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S Baehrendtz

Publications and source records attributed to S Baehrendtz.

At least 19 recordsLinked to original sources
PubMed1997

A comparison of pressure- and volume-controlled ventilation at different inspiratory to expiratory ratios.

BACKGROUND: Inverse ratio ventilation (IRV) is frequently used in severe acute respiratory failure. IRV may lead to intrinsic positive end-expiratory pressure (PEEP) and is thought to improve oxygenation and to have advantageous effects on lung mechanics. Published data to support the use of IRV are scarce. This animal study compares external PEEP with intrinsic PEEP in pressure- and volume-controlled ventilation. METHODS: Fifteen pigs were randomly treated with 1. volume-controlled PEEP ventilation (I:E ratio 1:2) (VCV PEEP), 2. volume-controlled ventilation (I:E ratio 4:1) (VCIRV) and 3. pressure-controlled ventilation (I:E ratio 4:1) (PCIRV). Baseline measurements were performed using volume-controlled ventilation (I:E ratio 1:2) (VCV ZEEP). Lung mechanics, haemodynamics and gas exchange were measured by standard methods and functional residual capacity (FRC) by the sulphur hexafluoride technique. RESULTS: In comparison to VCV PEEP, PCIRV resulted in reduced peak airway pressure (32 +/- 3 vs. 27 +/- 6 cm H2O, P < 0.001) and increased mean airway pressure (14 +/- 2 vs. 22 +/- 5 cm H2O, P < 0.001). FRC was 942 +/- 264 ml in VCV PEEP and 1024 +/- 390 ml in PCIRV (n.s.). Oxygen delivery was lower in PCIRV (458 +/- 193 vs. 346 +/- 150 ml/min, P < 0.05). Physiologic dead space was 14 +/- 4% in PCIRV and 20 +/- 6% in VCV PEEP and VCIRV (P < 0.005). CONCLUSIONS: Inverse ratio ventilation did not result in improved FRC in comparison to conventional volume-controlled PEEP ventilation. PCIRV allows for a reduction in minute ventilation but the increase in mean airway pressure compromises circulation.

Airway Resistance↗
PubMed1995

Clinical application of differential ventilation with selective positive end-expiratory pressure in adult respiratory distress syndrome.

Differential ventilation in the lateral position with positive end-expiratory pressure (PEEP) selectively applied to the dependent lung (DVSP) has been shown to reduce venous admixture and improve oxygenation without compromising cardiac output in short term studies of patients with acute respiratory failure. We have applied this ventilation technique as a long-term treatment in severe adult respiratory distress syndrome (ARDS) in an open clinical trial. Eleven patients with ARDS of varying aetiology were treated with DVSP for a total of 34 days. Median duration of conventional ventilatory therapy before start of DVSP was 5 days (1 to 18 days), inspiratory oxygen fraction (FIO2) was 0.61 +/- 0.16 (mean +/- s.d.), resulting in a mean arterial oxygen tension (PaO2) of 7.1 +/- 2.1 kPa (PaO2/FIO2 = 11 +/- 4 kPa). A gradual improvement in gas exchange was seen during the first 24 h of DVSP such that PaO2 increased to 8.4 +/- 1.4 with a decreased FIO2 (0.52 +/- 0.14) resulting in an increased PaO2/FIO2 (16 +/- 5 kPa). Five out of the eleven patients survived. No major complication was noted using DVSP as a method. We found a steady improvement in gas exchange over the first 24 hours in most patients. However, mortality rate was no lower than expected. Drawbacks with DVSP were increased demand on staff and difficulties with adequate endo-bronchial suctioning.

Adolescent↗
PubMed1995

Volume-controlled inverse ratio ventilation in oleic acid induced lung injury. Effects on gas exchange, hemodynamics, and computed tomographic lung density.

