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Dietrich Henzler

Publications and source records attributed to Dietrich Henzler.

13 recordsLinked to original sources
PubMed2006

Evaluation of a modified piezoresistive technique and a water-capsule technique for direct and continuous measurement of intra-abdominal pressure in a porcine model.

OBJECTIVE: Intravesical pressure measurement is considered to be the gold standard for the assessment of intra-abdominal pressure. However, this method is indirect and depends on a physiologic bladder function. We evaluated a modified piezoresistive technique and a water-capsule technique for direct and continuous intra-abdominal pressure measurement. DESIGN: Experimental study. SETTING: Animal research laboratory. SUBJECTS: Eleven male domestic pigs. INTERVENTIONS: In anesthetized and mechanically ventilated animals, CO2 was insufflated to stepwise increase the intra-abdominal pressure to 30 mm Hg. Pressure was then held constant for 9 hrs followed by decompression. Piezoresistive measurement and water-capsule measurement probes were placed intra-abdominally. MEASUREMENTS AND MAIN RESULTS: Readings of intravesical pressure measurement, piezoresistive measurement, and water-capsule measurement were taken hourly. Mean difference to insufflator readings, confidence intervals, and limits of agreement were calculated. Differences between applied pressure and intra-abdominal pressure readings were assessed using a two-factor analysis of variance. No significant differences between methods could be observed. During stepwise pressure increase, limits of agreements were -3.6 to 3.6 mm Hg. Confidence intervals were -3.4 to 3.5 (intravesical pressure measurement), -1.6 to 1.5 (piezoresistive measurement), and 0.5 to 2.9 mm Hg (water-capsule measurement). In the presence of constantly elevated intra-abdominal pressure, limits of agreement ranged from -8.2 to +8.2 mm Hg. Confidence intervals were -0.4 to 6.2 (intravesical pressure measurement), -0.2 to 2.7 (piezoresistive measurement), and 1.1 to 5.1 mm Hg (water-capsule measurement). CONCLUSIONS: Both piezoresistive measurement and water-capsule measurement had smaller confidence intervals than intravesical pressure measurement, indicating higher precision, whereas water-capsule measurement had a significant offset. Piezoresistive measurement could be the most suitable device for continuous direct intra-abdominal pressure monitoring in specific patients.

Abdomen↗
PubMed2006

Effects of partial ventilatory support modalities on respiratory function in severe hypoxemic lung injury.

OBJECTIVE: The early phase of acute respiratory distress syndrome (ARDS) is characterized by impaired respiratory mechanics, ventilation-perfusion mismatch, and severe hypoxemia. Partial ventilatory support can effectively unload the respiratory workload and improve pulmonary gas exchange with less hemodynamic compromise. The partial ventilatory support mode most indicated in early phases of ARDS has not been determined. This study compares the effects of assisted ventilatory techniques on breathing pattern, gas exchange, hemodynamic function, and respiratory effort with those of controlled mechanical ventilation in similarly sedated subjects. DESIGN: Prospectively randomized crossover animal study. SETTING: Animal research laboratory. SUBJECTS: Eleven anesthetized and mechanically ventilated pigs. INTERVENTIONS: Acute lung injury was induced by lung lavage. Pressure-controlled ventilation (PCV), pressure-controlled assisted ventilation (P-ACV), bilevel positive airway pressure (BIPAP), and pressure support ventilation (PSV) with equal airway pressures and sedation were applied in random order. MEASUREMENTS AND MAIN RESULTS: Gas exchange, respiratory effort, and hemodynamic function were measured, and ventilation-perfusion distributions were calculated by multiple inert-gas-elimination techniques. The results revealed that partial ventilatory support was superior to PCV in maintaining adequate oxygenation and hemodynamic function with reduced sedation. The effects of P-ACV, BIPAP, and PSV were comparable with respect to gas exchange and hemodynamic function, except for a more pronounced reduction in shunt during BIPAP. P-ACV and PSV were superior to BIPAP to reduce respiratory drive and work of breathing. PSV affected the pattern of breathing and deadspace to a greater degree than did P-ACV. CONCLUSIONS: In acute lung injury, P-ACV preserves oxygenation and hemodynamic function with less respiratory effort compared with BIPAP and reduces the need for sedation compared with PCV.

