Lung-protective Ventilator Settings Research Articles

Intraoperative Extracorporeal Support during Lung Transplantation: Not Just for the High-Risk Patient.

The use of intraoperative mechanical support during lung transplantation has traditionally been a controversial topic. Trends for intraoperative mechanical support strategies swing like a pendulum. Historically, cardiopulmonary bypass (CPB) was the modality of choice during transplantation. It provides full hemodynamic support including oxygenation and decarboxylation. Surgical exposure is improved by permitting the drainage of the heart and provides more permissive retraction. CPBs contain drainage reservoirs with hand-held pump suction catheters promoting blood conservation through collection and re-circulation. But CPB has its disadvantages. It is known to cause systemic inflammation and coagulopathy. CPB requires high doses of heparinization, which increases bleeding risks. As transplantation progressed, off-pump transplantation began to trend as a preferable option. ECMO, however, has many of the benefits of CPB with less of the risk. Outcomes were improved with ECMO compared to CPB. CPB has a higher blood transfusion requirement, a higher need for post-operative ECMO support, a higher re-intubation rate, high rates of kidney injury and need for hemodialysis, longer ICU stays, higher incidences of PGD grade 3, as well as overall in-hospital mortality when compared with ECMO use. The focus now shifts to using intraoperative mechanical support to protect the graft, helping to reduce ischemia-reperfusion injury and allowing for lung protective ventilator settings. Studies show that the routine use of ECMO during transplantation decreases the rate of primary graft dysfunction and many adverse outcomes including ventilator time, need for tracheostomy, renal failure, post-operative ECMO requirements, and others. As intraoperative planned ECMO is considered a safe and effective approach, with improved survival and better overall outcomes compared to both unplanned ECMO implementation and off-pump transplantation, its routine use should be taken into consideration as standard protocol.

Extracorporeal Membrane Oxygenation to Support COVID-19 Patients: A Propensity-Matched Cohort Study.

In patients with severe respiratory failure from COVID-19, extracorporeal membrane oxygenation (ECMO) treatment can facilitate lung-protective ventilation and may improve outcome and survival if conventional therapy fails to assure adequate oxygenation and ventilation. We aimed to perform a confirmatory propensity-matched cohort study comparing the impact of ECMO and maximum invasive mechanical ventilation alone (MVA) on mortality and complications in severe COVID-19 pneumonia. All 295 consecutive adult patients with confirmed COVID-19 pneumonia admitted to the intensive care unit (ICU) from March 13th, 2020, to July 31st, 2021 were included. At admission, all patients were classified into 3 categories: (1) full code including the initiation of ECMO therapy (AAA code), (2) full code excluding ECMO (AA code), and (3) do-not-intubate (A code). For the 271 non-ECMO patients, match eligibility was determined for all patients with the AAA code treated with MVA. Propensity score matching was performed using a logistic regression model including the following variables: gender, P/F ratio, SOFA score at admission, and date of ICU admission. The primary endpoint was ICU mortality. A total of 24 ECMO patients were propensity matched to an equal number of MVA patients. ICU mortality was significantly higher in the ECMO arm (45.8%) compared with the MVA cohort (16.67%) (OR 4.23 (1.11, 16.17); p=0.02). Three-month mortality was 50% with ECMO compared to 16.67% after MVA (OR 5.91 (1.55, 22.58); p < 0.01). Applied peak inspiratory pressures (33.42 ± 8.52 vs. 24.74 ± 4.86 mmHg; p < 0.01) and maximal PEEP levels (14.47 ± 3.22 vs. 13.52 ± 3.86 mmHg; p=0.01) were higher with MVA. ICU length of stay (LOS) and hospital LOS were comparable in both groups. ECMO therapy may be associated with an up to a three-fold increase in ICU mortality and 3-month mortality compared to MVA despite the facilitation of lung-protective ventilation settings in mechanically ventilated COVID-19 patients. We cannot confirm the positive results of the first propensity-matched cohort study on this topic. This trial is registered with NCT05158816.

Mechanical Ventilation during ECMO: Lessons from Clinical Trials and Future Prospects.