STUDY OBJECTIVE: To compare volume-controlled inverse ratio ventilation (VCIRV) with volume-controlled ventilation with conventional inspiratory to expiratory (I:E) ratio (VCV PEEP) at equal levels of end-expiratory pressure. DESIGN: Animal study using an oleic acid lung injury model with random application of VCV PEEP and VCIRV. SETTING: Experimental investigation at the Department of Clinical Physiology at Uppsala University. ANIMALS: Seven pigs. INTERVENTIONS: VCV PEEP, VCIRV at an end-expiratory pressure level of 10 cm H2O. MEASUREMENTS AND RESULTS: Lung mechanics, hemodynamics, gas exchange, and functional residual capacity. Recruitment of lung tissue, regional lung density, and distribution of inspired gas by computed tomography. Mean and peak airway pressures were 22 +/- 4 and 41 +/- 8 cm H2O with VCIRV and 18 +/- 2 and 45 +/- 7 cm H2O with VCV PEEP. Cardiac output and arterial oxygen tension were equal with VCV PEEP and VCIRV as were static compliance, physiologic dead space, and functional residual capacity. End-expiratory, end-inspiratory, and CT densities during a full ventilatory cycle were not statistically different and the amounts of nonaerated and poorly aerated lung areas were of equal size with VCV PEEP and VCIRV. CONCLUSIONS: VCIRV was comparable to VCV PEEP at similar PEEP levels in alveolar recruitment, aeration of the lung tissues, and in oxygenating the blood. Since cardiac output also remained unchanged, oxygen delivery to peripheral tissues did not differ significantly between the two modes. Neither method has thus proved superior to the other one.

Animals↗
PubMed1994

A functional and morphologic analysis of pressure-controlled inverse ratio ventilation in oleic acid-induced lung injury.

STUDY OBJECTIVE: To compare volume-controlled ventilation (VCV PEEP) with pressure-controlled inverse ratio ventilation (PCIRV) at equal levels of end-expiratory pressure. DESIGN: Animal study using an oleic acid lung injury model with random application of VCV PEEP and PCIRV. SETTING: Experimental laboratory investigation at the Department of Clinical Physiology at Uppsala University. ANIMALS: Twelve pigs. INTERVENTIONS: VCV PEEP and PCIRV at an end-expiratory pressure level of 10 cm H2O. MEASUREMENTS AND RESULTS: Lung mechanics, hemodynamics, and gas exchange. Recruitment of lung tissue, regional lung density, and distribution of inspired gas by computed tomography. Mean and peak airway pressures were 29 and 35 cm H2O with PCIRV and 17 and 45 cm H2O with VCV PEEP. Cardiac output and mean systemic blood pressure were lower with PCIRV (2.5 L/min and 82 mm Hg) than with VCV PEEP (3.1 L/min and 97 mm Hg). Physiologic dead space was 24 percent with VCV PEEP and 20 percent with PCIRV. Static compliance, arterial oxygen tension, and functional residual capacity were equal between the two ventilatory modes. End-expiratory, end-inspiratory, and dynamic computed tomographic densities were equal between VCV PEEP and PCIRV. Nonaerated and poorly aerated lung areas were of equal size with VCV PEEP and PCIRV. CONCLUSIONS: PCIRV was no better than VCV with similar PEEP levels in alveolar recruitment and aeration of the lung tissues or in oxygenating the blood. Cardiac output was lower with PCIRV than with VCV, causing lower oxygen delivery to peripheral tissues. PCIRV does allow for a reduction in minute ventilation and for lowering peak airway pressure.

Analysis of Variance↗
PubMed1991

Mechanical ventilation in medical and neurological diseases: 11 years of experience.