Animals↗
PubMed2005

Multislice spiral computed tomography to determine the effects of a recruitment maneuver in experimental lung injury.

Although recruitment of atelectatic lung is a common aim in acute respiratory distress syndrome (ARDS), the effects of a recruitment maneuver have not been assessed quantitatively. By multislice spiral CT (MSCT), we analyzed the changes in lung volumes calculated from the changes in the CT values of hyperinflated (V(HYP)), normally (V(NORM)), poorly (V(POOR)) and nonaerated (V(NON)) lung in eight mechanically ventilated pigs with saline lavage-induced acute lung injury before and after a recruitment maneuver. This was compared to single slice analysis near the diaphragm. The increase in aerated lung was mainly for V(POOR) and the less in V(NORM). Total lung volume and intrathoracic gas increased. No differences were found for tidal volumes measured by spirometry or determined by CT. The inspiratory-expiratory volume differences were not different after the recruitment maneuver in V(NON) (from 62+/-18 ml to 43+/-26 ml, P = 0.114), and in V(NORM) (from 216+/-51 ml to 251+/-37 ml, P = 0.102). Single slice analysis significantly underestimated the increase in normally and poorly aerated lung. Quantitative analysis of lung volumes by whole lung MSCT revealed the increase of poorly aerated lung as the main mechanism of a standard recruitment maneuver. MSCT can provide additional information as compared to single slice CT.

Animals↗
PubMed2005

Respiratory compliance but not gas exchange correlates with changes in lung aeration after a recruitment maneuver: an experimental study in pigs with saline lavage lung injury.

INTRODUCTION: Atelectasis is a common finding in acute lung injury, leading to increased shunt and hypoxemia. Current treatment strategies aim to recruit alveoli for gas exchange. Improvement in oxygenation is commonly used to detect recruitment, although the assumption that gas exchange parameters adequately represent the mechanical process of alveolar opening has not been proven so far. The aim of this study was to investigate whether commonly used measures of lung mechanics better detect lung tissue collapse and changes in lung aeration after a recruitment maneuver as compared to measures of gas exchange METHODS: In eight anesthetized and mechanically ventilated pigs, acute lung injury was induced by saline lavage and a recruitment maneuver was performed by inflating the lungs three times with a pressure of 45 cmH2O for 40 s with a constant positive end-expiratory pressure of 10 cmH2O. The association of gas exchange and lung mechanics parameters with the amount and the changes in aerated and nonaerated lung volumes induced by this specific recruitment maneuver was investigated by multi slice CT scan analysis of the whole lung. RESULTS: Nonaerated lung correlated with shunt fraction (r = 0.68) and respiratory system compliance (r = 0.59). The arterial partial oxygen pressure (PaO2) and the respiratory system compliance correlated with poorly aerated lung volume (r = 0.57 and 0.72, respectively). The recruitment maneuver caused a decrease in nonaerated lung volume, an increase in normally and poorly aerated lung, but no change in the distribution of a tidal breath to differently aerated lung volumes. The fractional changes in PaO2, arterial partial carbon dioxide pressure (PaCO2) and venous admixture after the recruitment maneuver did not correlate with the changes in lung volumes. Alveolar recruitment correlated only with changes in the plateau pressure (r = 0.89), respiratory system compliance (r = 0.82) and parameters obtained from the pressure-volume curve. CONCLUSION: A recruitment maneuver by repeatedly hyperinflating the lungs led to an increase of poorly aerated and a decrease of nonaerated lung mainly. Changes in aerated and nonaerated lung volumes were adequately represented by respiratory compliance but not by changes in oxygenation or shunt.

Animals↗
PubMed2005

S-100 protein and neurohistopathologic changes in a porcine model of acute lung injury.

