Distribution of regional lung function in upright healthy subjects determined by electrical impedance tomography in two chest examination planes.

Objective. The variation in pulmonary gas content induced by ventilation is not uniformly distributed in the lungs. The aim of our study was to characterize the differences in spatial distribution of ventilation in two transverse sections of the chest using electrical impedance tomography (EIT).Approach. Twenty adult never-smokers, 10 women and 10 men (mean age ± SD, 31 ± 9 years), were examined in a sitting position with the EIT electrodes placed consecutively in a caudal (6th intercostal space) and a cranial (4th intercostal space) chest location. EIT data were acquired during quiet breathing, slow and forced full expiration manoeuvres. Impedance variations representing tidal volume (VT), vital capacity (VC), forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were calculated at the level of individual image pixels and their spatial distribution was determined using the following EIT measures: the centres of ventilation in ventrodorsal (CoVvd) and right-to-left direction (CoVrl), the dorsal and right fractions of ventilation, the coefficient of variation (CV) and the global inhomogeneity (GI) index.Main results. The sums of pixel ventilation-related impedance variations reproduced reliably the volumetric dissimilarities amongVT, VC, FEV1and FVC, with no significant differences noted between the two examination planes. Significant differences in ventilation distribution were found between the planes during tidal breathing and slow full expiration, mainly regarding the ventrodorsal direction, with higher values of CoVvdand dorsal fraction of ventilation in the caudal plane (p< 0.01). No significant differences in the spatial distribution of FEV1and FVC were detected between the examination planes.Significance. The spatial distribution of ventilation differed between the two examination planes only during the relaxed (quiet breathing and slow VC manoeuvre) but not during the forced ventilation. This effect is attributable to the differences in thoracoabdominal mechanics between these types of ventilation.

[Ultrasound visualization of the guidewire and positioning of the central venous catheter : A prospective observational study]. / Sonographische Visualisierung des Führungsdrahtes und Positionierung des zentralen Venenkatheters : Eine prospektive Beobachtungsstudie.

BACKGROUND: After insertion of a central venous catheter (CVC) the catheter position must be controlled and a pneumothorax ruled out. OBJECTIVE: The aim was to examine whether the use of two standard acoustic windows known from emergency sonography examination techniques is feasible to 1) verify the correct intravenous localization and direction of the guidewire before final CVC insertion and 2) correctly predict the required CVC length for positioning of the catheter tip in the lower third of the superior vena cava. MATERIAL AND METHODS: This single center prospective observational study included adult patients (age ≥18 years) with an indication for CVC insertion after institutional ethics approval was obtained. Puncture sites were restricted to bilateral internal jugular and subclavian veins and except for duplicate examinations no further exclusion criteria were defined. After vessel puncture and insertion of the guidewire, the vena cava was displayed by an additional ultrasound examiner (sector scanner 1.5-3.6 MHz) using the transhepatic or subcostal acoustic window to localize the guidewire. For positioning of the CVC tip, the required catheter length in relation to the cavoatrial junction was measured using the guidewire marks during slow retraction and consecutive disappearance of the J­shaped guidewire tip from each acoustic window. From the resulting insertion length of the guidewire 4 cm was subtracted for the transhepatic and 2 cm for the subcostal window under the assumption that this length correlates to the distance from the cavoatrial junction. The CVC was finally inserted and a chest radiograph was performed for radiological verification of the CVC position. RESULTS: Of 100 included patients, 94 could finally be analyzed. The guidewire could be identified in the vena cava in 91 patients (97%) within a time period of 2.2 ± 1.9 min. In three patients, the wire could not be visualized, although two catheters had the correct position, while one catheter was incorrectly positioned in the opposite axillary vein. In the second study part, positioning of the CVC was evaluated in 44 of the 94 patients. In 5 of these 44 patients, the correct direction and disappearance of the guidewire from the acoustic window could also be reliably visualized; however, with the left subclavian vein as the puncture site, the respective catheters were up to 6 cm too short for correct positioning. Thus, these 5 patients were excluded from this analysis. In the remaining 39 patients, the position of the CVC tip was optimally located in the lower third of the superior vena cava according to the chest radiograph in 20 patients (51%), while it was relatively too high in 5 patients (13%) and too low (entrance of the right atrium) in 9 patients. In the other 5 patients, disappearance of the guidewire from the acoustic window was not definitely detectable. CONCLUSION: The presented intraprocedural ultrasound-based method using two standard acoustic windows is reliable for verification of the correct intravenous location and direction of the guidewire even before dilatation of the vessel puncture site for insertion of the catheter. Furthermore, the method allows the clinically acceptable measurement of the required length for catheter positioning. A chest radiograph can be waived provided the ultrasound examination (identification of the guidewire and exclusion of puncture-related complications such as pneumothorax) is unambiguous.

