, and pulmonary hemodynamics in 10 swine. MEASUREMENTS AND MAIN RESULTS: In obese patients (body mass index, 48 ± 11 kg/m), 21.7 ± 3.7 cm H2O of positive end-expiratory pressure resulted in the lowest elastance of the respiratory system (18.6 ± 6.1 cm H2O/L) after a recruitment maneuver and decremental positive end-expiratory pressure and corresponded to a positive (2.1 ± 2.2 cm H2O) end-expiratory transpulmonary pressure. Ventilation at lowest elastance positive end-expiratory pressure preceded by a recruitment maneuver restored end-expiratory lung volume (30.4 ± 9.1 mL/kg ideal body weight) and oxygenation (273.4 ± 72.1 mm Hg). In the swine model, lung collapse and intratidal recruitment/derecruitment occurred when the positive end-expiratory transpulmonary pressure decreased below 2-4 cm H2O. After the development of atelectasis, a decremental positive end-expiratory pressure trial preceded by lung recruitment identified the positive end-expiratory pressure level (17.4 ± 2.1 cm H2O) needed to restore poorly and nonaerated lung tissue, reestablishing lung elastance and oxygenation while avoiding increased pulmonary vascular resistance. CONCLUSIONS: In obesity, low-to-negative values of transpulmonary pressure predict lung collapse and intratidal recruitment/derecruitment. A decremental positive end-expiratory pressure trial preceded by a recruitment maneuver reverses atelectasis, improves lung mechanics, distribution of ventilation and oxygenation, and does not increase pulmonary vascular resistance.

Respiratory Electrodialysis. A Novel, Highly Efficient Extracorporeal CO2 Removal Technique.

RATIONALE: We developed an innovative, minimally invasive, highly efficient extracorporeal CO2 removal (ECCO2R) technique called respiratory electrodialysis (R-ED). OBJECTIVES: To evaluate the efficacy of R-ED in controlling ventilation compared with conventional ECCO2R technology. METHODS: Five mechanically ventilated swine were connected to a custom-made circuit optimized for R-ED, consisting of a hemofilter, a membrane lung, and an electrodialysis cell. Electrodialysis regionally modulates blood electrolyte concentration to convert bicarbonate to CO2 before entering the membrane lung, enhancing membrane lung CO2 extraction. All animals underwent three repeated experimental sequences, consisting of four steps: baseline (1 h), conventional ECCO2R (2 h), R-ED (2 h), and final NO-ECCO2R (1 h). Blood and gas flow were 250 ml/min and 10 L/min, respectively. Tidal volume was set at 8 ml/kg, and respiratory rate was adjusted to maintain arterial Pco2 at 50 mm Hg. MEASUREMENTS AND MAIN RESULTS: During R-ED, chloride and H(+) concentration increased in blood entering the membrane lung, almost doubling CO2 extraction compared with ECCO2R (112 ± 6 vs. 64 ± 5 ml/min, P < 0.001). Compared with baseline, R-ED and ECCO2R reduced minute ventilation by 50% and 27%, respectively. Systemic arterial gas analyses remained stable during the experimental phases. No major complication occurred, but there was an increase in creatinine level. CONCLUSIONS: In this first in vivo application, we proved electrodialysis feasible and effective in increasing membrane lung CO2 extraction. R-ED was more effective than conventional ECCO2R technology in controlling ventilation. Further studies are warranted to assess the safety profile of R-ED, especially regarding kidney function.

High-Resolution Intracranial Pressure Burden and Outcome in Subarachnoid Hemorrhage.

