Search PubMed⌕ Search

Biomedical subjects

H Burchardi

Publications and source records attributed to H Burchardi.

At least 37 records · Page 2Linked to original sources
PubMed1999

Proportional assist versus pressure support ventilation: effects on breathing pattern and respiratory work of patients with chronic obstructive pulmonary disease.

OBJECTIVE: To investigate the breathing pattern and the inspiratory work of breathing (WOB(I)) in patients with chronic obstructive pulmonary disease (COPD) assisted with proportional assist ventilation (PAV) and conventional pressure support ventilation (PSV). DESIGN: Prospective controlled study. SETTING: Intensive care unit of a university hospital. PATIENTS: Thirteen COPD patients being weaned from mechanical ventilation. INTERVENTIONS: All patients were breathing PSV and two different levels of PAV. MEASUREMENTS AND MAIN RESULTS: During PAV (EVITA 2 prototype, Dräger, Germany), the resistance of the endotracheal tube (R(et)) was completely compensated while the patients' resistive and elastic loads were compensated for by approximately 80 % and 50 % (PAV(80) and PAV(50)), respectively. PSV was adjusted to match the same mean inspiratory pressure (Pinsp(mean)) as during PAV(80). Airway pressure, esophageal pressure and gas flow were measured over a period of 5 min during each mode. Neuromuscular drive (P(0.1)) was determined by inspiratory occlusions. Mean tidal volume (V(T)) was not significantly different between the modes. However, the coefficient of variation of V(T) was 10 +/- 4.%, 20 +/- 13 % and 15 +/- 8 % during PSV, PAV(80) and PAV(50), respectively. Respiratory rate (RR) and minute ventilation (V(E)) were significantly lower during PAV(80) as compared with both other modes, but the differences did not exceed 10 %. PAV(80) and PSV had comparable effects on WOB(I) and P(0.1), whereas WOB(I) and P(0.1) increased during PAV(50) compared with both other modes. CONCLUSION: Mean values of breathing pattern did not differ by a large amount between the investigated modes. However, the higher variability of V(T) during PAV indicates an increased ability of the patients to control V(T) in response to alterations in respiratory demand. A reduction in assist during PAV(50) resulted in an increase in WOB and indices of patient effort.

Aged↗
PubMed1998

Intensive care training and specialty status in Europe: international comparisons. Task Force on Educational issues of the European Society of Intensive Care Medicine.

OBJECTIVE: To describe current arrangements for postgraduate training and speciality status for intensive care medicine in Europe, and to compare these with three other geographical regions: the Middle East, North America, and Australia and New Zealand. METHODS: An iterative survey, by questionnaire and direct discussion, of council members of the European Society of Intensive Care Medicine, national specialist societies with involvement in intensive care, and national experts, representing four geographical regions and 47 countries. RESULTS: For the purposes of analysis, countries with common training structures have been grouped together; the denominator therefore includes both countries and regions. Formal training programmes in intensive care medicine (ICM) are available in 18 (85%) of the 21 countries or regions surveyed. Twelve (57%) offer multidisciplinary access to intensive care training with a common core curriculum. In six (28%) training in ICM is available solely through anaesthesia. The duration of intensive care training required for recognition as a specialist in the 18 countries or regions with a formal programme ranges from 18 to 30 months, with a median of 24 months. All countries assess competence in intensive care, but methods for doing so vary widely. Eighteen countries or regions offer specialist registration (accreditation) in ICM; in 12 this is provided as dual accreditation in a base speciality and in ICM. CONCLUSIONS: There is substantial support for multidisciplinary training in ICM, as demonstrated by collaborative interspeciality developments in many countries. We propose that these national developments should be strengthened within Europe by the recognition of 'supra-speciality' status for ICM by the European Commission, and by the establishment of a multidisciplinary Board for training in ICM, with international agreement on core competencies and duration of training programmes, and a common approach to the assessment of competence through formal examination.