Characteristic pattern of pleural effusion in electrical impedance tomography images of critically ill patients.

BACKGROUND: Electrical impedance tomography (EIT) is increasingly used for continuous monitoring of ventilation in intensive care patients. Clinical observations in patients with pleural effusion show an increase in out-of-phase impedance changes. We hypothesised that out-of-phase impedance changes are a typical EIT finding in patients with pleural effusion and could be useful in its detection. METHODS: We conducted a prospective observational study in intensive care unit patients with and without pleural effusion. In patients with pleural effusion, EIT data were recorded before, during, and after unilateral drainage of pleural effusion. In patients with no pleural effusion, EIT data were recorded without any intervention. EIT images were separated into four quadrants of equal size. We analysed the sum of out-of-phase impedance changes in the affected quadrant in patients with pleural effusion before, during, and after drainage and compared it with the sum of out-of-phase impedance changes in the dorsal quadrants of patients without pleural effusion. RESULTS: We included 20 patients with pleural effusion and 10 patients without pleural effusion. The median sum of out-of-phase impedance changes was 70 (interquartile range 49-119) arbitrary units (a.u.) in patients with pleural effusion before drainage, 25 (12-46) a.u. after drainage (P<0.0001) and 11 (6-17) a.u. in patients without pleural effusion (P<0.0001 vs pleural effusion before drainage). The area under the receiver operating characteristics curve was 0.96 (95% limits of agreement 0.91-1.01) between patients with pleural effusion before drainage and those without pleural effusion. CONCLUSIONS: In patients monitored with EIT, the presence of out-of-phase impedance changes is highly suspicious of pleural effusion and should trigger further examination.

Global and regional assessment of sustained inflation pressure-volume curves in patients with acute respiratory distress syndrome.

OBJECTIVE: Static or quasi-static pressure-volume (P-V ) curves can be used to determine the lung mechanical properties of patients suffering from acute respiratory distress syndrome (ARDS). According to the traditional interpretation, lung recruitment occurs mainly below the lower point of maximum curvature (LPMC) of the inflation P-V curve. Although some studies have questioned this assumption, setting of positive end-expiratory pressure 2 cmH2O above the LPMC was part of a 'lung-protective' ventilation strategy successfully applied in several clinical trials. The aim of our study was to quantify the amount of unrecruited lung at different clinically relevant points of the P-V curve. APPROACH: P-V curves and electrical impedance tomography (EIT) data from 30 ARDS patients were analysed. We determined the regional opening pressures for every EIT image pixel and fitted the global P-V curves to five sigmoid model equations to determine the LPMC, inflection point (IP) and upper point of maximal curvature (UPMC). Points of maximal curvature and IP were compared between the models by one-way analysis of variance (ANOVA). The percentages of lung pixels remaining closed ('unrecruited lung') at LPMC, IP and UPMC were calculated from the number of lung pixels exhibiting regional opening pressures higher than LPMC, IP and UPMC and were also compared by one-way ANOVA. MAIN RESULTS: As results, we found a high variability of LPMC values among the models, a smaller variability of IP and UPMC values. We found a high percentage of unrecruited lung at LPMC, a small percentage of unrecruited lung at IP and no unrecruited lung at UPMC. SIGNIFICANCE: Our results confirm the notion of ongoing lung recruitment at pressure levels above LPMC for all investigated model equations and highlight the importance of a regional assessment of lung recruitment in patients with ARDS.

