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Biomedical subjects

C Klingstedt

Publications and source records attributed to C Klingstedt.

18 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

The modifying influence of anaesthesia on postoperative protein catabolism.

We studied two groups of six patients scheduled for gastrointestinal surgery; they were allocated randomly to receive high- or low-dose fentanyl anaesthesia. The confounding effect of protein balance, before the trauma of surgery, on postoperative nitrogen excretion was controlled by standardized protein intake before operation, supplemented by adequate calories. The high-dose group had significantly lower stress levels during surgery, assessed by arterial blood concentrations of cortisone, adrenaline and glucose. After operation, protein catabolism was measured for 7 days. The high-dose group had significantly lower postoperative excretion of ammonia and slightly lower excretion of urea and 3-methylhistidine. Low-stress anaesthesia may thus diminish postoperative catabolism, which could be important in frail patients by reducing mortality, ICU resources, or both.

Ammonia↗
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↗
PubMed1990

Neural regulation of vascular tone and cold induced vasoconstriction in human finger skin.

Finger skin blood flow was measured by a laser Doppler during control conditions, after neural blockade at the finger base by prilocaine and after localized anaesthesia of the skin by lidocaine introduced iontophoretically into the finger skin. Vasoconstriction was achieved by local cooling of the finger and by iontophoretic administration of norepinephrine during the described three conditions. Compared to the control condition, blood flow increased after nerve block at the finger base but even more after local skin anaesthesia. This additional increase in blood flow after local application of lidocaine indicates that finger skin vascular tone is partly dependent on local reflexes. Vasoconstriction on local cooling was preserved after nerve blockade at the finger base but inhibited after local skin anaesthesia by iontophoresis of lidocaine. This inhibition was not due to paralysis of the vessel wall since vasoconstriction to norepinephrine was preserved. Thus, vasoconstriction in response to local cooling is mediated by local reflexes.

Blood Vessels↗
PubMed1990

The influence of body position and differential ventilation on lung dimensions and atelectasis formation in anaesthetized man.

The effects of body position and anaesthesia with mechanical ventilation on thoracic dimensions and atelectasis formation were studied by means of computerized tomography in 14 patients. Induction of anaesthesia in the supine position reduced the cross-sectional area for both lungs and caused atelectasis formation in dependent lung regions in 4/5 patients. Conventional ventilation with positive end-expiratory pressure (PEEP) increased thoracic dimensions and reduced, but did not eliminate, the atelectatic areas. The vertical diameters of both lungs were smaller in the lateral position as compared to the supine position (16.7 vs 10.4 cm in the left lung and 17.3 vs 12.8 cm in the right lung). The lateral positioning also caused a large reduction of the atelectatic area in the non-dependent lung. Differential ventilation with selective PEEP to the dependent lung eliminated (3/8 patients) or reduced (5/8 patients) dependent lung atelectasis. It can be concluded that lung geometry is altered in the lateral position: the shape of the lung makes the vertical diameter of each lung less in the lateral position, compared to the supine position. The atelectatic areas are mainly located in the dependent lung in the lateral position, and these atelectatic areas could be further reduced by selective PEEP to this lung.

Adult↗
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↗
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↗
PubMed1988

High- and low-dose fentanyl anaesthesia: hormonal and metabolic responses during cholecystectomy.

We have compared two groups of patients given low- or high-dose fentanyl anaesthesia. Arterial blood samples were collected for measurement of glucose, free fatty acids (FFA), glycerol, beta-hydroxy-butyrate, insulin, c-peptide, glucagon, human growth hormone (HGH), cortisol and adrenaline concentrations. After induction of anaesthesia, blood concentrations of most of these substances decreased. After the start of surgery the concentrations of cortisol, glucose, HGH, FFA and beta-hydroxy-butyrate increased significantly in the group anaesthetized with the lower dose of fentanyl. In the group that received high-dose fentanyl anaesthesia the plasma concentrations of almost all the hormones and substances measured remained relatively low. The differences between the two groups during surgery were significant for adrenaline (P less than 0.001) and cortisol (P less than 0.001). High-dose fentanyl appears to block the trauma-induced stress response seen in patients anaesthetized with low dose fentanyl.

Adult↗
PubMed1988

Paravertebral block during cholecystectomy: effects on circulatory and hormonal responses.

Surgical trauma induces a hormonal metabolic response which is partly responsible for postoperative catabolism. In this study 12 patients underwent cholecystectomy during isoflurane anaesthesia, six with a paravertebral block (PVB) in addition. Plasma concentrations of glucose, cortisol and adrenaline, and heart rate and arterial pressure were compared between the two groups. The patients with PVB showed a significantly diminished response to noxious stimuli.

Adult↗
PubMed1987

High- and low-dose fentanyl anaesthesia: circulatory and plasma catecholamine responses during cholecystectomy.

The cardiovascular and neuroendocrine effects of a high-dose fentanyl anaesthesia (100 micrograms/kg body weight) were compared with those of a balanced type of fentanyl anaesthesia (5 micrograms kg-1) during upper abdominal surgery. High-dose fentanyl anaesthesia prevented the increase in catecholamine concentrations and attenuated the circulatory response to surgical stress seen in the group anaesthetized with the balanced technique of anaesthesia.

Adult↗
PubMed1985

Lung and chest wall mechanics during differential ventilation with selective PEEP.

