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Baumgardner J.E.,Oscillogy LLC | Otto C.M.,University of Pennsylvania | Markstaller K.,Medical University of Vienna
Trends in Anaesthesia and Critical Care | Year: 2013

Atelectrauma refers to lung injury due to recruitment of collapsed lung with each inspiration and de-recruitment with each exhalation. Atelectrauma has long been hypothesized to be a mechanism of ventilator-associated lung injury, but only recently have experimental tools become available to study this phenomenon. Cyclical recruitment of atelectasis has now been clearly demonstrated in specific animal models of lung injury. These animal studies have also shown that recruitment and collapse are time-dependent processes and cannot be predicted solely on the basis of end-inspiratory and end-expiratory pressures. To determine if this is a concern in patients, we need to know the incidence of cyclical recruitment, and we need to know if it injures the lung. Definitive answers are not currently available for either question, and will await the application of new high temporal resolution methods for measuring cyclical recruitment in patients. Recent animal studies suggest that cyclical recruitment, when present, can be very damaging to the lung. Avoiding cyclical recruitment may therefore become an important consideration in clinical ventilator management. © 2013 Elsevier Ltd.

Kretzschmar M.,Uppsala University | Kretzschmar M.,Otto Von Guericke University of Magdeburg | Schilling T.,Otto Von Guericke University of Magdeburg | Vogt A.,University of Bern | And 7 more authors.
Journal of Applied Physiology | Year: 2013

The mismatching of alveolar ventilation and perfusion (VA/Q) is the major determinant of impaired gas exchange. The gold standard for measuring VA/Q distributions is based on measurements of the elimination and retention of infused inert gases. Conventional multiple inert gas elimination technique (MIGET) uses gas chromatography (GC) to measure the inert gas partial pressures, which requires tonometry of blood samples with a gas that can then be injected into the chromatograph. The method is laborious and requires meticulous care. A new technique based on micropore membrane inlet mass spectrometry (MMIMS) facilitates the handling of blood and gas samples and provides nearly real-time analysis. In this study we compared MIGET by GC and MMIMS in 10 piglets: 1) 3 with healthy lungs; 2) 4 with oleic acid injury; and 3) 3 with isolated left lower lobe ventilation. The different protocols ensured a large range of normal and abnormal VA/Q distributions. Eight inert gases (SF6, krypton, ethane, cyclopropane, desflurane, enflurane, diethyl ether, and acetone) were infused; six of these gases were measured with MMIMS, and six were measured with GC. We found close agreement of retention and excretion of the gases and the constructed VA/Q distributions between GC and MMIMS, and predicted PaO2 from both methods compared well with measured PaO2. VA/Q by GC produced more widely dispersed modes than MMIMS, explained in part by differences in the algorithms used to calculate VA/Q distributions. In conclusion, MMIMS enables faster measurement of VA/Q, is less demanding than GC, and produces comparable results. Copyright © 2013 the American Physiological Society.

Kretzschmar M.,Uppsala University | Kretzschmar M.,Otto Von Guericke University of Magdeburg | Kozian A.,Uppsala University | Kozian A.,Otto Von Guericke University of Magdeburg | And 7 more authors.
Respiratory Physiology and Neurobiology | Year: 2016

Bronchoconstriction is a hallmark of asthma and impairs gas exchange. We hypothesized that pharmacokinetics of volatile anesthetics would be affected by bronchoconstriction. Ventilation/perfusion (VA/Q) ratios and pharmacokinetics of desflurane in both healthy state and during inhalational administration of methacholine (MCh) to double peak airway pressure were studied in a piglet model. In piglets, MCh administration by inhalation (100μg/ml, n=6) increased respiratory resistance, impaired VA/Q distribution, increased shunt, and decreased paO2 in all animals. The uptake and elimination of desflurane in arterial blood was delayed by nebulization of MCh, as determined by Micropore Membrane Inlet Mass Spectrometry (wash-in time to P50, healthy vs. inhalation: 0.5min vs. 1.1min, to P90: 4.0min vs. 14.8min). Volatile elimination was accordingly delayed. Inhaled methacholine induced severe bronchoconstriction and marked inhomogeneous VA/Q distribution in pigs, which is similar to findings in human asthma exacerbation. Furthermore, MCh-induced bronchoconstriction delayed both uptake and elimination of desflurane. These findings might be considered when administering inhalational anesthesia to asthmatic patients. © 2015 Elsevier B.V.