[Health-related quality of life after mechanical ventilation in the intensive care unit]. / Gesundheitsbezogene Lebensqualität nach Beatmung auf der Intensivstation.

BACKGROUND: It is unknown whether health related quality of life measured in German patients one year after mechanical ventilation in the intensive care unit is impaired or not. OBJECTIVES: The aim of this study was to assess health related quality of life one year after inclusion into a randomized controlled trial for weaning from mechanical ventilation with the help of a questionnaire that has never been used in critically ill patients and to investigate whether health related quality of life scores differ between the study population and a general German population. METHODS: We followed up with patients one year after inclusion into a randomized control trial investigating the effect of SmartCare/PS on total ventilation time compared to protocol-driven weaning (ASOPI trial, clinicaltrials.gov ID00445289). Health related quality of life was measured using the quality of life questionnaire C­30 version 3.0 from the European Organization of Research and Treatment of Cancer (EORTC). Mean differences of at least 10 score points in the quality of life scales were considered clinically significant. RESULTS: Of the 232 patients who were alive 90 days after study inclusion, 24 patients died one year after study inclusion and 64 patients were lost to follow-up. Of the remaining145 patients who were successfully contacted, 126 patients agreed to fill out the questionnaire. Questionnaires were sent back to the study site by 83 patients and these were analyzed. Health-related quality of life was significantly lower in five of the six functional scales (physical functioning, role functioning, cognitive functioning, social functioning, global health status) and in eight of the nine symptom scales (fatigue, pain, dyspnea, insomnia, appetite loss, constipation, diarrhea, financial difficulties) compared to the reference values of a German normal population. CONCLUSIONS: The EORTC QLQ-C30 questionnaire is suitable for the acquisition of the health-related quality of life in formerly critically ill patients. Health-related quality of life is severely impaired after mechanical ventilation in the intensive care unit. Future studies should consider health related quality of life as a possible study endpoint.

Influence of tidal volume on ventilation inhomogeneity assessed by electrical impedance tomography during controlled mechanical ventilation.

The global inhomogeneity (GI) index is a parameter of ventilation inhomogeneity that can be calculated from images of tidal ventilation distribution obtained by electrical impedance tomography (EIT). It has been suggested that the GI index may be useful for individual adjustment of positive end-expiratory pressure (PEEP) and for guidance of ventilator therapy. The aim of the present work was to assess the influence of tidal volume (VT) on the GI index values. EIT data from 9 patients with acute respiratory distress syndrome ventilated with a low and a high VT of 5 ± 1 (mean ± SD) and 9 ± 1 ml kg(-1) predicted body weight at a high and a low level of PEEP (PEEPhigh, PEEPlow) were analyzed. PEEPhigh and PEEPlow were set 2 cmH2O above and 5 cmH2O below the lower inflection point of a quasi-static pressure volume loop, respectively. The lower inflection point was identified at 8.1 ± 1.4 (mean ± SD) cmH2O, resulting in a PEEPhigh of 10.1 ± 1.4 and a PEEPlow of 3.1 ± 1.4 cmH2O. At PEEPhigh, we found no significant trend in GI index with low VT when compared to high VT (0.49 ± 0.15 versus 0.44 ± 0.09, p = 0.13). At PEEPlow, we found a significantly higher GI index with low VT compared to high VT (0.66 ± 0.19 versus 0.59 ± 0.17, p = 0.01). When comparing the PEEP levels, we found a significantly lower GI index at PEEPhigh both for high and low VT. We conclude that high VT may lead to a lower GI index, especially at low PEEP settings. This should be taken into account when using the GI index for individual adjustment of ventilator settings.

The wingless-related integration site-5a/secreted frizzled-related protein-5 system is dysregulated in human sepsis.