BACKGROUND AND PURPOSE: Intracranial pressure (ICP) control is a therapeutic target in patients with aneurysmal subarachnoid hemorrhage, although only a limited number of studies assessed its course and effect on outcome. Pressure-time dose (PTDICP) is a method to quantify the burden and the time spent above a defined threshold of ICP. PTDICP or its relationship with outcome has never been evaluated in aneurysmal subarachnoid hemorrhage. METHODS: Analysis of data prospectively collected from aneurysmal subarachnoid hemorrhage patients admitted to Neurointensive Care Unit. Monitored data, including intraparenchymal ICP, were digitally recorded minute-by-minute in the first 7 days. PTDICP (mm Hg h) was computed using 4 predefined thresholds (15, 20, 25, and 30 mm Hg). Outcome was assessed through Extended Glasgow Outcome Scale at hospital discharge and at 6 months. RESULTS: Fifty-five patients were enrolled. Forty-two patients (76%) presented with a poor clinical grade. Overall, mortality was 17% at hospital discharge and 34% at 6 months. Half of patients required extensive therapy to control high ICP during day 1. Median ICP was 10 mm Hg (4-75), whereas median PTDICP15, PTDICP20, PTDICP25, PTDICP30 were, respectively, 13, 4, 2, and 1 mm Hg h. We observed an association between mortality at hospital discharge and higher level of PTDICP using 20, 25, and 30 mm Hg as thresholds and between exposure to a moderate-level PTDICP30 and unfavorable long-term outcome. CONCLUSIONS: PTDICP may better define one of the insults that the brain suffers after aneurysmal rupture, and exposure to moderate PTDICP30 was significant prognostic factor of 6-month unfavorable outcome.

Effects on membrane lung gas exchange of an intermittent high gas flow recruitment maneuver: preliminary data in veno-venous ECMO patients.

Gas exchange capabilities of polymethylpentene membrane lungs (MLs) worsen over time. ML deterioration is related to protein deposit and clot formation. Condensation and trapping of water vapor inside ML hollow fibers might affect ML performances as well. Increasing sweep gas flow (GF) could remove such fluid. The purpose of this study was to evaluate the effects on ML gas exchange of a recruitment maneuver (RM) based on a brief increase in GF, during veno-venous ECMO support. Short-term (15 min) effects of 20 RMs were assessed. RM raised ML CO2 removal from 149 ± 37 to 174 ± 41 ml/min (p < 0.001). Conversely, RM did not improve ML O2 transfer (155 ± 31 and 158 ± 31 ml/min before and after RM, respectively). ML outlet pCO2 decreased after RM from 51.2 ± 5.8 to 45.8 ± 5.4 mmHg (p < 0.001), while ML outlet pO2 increased from 520 ± 61 to 555 ± 51 mmHg (p < 0.001). Both ML dead space and shunt fractions decreased from 47.8 ± 15.3 to 29.6 ± 14.7 % (p < 0.001) and from 8.8 ± 4.2 to 7.0 ± 3.8 % (p < 0.001), respectively. Furthermore, a subset of 5 RMs was evaluated on a 6-h time frame. The beneficial effects on ML performances due to the RM gradually diminished and waned over a 6-h interval after the RM. The RM improved ML CO2 removal substantially, albeit temporarily. ML oxygenation performance was marginally affected.

Electrophysiological findings during re-do procedures after single-shot pulmonary vein isolation for atrial fibrillation with pulsed field ablation.

BACKGROUND: Pulsed field ablation (PFA) is a novel ablation technology recently adopted in the treatment of atrial fibrillation (AF). Currently, little is known about the durability of PFA ablation lesions. METHODS: We investigated patients who underwent redo-ablation due to recurrent AF/atrial-flutter or tachycardia (AFL/AT) following PVI with PFA. We report electrophysiological findings and ablation strategy during redo-ablation. RESULTS: Of 447 patients undergoing index PVI with PFA, 14 patients (age: 61.9±10.8 years; 7 (50.0%) males; left atrial volume index (n=10): 39.4±14.6 mL/m2) were referred for redo-ablation. Initial indication was paroxysmal-AF in 7 patients, persistent-AF in 6 and long-standing-persistent-AF in one patient. Mean time-to-recurrence was 4.9±1.9 months. Three patients received additional posterior-wall-isolation during index PFA. Twelve (85.7%) patients suffered AF recurrence and 5/12 had concomitant AFL. In the remaining 2 patients, one had a (box-dependent) AFL, and one had an atypical AT. No patients had all PVs reconnected. Reconnection in zero, one, two or three PVs was found in 35.7%, 21.4%, 14.3%, and 28.6% of patients, respectively. All 7 patients with zero or one reconnection with AF recurrence received additional/repeat posterior-wall-isolation during re-ablation, while in the others, PVs were re-isolated. Patients with only AFL/AT had no reconnection of PVs, and the substrate was successfully ablated. CONCLUSIONS: Durable PVI (all PV's isolated) was observed in over one-third of patients at re-do. The predominant recurrent arrhythmia following PVI-only was AF. Concomitant (35.7%) or isolated (14.3%) AFL/AT recurrence was observed in 50% of patients.

