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Burkhard Lachmann

Publications and source records attributed to Burkhard Lachmann.

32 records · Page 2Linked to original sources
PubMed2003

Oxygen tension under hyperbaric conditions in healthy pig brain.

OBJECTIVE: To investigate the effect of hyperbaric conditions on brain oxygenation, intracranial pressure and brain glucose/lactate levels in healthy non-brain-traumatized animals. DESIGN AND SETTING: Prospective animal study in a hyperbaric chamber. SUBJECTS: Twelve adult Landrace/Yorkshire pigs. INTERVENTIONS: The animals were normoventilated in a pressure-controlled mode according to the open lung concept first at normobaric pressures (FiO2 of 0.4 and 1.0) and subsequently in the hyperbaric chamber at 1.9 and 2.8 bar (both at an FiO2 of 1.0). Under these conditions brain oxygen tension and intracranial pressure were recorded and brain glucose/lactate levels were measured by microdialysis. RESULTS: At normobaric conditions, increasing the FiO2 from 0.4 (baseline) to 1.0 resulted in a significant increase in brain oxygen tension from 33 +/- 14 to 63 +/- 28 mmHg (P<0.05). Compared with baseline, both hyperbaric conditions (at an FiO2 of 1.0) led to a significant increase in brain oxygen tension to 151 +/- 65 mmHg (P<0.001) at 1.9 bar and to 294 +/- 134 mmHg (P<0.001) at 2.8 bar. CONCLUSIONS: If there is a need for increased oxygenation in the brain, then one way to achieve this is to apply hyperbaric conditions at 100% oxygen. Compared with an atmospheric pressure with a FiO2 of 0.4, a nine-fold increase (900%) in PbrO2 values can be reached by increasing the FiO2 to 1.0 and the pressure to 2.8 bar. In this study, hyperbaric oxygen pressure in the brain did not lead to changes in intracranial pressure or in brain glucose/lactate levels.

Air Pressure↗
PubMed2003

Human SP-A and a pharmacy-grade porcine lung surfactant extract can be reconstituted into tubular myelin--a comparative structural study of alveolar surfactants using cryo-transmission electron microscopy.

Cryo-transmission electron microscopy (cryo-TEM) is a rather artefact-free method, well suited to study the alveolar surfactant system. A pharmacy grade porcine lung surfactant extract (HL-10) was mixed with human SP-A and Ringer's solution (for calcium ions), and it was shown by cryo-TEM that the tubular myelin (TM) type of structure was reconstituted. These aggregates were associated to liposomal aggregates, and resulted in macroscopic phase-separation. This phase showed a weak birefringence in the polarising microscope, which is characteristic for a liquid-crystalline type of structure. TM from rabbit lung lavage was also examined, and showed the same periodic arrangement of bilayers as alveolar surface layer from freshly cut rabbit lungs deposited directly on the cryo-TEM grids. The distance between the bilayers of TM was 40-50 nm, and an electron dense material, assumed to be SP-A, was sometimes seen to occur periodically along the bilayers, oriented perpendicularly to the tubuli. The results are consistent with the surface-phase model of the alveolar lining.

Animals↗
PubMed2003

Gas embolism: pathophysiology and treatment.

Based on a literature search, an overview is presented of the pathophysiology of venous and arterial gas embolism in the experimental and clinical environment, as well as the relevance and aims of diagnostics and treatment of gas embolism. The review starts with a few historical observations and then addresses venous air embolism by discussing pulmonary vascular filtration, entrapment, and the clinical occurrence of venous air emboli. The section on arterial gas embolism deals with the main mechanisms involved, coronary and cerebral air embolism (CAE), and the effects of bubbles on the blood-brain barrier. The diagnosis of CAE uses various techniques including ultrasound, perioperative monitoring, computed tomography, brain magnetic resonance imaging and other modalities. The section on therapy starts by addressing the primary treatment goals and the roles of adequate oxygenation and ventilation. Then the rationale for hyperbaric oxygen as a therapy for CAE based on its physiological mode of action is discussed, as well as some aspects of adjuvant drug therapy. A few animal studies are presented, which emphasize the importance of the timing of therapy, and the outcome of patients with air embolism (including clinical patients, divers and submariners) is described.