Accreditation↗
PubMed1998

Determination of functional residual capacity (FRC) by multibreath nitrogen washout in a lung model and in mechanically ventilated patients. Accuracy depends on continuous dynamic compensation for changes of gas sampling delay time.

OBJECTIVE: Validation of an open-circuit multibreath nitrogen washout technique (MBNW) for measurement of functional residual capacity (FRC). The accuracy of FRC measurement with and without continuous viscosity correction of mass spectrometer delay time (TD) relative to gas flow signal and the influence of baseline FIO2 was investigated. DESIGN: Laboratory study and measurements in mechanically ventilated patients. SETTING: Experimental laboratory and anesthesiological intensive care unit of a university hospital. PATIENTS: 16 postoperative patients with normal pulmonary function (NORM), 8 patients with acute lung injury (ALI) and 6 patients with chronic obstructive pulmonary disease (COPD) were included. INTERVENTIONS: Change of FIO2 from baseline to 1.0. MEASUREMENTS AND MAIN RESULTS: FRC was determined by MBNW using continuous viscosity correction of TD(TDdyn), a constant TD based on the viscosity of a calibration gas mixture (TD0) and a constant TD referring to the mean viscosity between onset and end of MBNW (TDmean). Using TDdyn, the mean deviation between 15 measurements of three different lung model FRCs (FRCmeasured) and absolute volumes (FRCmodel) was 0.2%. For baseline FIO2 ranging from 0.21 to 0.8, the mean deviation between FRCmeasured and FRCmodel was -0.8%. However, depending on baseline FIO2, the calculation of FRC using TDmean and TD0 increased the mean deviation between FRCmeasured and FRCmodel to 2-4% and 8-12%, respectively. In patients (n = 30) the average repeatability coefficient was 6.0%. FRC determinations with TDmean and TD0 were 0.8-13.3% and 4.2-23.9% (median 2.7% and 8.7%) smaller than those calculated with TDdyn. CONCLUSION: A dynamic viscosity correction of TD improves the accuracy of FRC determinations by MBNW considerably, when gas concentrations are measured in a sidestream. If dynamic TD correction cannot be performed, the use of constant TDmean might be suitable. However, in patient measurements this can cause an FRC underestimation of up to 13%.

Adult↗
PubMed1998

Effects of anti-C5a monoclonal antibodies on oxygen use in a porcine model of severe sepsis.

METHODS: We analysed the effects of complement depletion and of C5a inhibition on haemodynamic parameters, oxygen delivery (DO2), oxygen consumption (VO2), oxygen extraction ratio (OER) and blood lactate levels after live bacteria infusion in pigs. RESULTS: In the first series of experiments, animals were decomplemented by cobra venom factor (CVF, 125 micrograms kg-1) and challenged with 1.3 x 10(9) Escherichia coli kg-1. In a second series, animals were treated with neutralizing anti-C5a monoclonal antibodies (mAb) T13/9 before infusion of an increased E. coli dosage (1 x 10(10) E. coli kg-1). Administration of Gram-negative bacteria resulted in hypotension, tachycardia, pulmonary hypertension and decreased cardiac output typical for severe sepsis. These alterations were more pronounced in animals challenged with a higher bacteria concentration (1 x 10(10) E. coli kg-1, n = 5) than with a lower dosage (1.3 x 10(9) E. coli kg-1, n = 4). Complement depletion by CVF injection 24 h before E. coli infusion (n = 4), or anti-C5a mAb T13/9 administration (n = 4) had no effect on the changes in haemodynamic parameters and in DO2 associated with E. coli challenge. Application of either 1.3 x 10(9) or 1 x 10(10) E. coli kg-1 resulted in a marked decrease in VO2 and an increase in blood lactate levels, whereas the OER did not change throughout the experiment. In contrast, pretreatment with CVF 24 h before low-dose E. coli (1.3 x 10(9) kg-1) administration resulted in a significant increase in VO2 (P < 0.05) and in OER (P < 0.05) compared with untreated septic animals (n = 4). No hyperlactaemia occurred in complement-depleted septic animals compared with complement-sufficient animals (P < 0.05). Animals challenged with a high E. coli dose (1 x 10(1) kg-1) and treated with anti-C5a mAbs showed a pronounced increase in VO2 and OER (P < 0.05) accompanied by an attenuated increase in lactate levels (P < 0.05) compared with untreated septic animals. CONCLUSION: The results demonstrate an improved oxygen use after complement depletion in this model of severe Gram-negative sepsis. Furthermore, a similar effect was seen after specifically neutralizing C5a by mAbs, indicating a role of C5a in the underlying mechanism.