Mechanical ventilation (MV) is imperative in many forms of acute respiratory failure (ARF). The aim of this work was to review all episodes of MV in a Medical Intensive Care Unit (MICU) during the 11-year period 1976-1986. Four per cent (n = 1008) of 24,899 admissions to the MICU were treated with MV. The mean age of ventilator-treated patients was 53 +/- 18 years, and obviously it increased during the period of study. The average duration of MV was 4.7 d. MICU mortality, hospital mortality and 2-year mortality rates for patients subjected to MV were 33%, 38% and 46%, respectively. The mortality rate did not change during the study period. Cerebrovascular and malignant diseases carried the highest mortality rates, 75 and 79%, respectively, whereas mortality in patients ventilated because of drug overdose (n = 313) was only 2%. The results of this study confirm previously published findings concerning the outcome of MV, and we conclude that the effects of MV remain discouraging in medical and neurological patients. Improved quality of ventilator therapy and monitoring, as well as continued research directed at the causes of ARF, are equally important in reducing the mortality in ARF.

Adolescent↗
PubMed1991

A placebo-controlled trial of flumazenil given by continuous infusion in severe benzodiazepine overdosage.

A controlled trial was performed to study the effect and any adverse reactions of continuously infused flumazenil in severe benzodiazepine overdosage. The study comprised 51 adults admitted to an intensive care unit with poisoning. Enrollment criteria were unconsciousness on admission and a clear response within 5 min after an i.v. bolus injection of 1 mg flumazenil. The level of consciousness was assessed according to a modified Glasgow coma scale immediately before and at defined intervals up to 12 h after injection. A double-blind infusion was started 15 min after the bolus injection and administered for 5 h. The patients were randomly allocated to one of three groups: a group given flumazenil 0.5 mg/h, a group given flumazenil 0.1 mg/h and a placebo group. The groups were comparable in age, sex and toxicological laboratory results. There were no significant differences between the groups in the average coma score on admission or 15 min after the bolus injection. In the flumazenil 0.5 mg/h group the level of consciousness remained unchanged between the 15-min recording and the subsequent assessments. In the two other groups the level of consciousness decreased significantly during the course of the infusion. The infusions were well tolerated. It is concluded that a continuous infusion of 0.5 mg of flumazenil per hour can prevent relapse into coma in patients with severe benzodiazepine poisoning aroused with a single injection of the antagonist.

Adolescent↗
PubMed1990

Diagnostic utility of flumazenil in coma with suspected poisoning: a double blind, randomised controlled study.

OBJECTIVE: To assess the diagnostic value and safety of the benzodiazepine antagonist flumazenil in patients with coma of unclear origin with suspected poisoning. DESIGN: Double blind, placebo controlled, randomised study. SETTING: Intensive care unit at a major teaching hospital. PATIENTS: 105 Unconscious adults admitted consecutively with suspected drug overdosage during 18 months from a total of 362 cases of poisoning. Exclusion criteria were pregnancy, epilepsy, obvious poisoning with drugs identified unequivocally from information from relatives or others as other than benzodiazepines, and coma score greater than 10 on a scale graded from 4 to 20. Patients were allocated randomly to receive flumazenil (21 men and 32 women) or placebo (25 men and 27 women). INTERVENTIONS: Intravenous injection of flumazenil (10 ml, 0.1 mg/ml) or placebo (10 ml vehicle alone) given double blind over three minutes. MAIN OUTCOME MEASURES: Serum and urine concentrations of benzodiazepines, antidepressants, and several other agents; blood gas tensions; standardised evaluation on admission and five minutes after the injection by means of coma scale score and urgent diagnostic or therapeutic interventions indicated according to the history and clinical examination; standardised interview after the injection to try to ascertain further information; and adverse reactions. RESULTS: Benzodiazepines were found in the serum in 36 of the 53 patients in the flumazenil group and in 37 of the 52 who received placebo. The average coma scale score increased significantly after injection in the flumazenil group (6.4 v 12.1, p less than 0.001) but not in the placebo group. In the flumazenil group several interventions were rendered unnecessary by the injection: gastric lavage and urinary catheterisation (19 patients each), intubation (21), artificial ventilation and computed tomography of the brain (three patients each), blood culture and lumbar puncture (one patient each), and electroencephalography (two). In the placebo group the indications for these procedures did not change in any patient after injection. The 95% confidence interval for the difference in reduction of the frequency of indications for gastric lavage after injection between the two groups was 21% to 51%, that for intubation 25% to 55%, and that for urinary catheterisation 21% to 51%. In the flumazenil group 21 patients gave valuable information on their drug ingestion within 10 minutes after injection compared with only one in the placebo group (p less than 0.001). Nine adverse reactions were recorded in the flumazenil group, eight of which were graded as mild and one severe. The safety of the antagonist was acceptable, even though 60% of the patients in the flumazenil group had multiple drug poisoning including benzodiazepine. No epileptic seizures or arrhythmias were recorded. CONCLUSION: Flumazenil is a valuable and safe differential diagnostic tool in unclear cases of multiple drug poisoning.