BACKGROUND: Survivors of acute respiratory distress syndrome exhibit neuropsychological sequelae that might be attributable to hippocampal damage. The authors sought to determine the effects of hypoxemia in a pig model of acute lung injury on the hippocampal region and the release of S-100 protein in comparison to a control group in which hypoxemia was induced by reducing the inspired oxygen fraction. METHODS: Hypoxemia was induced in 14 female pigs by repeated lung lavages (lung injury group; n = 7) or by reducing the inspired oxygen fraction (hypoxia-only group; n = 7). Hemodynamic variables, gas exchange, and serum concentrations of S-100 protein were measured at baseline, after induction of acute lung injury, and subsequently for 12 h. Animals were euthanized, and the brains were removed for histopathologic examination. RESULTS: Comparable blood gases were seen in both groups. Serum S-100 protein concentrations were comparable for both groups at baseline. At all other time points, S-100 concentrations were significantly higher in the lung injury group. Neuropathologic examination showed basophilic and shrunken neurons of the pyramidal cell layer in the hippocampal CA1 subregion of all pigs in the lung injury group. Few abnormalities were seen in the hypoxia-only group. CONCLUSIONS: The same degree of hypoxemia induced in a lavage model of acute lung injury results in greater brain damage assessed by S-100 protein and histopathologic findings when compared to a group in which hypoxemia at the same degree was induced by reducing the inspired oxygen fraction. This suggests that acute lung injury leads to neuropathologic changes independent of hypoxemia.

Animals↗
PubMed2004

Repeated generation of the pulmonary pressure-volume curve may lead to derecruitment in experimental lung injury.

OBJECTIVE: Measurements from the pulmonary pressure-volume (PV) curve have been proposed to adjust ventilator settings. We investigated the effects of repeated construction of an inflation PV curve implemented in a standard ventilator on recruitment or derecruitment in acutely injured lungs. DESIGN AND SETTING: Prospective experimental animal study in eight anesthetized and mechanically ventilated pigs. INTERVENTIONS: Acute lung injury was induced by lung lavage and animals were ventilated in volume controlled mode with PEEP 10 cmH(2)O. The PV curve was constructed five times repeatedly by constant pressure rise, after which ventilation with the preset PEEP was resumed immediately. Studies of hemodynamics, lung mechanics, blood gases and computed tomography were carried out before and after maneuvers. MEASUREMENTS AND RESULTS: Derecruitment was assessed as an increase in nonaerated lung volume (V(NON)), and V(PEEP) was the end-expiratory volume difference between PEEP and ZEEP. There was a significant decrease in PaO(2) from 90.4+/-33.3 to 70.9+/-36.3 mmHg and a rise in venous admixture from 47.8+/-12.7 to 59.1+/-16.6%. V(PEEP) was reduced from 244 to 202 ml. A corresponding decrease in normally aerated lung volume was observed, while regression analysis revealed increase in V(NON) depending on the amount of preexisting atelectasis. CONCLUSIONS: Repeated generation of the PV curve with a readily available tool resulted in worsened oxygenation. Derecruitment of the lungs occurred with loss of PEEP at the start of the maneuver, which could not be recovered by a maximum inflation pressure of 40 cmH(2)O. Repeated use of the investigated tool should be cautioned, and users should consider measures to preserve aerated lung volumes.

Animals↗
PubMed2004

Ventilation with biphasic positive airway pressure in experimental lung injury. Influence of transpulmonary pressure on gas exchange and haemodynamics.