Bodenstein M.,Johannes Gutenberg University Mainz | Wang H.,Johannes Gutenberg University Mainz | Wang H.,Beijing Institute of Pharmacology and Toxicology | Boehme S.,Johannes Gutenberg University Mainz | And 6 more authors.
Experimental Lung Research | Year: 2010

High arterial partial oxygen pressure (Pao2) oscillations within the respiratory cycle were described recently in experimental acute lung injury. This phenomenon has been related to cyclic recruitment of atelectasis and varying pulmonary shunt fractions. Noninvasive detection of Spo2 (oxygen saturation measured by pulse oximetry) as an indicator of cyclic collapse of atelectasis, instead of recording Pao2 oscillations, could be of clinical interest in critical care. Spo2 oscillations were recorded continuously in three different cases of lung damage to demonstrate the technical feasibility of this approach. To deduce Pao2 from Spo2, a mathematical model of the hemoglobin dissociation curve including left and right shifts was derived from the literature and adapted to the dynamic changes of oxygenation. Calculated Pao2 amplitudes (derived from Spo2 measurements) were compared to simultaneously measured fast changes of Pao 2, using a current standard method (fluorescence quenching of ruthenium). Peripheral hemoglobin saturation was capable to capture changes of Spo2 within each respiratory cycle. For the first time, Spo2 oscillations due to cyclic recruitment of atelectasis within a respiratory cycle were determined by photoplethysmography, a technology that can be readily applied noninvasively in clinical routine. A mathematic model to calculate the respective Pao 2 changes was developed and its applicability tested. Copyright © 2010 Informa Healthcare USA, Inc.

Hartmann E.K.,Johannes Gutenberg University Mainz | Duenges B.,Johannes Gutenberg University Mainz | Baumgardner J.E.,Oscillogy LLC | Markstaller K.,Johannes Gutenberg University Mainz | And 2 more authors.
Intensive Care Medicine | Year: 2013

Purpose: This study examines the correlation between the transpulmonary thermodilution derived extravascular lung water content (EVLW) and the ventilation/perfusion-distribution (V/Q) measured by multiple inert gas elimination (MIGET) in a porcine model. Methods: V/Q measured by micropore membrane inlet mass spectrometry-MIGET (MMIMS-MIGET) and EVLW were simultaneously measured in twelve pigs in the heathy state, with impaired gas exchange from repetitive lung lavage and after 3 h of ventilation. The relationship between V/Q compartments and EVLW was analysed by linear correlation and regression. Results: Considerable increases in EVLW and V/Q mismatching were induced through the lavage procedure. Significant correlations between the EVLW and the V/Q fractions representing pulmonary shunt and low V/Q were found. Perfusion to the normal V/Q regions was inversely correlated to the EVLW. Conclusions: Increased EVLW is associated with increased low V/Q and shunt, but not equal to pulmonary shunt alone. Beneath true shunt EVLW can also be associated with low V/Q regions. © 2013 Springer-Verlag Berlin Heidelberg and ESICM.

Hartmann E.K.,Johannes Gutenberg University Mainz | Boehme S.,Medical University of Vienna | Bentley A.,Johannes Gutenberg University Mainz | Duenges B.,Johannes Gutenberg University Mainz | And 5 more authors.
Critical Care | Year: 2012

Introduction: Cyclic alveolar recruitment/derecruitment (R/D) is an important mechanism of ventilator-associated lung injury. In experimental models this process can be measured with high temporal resolution by detection of respiratory-dependent oscillations of the paO 2(ΔpaO 2). A previous study showed that end-expiratory collapse can be prevented by an increased respiratory rate in saline-lavaged rabbits. The current study compares the effects of increased positive end-expiratory pressure (PEEP) versus an individually titrated respiratory rate (RR ind) on intra-tidal amplitude of Δ paO 2and on average paO 2in saline-lavaged pigs.Methods: Acute lung injury was induced by bronchoalveolar lavage in 16 anaesthetized pigs. R/D was induced and measured by a fast-responding intra-aortic probe measuring paO 2. Ventilatory interventions (RR ind(n = 8) versus extrinsic PEEP (n = 8)) were applied for 30 minutes to reduce Δ paO 2. Haemodynamics, spirometry and Δ paO 2were monitored and the Ventilation/Perfusion distributions were assessed by multiple inert gas elimination. The main endpoints average and Δ paO 2following the interventions were analysed by Mann-Whitney-U-Test and Bonferroni's correction. The secondary parameters were tested in an explorative manner.Results: Both interventions reduced Δ paO 2. In the RR indgroup, ΔpaO 2was significantly smaller (P < 0.001). The average paO 2continuously decreased following RR indand was significantly higher in the PEEP group (P < 0.001). A sustained difference of the ventilation/perfusion distribution and shunt fractions confirms these findings. The RR indapplication required less vasopressor administration.Conclusions: Different recruitment kinetics were found compared to previous small animal models and these differences were primarily determined by kinetics of end-expiratory collapse. In this porcine model, respiratory rate and increased PEEP were both effective in reducing the amplitude of paO 2oscillations. In contrast to a recent study in a small animal model, however, increased respiratory rate did not maintain end-expiratory recruitment and ultimately resulted in reduced average paO 2and increased shunt fraction. © 2012 Hartmann et al.; licensee BioMed Central Ltd.