Acute Respiratory Distress Syndrome (ARDS) accounts for 10% of ICU admissions and affects 3 million patients each year. Despite decades of research, it is still associated with one of the highest mortality rates in the critically ill. Advances in supportive care, innovations in technologies and insights from recent clinical trials have contributed to improved outcomes and a renewed interest in the scope and use of Extracorporeal life support (ECLS) as a treatment for severe ARDS, including high flow veno-venous Extracorporeal Membrane Oxygenation (VV-ECMO) and low flow Extracorporeal Carbon Dioxide Removal (ECCO2R). The rationale being that extracorporeal gas exchange allows the use of lung protective ventilator settings, thereby minimizing ventilator-induced lung injury (VILI). Ventilation strategies are adapted to the patient's condition during the different stages of ECMO support. Several areas in the management of mechanical ventilation in patients on ECMO, such as the best ventilator mode, extubation-decannulation sequence and tracheostomy timing, are tailored to the patients' recovery. Reduction in sedation allowing mobilization, nutrition and early rehabilitation are subsequent therapeutic goals after lung rest has been achieved.

Quality Improvement Intervention associated with Improved Lung Protective Ventilation Settings in an Emergency Department

INTRODUCTIONPatients requiring endotracheal intubation and mechanical ventilation in the emergency department (ED) are critically ill, and their ventilator management is crucial for their subsequent clinical outcomes. Lung-protective ventilation (LPV) setting strategies are key considerations for this care. The objectives of this 2019-2020 community-based quality improvement project were to: a) identify patients at greater risk of not receiving LPV, and b) evaluate the effectiveness of a series of brief quality improvement educational sessions to improve LPV setting protocol adherence rates.METHODSA 15-month retrospective chart review of ventilator settings and subject characteristics (N = 200) was conducted before and after a series of 10-15-minute educational sessions were delivered to improve LPV adherence. This information was presented at a series of four educational sessions for 25 attending physicians (n = two sessions) and 27 residents at conferences (n = two sessions). Two additional materials (e.g., LPV reference charts, tape measures to gauge patients’ heights) were also posted in three ED resuscitation rooms and on cabinets containing emergency airway equipment. The pre and post-intervention occurrence rates of LPV setting orders were inferentially compared before and after educational sessions.RESULTSPatients ventilated using LPV increased from 70% to 82% after the educational sessions (p = 0.04). All patients who were 67 inches or greater in height were ventilated appropriately before and after sessions. For patients under 65 inches in height, post-session LPV adherence increased from 13% to 53% (p = 0.01).CONCLUSIONSBased on these results, a brief ED provider educational intervention can significantly improve the utilization of LPV guideline-based settings. Patients under 65 inches in height may also be especially at risk of receiving non-LPV ventilator setting orders.

Extracorporeal carbon dioxide removal (ECCO2R) in COPD and ARDS patients with severe hypercapnic respiratory failure. A retrospective case-control study

Background/aim Treatment of severe hypercapnic respiratory failure (HRF) has some challenges in patients with chronic obstructive pulmonary disease (COPD) and acute respiratory distress syndrome (ARDS), especially when lung protective ventilation (LPV) strategies are required. Extracorporeal CO2 removal (ECCO2R) therapy is an emerging option to manage hypercapnia while allowing LPV in these cases. However, further data on ECCO2R use is still needed to make clear recommendations.Materials and methods This study was conducted on patients admitted to intensive care unit (ICU) between January 1st, 2016 to December 31st, 2019. The medical records were retrospectively scanned in institutional software database. Patients who received invasive mechanic ventilation (iMV) support due to severe HRF related to COPD or ARDS were included in the analyses. Patients were grouped according to treatment approaches as that ECCO2R therapy in addition to conventional treatments and conventional treatments alone (controls). Groups were compared for 28-day survival, iMV duration, and length of stay (LOS).Results ECCO2R therapy was noted in 75 of the cases among included 395 patients (COPD n = 256, ARDS n = 139) out of scanned 1715 medical records. The survival rate of ECCO2R patients was 68% and significantly higher than 58% survival rate of controls (p = 0.025), with relative risk reduction (RRR) = 0.16, absolute risk reduction (ARR)= 0.10, number need to treat (NNT) = 10, and odds ratio (OR) = 1.5. In addition, iMV duration (12.8 ± 2.6 vs. 17.1 ± 4.9 days, p = 0.007) and LOS (16.9 ± 4.1 vs. 18.9 ± 5.5 days, p = 0.032) were significantly shorter than controls. Repeated measure analyses showed that LPV settings were successfully provided by 72 h of ECCO2R therapy. Subgroup analyses according to diagnoses of COPD and ARDS also favored ECCO2R.Conclusion ECCO2R therapy significantly improved survival, iMV duration and LOS in patients with severe HRF due to COPD or ARDS, and successfully provided LPV approaches. Further studies are needed to assess promising benefits of ECCO2R therapy.