Adolescent↗
PubMed1990

Lung function analysis and optimization during artificial ventilation. A personal computer-based system.

In an intensive care unit a personal computer (PC) application for lung function analysis has been in use for 5 years. The PC system is applied to measure conventional and new parameters for diagnosis and therapy. The primary goal was to find parameters which could be used as optimization indices in optimal control systems for mechanical ventilation. Another clinical application of the PC system was as an automatic controller that stabilizes end-tidal CO2 concentration. The controller and the next application, the optimizer, could be integrated into an optimal control system. Such a system is described and a simulation trial of the integrated structure has demonstrated the potential.

Humans↗
PubMed1990

Ventilation-perfusion relationships and atelectasis formation in the supine and lateral positions during conventional mechanical and differential ventilation.

Patients without respiratory symptoms were studied awake and during general anesthesia with mechanical ventilation prior to elective surgery. Ventilation-perfusion (VA/Q) relationships, gas exchange and atelectasis formation were studied during five different conditions: 1) supine, awake; 2) supine during anesthesia with conventional mechanical ventilation (CV); 3) in the left lateral position during CV; 4) as 3) but with 10 cm of positive end-expiratory pressure (PEEP) and 5) as 3) but using differential ventilation with selective PEEP (DV + SPEEP) to the dependent lung. Atelectatic areas and increases of shunt blood flow and blood flow to regions with low VA/Q ratios appeared after induction of anesthesia and CV. With the patients in the lateral position, further VA/Q mismatch with a fall in PaO2 and increased dead space ventilation was observed. Atelectatic lung areas were still present, although the total atelectatic area was slightly decreased. Some of the effects caused by the lateral position could be counteracted by adding PEEP. Perfusion of regions with low VA/Q ratios and venous admixture were then diminished, while PaO2 was slightly increased; shunt blood flow and dead space ventilation were essentially unchanged. During CV + PEEP, there was a decrease in cardiac output, compared to CV in the lateral position. DV + SPEEP was more effective than CV + PEEP in decreasing shunt flow and increasing PaO2 in the lateral position; in addition to this, cardiac output was not affected.

Adult↗
PubMed1990

The stability of flumazenil in infusion solution.

Flumazenil, the first benzodiazepine antagonist to be marketed, is available only for intravenous injection (0.1 mg/ml). The half-life of the compound in plasma is short compared with that of the conventional benzodiazepines, and administration of the drug as a continuous infusion is therefore frequently required. However, the stability of flumazenil in infusion solution has not previously been known, which has meant that controlled studies of the drug in this administration form have been difficult to perform. In the present study, infusion solutions of flumazenil in concentrations of 1.0 and 5.0 micrograms/ml were produced and stored for periods of up to 9 months. The concentrations of the drug in the different solutions were determined by gas chromatography at defined intervals, and were found not to change during the study period. We conclude that the stability of flumazenil in infusion solution is satisfactory.

Drug Stability↗
PubMed1989

A microcomputer system for on-line monitoring of pulmonary function during artificial ventilation.