OBJECTIVE: We investigated whether improvement in ventilation perfusion (.V(A)/.Q) distribution during mechanical ventilation using biphasic positive airway pressure (BIPAP) with spontaneous breathing may be attributed to an effectively increased transpulmonary pressure (P(TP)) and can also be achieved by increasing P(TP) during controlled ventilation. DESIGN: In 12 pigs with saline lavage-induced lung injury we compared the effects of BIPAP to pressure-controlled ventilation with equal airway pressure (PCV(AW)) or equal transpulmonary pressure (PCV(TP)) on V(A)/.Q distribution assessed by the multiple inert gas elimination technique (MIGET). SETTING: Animal laboratory study. MEASUREMENTS AND RESULTS: Intrapulmonary shunt was 33+/-11% during BIPAP, 36+/-10% during PCV(AW) and 33+/-15% during PCV(TP) ( p= n.s.). BIPAP resulted in higher PaO(2) than PCV(AW) (188+/-83 versus 147+/-82 mmHg, p < 0.05), but not than PCV(TP) (187+/-139 mmHg). Oxygen delivery was significantly higher during BIPAP (530+/-109 ml/min) versus 374+/-113 ml/min during PCV(AW) and 353+/-93 ml/min during PCV(TP) ( p < 0.005). Tidal volume with PCV(TP) increased to 11.9+/-2.3 ml/kg, compared to 8.5+/-0.8 with BIPAP and 7.6+/-1.4 with PCV(AW) ( p <0.001) and cardiac output decreased to 3.5+/-0.6 l/min (BIPAP 4.9+/-0.8 and PCV(AW) 3.9+/-0.8, p<0.006). CONCLUSIONS: In experimental lung injury, BIPAP with preserved spontaneous breathing was effective in increasing regional P(TP), since pressure-controlled ventilation with the same P(TP) resulted in similar gas exchange effects. However, PCV(TP) caused increased airway pressures and tidal volumes, whereby, with BIPAP, less depression of oxygen delivery and cardiac output were observed. BIPAP could be useful in maintaining pulmonary gas exchange and slightly improving oxygenation without interfering with circulation as strongly as PCV does.

Animals↗
PubMed2004

MR-guided radiofrequency ablation of hepatic malignancies at 1.5 T: initial results.

PURPOSE: To assess the feasibility of magnetic resonance (MR)-guided radiofrequency ablation (RFA) of hepatic malignancies using a high-field MR scanner. MATERIALS AND METHODS: A total of 10 patients with 14 primary (N = 1) or secondary (N = 13) hepatic malignancies underwent MR-guided RFA using a closed-bore 1.5 T MR scanner. Lesion diameters ranged from 2.0 cm to 4.7 cm. RFA was performed using a 200-W generator in combination with a 3.5-cm LeVeen electrode applying a standardized energy protocol. RESULTS: RFA was technically feasible in all patients. Necrosis diameter ranged from 2.5 cm to 6.8 cm. The mean follow-up period is 12.2 (1-18) months. In nine out of 10 patients, local tumor control was achieved. For this purpose, a second CT-guided RFA was required in two patients. In four patients, multifocal hepatic tumor progression occurred, with the treated lesion remaining tumor-free in three of these patients. Two patients showed extrahepatic tumor progression. Four patients remained tumor-free. No major complications occurred. CONCLUSION: MR-guided RFA of hepatic malignancies in a closed-bore high-field MR scanner is technically feasible and safe. It can be advantageous in locations considered unfavorable for CT-guided puncture or in patients in which iodinated contrast material is contraindicated.

Aged↗
PubMed2004

Determination of cardiac output with multislice spiral computed tomography: a validation study.

OBJECTIVE: To validate and to determine the reproducibility of cardiac output (CO) measurements based on a test-bolus examination in multislice spiral computed tomography (MSCT) in comparison with invasively measured CO using the thermal dilution technique. MATERIAL AND METHODS: In 8 swine, CO was determined by invasive thermal dilution technique and by analysis of enhancement data from dynamic MSCT test-bolus examinations. To assess reproducibility, all MSCT examinations were performed twice. Results were compared using Pearson's correlation coefficient and Bland-Altman plots. RESULTS: Measure by thermal dilution technique CO was 3.71 +/- 1.12 L/min, whereas CO was 3.67 +/- 1.30 L/min using MSCT. Pearson's correlation coefficient was 0.89. The average deviation between MSCT and thermal dilution technique was 0.04 L/min with a standard deviation of 0.59 L/min. There was a good agreement between both MSCT measurements with a mean deviation of -0.03 L/min and a standard deviation of 0.51 L/min. CONCLUSION: CO can reliably be determined from MSCT by means of indicator dilution technique. Measurements are reproducible and provide valuable information on the overall cardiovascular performance without application of additional contrast material or radiation. As this technique does not require time-consuming postprocessing it can be added to routine reporting.

Animals↗
PubMed2004

Ventilation-perfusion distribution related to different inspiratory flow patterns in experimental lung injury.