Clinicians' Perceptions of Behavioral Economic Strategies to Increase the Use of Lung-Protective Ventilation.

Rationale: Lung-protective ventilation (LPV) improves outcomes in patients with acute respiratory distress syndrome (ARDS) and has also shown benefits in patients without ARDS. Despite this evidence, LPV use remains low.Objectives: To understand clinicians' perceptions of using behavioral economic strategies to improve rates of LPV use.Methods: We conducted semistructured interviews of clinicians across seven intensive care units within a university health system. We purposefully sampled clinicians of different professional backgrounds and experience levels. Each interview included descriptions of three of five strategies grounded in behavioral economic theory designed to facilitate clinicians' use of LPV: 1) an order set autopopulated with LPV settings ("default"), 2) an order set providing a choice between autopopulated LPV settings and open-ended order entry for alternative settings ("active choice"), 3) requirement of written justification if settings other than LPV were ordered or documented ("accountable justification"), 4) automated ARDS identification and clinician prompting ("alert"), and 5) provision of clinicians' and their peers' individual rates of LPV use ("peer comparison"). Descriptions were followed by open-ended questions to elicit perceptions about advantages, disadvantages, and acceptability. Initial interview transcripts were reviewed by two investigators to develop a thematic codebook, which was refined iteratively with the use of constant comparative methods.Results: We completed 17 interviews of physicians, nurse practitioners, and respiratory therapists. Strategies that prepopulated settings (default, active choice, and accountable justification) were perceived as providing benefit by reducing workloads and serving as cognitive prompts. The default and active choice strategies were more acceptable than accountable justification, which was perceived as potentially frustrating due to workflow impedance. The alert strategy was met with concerns about alert accuracy and alarm fatigue. The peer comparison strategy led to concerns about timing and fear of punitive measures. Participants believed that the default and active choice strategies would be highly acceptable, whereas few interviewees thought the alert would be acceptable. The active choice strategy was most consistently identified as potentially highly effective.Conclusions: Behavioral economic strategies have great potential as acceptable and potentially effective strategies to increase the use of LPV.

Adaptive mechanical ventilation with automated minimization of mechanical power\u2014a pilot randomized cross-over study