Animals↗
PubMed1998

Monitoring perioperative changes in distribution of pulmonary ventilation by functional electrical impedance tomography.

BACKGROUND: Electrical impedance tomography (EIT) is a noninvasive technique providing cross-sectional images of the thorax. We have tested an extended evaluation procedure, the functional EIT (f-EIT), to identify the local shifts of ventilation known to occur during the transition between spontaneous, controlled and assisted ventilation modes. METHODS: Ten patients scheduled for elective laparotomy were studied in the surgical ward, operating theatre and ICU during spontaneous and different modes of mechanical ventilation. Sixteen ECG electrodes were placed on the circumference of the thorax and connected with an EIT device (APT System Mark I, IBEES, Sheffield, UK). Measurements lasting 180 s were performed and f-EIT images of regional ventilation computed. The geometrical centre of ventilation was determined to quantify the regional distribution of lung ventilation during individual modes of ventilation. RESULTS: F-EIT confirmed the differences in the distribution of ventilation associated with various modes of artificial ventilation. Accentuated ventilation of the dependent lung regions was observed during spontaneous breathing, whereas a shift of the centre of ventilation to the nondependent regions was found during controlled ventilation. In the course of assisted ventilation a continuous displacement of the centre of ventilation back towards the dependent lung regions, consistent with an increased proportion of spontaneous breathing, was detected. Unassisted spontaneous breathing after weaning from mechanical ventilation resulted in a similar ventilation distribution as during tidal breathing prior to surgery. CONCLUSION: F-EIT determined the redistribution of lung ventilation during different modes of mechanical ventilation. We expect that f-EIT will become a useful noninvasive bedside monitoring technique for imaging regional ventilation in pulmonary diseased patients during mechanical ventilation.

Abdomen↗
PubMed1998

Evaluation of respiratory inductive plethysmography in controlled ventilation: measurement of tidal volume and PEEP-induced changes of end-expiratory lung volume.

STUDY OBJECTIVE: To determine the accuracy of respiratory inductive plethysmography (RIP) with a respiratory monitor (Respitrace Plus; NIMS Inc., Miami) operating in the DC-mode for the measurement of tidal volumes (VT) and positive end-expiratory pressure (PEEP)-induced changes of end-expiratory lung volume (deltaEELV) in patients with normal pulmonary function, acute lung injury (ALI), and COPD during volume-controlled ventilation. DESIGN: Prospective comparison of RIP with pneumotachography (PT) for assessment of VT and with multibreath nitrogen washout procedure (N2WO) for determination of deltaEELV as reference methods. SETTING: Mixed ICU at a university hospital. PATIENTS: Thirty-one sedated and paralyzed patients: 12 patients with normal pulmonary function mechanically ventilated after major surgery, 10 patients with respiratory failure due to ALI, and 9 patients with a known history of COPD ventilated after surgery or because of respiratory failure due to bronchopulmonary infection. INTERVENTIONS: Stepwise increase of PEEP from 0 to 5 to 10 cm H2O and reduction to 0 cm H2O again. On each PEEP level, N2WO was performed. MEASUREMENTS AND MAIN RESULTS: The baseline drift of RIP averaged 25.4+/-29.1 mL/min but changed over a wide range even in single patient measurements. Determination of VT for single minutes revealed that 66.5% and 90.0% of all values were accurate within a range of +/-10% and +/-20%, respectively. The deviation for VT measurements between RIP and PT in patients with COPD was significantly (p<0.05) higher compared to patients with ALI or normal pulmonary function. The difference of deltaEELV between RIP and N2WO was 11.6+/-174.1 mL with correlation coefficients of 0.77 (postoperative and COPD patients) and 0.86 (ALI patients). However, just 25.8% and 46.2% were precise within +/-10% and +/-20%, respectively. deltaEELV determination in COPD patients differed more between RIP and N2WO than in the other groups, but this was not significant. CONCLUSION: In a mixed group of patients undergoing controlled ventilation, RIP using the Respitrace Plus monitor was not consistently precise enough for quantitative evaluation of VT and EELV when compared to our reference methods. This was most evident in patients with COPD. For long-term volume measurements, a better control of the baseline drift of RIP should be achieved.