Sepsis and type 2 diabetes exhibit insulin resistance as a common phenotype. In type 2 diabetes we and others have recently provided evidence that alterations of the proinflammatory wingless-related integration site (wnt)-5a/anti-inflammatory secreted frizzled-related protein (sFRP)-5 system are involved in the pathogenesis of insulin resistance. The aim of the present study was to investigate whether this novel cytokine system is dysregulated in human sepsis, which may indicate a potential mechanism linking inflammation to metabolism. In this single-centre prospective observational study, critically ill adult septic patients were examined and proinflammatory wnt5a and wnt5a inhibitor sFRP5 were measured in serum samples by enzyme-linked immunosorbent assay (ELISA) at admission to the intensive care unit (ICU) and 5 days later. Sixty sepsis patients were included, and 30 healthy individuals served as controls. Wnt5a levels were found to be increased significantly in septic patients compared to healthy controls (2·21 ± 0·33 versus 0·32 ± 0·03 ng/ml, P < 0·0001). In contrast, sFRP5 was not altered significantly in septic patients (19·72 ± 3·06 versus 17·48 ± 6·38 ng/ml, P = 0·07). On admission to the ICU, wnt5a levels exhibited a significant positive correlation with the leucocyte count (rs = 0·3797, P = 0·004). Interestingly, in patients recovering from sepsis, wnt5a levels declined significantly within 5 days (2·17 ± 0·38-1·03 ± 0·28 ng/ml, P < 0·01). In contrast, if sepsis was worsening, wnt5a levels increased in the same time-period by trend (2·34 ± 0·59-3·25 ± 1·02 ng/ml, P > 0·05). sFRP5 levels did not change significantly throughout the study period. The wnt5a/sFRP5 system is altered in human sepsis and might therefore be of interest for future studies on molecular pathophysiology of this common human disease.

Unilateral empyema impacts the assessment of regional lung ventilation by electrical impedance tomography.

Several studies have shown the ability of electrical impedance tomography (EIT) to assess regional ventilation distribution in human lungs. Fluid accumulation in the pleural space as in empyema, typically occurring on one chest side, may influence the distribution of ventilation and the corresponding EIT findings. The aim of our study was to examine this effect on the assessment of regional ventilation by EIT. Six patients suffering from unilateral empyema and intubated with a double-lumen endotracheal tube were studied. EIT data were acquired during volume-controlled ventilation with bilateral (tidal volume (V(T)): 800 ml) and unilateral ventilation (V(T): 400 ml) of the right and left lungs. Mean tidal amplitudes of the EIT signal were calculated in all image pixels. The sums of these values, expressed as relative impedance change (rel. ΔZ), were then determined in whole images and functionally defined regions-of-interest (ROI). The sums of rel. ΔZ calculated during the two cases of one-lung ventilation either on the affected or unaffected side were significantly smaller than during bilateral ventilation. However, in contrast to previous findings in patients with no pleural pathology, very low values of rel. ΔZ were found when the lung on the affected side was ventilated. ROI-based analysis rendered higher values than the whole-image analysis in this case, nonetheless, the values were significantly smaller than when the unaffected side was ventilated in spite of identical VT. In conclusion, our results indicate that the presence of empyema may affect the quantitative evaluation of regional lung ventilation by EIT.

Model-based setting of inspiratory pressure and respiratory rate in pressure-controlled ventilation.