BackgroundAdaptive mechanical ventilation automatically adjusts respiratory rate (RR) and tidal volume (VT) to deliver the clinically desired minute ventilation, selecting RR and VT based on Otis’ equation on least work of breathing. However, the resulting VT may be relatively high, especially in patients with more compliant lungs. Therefore, a new mode of adaptive ventilation (adaptive ventilation mode 2, AVM2) was developed which automatically minimizes inspiratory power with the aim of ensuring lung-protective combinations of VT and RR. The aim of this study was to investigate whether AVM2 reduces VT, mechanical power, and driving pressure (ΔPstat) and provides similar gas exchange when compared to adaptive mechanical ventilation based on Otis’ equation.MethodsA prospective randomized cross-over study was performed in 20 critically ill patients on controlled mechanical ventilation, including 10 patients with acute respiratory distress syndrome (ARDS). Each patient underwent 1 h of mechanical ventilation with AVM2 and 1 h of adaptive mechanical ventilation according to Otis’ equation (adaptive ventilation mode, AVM). At the end of each phase, we collected data on VT, mechanical power, ΔP, PaO2/FiO2 ratio, PaCO2, pH, and hemodynamics.ResultsComparing adaptive mechanical ventilation with AVM2 to the approach based on Otis’ equation (AVM), we found a significant reduction in VT both in the whole study population (7.2 ± 0.9 vs. 8.2 ± 0.6 ml/kg, p < 0.0001) and in the subgroup of patients with ARDS (6.6 ± 0.8 ml/kg with AVM2 vs. 7.9 ± 0.5 ml/kg with AVM, p < 0.0001). Similar reductions were observed for ΔPstat (whole study population: 11.5 ± 1.6 cmH2O with AVM2 vs. 12.6 ± 2.5 cmH2O with AVM, p < 0.0001; patients with ARDS: 11.8 ± 1.7 cmH2O with AVM2 and 13.3 ± 2.7 cmH2O with AVM, p = 0.0044) and total mechanical power (16.8 ± 3.9 J/min with AVM2 vs. 18.6 ± 4.6 J/min with AVM, p = 0.0024; ARDS: 15.6 ± 3.2 J/min with AVM2 vs. 17.5 ± 4.1 J/min with AVM, p = 0.0023). There was a small decrease in PaO2/FiO2 (270 ± 98 vs. 291 ± 102 mmHg with AVM, p = 0.03; ARDS: 194 ± 55 vs. 218 ± 61 with AVM, p = 0.008) and no differences in PaCO2, pH, and hemodynamics.ConclusionsAdaptive mechanical ventilation with automated minimization of inspiratory power may lead to more lung-protective ventilator settings when compared with adaptive mechanical ventilation according to Otis’ equation.Trial registrationThe study was registered at the German Clinical Trials Register (DRKS00013540) on December 1, 2017, before including the first patient.

Dead space analysis at different levels of positive end-expiratory pressure in acute respiratory distress syndrome patients

PurposeTo analyze the effects of positive end-expiratory pressure (PEEP) on Bohr's dead space (VDBohr/VT) in patients with acute respiratory distress syndrome (ARDS). Material and methodsFourteen ARDS patients under lung protective ventilation settings were submitted to 4 different levels of PEEP (0, 6, 10, 16 cmH2O). Respiratory mechanics, hemodynamics and volumetric capnography were recorded at each protocol step. ResultsTwo groups of patients responded differently to PEEP when comparing baseline with 16-PEEP: those in which driving pressure increased > 15% (∆P˃15%, n = 7, p = .016) and those in which the change was ≤15% (∆P≤15%, n = 7, p = .700). VDBohr/VT was higher in ∆P≤15% than in ∆P≤15% patients at baseline ventilation [0.58 (0.49–0.60) vs 0.46 (0.43–0.46) p = .018], at 0-PEEP [0.50 (0.47–0.54) vs 0.41 (0.40–0.43) p = .012], at 6-PEEP [0.55 (0.49–0.57) vs 0.44 (0.42–0.45) p = .008], at 10-PEEP [0.59 (0.51–0.59) vs 0.45 (0.44–0.46) p = .006] and at 16-PEEP [0.61 (0.56–0.65) vs 0.47 (0.45–0.48) p = .001]. We found a good correlation between ∆P and VDBohr/VT only in the ∆P˃15% group (r = 0.74, p < .001). ConclusionsIncreases in PEEP result in higher VDBohr/VT only when associated with an increase in driving pressure.

Basis function identification of lung mechanics in mechanical ventilation for predicting outcomes of therapy changes: A first virtual patient

Mechanical ventilation is a primary therapy for patients with acute respiratory failure. However, incorrect ventilator settings can cause further lung damage with inter- and intra- patient heterogeneity an issue. Lung protective ventilator settings include titrating positive end-expiratory pressure (PEEP) to the point of minimum elastance. However, predicting minimum elastance can be difficult, and use of high PEEP can lead to ventilator induced lung injury. In this study, a basis function elastance and resistance model is developed to allow use of information available at a lower PEEP level to identify patient-specific mechanics and predict lung mechanics at a higher PEEP. Accurate prediction of pressure and PEEP to within 5% over 8 recruitment manoeuvres validates the functionality of this virtual patient modelling and system identification approach.

Patients with uninjured lungs may also benefit from lung-protective ventilator settings.