Aged↗
PubMed1998

History and development of continuous renal replacement techniques.

In 1966 two research groups, one in the United States and the other in Germany, were independently evaluating new membranes for renal replacement techniques. These filters were characterized by high filtration rates, where solutes up to a certain molecular weight were filtered by convection. At the same time the understanding of the transport mechanisms through membranes was improving. In 1976 Burton created the term "hemofiltration" for this new convective technique, and the first multicenter trial was initiated to evaluate its effectiveness for treating chronic renal failure. In 1977 Kramer in Göttingen (Germany) developed the continuous arteriovenous hemofiltration (CAVH) technique, which used a systemic arteriovenous pressure difference in an extracorporeal circuit to continuously produce an ultrafiltrate. The advantages of this effective method for elimination of fluid and solutes were its technical simplicity and the hemodynamic stability of even critically ill patients. Therefore, it soon became a widely used method for treating acute renal failure in intensive care patients. However, its limited capacity to remove nephrotoxins in the presence of high catabolism and complications connected to the arterial access lead to the development of a venovenous pump-driven technique (CVVH) in order to become independent from the systemic circulation and the arterial access. Further progress to improve solute clearance was made by combining the convective principle of hemofiltration with the diffusive transport of dialysis (continuous arteriovenous hemodialysis or hemodiafiltration). Today this combination has become the most effective renal replacement technique for treating acute renal failure in critically ill patients.

Acute Kidney Injury↗
PubMed1997

Effects of early treatment with immunoglobulin on critical illness polyneuropathy following multiple organ failure and gram-negative sepsis.

OBJECTIVE: The evaluation of incidences and relating factors of severe persisting critical illness polyneuropathy (CIP) in survivors of multiple organ failure (MOF). DESIGN: Prospective study with an entry period of 24 months. Electrophysiological studies for the diagnosis of CIP were performed 1 or 2 days before the patients were discharged from the intensive care unit (ICU). Factors which might have been related to the development of CIP were identified by a retrospective chart analysis. SETTING: The interdisciplinary ICU of a university hospital. PATIENTS: Thirty-three patients who survived MOF. Sixteen of these critically ill patients developed severe sepsis due to nosocomial infections with gram-negative bacteria. RESULTS: In seven survivors of MOF and sepsis typical electrophysiological features of CIP, like spontaneous fibrillations and low compound muscle action potentials, were detectable at the time of discharge from the ICU. Seventeen patients with MOF following multiple trauma who developed no sepsis, and nine survivors of MOF with sepsis showed no signs of persisting CIP at the end of their ICU stay. Chart analysis revealed that eight survivors of MOF with sepsis and without the development of CIP had been treated with intravenous immunoglobulin (IVIG) with a dosage of 0.3 g/kg per day for 3 days immediately (within 24 h) after the diagnosis of sepsis. Four out of seven patients with MOF and sepsis who developed CIP were transferred to our ICU after the onset of sepsis and had not received IVIG treatment. The IVIG treatment in three patients was delayed for more than 24 h after the diagnosis of sepsis and was then omitted. Obviously not related to the development of CIP were aminoglycoside antibiotics, steroids, nutritional disturbances and episodes of hypotension or hypoxia. Neuromuscular blocking agents were not used during intensive care treatment. CONCLUSIONS: A high incidence of severe CIP persisting until the day of discharge from the ICU was related to gram-negative sepsis but not to MOF alone. Retrospective chart analysis suggested that early application of IVIG may prevent or mitigate this severe complication. However, these results have to be confirmed in a prospective, placebo-controlled study.