UNLABELLED: In acute lung injury (ALI), controlled mechanical ventilation with decelerating inspiratory flow (.V(dec)) has been suggested to improve oxygenation when compared with constant flow (.V(con)) by improving the distribution of ventilation and perfusion (.V(A)/.Q). We performed the present study to test this hypothesis in an animal model of ALI. Furthermore, the effects of combined decelerating and constant flow (Vdot;(deco)) were evaluated. Thus, 18 pigs with experimental ALI were randomized to receive mechanical ventilation with either .V(con), .V(dec) or a fixed combination of both flow wave forms (.V(deco)) at the same tidal volume and positive end-expiratory pressure level for 6 h. Hemodynamics, gas exchange, and .V(A)/.Q distribution were determined. The results revealed an improvement of oxygenation resulting from a decrease of pulmonary shunt within each group (P < 0.05). However, blood flow to lung areas with a normal .V(A)/.Q distribution increased only during ventilation with .V(con) (P < 0.05). Accordingly, PaO(2) was higher with .V(con) than with .V(dec) and .V(deco) (P < 0.05). We conclude that contrary to the hypothesis, .V(con)provides a more favorable .V(A)/.Q distribution, and hence better oxygenation, when compared with .V(dec) and .V(deco) in this model of ALI. IMPLICATIONS: In acute lung injury, mechanical ventilation with decelerating flow has been suggested to improve ventilation-perfusion distribution when compared with constant flow. We tested this hypothesis in an animal model. Contrary to the hypothesis, we found a more favorable ventilation-perfusion distribution during constant flow when compared with decelerating flow.

Airway Resistance↗
PubMed2003

Extracorporeal gas exchange with the DeltaStream rotary blood pump in experimental lung injury.

In most severe cases of the acute respiratory distress syndrome, veno-venous extracorporeal membrane oxygenation (ECMO) can be used to facilitate gas exchange. However, the clinical use is limited due to the size and the concomitant risk of severe adverse events of conventionally-used centrifugal blood pumps with high extracorporeal blood volumes. The DeltaStream blood pump is a small-sized rotary blood pump that may reduce extracorporeal blood volume, foreign surfaces, contact activation of the coagulation system, and blood trauma. The aim of the present study was to test the safety and efficacy of the DeltaStream pump for ECMO in animals with normal lung function and experimental acute lung injury (ALI). Therefore, veno-venous ECMO was performed for 6 hours in mechanically ventilated pigs with normal lung function (n=6) and with ALI induced by repeated lung lavage (n=6) with a blood flow of 30% of the cardiac output. Gas flow with a FiO2 of 1.0 was set to equal blood flow. With a mean activated clotting time of 121 +/- 22 s, no circulatory impairment or thrombus formation was revealed during ECMO. Furthermore, free plasma Hb did not increase. In controls, hemodynamics and gas exchange remained unchanged. In animals with ALI, hemodynamics remained stable and gas transfer across the extracorporeal oxygenators was optimal, but only in 2 animals was a marked increase in PaO2 observed. CO2 removal was efficacious in all animals. We concluded that the DeltaStream blood pump may be used for veno-venous ECMO without major blood damage or hemodynamic impairment.

Animals↗
PubMed2003

Anaesthetic considerations in patients with chronic pulmonary disease.

PURPOSE OF REVIEW: Chronic pulmonary diseases are getting more important in daily anaesthetic practice, because prevalence is increasing and improved anaesthetic techniques have led to the abandonment of previous contraindications to anaesthesia. It is therefore essential for the anaesthetist to be up to date with current clinical concepts and their impact on the conduction of anaesthesia as well as new insights into how to anaesthetise these patients safely. RECENT FINDINGS: If patients are treated adequately, open and minimally invasive operations can be safely performed under regional and general anaesthesia. The management of acute exacerbations remains challenging, and first-line medical treatment should be supported by non-invasive ventilation. In controlled mechanical ventilation, parameters should be set to avoid dynamic hyperinflation. SUMMARY: Assessing the functional status of patients admitted for surgery remains a difficult task, and in patients identified as being at risk by clinical examination additional spirometry and blood gas measurements may be helpful. If there are flow limitations and signs of respiratory failure, the anaesthetist should be highly alarmed and monitor the patient closely and invasively, yet there is no reason to deny any patient a substantially beneficial operation.

Journal Article↗