Although mechanical ventilation is a life-saving strategy in critically ill patients and an indispensable tool in patients under general anesthesia for surgery, it also acts as a double-edged sword. Indeed, ventilation is increasingly recognized as a potentially dangerous intrusion that has the potential to harm lungs, in a condition known as ‘ventilator-induced lung injury’ (VILI). So-called ‘lung-protective’ ventilator settings aiming at prevention of VILI have been shown to improve outcomes in patients with acute respiratory distress syndrome (ARDS), and, over the last few years, there has been increasing interest in possible benefit of lung-protective ventilation in patients under ventilation for reasons other than ARDS. Patients without ARDS could benefit from tidal volume reduction during mechanical ventilation. However, it is uncertain whether higher levels of positive end-expiratory pressure could benefit these patients as well. Finally, recent evidence suggests that patients without ARDS should receive low driving pressures during ventilation.

The Homburg Lung: Efficacy and Safety of a Minimal-Invasive Pump-Driven Device for Veno-Venous Extracorporeal Carbon Dioxide Removal.

Extracorporeal carbon dioxide removal (ECCO2R) is increasingly considered a viable therapeutic approach in the management of hypercapnic lung failure to avoid intubation or to allow lung-protective ventilator settings. This study aimed to analyze efficacy and safety of a minimal-invasive ECCO2R device, the Homburg lung. The Homburg lung is a pump-driven system for veno-venous ECCO2R with ¼″ tubing and a 0.8 m surface oxygenator. Vascular access is usually established via a 19F/21 cm bilumen cannula in the right internal jugular vein. For this work, we screened patient registries from two German centers for patients who underwent ECCO2R with the Homburg lung because of hypercapnic lung failure since 2013. Patients who underwent extracorporeal membrane oxygenation before ECCO2R were excluded. Patients who underwent ECCO2R more than one time were only included once. In total, 24 patients (aged 53.86 ± 12.49 years; 62.5% male) were included in the retrospective data analysis. Ventilatory failure occurred because of chronic obstructive pulmonary disease (50%), cystic fibrosis (16.7%), acute respiratory distress syndrome (12.5%), and other origins (20.8%). The system generated a blood flow of 1.18 ± 0.23 liters per minute (lpm). Sweep gas flow was 3.87 ± 2.97 lpm. Within 4 hours, paCO2 could be reduced significantly from 82.05 ± 15.57 mm Hg to 59.68 ± 12.27 mm Hg, thereby, increasing pH from 7.23 ± 0.10 to 7.36 ± 0.09. Cannulation-associated complications were transient arrhythmia (1/24 patients) and air embolism (1/24). Fatal complications did not occur. In conclusion, the Homburg lung provides effective carbon dioxide removal in hypercapnic lung failure. The cannulation is a safe procedure, with complication rates comparable to those in central venous catheter implantation.

Gas Exchange Disturbances Regulate Alveolar Fluid Clearance during Acute Lung Injury.

Disruption of the alveolar–capillary barrier and accumulation of pulmonary edema, if not resolved, result in poor alveolar gas exchange leading to hypoxia and hypercapnia, which are hallmarks of acute lung injury and the acute respiratory distress syndrome (ARDS). Alveolar fluid clearance (AFC) is a major function of the alveolar epithelium and is mediated by the concerted action of apically-located Na+ channels [epithelial Na+ channel (ENaC)] and the basolateral Na,K-ATPase driving vectorial Na+ transport. Importantly, those patients with ARDS who cannot clear alveolar edema efficiently have worse outcomes. While hypoxia can be improved in most cases by O2 supplementation and mechanical ventilation, the use of lung protective ventilation settings can lead to further CO2 retention. Whether the increase in CO2 concentrations has deleterious or beneficial effects have been a topic of significant controversy. Of note, both low O2 and elevated CO2 levels are sensed by the alveolar epithelium and by distinct and specific molecular mechanisms impair the function of the Na,K-ATPase and ENaC thereby inhibiting AFC and leading to persistence of alveolar edema. This review discusses recent discoveries on the sensing and signaling events initiated by hypoxia and hypercapnia and the relevance of these results in identification of potential novel therapeutic targets in the treatment of ARDS.