Standard monitoring of the artificially ventilated patient in the intensive care unit (ICU) and during anaesthesia includes repeated determinations of arterial blood gases, airway pressure and expired volume. However, there is a need for more extensive monitoring of the critically ill ventilator treated patient, and this is possible by better utilization of modern technology. Information on a variety of variables related to both pulmonary mechanics and gas exchange has long been accessible in the lung-function laboratory. Small, inexpensive microcomputers (PCs), accurate and fast bedside monitors and modern ventilators have also made this information directly available to the ICU staff. This paper describes a microcomputer (PC-XT) system for on-line bedside monitoring of pulmonary function. The microcomputer receives airway pressure, gas-flow and timing signals from the ventilator and signals for carbon dioxide concentration from an infrared analyzer. Data related to pulmonary mechanics and gas exchange are derived and displayed on the computer screen, both numerically and as graphs. In studies of ten artificially ventilated patients the coefficients of variation (CV) were below 10% for directly obtained variables (tidal volume, airway pressure, end-tidal and mixed expired carbon dioxide, carbon dioxide production, airway dead space), whereas the derived variables (compliance, phase III carbon dioxide slope) were associated with greater variability, with CVs ranging from 1.3 to 24% (median 6.25% and 8.65% respectively). The accuracy in estimating dead space variations was checked in two ventilator-treated patients by adding known dead space volumes. Simple regression analysis yielded an r value of 0.98 indicating adequate correctness of measurements and calculations.

Airway Resistance↗
PubMed1989

Benzodiazepine poisoning: experience of 702 admissions to an intensive care unit during a 14-year period.

A retrospective study covering a 14-year period was carried out to estimate the incidence and assess the clinical features of benzodiazepine (BZD) poisoning. The annual contribution of BZDs to the total number of drug overdose cases admitted to an intensive care unit displayed an increasing trend over the period, and during the last years BZDs were involved in nearly one-third of all cases. Among the 702 cases of BZD overdosage, 144 had ingested BZD alone, 200 had poisoned themselves with BZD combined with alcohol and 358 had taken BZD with other miscellaneous drugs. In 56% of all the cases the patients had severe central nervous system depression on admission. In 47% orotracheal intubation was performed and in 18% artificial ventilation was administered. Complications were recorded in 69 of the 702 cases (9.8%) and five cases were fatal. These clinical features were essentially the same in the group that had overdosed with just BZD. In conclusion, patients with drug overdosage involving BZD have a low hospital mortality, but the acute somatic risk is not negligible. Moreover, they consume a substantial proportion of the resources in the emergency room and the intensive care unit.

Adolescent↗
PubMed1988

The effect of flumazenil (Ro 15-1788) in the management of self-induced benzodiazepine poisoning. A double-blind controlled study.

A double-blind randomized study was performed to evaluate the efficacy and safety of flumazenil, a benzodiazepine antagonist. The study comprised 52 patients admitted to an intensive care unit because of suspected pure or mixed benzodiazepine poisoning. The degree of consciousness was assessed according to a modified Glasgow Coma Scale (MGCS), graded from 4 to 20, immediately before and at consecutive intervals after an i.v. injection of flumazenil or placebo. If there were no clear signs of arousal within 5 min after the blind injection, an injection of flumazenil was given in open design. Five minutes after the blind administration of active drug the MGCS score was increased by an average of 7.4 (p less than 0.001) in the flumazenil group. In the placebo group the average MGCS score of 7.8 on admission was not significantly increased by placebo, but 5 min after flumazenil injection it had increased by 7.3 to 15.1 (p less than 0.001). Patients who had ingested both alcohol and benzodiazepines were aroused as promptly and clearly (MGCS +8.8; p less than 0.001) as those who had taken benzodiazepines alone (MGCS +8.4; p less than 0.001). The patients poisoned with a combination of benzodiazepines and other hypnotic drugs responded less, but still highly significantly (MGCS +5.8; p less than 0.001). Flumazenil was well tolerated and the safety of the antidote seems acceptable. It is concluded that flumazenil can facilitate differential diagnosis and that it is an effective tool in the treatment of drug overdosage when benzodiazepines are involved.

Adult↗
PubMed1988

Flumazenil in self-induced benzodiazepine poisoning.