Animals↗
PubMed2003

Effects of recruitment maneuver on atelectasis in anesthetized children.

BACKGROUND: General anesthesia is known to promote atelectasis formation. High inspiratory pressures are required to reexpand healthy but collapsed alveoli. However, in the absence of positive end-expiratory pressure (PEEP), reexpanded alveoli collapse again. Using magnetic resonance imaging, the impact of an alveolar recruitment strategy on the amount and distribution of atelectasis was tested. METHODS: The authors prospectively randomized 24 children who met American Society of Anesthesiologists physical status I or II criteria, were aged 6 months-6 yr, and were undergoing cranial magnetic resonance imaging into three groups. After anesthesia induction, in the alveolar recruitment strategy (ARS) group, an alveolar recruitment maneuver was performed by manually ventilating the lungs with a peak airway pressure of 40 cm H2O and a PEEP of 15 cm H2O for 10 breaths. PEEP was then reduced to and kept at 5 cm H2O. The continuous positive airway pressure (CPAP) group received 5 cm H2O of continuous positive airway pressure without recruitment. The zero end-expiratory pressure (ZEEP) group received neither PEEP nor the recruitment maneuver. All patients breathed spontaneously during the procedure. After cranial magnetic resonance imaging, thoracic magnetic resonance imaging was performed. RESULTS: The atelectatic volume (median, first and third standard quartiles) detected in the ZEEP group was 1.25 (0.75-4.56) cm3 in the right lung and 4.25 (3.2-13.9) cm3 in the left lung. The CPAP group had 9.5 (3.1-23.7) cm3 of collapsed lung tissue in the right lung and 8.8 (5.3-28.5) cm3 in the left lung. Only one patient in the ARS group presented an atelectasis of less than 2 cm3. An uneven distribution of the atelectasis was observed within each lung and between the right and left lungs, with a clear predominance of the left basal paradiaphragmatic regions. CONCLUSION: Frequency of atelectasis was much less following the alveolar recruitment strategy, compared with children who did not have the maneuver performed. The mere application of 5 cm H2O of CPAP without a prior recruitment did not show the same treatment effect and showed no difference compared to the control group without PEEP.

Anesthesia, General↗
PubMed2003

Application of the open-lung concept during positive-pressure ventilation reduces pulmonary inflammation in newborn piglets.

It has been shown that application of the open-lung concept (OLC) during high-frequency oscillatory ventilation (HFOV) attenuates pulmonary inflammation. We hypothesized that this attenuation could also be achieved by applying the OLC during positive-pressure ventilation (PPV). After repeated whole-lung lavage, newborn piglets were assigned to one of three ventilation groups: (1) PPV(OLC); (2) HFOV(OLC), or (3) conventional PPV (PPV(CON)). After a ventilation period of 5 h, analysis of bronchoalveolar lavage fluid showed a reduced influx of polymorphonuclear neutrophils, interleukin 8, and thrombin activity in both OLC groups as compared with the PPV(CON) group. There were no differences in tumor necrosis factor alpha levels. We conclude that application of the OLC during PPV reduces pulmonary inflammation as compared with conventional PPV and that the magnitude of this reduction is comparable to that of HFOV.

Animals↗
PubMed2003

Positive pressure ventilation with the open lung concept optimizes gas exchange and reduces ventilator-induced lung injury in newborn piglets.