APACHE↗
PubMed1997

The influence of controlled mandatory ventilation (CMV), intermittent mandatory ventilation (IMV) and biphasic intermittent positive airway pressure (BIPAP) on duration of intubation and consumption of analgesics and sedatives. A prospective analysis in 596 patients following adult cardiac surgery.

The aim of the study was the determination of the influence of ventilation modes on the consumption of analgesics and sedatives, duration of intubation and pulmonary gas exchange. Assist/controlled mandatory ventilation (S-CMV, 123 patients), synchronized intermittent mandatory ventilation (S-IMV, 431 patients) and biphasic positive airway pressure ventilation (BIPAP, 42 patients) were compared in a prospective, controlled, open clinical trial over an 18-month period. Five hundred and ninety-six adult patients with normal pulmonary function before surgery and uneventful course following coronary artery bypass graft surgery were studied. Patients ventilated with BIPAP had a significantly shorter mean duration of intubation (10.1 h, P < 0.05) than patients treated with S-IMV (14.7 h) and S-CMV (13.2 h). In the S-CMV group, 39.9% of the patients required single or multiple doses of midazolam, but only 13.5% in the S-IMV group and 9.5% in the BIPAP group. The mean total amount of midazolam administered to these patients was significantly higher in the S-CMV group (8.8 mg) than in the S-IMV group (6.6 mg, P < 0.05) and in the BIPAP group (4.3 mg, P < 0.05). The consumption of pethidine and piritramide did not differ between S-CMV and S-IMV, but was significantly lower during BIPAP (P < 0.05). After extubation the patients' PaCO2 was highest in the S-CMV group. We conclude that ventilatory support with BIPAP reduces the consumption of analgesics and sedatives, and the duration of intubation. The possibility of unrestricted spontaneous breathing in all phases of the respiratory cycle is considered to be the reason. BIPAP seems to be an alternative to S-CMV and S-IMV in short-term ventilated patient.

Analgesics↗
PubMed1996

Inhibition of interleukin-6 synthesis in an animal model of septic shock by anti-C5a monoclonal antibodies.

The complement activation fragment C5a was recently shown to induce interleukin (IL)-6 synthesis by peripheral blood mononuclear cells. To understand better the role of C5a in cytokine regulation in vivo, we investigated the effects of complement depletion by cobra venom factor (CVF) or of anti-C5a monoclonal antibodies (mAb) on IL-6 generation in an animal model of septic shock. Complement-depleted pigs which were subsequently challenged with Escherichia coli generated significantly (p < 0.05) less IL-6 during the 6-h observation period than complement-sufficient controls. To address specifically the role of C5a in IL-6 regulation, we produced a C5a(57-74) peptide-specific mAb (T13/9) which neutralizes the bioactivity of porcine C5a. The mAb T13/9 does not cross-react with the precursor protein C5. The pretreatment of pigs with anti-C5a mAb T13/9 prior to the induction of sepsis resulted in a decrease of over 75% in serum IL-6 bioactivity compared to control animals (p < 0.0001). These results indicate a role for C5a in the modulation of IL-6 synthesis in Gram-negative bacteremia.

Amino Acid Sequence↗