Low-Flow Extracorporeal Carbon Dioxide Removal Using the Hemolung Respiratory Dialysis System® to Facilitate Lung-Protective Mechanical Ventilation in Acute Respiratory Distress Syndrome

Extracorporeal carbon dioxide removal (ECCO2R) permits reductions in alveolar ventilation requirements that the lungs would otherwise have to provide. This concept was applied to a case of hypercapnia refractory to high-level invasive mechanical ventilator support. We present a case of an 18-year-old man who developed post-pneumonectomy acute respiratory distress syndrome (ARDS) after resection of a mediastinal germ cell tumor involving the left lung hilum. Hypercapnia and hypoxemia persisted despite ventilator support even at traumatic levels. ECCO2R using a miniaturized system was instituted and provided effective carbon dioxide elimination. This facilitated establishment of lung-protective ventilator settings and lung function recovery. Extracorporeal lung support increasingly is being applied to treat ARDS. However, conventional extracorporeal membrane oxygenation (ECMO) generally involves using large cannulae capable of carrying high flow rates. A subset of patients with ARDS has mixed hypercapnia and hypoxemia despite high-level ventilator support. In the absence of profound hypoxemia, ECCO2R may be used to reduce ventilator support requirements to lung-protective levels, while avoiding risks associated with conventional ECMO.

Respiratory mechanics in brain injury: A review.

Several clinical and experimental studies have shown that lung injury occurs shortly after brain damage. The responsible mechanisms involve neurogenic pulmonary edema, inflammation, the harmful action of neurotransmitters, or autonomic system dysfunction. Mechanical ventilation, an essential component of life support in brain-damaged patients (BD), may be an additional traumatic factor to the already injured or susceptible to injury lungs of these patients thus worsening lung injury, in case that non lung protective ventilator settings are applied. Measurement of respiratory mechanics in BD patients, as well as assessment of their evolution during mechanical ventilation, may lead to preclinical lung injury detection early enough, allowing thus the selection of the appropriate ventilator settings to avoid ventilator-induced lung injury. The aim of this review is to explore the mechanical properties of the respiratory system in BD patients along with the underlying mechanisms, and to translate the evidence of animal and clinical studies into therapeutic implications regarding the mechanical ventilation of these critically ill patients.

Protocol for a systematic review and individual patient data meta-analysis of benefit of so-called lung-protective ventilation settings in patients under general anesthesia for surgery

BackgroundAlmost all patients under general anesthesia for surgery need mechanical ventilation. The harmful effects of short-term intra-operative ventilation on pulmonary integrity are increasingly recognized. Recent investigations suggest protection against so-called ventilation-associated lung injury with the use of lower tidal volumes and/or the use of higher levels of positive end-expiratory pressure (PEEP). This review and meta-analysis will evaluate the effects of these protective measures on pulmonary and extra-pulmonary complications, and try to discriminate the effects of lower tidal volumes from those of higher levels of PEEP.Methods/designThe Medline database will be searched for observational studies and randomized controlled trials of intra-operative ventilation. Individual patient data will be collected from databases obtained via direct contact with corresponding authors of original articles. The primary endpoint is development of postoperative acute respiratory distress syndrome, the most important postoperative pulmonary complication. Secondary endpoints include hospital length of stay and hospital mortality, and reported intra-operative and postoperative pulmonary and extra-pulmonary complications. Emphasis is put on separating the effects of lower tidal volumes from those of higher levels of PEEP.DiscussionThis will be the first meta-analysis of intra-operative ventilation using individual patient data from observational studies and randomized controlled trials. The large sample size could allow discrimination of the effect of the two most frequently used protective measures - that is, lower tidal volumes and higher levels of PEEP. The results of this review and meta-analysis can be used in designing future trials of ventilation.

A Case of Pumpless Interventional Lung Assist Application in a Tuberculosis Destroyed Lung Patient with Severe Hypercapnic Respiratory Failure

Pumpless extracorporeal interventional lung assist (iLA) is a rescue therapy allowing effective carbon dioxide re- movals and lung protective ventilator settings. Herein, we report the use of a pumpless extracorporeal iLA in a tu- berculosis destroyed lung (TDL) patient with severe hypercapnic respiratory failures. A 35-year-old male patient with TDL was intubated due to CO2 retention and altered mentality. After 11 days, Ventilator Associated Pneumonia (VAP) had developed. Despite the maximal mechanical ventilator support, his severe respiratory acidosis was not corrected. We applied the iLA for the management of refractory hypercapnia with respiratory acidosis. This case suggests that the iLA is an effective rescue therapy for TDL patients with ventilator refractory hypercapnia.