Previous studies demonstrated that high-frequency oscillatory ventilation using the open lung concept (OLC) resulted in superior gas exchange and a reduction in ventilator-induced lung injury (VILI). We hypothesized that these beneficial effects could also be achieved by applying the OLC during positive pressure ventilation. After repeated whole-lung-lavage, newborn piglets were assigned to either OLC positive pressure ventilation (PPV(OLC)), OLC high-frequency oscillatory ventilation (HFOV(OLC)), or conventional positive pressure ventilation (PPV(CON)) and ventilated for 5 h. In both OLC groups, collapsed alveoli were actively recruited and thereafter stabilized using the lowest possible airway pressures. In the PPV(CON) group, ventilator settings were adjusted to prevent critical hypoxia. Airway pressure, blood gas analysis, pressure-volume curve, and alveolar protein infiltration was recorded. A lung injury score was used for histologic comparison. Mean airway pressures were comparable in the three ventilation groups over time (1.2-1.5 kPa). Arterial oxygenation increased to mean values above 60 kPa in both OLC groups compared with 10 kPa in the PPV(CON) group (p < 0.001). Maximal lung compliance was superior in both OLC groups (PPV(OLC): 91 +/- 23; HFOV(OLC): 90 +/- 31 mL/kPa/kg, p < 0.01) compared with the PPV(CON) group (39 +/- 14 mL/kPa/kg). Alveolar protein infiltration was significantly reduced in the PPV(OLC) group (0.33 +/- 0.10 mg/mL, p < 0.01) and the HFOV(OLC) group (0.40 +/- 0.13 mg/mL, p < 0.01) compared with the PPV(CON) group (0.70 +/- 0.15 mg/mL). Lung injury scores were significantly higher in the PPV(CON) group (33.5 +/- 9.5, p < 0.01) compared with both OLC groups (PPV(OLC): 10.5 +/- 2.6; HFOV(OLC): 11 +/- 2.2). There were no differences between the two OLC groups. We conclude that, in surfactant-depleted newborn piglets, application of the OLC during PPV is feasible and results in superior gas exchange and a reduction in VILI compared with conventional PPV. These beneficial effects are comparable to HFOV.

Animals↗
PubMed2003

Open lung in ARDS.

Every year, millions of patients worldwide receive ventilator support during surgery. Mechanical ventilation has become an important therapy in the treatment of patients with impaired pulmonary function and particularly in patients suffering from adult respiratory distress syndrome (ARDS). ARDS is caused by multiple factors and is characterized by respiratory dysfunction including hypoxemia and decreased lung compliance. It is known that the decrease in lung distensibility is due to a disturbed surfactant system with an elevated surface tension. This increase in surface tension leads to an increase in forces acting at the air-liquid interface, resulting finally in end-expiratory collapse, atelectasis, an increase in right-to-left shunt and a decrease in paO2.

Animals↗
PubMed2002

Exogenous surfactant reduces ventilator-induced decompartmentalization of tumor necrosis factor alpha in absence of positive end-expiratory pressure.

OBJECTIVE: To determine the effect of pretreatment with exogenous surfactant on ventilator-induced decompartmentalization of TNF-alpha. DESIGN AND SETTING: Prospective, randomized, animal study in the experimental laboratory of a university. SUBJECTS AND INTERVENTIONS: Male Sprague-Dawley rats (n=102) received lipopolysaccharide either intratracheally or intraperitoneally to stimulate TNF-alpha production; one-half of the animals were pretreated with surfactant. Animals were ventilated for 20 min with a peak inspiratory pressure/positive end-expiratory pressure (PEEP) ratio of either 45/0 or 45/10 (frequency 30 bpm, I/E ratio 1:2, FIO(2)=1). MEASUREMENTS AND RESULTS: Blood gas tension and arterial pressures were recorded 1, 10, and 20 min after the start of mechanical ventilation. After the animals were killed pressure-volume curves were recorded, and bronchoalveolar lavage was performed for assessment of protein content and the small/large surfactant aggregate ratio. TNF-alpha was determined in serum and bronchoalveolar lavage. Pretreatment with surfactant decreased decompartmentalization of TNF-alpha during 45/0 ventilation. Addition of a PEEP level of 10 cm H(2)O reduced decompartmentalization even further. In addition, surfactant prevented deterioration in oxygenation and decreased accumulation of protein in the bronchoalveolar lavage in the zero-PEEP group. CONCLUSIONS: An excess of active surfactant decreases transfer of cytokines across the alveolar-capillary membrane similar to PEEP. The combination of PEEP and surfactant reduces decompartmentalization of TNF-alpha even further.