Mechanical ventilation carries the risk of ventilator-induced-lung-injury (VILI). To minimize the risk of VILI, ventilator settings should be adapted to the individual patient properties. Mathematical models of respiratory mechanics are able to capture the individual physiological condition and can be used to derive personalized ventilator settings. This paper presents model-based calculations of inspiration pressure (pI), inspiration and expiration time (tI, tE) in pressure-controlled ventilation (PCV) and a retrospective evaluation of its results in a group of mechanically ventilated patients. Incorporating the identified first order model of respiratory mechanics in the basic equation of alveolar ventilation yielded a nonlinear relation between ventilation parameters during PCV. Given this patient-specific relation, optimized settings in terms of minimal pI and adequate tE can be obtained. We then retrospectively analyzed data from 16 ICU patients with mixed pathologies, whose ventilation had been previously optimized by ICU physicians with the goal of minimization of inspiration pressure, and compared the algorithm's 'optimized' settings to the settings that had been chosen by the physicians. The presented algorithm visualizes the patient-specific relations between inspiration pressure and inspiration time. The algorithm's calculated results highly correlate to the physician's ventilation settings with r = 0.975 for the inspiration pressure, and r = 0.902 for the inspiration time. The nonlinear patient-specific relations of ventilation parameters become transparent and support the determination of individualized ventilator settings according to therapeutic goals. Thus, the algorithm is feasible for a variety of ventilated ICU patients and has the potential of improving lung-protective ventilation by minimizing inspiratory pressures and by helping to avoid the build-up of clinically significant intrinsic positive end-expiratory pressure.

Enteral nutrition is associated with improved outcome in patients with severe sepsis. A secondary analysis of the VISEP trial.

INTRODUCTION: The optimal nutritional strategy remains controversial, particularly in severely septic patients. Our aim was to analyze the effect of three nutritional strategies--enteral (EN), parenteral (PN), and combined nutrition (EN+PN)--on the outcome of patients with severe sepsis or septic shock. PATIENTS AND METHODS: This secondary analysis of the prospective, randomized-controlled, multicenter "Intensive Insulin Therapy and Pentastarch Resuscitation in Severe Sepsis (VISEP)" trial only included patients with a length of stay in the intensive care unit (ICU) of more than 7 days. Besides patient characteristics, data on nutrition therapy were collected daily for up to 21 days. Morbidity as measured by the mean Sequential Organ Failure Assessment (SOFA) score, incidence of secondary infections, renal replacement therapy, ventilator-free days and severe hypoglycemia, length of ICU stay, and mortality at 90 days were compared between the three nutritional strategies. RESULTS: In all, 353 patients were included in the analysis with the majority (68.5 %) receiving EN+PN, 24.4 % receiving EN, and only 7.1 % receiving PN. Median caloric intake was 918 kcal/day (EN), 1,210 kcal/day (PN), and 1,343 kcal/day (EN+PN; p < 0.001). In the latter group, calories were predominantly administered via the parenteral route within the first week. The rate of death at 90 days was lower with EN than with EN+PN (26.7 % vs. 41.3 %, p = 0.048), as was the rate of secondary infections, renal replacement therapy, and duration of mechanical ventilation. In the adjusted Cox regression analysis, the effect on mortality [hazard ratio (HR)= 1.86, 95 % confidence interval (CI): 1.16-2.98, p = 0.010] and the rate of secondary infections (HR= 1.89, 95 % CI: 1.27-2.81, p = 0.002) remained different between EN and EN+PN. CONCLUSION: In patients with severe sepsis or septic shock and prolonged ICU stay, EN alone was associated with improved clinical outcome compared to EN+PN. This hypothesis-generating result has to be confirmed by a randomized-controlled trial in this specific patient population.

Ventilatory strategies in septic patients. Results from a nationwide observational trial.