Iterative integral parameter identification of a respiratory mechanics model.

BackgroundPatient-specific respiratory mechanics models can support the evaluation of optimal lung protective ventilator settings during ventilation therapy. Clinical application requires that the individual’s model parameter values must be identified with information available at the bedside. Multiple linear regression or gradient-based parameter identification methods are highly sensitive to noise and initial parameter estimates. Thus, they are difficult to apply at the bedside to support therapeutic decisions.MethodsAn iterative integral parameter identification method is applied to a second order respiratory mechanics model. The method is compared to the commonly used regression methods and error-mapping approaches using simulated and clinical data. The clinical potential of the method was evaluated on data from 13 Acute Respiratory Distress Syndrome (ARDS) patients.ResultsThe iterative integral method converged to error minima 350 times faster than the Simplex Search Method using simulation data sets and 50 times faster using clinical data sets. Established regression methods reported erroneous results due to sensitivity to noise. In contrast, the iterative integral method was effective independent of initial parameter estimations, and converged successfully in each case tested.ConclusionThese investigations reveal that the iterative integral method is beneficial with respect to computing time, operator independence and robustness, and thus applicable at the bedside for this clinical application.

Care of the Intubated Emergency Department Patient

Emergency physicians perform tracheal intubation and initiate mechanical ventilation for critically ill patients on a daily basis. With the current national challenges of intensive care unit bed availability, intubated patients now often remain in the emergency department (ED) for exceedingly long periods of time. As a result, care of the intubated patient falls to the emergency physician (EP). Given the potential for significant morbidity and mortality, it is crucial for the EP to possess the most current, up-to-date information pertaining to the care of intubated patients. This article discusses critical aspects in the ED management of intubated and mechanically ventilated patients. Specifically, emphasis is placed on providing adequate sedation and analgesia, limiting the use of neuromuscular blocking agents, correctly setting and adjusting the mechanical ventilator, utilizing appropriate monitoring modalities, and providing key supportive measures. Despite these measures, inevitably, some patients deteriorate while receiving mechanical ventilation. The article concludes with a discussion outlining a step-wise approach to evaluating the intubated patient who develops respiratory distress or circulatory compromise. With this information, the EP can more effectively care for ventilated patients while minimizing morbidity, and ultimately, improving outcome. Essential components of the care of intubated ED patients includes administering adequate sedative and analgesic medications, using lung-protective ventilator settings with attention to minimizing ventilator-induced lung injury, elevating the head of the bed in the absence of contraindications, early placement of an orogastric tube, and providing prophylaxis for stress-related mucosal injury and deep venous thrombosis when indicated.

Parameters Derived from the Pulmonary Pressure–Volume Curve, but Not the Pressure–Time Curve, Indicate Recruitment in Experimental Lung Injury

In acute lung injury, ventilation avoiding tidal hyperinflation and tidal recruitment has been proposed to prevent ventilator-associated lung injury. Information about dynamic recruitment may be obtained from the characteristics of pressure-volume (PV) curves or the profile of pressure-time (Paw-t) curves. Six anesthetized pigs with lung lavage-induced acute lung injury were ventilated with lung-protective settings. We measured the effects of a standard recruitment maneuver on hysteresis area and ratio obtained from the PV curve and on the stress index obtained from the Paw-t curve and correlated this with aerated and nonaerated lung volumes as measured by multislice computed tomography. Hysteresis area and ratio correlated with aerated lung volume (r = 0.886). The recruitment maneuver resulted in an increase in aerated (+12%) and a decrease (-18%) in nonaerated lung. Hysteresis area correlated with alveolar recruitment, represented by an increase in aerated lung (r = 0.886) and a decrease in nonaerated lung (r = -0.829) during tidal ventilation. The stress index was always >1 and indicated tidal hyperinflation only. Values did not change after the recruitment maneuver and did not correlate with any other lung volume. Parameters derived from the PV curve may help in characterizing the lung aeration of the lung and in indicating recruitment. In the presence of lung-protective ventilator settings, the stress index derived from the Paw-t curve was not able to indicate recruitment.