Changes in upper airways microbiota in ventilator-associated pneumonia.

BACKGROUND: The role of upper airways microbiota and its association with ventilator-associated pneumonia (VAP) development in mechanically ventilated (MV) patients is unclear. Taking advantage of data collected in a prospective study aimed to assess the composition and over-time variation of upper airway microbiota in patients MV for non-pulmonary reasons, we describe upper airway microbiota characteristics among VAP and NO-VAP patients. METHODS: Exploratory analysis of data collected in a prospective observational study on patients intubated for non-pulmonary conditions. Microbiota analysis (trough 16S-rRNA gene profiling) was performed on endotracheal aspirates (at intubation, T0, and after 72 h, T3) of patients with VAP (cases cohort) and a subgroup of NO-VAP patients (control cohort, matched according to total intubation time). RESULTS: Samples from 13 VAP patients and 22 NO-VAP matched controls were analyzed. At intubation (T0), patients with VAP revealed a significantly lower microbial complexity of the microbiota of the upper airways compared to NO-VAP controls (alpha diversity index of 84 ± 37 and 160 ± 102, in VAP and NO_VAP group, respectively, p-value < 0.012). Furthermore, an overall decrease in microbial diversity was observed in both groups at T3 as compared to T0. At T3, a loss of some genera (Prevotella 7, Fusobacterium, Neisseria, Escherichia-Shigella and Haemophilus) was found in VAP patients. In contrast, eight genera belonging to the Bacteroidetes, Firmicutes and Fusobacteria phyla was predominant in this group. However, it is unclear whether VAP caused dysbiosis or dysbiosis caused VAP. CONCLUSIONS: In a small sample size of intubated patients, microbial diversity at intubation was less in patients with VAP compared to patients without VAP.

Assessment of sex-related differences and outcome in patients who underwent cryoballoon pulmonary vein isolation for atrial fibrillation: an observational cohort study.

OBJECTIVES: Pulmonary vein isolation (PVI) is widely accepted as an effective and safe treatment for symptomatic atrial fibrillation (AF). However, data on sex-related differences and associations with clinical outcome and safety of PVI with cryoballoon ablation are limited. We sought to compare sexrelated efficacy and safety of cryoballoon ablation and identify sex-related associations with clinical outcomes. METHODS AND RESULTS: We included 650 consecutive patients with AF undergoing PVI with cryoballoon ablation at our institution between 2013 and 2017. The efficacy outcome was the first documented recurrence (>30 s) of AF, atrial flutter or atrial tachycardia (AF/AT) or repeat ablation during follow-up, after a 90-day blanking period. The safety outcome was the incidence of periprocedural complications. Mean age of the population was 58±10, and 210 (32.3%) patients were women. Women were older, had a higher body mass index, had more renal dysfunction and less coronary artery disease as compared with men. The rate of AF/AT recurrence was similar between women and men at 12-month follow-up (27.6% vs 24.8%, p=0.445). The incidence of periprocedural complications was higher in women (12.9% vs 4.6%; p<0.001), specifically groin haematomas and phrenic nerve palsy. On multivariate analysis, left atrial volume index (adjusted OR 1.05, 95% CI 1.00 to 1.10; p=0.032) was associated with the incidence of procedural complications in women. For men, no relation with complications could be found. CONCLUSION: The efficacy of cryoballoon ablation was similar between women and men; however, women had a higher risk of procedural complications.

Initial experience with pulsed field ablation for atrial fibrillation.