BACKGROUND: Mortality in intensive care unit (ICU) patients is affected by multiple variables. The possible impact of the mode of ventilation has not yet been clarified; therefore, a secondary analysis of the "epidemiology of sepsis in Germany" study was performed. The aims were (1) to describe the ventilation strategies currently applied in clinical practice, (2) to analyze the association of the different modes of ventilation with mortality and (3) to investigate whether the ratio between arterial partial pressure of oxygen and inspired fraction of oxygen (PF ratio) and/or other respiratory variables are associated with mortality in septic patients needing ventilatory support. METHODS: A total of 454 ICUs in 310 randomly selected hospitals participated in this national prospective observational 1-day point prevalence of sepsis study including 415 patients with severe sepsis or septic shock according to the American College of Chest Physicians/Society of Critical Care Medicine criteria. RESULTS: Of the 415 patients, 331 required ventilatory support. Pressure controlled ventilation (PCV) was the most frequently used ventilatory mode (70.6 %) followed by assisted ventilation (AV 21.7 %) and volume controlled ventilation (VCV 7.7 %). Hospital mortality did not differ significantly among patients ventilated with PCV (57 %), VCV (71 %) or AV (51 %, p=0.23). A PF ratio equal or less than 300 mmHg was found in 83.2 % of invasively ventilated patients (n=316). In AV patients there was a clear trend to a higher PF ratio (204±70 mmHg) than in controlled ventilated patients (PCV 179±74 mmHg, VCV 175±75 mmHg, p=0.0551). Multiple regression analysis identified the tidal volume to pressure ratio (tidal volume divided by peak inspiratory airway pressure, odds ratio OR=0.94, 95 % confidence interval 95% CI=0.89-0.99), acute renal failure (OR=2.15, 95% CI=1.01-4.55) and acute physiology and chronic health evaluation (APACHE) II score (OR=1.09, 95% CI=1.03-1.15) but not the PF ratio (univariate analysis OR=0.998, 95 % CI=0.995-1.001) as independent risk factors for in-hospital mortality. CONCLUSIONS: This representative survey revealed that severe sepsis or septic shock was frequently associated with acute lung injury. Different ventilatory modes did not affect mortality. The tidal volume to inspiratory pressure ratio but not the PF ratio was independently associated with mortality.

Measurement of regional pulmonary oxygen uptake--a novel approach using electrical impedance tomography.

Pulmonary oxygen (O(2)) uptake during apnoea results in a fall in lung volume. Given that electrical impedance tomography (EIT) provides reliable data on regional lung volume changes we hypothesized that EIT could be used to measure regional O(2) uptake. A total of 12 lung healthy supine patients were studied. EIT measurements were performed during volume-controlled mechanical ventilation followed by apnoea with the endotracheal tube clamped at end-expiration. Lung function parameters were assessed by spirometry. A device for breath-by-breath monitoring metabolic gas exchange was used to measure global O(2) uptake. Relative impedance changes during ventilation and apnoea were related to the corresponding tidal volumes. Regional O(2) uptake was analysed as absolute values and as a ratio to regional ventilation in two regions of interest (ventral and dorsal). The global O(2) uptake measured by EIT was 208 ± 79 ml min(-1) corresponding to the values obtained by metabolic gas exchange (259 ± 73 ml min(-1); Spearman correlation coefficient: 0.81, p = 0.02). Regional O(2) uptake was significantly higher in the ventral lung region, while the regional O(2) uptake/ventilation ratio showed no significant difference between the regions. In conclusion, our pilot study indicates that EIT holds substantial potential to detect global and regional pulmonary O(2) uptake concordant with a linear lung volume decrease during apnoea.

Effects of restricted thoracic movement on the regional distribution of ventilation.

BACKGROUND: Restricted thoracic movement is often encountered in patients, necessitating mechanical ventilation during surgery or intensive care treatment. High intraabdominal pressure, obesity or thorax rigidity and deformity reduce the chest distensibility and deteriorate the lung function. They render the selection of proper ventilator settings difficult and complicate the weaning process. Electrical impedance tomography (EIT) is currently being proposed as a bedside imaging method for monitoring regional lung ventilation. The objective of our study was to establish whether the effects of decreased chest compliance on regional lung ventilation can be determined by EIT. METHODS: Ten healthy male volunteers were studied in our pilot study under three conditions: (1) unrestricted breathing and (2) restricted breathing by abdominal and (3) lower rib cage strapping. The subjects were followed during spontaneous tidal breathing in five postures (sitting, supine, prone, left and right side). EIT and spirometry data were acquired in each condition. RESULTS: The distribution of ventilation in subjects with unrestricted breathing corresponded with the physiologically expected values. In the left and right lateral postures, abdominal and thoracic cage restrictions reduced the ventilation in the dependent lung areas; the non-dependent areas were unaffected. In the prone position, the ventilation of the dependent and non-dependent areas was reduced. The effects of strapping were least pronounced in the supine posture. CONCLUSIONS: We conclude that EIT is able to measure changes in the regional distribution of ventilation induced by restricted chest movement and has the potential for optimising artificial ventilation in patients with limited chest compliance of different origins.