In Sweden the pattern of consumption of hypnotics has changed over the last two decades in favour of benzodiazepines (BZ), at the expense, mainly, of barbiturates. The agents chosen in cases of self-induced poisoning relfect this altered pattern of consumption. The frequency of BZ poisoning alone or in combinations at the Intensive Care Unit (ICU) of one of the largest hospitals in Stockholm increased by an average of 13% per year between 1972 and 1986. Today BZ poisoning constitutes 57% of all self-induced poisonings with hypnotics and sedatives. The mortality is negligible, but the cost of ICU treatment is substantial. The discovery of the BZ antidote flumazenil therefore opens up interesting diagnostic and therapeutic possibilities. The drug's efficacy in reversing iatrogenic BZ overdose has been well documented. Its use in cases of self-induced poisoning has also been advocated. Various authors have reported independently successful use of flumazenil in series of patients admitted because of self-induced hypnotic-drug overdose. The results clearly demonstrate that flumazenil is a potent, quick-acting antidote to BZ. However, the duration of its action is short.

Anesthesia↗
PubMed1985

Hypoxic pulmonary vasoconstriction in the human lung: effect of repeated hypoxic challenges during anesthesia.

Six patients, ages 29-58 yr, were investigated during barbiturate and fentanyl anesthesia. After intubation with a double-lumen bronchial catheter, one lung was ventilated continuously with 100% O2, and the other was rendered hypoxic during three 15-min periods by ventilation with 95% N2 + 5% O2, with intervening 15-min periods of oxygen ventilation. Cardiac output was determined by thermodilution, and the distribution of blood flow between the lungs was assessed from the excretion of a continuously infused poorly soluble gas (SF6). The first hypoxic challenge resulted in a 10% increase in cardiac output (QT) and a reduction in the fractional perfusion of the test lung from 57% to 31% of QT. The pulmonary artery mean pressure increased by 54%, and the vascular resistance of the test lung increased threefold. The venous admixture increased from 19% to 40% of QT, whereas the inert gas shunt remained unaltered at 15% (inert gases also being eliminated by nitrogen-ventilated areas). The arterial oxygen tension decreased from 353 mmHg to 79 mmHg. On resumption of the control state, central hemodynamics and gas exchange returned to the initial values. The second and third hypoxic challenges resulted in reductions in the fractional perfusion of the test lung to 35% and 37% of QT. All other variables were altered to the same degree as during the first challenge. The authors conclude that hypoxic challenge of one lung in an intravenously anesthetized human subject elicits a maximum vasoconstrictor response within the first 15 min, and this response cannot be potentiated by repeated challenges.

Adult↗
PubMed1985

Development and evaluation of a flow-dividing unit for differential ventilation and selective PEEP.

Differential ventilation with selective positive end-expiratory pressure (PEEP) was studied in a two-compartment lung model, using one ventilator and a flow-dividing unit consisting of inspiratory flow resistors and an inspiratory threshold valve. The compliance of each lung compartment was varied between 0.15 and 0.23 1 X kPa-1 and the resistance was varied from 0 to 3.5 kPa X 1(-1) X s. The minute volume was 12 1 and the respiratory frequency 12/min, with an inspiratory:expiratory ratio of 1:2. An even distribution of ventilation to the two lung compartments was obtained with the inspiratory flow resistors or the threshold valve under all conditions studied. However, a stepwise increase in the inspiratory resistance of one lung compartment from 1.0 to 2.5 or from 2.5 to 3.5 kPa X 1(-1) X s required readjustment of the inspiratory flow resistor to achieve an even distribution of ventilation, whereas the inspiratory threshold valve needed no readjustment. Large differences in the inspiratory impedance of the two lung compartments caused asynchronous gas delivery when the ventilation distribution was adjusted by means of the flow resistors. Use of the threshold valve resulted in synchronous gas delivery. The flow-dividing unit consists of non-active elements and can thus be connected to any ventilator.

Humans↗