Introduction: Pulsed field ablation (PFA) was recently introduced for the treatment of symptomatic atrial fibrillation (AF) with the claim of selectively ablating the myocardium while sparing surrounding tissues. We present our initial experience with a PFA catheter for pulmonary vein isolation (PVI) and describe procedural findings and peri-procedural safety of the first 100 patients. Materials and methods: We investigated 100 patients treated for symptomatic AF using the FARAWAVE PFA catheter (Farapulse, Menlo Park, CA, USA) between July 2021 and March 2022. Procedure workflow and electrophysiological findings at the time of ablation, peri-procedural complications, and operator learning curves are described. Results: The mean age of patients was 62.9 ± 9.4 years, 62% were male subjects and 80% had paroxysmal AF. The median CHA2DS2-VASc score was 1.5 (IQR: 1.0-2.0) and the mean left atrial volume index was 35.7 ± 9.6 ml/m2. In 88 (88%) patients, PVI alone was performed and in 12 (12%) patients additional ablation of the posterior wall was performed. 3D-electroanatomic mapping was performed in 18 (18%) patients. Procedures without mapping lasted for 52.3 ± 16.6 min. The mean number of applications per pulmonary vein (PV) was 8.1 ± 0.6. In all patients (100%), all PVs were confirmed to be isolated. The learning curves of the two operators who performed > 20 procedures showed a negligible variation of performance over time and practice did not significantly predict procedure time [Operator 1 (senior): R 2 = 0.034, p = 0.35; Operator 2 (junior): R 2 = 0.004, p = 0.73]. There was no difference between the procedure times between senior and junior operators (Operator 1: 46.9 ± 9.7 min vs. Operator 2: 45.9 ± 9.9 min; p = 0.73). The only complications observed were two cases of bleeding at the site of percutaneous access. Conclusion: Our initial experience shows that use of the PFA catheter for pulmonary vein isolation (PVI) is safe, fast, and easy to learn.

Identifying patients with atrial fibrillation recurrences after two pulmonary vein isolation procedures.

INTRODUCTION: Pulmonary vein isolation (PVI) is an important treatment for atrial fibrillation (AF). However, many patients need more than one procedure to maintain long-term sinus rhythm. Even after two PVIs some may suffer from AF recurrences. We aimed to identify characteristics of patients who fail after two PVI procedures. METHODS AND RESULTS: We included 557 consecutive patients undergoing a first PVI procedure with a second-generation 28 mm cryoballoon. Follow-up procedures were performed using radiofrequency ablation targeting reconnected PVs only. Recurrent AF was defined as any episode of AF lasting >30 s on ECG or 24 hour Holter monitoring performed at 3, 6 and 12 months post procedure. Mean age was 59.1±10.2 years, 383 (68.8%) were male, 448 (80.4%) had paroxysmal AF and the most common underlying condition was hypertension (36.6%). A total of 140/557 (25.1%) patients underwent redo procedure with PVI only. Of these patients 45 (32.4%) had recurrence of AF. These patients were comparable regarding age and sex to those in sinus rhythm after one or two procedures. Multivariate logistic regression showed that non-paroxysmal AF (OR 1.08 (95% CI 1.01 to 1.15), estimated glomerular filtration rate (OR 0.96, 95% CI 0.94 to 0.99), bundle branch block (OR 4.17, 95% CI 1.38 to 12.58), heart failure (OR 4.17, 95% CI 1.38 to 12.58) and Left Atrium Volume Index (OR 1.04, 95% CI 1.01 to 1.08) were associated with AF recurrence after two PVIs. The area under the curve for the identified risk factors was 0.74. CONCLUSIONS: Using a PVI-only approach, recurrence of AF after two AF ablation procedures is associated with more advanced underlying disease and persistent types of AF.

Intracerebral hemorrhage in Intensive Care Unit: early prognostication fallacies. A single center retrospective study.