Performance of electrical impedance tomography in detecting regional tidal volumes during one-lung ventilation.

BACKGROUND: Electrical impedance tomography (EIT) is becoming a new medical imaging modality for continuous monitoring of regional lung function in the intensive care unit or operating room. The aim of our study was to evaluate the performance of EIT in detecting regional tidal volumes in patients during volume-controlled mechanical ventilation of one or both lungs. METHODS: Ten adult patients undergoing elective thoracic surgery were included. EIT measurements were performed with the Goe-MF II EIT system. Data were collected before surgery during ventilation of both, the right and left lungs. Tidal volumes of 800 and 400 ml were applied during bilateral and unilateral ventilation, respectively. RESULTS: Ventilation-related impedance changes determined in the whole chest cross-section during the right and left lung ventilation did not significantly differ from each other and were equal to 47.6+/-5.6% and 48.5+/-7.8% (mean+/-SD) of the value determined during bilateral ventilation. During unilateral ventilation, EIT clearly separated the ventilated and non-ventilated lung regions; nevertheless, ventilation-related impedance changes were also detected at the non-ventilated sides in areas corresponding to 3.4+/-4.1% and 12.4+/-6.9% of the scan halves during ventilation of the left and right lung, respectively. Changes in global tidal volumes were adequately detected by EIT during both bilateral and unilateral lung ventilation. CONCLUSION: Although good separation of the ventilated and non-ventilated sides of the chest was possible, the data indicate that reliable quantification of regional tidal volumes during asymmetric or inhomogeneous distribution patterns requires regions-of-interest analysis.

Reproducibility of regional lung ventilation distribution determined by electrical impedance tomography during mechanical ventilation.

Electrical impedance tomography (EIT) has the potential to become a new tool for bedside monitoring of regional lung ventilation. The aim of our study was to assess the reproducibility of regional lung ventilation distribution determined by EIT during mechanical ventilation under identical ventilator settings. The experiments were performed on 10 anaesthetized supine pigs ventilated in a volume-controlled mode. EIT measurements were performed with the Goe-MF II device (Viasys Healthcare, Höchberg, Germany) during repeated changes in positive end-expiratory pressure (PEEP) from 0 to 10 cm H2O. Regional lung ventilation was determined in the right and left hemithorax as well as in 64 regions of interest evenly distributed over each chest side in the ventrodorsal direction. Ventilation distributions in both lungs were visualized as ventrodorsal ventilation profiles and shifts in ventilation distribution quantified in terms of centres of ventilation in relation to the chest diameter. The proportion of the right lung on total ventilation in the chest cross-section was 0.54+/-0.04 and remained unaffected by repetitive PEEP changes. Initial PEEP increase resulted in a redistribution of ventilation towards dorsal lung regions with a shift of the centre of ventilation from 45+/-3% to 49+/-3% of the chest diameter in the right and from 47+/-2% to 50+/-2% in the left hemithorax. Excellent reproducibility of the results in the individual regions of interest with almost identical patterns of ventilation distribution was found during repeated PEEP changes.

Some effects of tentoxin on mature and developing chloroplasts.

Tentoxin affected chloroplasts of all stages of development; it caused chlorosis of expanded and developing bean and lettuce leaves when introduced through the stem or roots and inhibited greening of etiolated lettuce seedlings. Cotyledons from 6-day-old lettuce seedlings grown in 10 mug/ml tentoxin had 50-68% of the monogalactosyldiglyceride and digalactosyldiglyceride content of healthy tissue whereas the sulfolipid, phosphatidyl-glycerol, -ethanolamine, -choline and -inositol levels were unchanged. Toxin-treated tissue also showed selective increases in C-16 and C-18 saturated fatty acids.