Animals↗
PubMed2002

Enhanced efficacy of porcine lung surfactant extract by utilization of its aqueous swelling dynamics.

This study investigates the interactions between a porcine lung surfactant (PLS) extract and distilled water, saline solution or Ringer solution. The phases which coexist in equilibrium with water or electrolyte solutions were analysed by X-ray diffraction and cryo transmission electron microscopy (cryo-TEM). A lamellar phase with a structure unit consisting of double bilayers was observed in water, whereas lamellar phases with the usual bilayer structure unit were formed in saline and in Ringer solutions. At 25 degrees C the presence of a 4.2-A peak in the X-ray diffraction wide-angle region of these three maximally swollen phases showed that most of the hydrocarbon chains were organized in a crystalline packing. At 42 degrees C the chains in all three phases were melted which, in combination with the low-angle diffraction, shows that they were liquid-crystalline. Polyhedral-like vesicles and spherically shaped multilamellar vesicles were observed in cryo-TEM. The bilayer unit structures were consistent with the periodicity seen by X-ray diffraction. The dynamic swelling behaviour was followed in the polarizing microscope. A remarkable growth of birefringent networks was seen at the air interface of samples swollen in Ringer solution and saline solution. No such interfacial growth phenomena were observed during swelling in water without electrolytes. Then, these dynamics were analysed in relation to time-dependent pulmonary administration of the surfactant extract in rats. Variation in the time of administration (20 and 60 min) after mixing the extract with saline or Ringer solution showed clear differences in physiological effects. At pulmonary administration when the swelling behaviour in vitro showed a maximum in dynamics, the arterial oxygenation was superior to that of administration at a time after a steady-state had been reached. This means that the clinical performance of mammalian lung surfactant extracts can be significantly improved by taking the time-dependent aqueous swelling of the extract into account.

Animals↗
PubMed2001

Intracranial pressure, brain PCO2, PO2, and pH during hypo- and hyperventilation at constant mean airway pressure in pigs.

OBJECTIVE: To evaluate in healthy, non-brain-traumatized animals the effects of hypo- and hyperventilation on intracranial pressure (ICP) and brain carbon dioxide, oxygen, and pH during the use of a ventilatory mode at constant mean airway pressure (MAwP). DESIGN AND SETTING: Prospective animal study in a university laboratory. SUBJECTS: Eight crossbred Landrace/Yorkshire pigs. INTERVENTIONS: The animals were ventilated in a pressure-controlled mode according to the open lung concept with an inspired oxygen fraction of 1.0. Starting at normoventilation, a stepwise hypo- and hyperventilation was performed to PaCO2 values of 90.4+/-10.4 and 26.9+/-4.1 mmHg, respectively. The ICP and brain parenchyma values [carbon dioxide (PbrCO2), oxygen (PbrO2), and pH (brpH)] measured by multiparameter sensors were recorded continuously during these maneuvres. RESULTS: During hypoventilation there was a significant increase in PbrCO2 tension, PbrO2 tension, and ICP. During hyperventilation there was a significant decrease in PbrCO2 tension and ICP while the change in PbrO2 was not significant. MAwP was kept stable during the stepwise hypo- and hyperventilation, and this resulted in a constant mean arterial pressure. CONCLUSIONS: Controlled hypo- and hyperventilation at constant MAwP in non-brain-traumatized pigs appears to induce changes in ICP and cerebral perfusion pressure which, however, do not necessarily lead to cerebral ischemia. To achieve adequate cerebral perfusion at an increased ICP level due to hypoventilation one must maintain sufficient arterial blood pressure. Hypercapnia resulted in a significant increase in brain oxygenation; however, this does not necessarily mean that permissive hypercapnia is neuroprotective.

Animals↗
PubMedDate not supplied

Exogenous surfactant restores lung function but not peripheral immunosuppression in ventilated surfactant-deficient rats.