BACKGROUND: Intracerebral hemorrhage (ICH) admitted to Intensive Care is deem of poor prognosis. The aim of this study was to compare observed and predicted 30-day mortality and to evaluate long term functional outcome in a consecutive ICH cohort. METHODS: Retrospective analysis of prospectively collected data of ICH patients managed in a Neuro-ICU from 2012 to 2015. RESULTS: Out of 136 consecutive patients, 34 (25%) had "withholding of life-sustaining treatment" (WLST) order and 102 (75%) received a "full treatment" (FT). WLST cohort: median (IQR): 72 (70-77) years old, Glasgow Coma Scale (GCS) 4 (3-4) at admission, ICH volume 114 cm3 (68-152); all patients died during neuro-ICU recovery, 28 (82%) patients had brain death diagnosis and 15 (54%) of these were organ donors. FT cohort: 67 (51-73) years old, GCS 9 (6-12) at admission, ICH volume 46 (24-90) cm3, neurosurgery for clot removal in 65 (64%) (P<0.05 vs. WLST cohort for each of previously listed variables); 13 (13%) patients died during neuro-ICU recovery, of these 11 (85%) patients had brain death diagnosis and 4 (36%) of them were organ donors. Overall 30-day observed mortality for FT group was 18% (95% CI: 11-26%). Patients with ICH Score 1, 2, 3, 4+ had 0%, 10%, 16% and 26% 30-day mortality, respectively (P<0.01 vs. ICH Score). Full treatment group 180-day mortality was 32% (95% CI: 24-42%). Modified Rankin Scale (mRS) after one year was ≤3 in 35 (35%), i.e. good recovery, and >3 in 64 (65%). Neurosurgery for clot removal was associated with a lower 30 and 180-day mortality (P=0.01 and P=0.03, respectively) and along with GCS at admission it was an independent significant prognostic factor. CONCLUSIONS: Mortality and functional outcome is less severe than predicted in patients with ICH receiving a full medical and/or surgical treatment.

Ion-Exchange Resin Anticoagulation (I-ERA): A Novel Extracorporeal Technique for Regional Anticoagulation.

BACKGROUND: Extracorporeal treatments always require blood anticoagulation. We tested feasibility and efficacy of a novel technique for regional extracorporeal blood anticoagulation based on calcium removal by ion-exchange resins (i-ER), called ion-exchange resin anticoagulation (i-ERA). METHODS: Eight swine were connected to a veno-venous extracorporeal circuit comprising a hemodiafilter and an i-ER. Blood flow was 150 mL/min. Hemodiafiltrate was generated at 975 mL/min and passed through the i-ER. A fraction of the calcium-free hemodiafiltrate was returned to the hemodiafilter (675 mL/min), while the remaining was recirculated prior the hemodiafilter (300 mL/min) to dilute blood entering the hemodiafilter. A calcium replacement solution was continuously infused. Two hours after i-ERA start, blood was sampled from inlet, before the hemodiafilter (prehemodiafilter blood) and from outlet of the extracorporeal circuit for ionized calcium (iCa) concentration and thromboelastography (TEG). Arterial blood was collected for blood gas analyses, electrolytes concentrations, and plasma free hemoglobin. Hemodynamics and ventilation were monitored. RESULTS: i-ERA reduced iCa from 1.28 ±â€Š0.05 mmol/L (inlet) to 0.47 ±â€Š0.03 mmol/L (prehemodiafilter blood) and 0.25 ±â€Š0.03 mmol/L (outlet). Prehemodiafilter blood and outlet samples showed no sign of clot formation (reaction time (R) >60 min; maximal amplitude (MA) = 0 (0-0) mm), while blood-inlet had normal coagulation (R = 8.5 (5.8-10.2) min; MA = 65.2 (63.2-68.7) mm). Arterial gas analyses and electrolytes concentrations, hemodynamics, and ventilation were unchanged. No hemolysis was recorded. CONCLUSIONS: In a swine model, i-ERA proved feasible and effective in reducing iCa and preventing clot formation with TEG analyses. Further studies are warranted to evaluate the long-term efficacy and safety of i-ERA. LEVEL OF EVIDENCE: V-therapeutic animal experiment.

Extracorporeal CO2 Removal by Respiratory Electrodialysis: An In Vitro Study.