Hartmann E.K.,Johannes Gutenberg University Mainz | Duenges B.,Johannes Gutenberg University Mainz | Boehme S.,Johannes Gutenberg University Mainz | Boehme S.,Medical University of Vienna | And 8 more authors.
Acta Anaesthesiologica Scandinavica | Year: 2014

Background During cardiopulmonary resuscitation (CPR) the ventilation/perfusion distribution (VA/Q) within the lung is difficult to assess. This experimental study examines the capability of multiple inert gas elimination (MIGET) to determine VA/Q under CPR conditions in a pig model. Methods Twenty-one anaesthetised pigs were randomised to three fractions of inspired oxygen (1.0, 0.7 or 0.21). VA/Q by micropore membrane inlet mass spectrometry-derived MIGET was determined at baseline and during CPR following induction of ventricular fibrillation. Haemodynamics, blood gases, ventilation distribution by electrical impedance tomography and return of spontaneous circulation were assessed. Intergroup differences were analysed by non-parametric testing. Results MIGET measurements were feasible in all animals with an excellent correlation of measured and predicted arterial oxygen partial pressure (R2 = 0.96, n = 21 for baseline; R2 = 0.82, n = 21 for CPR). CPR induces a significant shift from normal V A/Q ratios to the high VA/Q range. Electrical impedance tomography indicates a dorsal to ventral shift of the ventilation distribution. Diverging pulmonary shunt fractions induced by the three inspired oxygen levels considerably increased during CPR and were traceable by MIGET, while 100% oxygen most negatively influenced the VA/Q. Return of spontaneous circulation were achieved in 52% of the animals. Conclusions VA/Q assessment by MIGET is feasible during CPR and provides a novel tool for experimental purposes. Changes in VA/Q caused by different oxygen fractions are traceable during CPR. Beyond pulmonary perfusion deficits, these data imply an influence of the inspired oxygen level on VA/Q. Higher oxygen levels significantly increase shunt fractions and impair the normal VA/Q ratio. © 2014 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Shi C.,Johannes Gutenberg University Mainz | Shi C.,Beijing Institute of Pharmacology and Toxicology | Boehme S.,Johannes Gutenberg University Mainz | Boehme S.,Medical University of Vienna | And 10 more authors.
PLoS ONE | Year: 2014

Background: Vibration response imaging (VRI) is a bedside technology to monitor ventilation by detecting lung sound vibrations. It is currently unknown whether VRI is able to accurately monitor the local distribution of ventilation within the lungs. We therefore compared VRI to electrical impedance tomography (EIT), an established technique used for the assessment of regional ventilation. Methodology/Principal Findings: Simultaneous EIT and VRI measurements were performed in the healthy and injured lungs (ALI; induced by saline lavage) at different PEEP levels (0, 5, 10, 15 mbar) in nine piglets. Vibration energy amplitude (VEA) by VRI, and amplitudes of relative impedance changes (rel.ΔZ) by EIT, were evaluated in seven regions of interest (ROIs). To assess the distribution of tidal volume (VT) by VRI and EIT, absolute values were normalized to the VT obtained by simultaneous spirometry measurements. Redistribution of ventilation by ALI and PEEP was detected by VRI and EIT. The linear correlation between pooled VT by VEA and rel.ΔZ was R2 = 0.96. Bland-Altman analysis showed a bias of -1.07±24.71 ml and limits of agreement of -49.05 to +47.36 ml. Within the different ROIs, correlations of VT-distribution by EIT and VRI ranged between R2 values of 0.29 and 0.96. ALI and PEEP did not alter the agreement of VT between VRI and EIT. Conclusions/Significance: Measurements of regional ventilation distribution by VRI are comparable to those obtained by EIT. © 2014 Shi et al.

Baumgardner J.E.,Oscillogy LLC | Hedenstierna G.,Uppsala University
Current Opinion in Anaesthesiology | Year: 2016

Methods are continuously developing to simplify measurement of VA/Q and also to relate VA/Q to inflammation. The recording of VA/Q has helped to explain important aspects of gas exchange in thoracic anesthesiology and in intensive care medicine. © 2016 Wolters Kluwer Health, Inc. All rights reserved.

A system for controlling the temperature of fluidic samples includes a device having a first outer surface and a second outer surface which are parallel to one another. The interior of the device contains two or more channels suitable for accommodating samples. The channels lay on a common plane that is also parallel to the first and second outer surfaces. A temperature sensor is positioned between the channels along the common plane. A heater is thermally coupled to one of the two outer surfaces while a heat sink is coupled to the other of the two outer surfaces, thereby establishing a temperature gradient between the first and second outer surfaces. A temperature controller receives sensed temperature input from the temperature sensor and adjusts the heater in response thereto.

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