The authors have previously shown that mechanical ventilation can result in increased pulmonary inflammation and suppressed peripheral leukocyte function. In the present study the effect of surfactant therapy on pulmonary inflammation and peripheral immune function in ventilated surfactant-deficient rats was assessed. Surfactant deficiency was induced by repeated lung lavage, treated rats with surfactant or left them untreated, and ventilated the rats during 2 hours. Nonventilated rats served as healthy control group. Expression of macrophage inflammatory protein (MIP)-2 was measured in bronchoalveolar lavage (BAL), interleukin (IL)-1beta, and heat shock protein 70 (HSP70) were measured in total lung homogenates. Outside the lung phytohemagglutinin (PHA)-induced lymphocyte proliferation, interferon (IFN)-gamma and IL-10 production, and natural killer activity were measured in splenocytes. After 2 hours of mechanical ventilation, expression of MIP-2, IL-1beta, and HSP70 increased significantly in the lungs of surfactant-deficient rats. Outside the lung, mitogen-induced proliferation and production of IFN-gamma and IL-10 reduced significantly. Only natural killer cell activity remained unaffected. Surfactant treatment significantly improved lung function, but could not prevent increased pulmonary expression of MIP-2, IL-1beta, and HSP70 and decreased peripheral mitogen-induced lymphocyte proliferation and IFN-gamma and IL-10 production in vitro. In conclusion, 2 hours of mechanical ventilation resulted in increased lung inflammation and partial peripheral leukocyte suppression in surfactant-deficient rats. Surfactant therapy ameliorated lung function but could not prevent or restore peripheral immunosuppression. The authors postulate that peripheral immunosuppression may occur in ventilated surfactant deficient patients, which may enhance susceptibility for infections.

Animals↗
PubMedDate not supplied

Quantitative EEG monitoring during cerebral air embolism and hyperbaric oxygen treatment in a pig model.

The purpose of this study was to evaluate the contribution of quantitative EEG (qEEG) to an animal model of cerebral air embolism (CAE). In 12 anesthetized pigs, air was injected into the internal carotid artery, and hyperbaric oxygen (HBO) treatment was started either after 3 minutes or after 60 minutes (United States Navy Treatment Table 6). Off-line spectral analysis was used to determine the frequency content of the EEG signal, and factor analysis was performed to determine the frequency ranges that optimally showed the changes in the power spectrum. Factor analysis revealed two factors that represented different and independent spectral changes during embolization: 0.5 to 7.3 Hz (band 1) and 26.4 to 30.3 Hz (band 2). Shortly after embolization, the power in both bands decreased to a minimum, representing an isoelectric EEG in 11 out of the 12 animals. EEG differences between animals were considerable, despite standardized doses of injected air, and qEEG can objectively assess and quantify these differences in immediate impact of air embolism on brain function. Also, qEEG enabled monitoring of the recovery from the initial embolic event and of the response on treatment. The initial recovery was much more protracted in band 2 than in band 1, but even after completing HBO treatment, qEEG values did not return to baseline values in all animals. In addition, two animals did not survive until the end of the HBO treatment, and qEEG proved to be superior to the other measured hemodynamic variables to detect and ensure a deterioration of brain function. This study showed that qEEG monitoring has significant additional value to monitoring HBO treatment.

Animals↗
PubMedDate not supplied

The open lung concept of alveolar recruitment can improve outcome in respiratory failure and ARDS.

Respiratory failure is a common finding in the ICU and in the management of complex cases in the operating room. Over the last ten years, it has become clear that modes of mechanical ventilation and lung recruitment may play a role both in cytokine modulation and patient outcome. Early lung recruitment and alveolar stabilization may play a very important role in the management of patients with respiratory failure and adult respiratory distress syndrome (ARDS). The open lung concept may be the key to decreasing mortality and morbidity in these patients. This technique not only improves oxygenation, but also affects surfactant function and cytokine modulation. The open lung concept is physiologically based on the Law of Laplace. Adhering to the principles of the open lung concept, pressure-controlled ventilation may improve patient outcome by reducing the extent of irreversible structural damage to the lungs caused by mechanical ventilation.

Humans↗