We previously described a highly efficient extracorporeal CO2 removal technique called respiratory electrodialysis (R-ED). Respiratory electrodialysis was composed of a hemodiafilter and a membrane lung (ML) positioned along the extracorporeal blood circuit, and an electrodialysis (ED) cell positioned on the hemodiafiltrate. The ED regionally increased blood chloride concentration to convert bicarbonate to CO2 upstream the ML, thus enhancing ML CO2 extraction (VCO2ML). In this in vitro study, with an aqueous polyelectrolytic carbonated solution mimicking blood, we tested a new R-ED setup, featuring an ML positioned on the hemodiafiltrate after the ED, at increasing ED current levels (0, 2, 4, 6, and 8 A). We measured VCO2ML, electrolytes concentrations, and pH of the extracorporeal circuit. Raising levels of ED-current increased chloride concentration from 107.5 ± 1.6 to 114.6 ± 1.3 mEq/L (0 vs. 8 A, p < 0.001) and reduced pH from 7.48 ± 0.01 to 6.51 ± 0.05 (0 vs. 8 A, p < 0.001) of the hemodiafiltrate entering the ML. Subsequently, VCO2ML increased from 27 ± 1.7 to 91.3 ± 1.5 ml/min (0 vs. 8 A, p < 0.001). Respiratory electrodialysis is efficient in increasing VCO2ML of an extracorporeal circuit featuring an ML perfused by hemodiafiltrate. During R-ED, the VCO2ML can be significantly enhanced by increasing the ED current.

A mathematical model of oxygenation during venovenous extracorporeal membrane oxygenation support.

PURPOSE: To develop a mathematical model of oxygenation during venovenous extracorporeal membrane oxygenation (vv-ECMO). MATERIAL AND METHODS: Total oxygen consumption, cardiac output, blood flow, recirculation, intrapulmonary shunt, hemoglobin, natural lung, and membrane lung oxygen fractions were chosen as inputs. Content, partial pressure, and hemoglobin saturation of oxygen in arterial, venous, pulmonary, and extracorporeal blood were outputs. To assess accuracy and predictive power of the model, we retrospectively analyzed data of 25 vv-ECMO patients. We compiled 2 software (with numerical, 2D and 3D graphical outputs) to study the impact of each variable on oxygenation. RESULTS: The model showed high accuracy and predictive power. Raising blood flow and oxygen fraction to the membrane lung or reducing total oxygen consumption improves arterial and venous oxygenation, especially in severe cases; raising oxygen fraction to the natural lung improves oxygenation only in milder cases; raising hemoglobin always improves oxygenation, especially in the venous district; recirculation fraction severely impairs oxygenation. In severely ill patients, increasing cardiac output worsens arterial oxygenation but enhances venous oxygenation. Oxygen saturation of ECMO inlet is critical to evaluate the appropriateness of oxygen delivery. CONCLUSIONS: The model with the software can be a useful teaching tool and a valuable decision-making aid for the management of hypoxic patients supported by vv-ECMO.

Performance of different continuous positive airway pressure helmets equipped with safety valves during failure of fresh gas supply.

PURPOSE: We assessed the performance of different continuous positive airway pressure (CPAP) helmets equipped with a safety valve during discontinuation of fresh gas flow. METHODS: This was a physiological study of five healthy volunteers. We delivered CPAP (fresh gas flow 60 l/min, FiO(2) 60%, PEEP 5 cmH(2)O) with three different helmets in a random sequence: 4Vent (Rüsch), HelmHAR-cp (Harol) and CaStar CP210 (StarMed). For each helmet we randomly applied, for up to 4 min, three disconnections of fresh gas flow: helmet inlet (D(inlet)), flowmeter (D(flowmeter)) and gas source (D(source)). We continuously recorded from a nostril: end-tidal CO(2) (PetCO(2)), inspiratory CO(2) (PiCO(2)), fraction of inspired oxygen (FiO(2)) and respiratory rate (RR). RESULTS: During every disconnection we observed an increase in PiCO(2) and PetCO(2) with a drop in FiO(2), while RR did not change. FiO(2) decreased more quickly in the CaStar, equipped with the largest safety valve, during D(source) and D(flowmeter), while FiO(2) decreased more quickly during D(inlet) in CaStar and in 4Vent. PiCO(2) resulted in a lower increase in CaStar during D(source) and D(flowmeter) compared to 4Vent. PetCO(2) in CaStar increases more slowly compared to 4Vent during D(source) and more slowly compared to the other two helmets during D(flowmeter). During D(inlet) similar degrees of CO(2) rebreathing and PetCO(2) were recorded among all the helmets. CONCLUSIONS: To minimize CO(2) rebreathing during disconnection of the fresh gas supply while performing helmet CPAP, it is desirable to utilize large helmets with a large anti-suffocation valve. Monitoring and alarm systems should be employed for safe application of helmet CPAP.