Eight patients free from cardio-pulmonary disease and with a mean age of 46 years were studied during general anaesthesia in the lateral position. Measurements of hemithoracic mechanics were made during four different modes of ventilation: 1. Conventional ventilation (free distribution of ventilation) with no positive end-expiratory pressure (PEEP) (CV), 2. differential ventilation (50% of ventilation to each lung) with no PEEP (DV:0), and 3 and 4. DV with selective PEEP of 0.8 and 1.6 kPa, respectively, to the dependent lung only (DV:8, DV:16). During CV, 60% of ventilation was distributed to the non-dependent lung. Non-dependent hemithoracic compliance was 64% greater and inspiratory resistance 39% lower than those of the dependent hemithorax. No significant differences between the two hemithoraces were noted during DV:0, but on application of selective PEEP the compliance of the dependent hemithorax increased and its resistance decreased. With DV:16, the compliances of the two hemithoraces were essentially equal, as were their resistances. Selective PEEP caused a larger volume increase in the dependent lung than general PEEP. Selective PEEP reduced the volume of the non-dependent lung but only by 1/3 of the simultaneous increase in that of the dependent lung. Oesophageal pressure increased only slightly on selective inflation of the dependent lung, and remained negative within the 21 volume range studied. It is suggested that the altered mechanics of the dependent lung during selective PEEP result in a more even distribution of the inspired gas within that lung.

Adult↗
PubMed1984

Ventilation and perfusion of each lung during differential ventilation with selective PEEP.

Lung perfusion was studied in 10 patients (mean age 58 yr) in the lateral position during enflurane anesthesia. They were ventilated through a double-lumen endotracheal catheter: 1) by one ventilator with free distribution of ventilation between the lungs, with no (zero) end-respiratory pressure (ZEEP); 2) as above but with a general positive end-expiratory pressure (PEEP) of 9 cmH2O; or 3) by two ventilators with equal distribution of ventilation between the lungs and with a selective PEEP of 8 cmH2O to the dependent lung only. Total ventilation was on average 8 l/min (BTPS) throughout the study. During the first method, 34% of ventilation was distributed to the dependent and 66% to the nondependent lung. Cardiac output (thermodilution) was 4.5 l/min, 57% being distributed to the dependent lung as assessed by iv boli of Xenon 133. During the second method, ventilation was assumed to be distributed equally between the lungs. Cardiac output was decreased to 3.8 l/min, and the dependent lung received 81% of lung blood flow. During the third method, cardiac output was significantly greater than during the second method (4.1 l/min), 51% passing to the dependent lung. Peak and end-inspiratory airway pressures were 5-18 cm H2O lower during selective than during general PEEP. Arterial oxygen tension was significantly greater during the third method than during either of the other ventilator settings and the alveolar-arterial oxygen tension difference was almost halved compared with the first method. It is concluded that differential ventilation with selective PEEP improves ventilation-perfusion matching and thus oxygenation.

Adult↗
PubMed1984

Differential ventilation and selective PEEP during anaesthesia in the lateral decubitus posture.

The potential of differential ventilation (DV) with selective positive end-expiratory pressure (PEEP) has been tested versus conventional ventilation with and without general PEEP. Gas exchange and central haemodynamics were studied in 15 subjects with no clinical or radiological signs of pulmonary disease. The rationale of the method was to ensure ventilation of the well-perfused dependent lung and to counteract airway closure within that lung. The subjects were intubated with a double-lumen catheter prior to scheduled abdominal surgery. During general anaesthesia in the lateral posture, they were given DV. The mean inspired oxygen fraction was 0.32. Fifty per cent ("even" tidal volume (VT) distribution) or 70% ("inverted" VT distribution) of the inspired volume was administered to the dependent lung. Two synchronized ventilators were used. In eight subjects DV was also combined with PEEP applied solely to the dependent lung (selective PEEP). The major findings were that DV with even VT distribution reduced venous admixture by 26% (P less than 0.05) and the alveolo-arterial oxygen tension gradient (P(A-a)o2) by 30% (P less than 0.05) in comparison with conventional ventilation in the lateral position. The addition of selective PEEP further reduced the P(A-a)o2 by 13%. P(A-a)o2 was consequently 43% lower than during conventional ventilation without PEEP in the lateral posture (P less than 0.01). Selective PEEP also had less impact on cardiac output than general PEEP (P less than 0.05). It is concluded that DV with even distribution of VT and selective PEEP can reduce the P(A-a)o2 in anaesthetized lung-healthy subjects in the lateral position.

Adult↗
PubMed1982

Regional differences in lung function during anaesthesia and intensive care: clinical implications.

Anaesthesia and most frequently acute respiratory failure are accompanied by a lowered functional residual capacity (FRC). This lowering promotes airway closure in dependent lung units and forces ventilation to non-dependent regions. Perfusion, on the other hand, is forced towards dependent lung units. A ventilation-perfusion mismatch is created and hypoxaemia may develop. General PEEP counters airway closure, but impedes cardiac output and forces perfusion further to dependent regions. In addition, barotrauma may occur. Improved matching of ventilation and perfusion can be achieved by: (1) positioning the subject in the lateral posture; (2) ventilating each lung separately in proportion to its perfusion (differential ventilation); and (3) applying PEEP only to the dependent lung (selective PEEP). Because of less overall intrathoracic pressure and lung expansion, interference with the total lung blood flow and the danger of barotrauma should be less than with general PEEP. Improved gas exchange with a 50-100% increase in PaO2 has been observed in a limited number of patients with acute bilateral lung disease studied so far during differential ventilation and selective PEEP.

Anesthesia↗