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Biomedical subjects

S Lindahl

Publications and source records attributed to S Lindahl.

13 recordsLinked to original sources
PubMed1989

Dynamic changes in the dimensions of the lumbar spinal canal: an experimental study in vitro.

The variation in the dimensions of the lumbar spinal canal under both flexion-extension and axial compression-distraction was studied using computerized tomography (CT) scans in human cadaver lumbar spine specimens. In 3-mm-thick CT slices through the disk at L3-L4, the cross-sectional area of the spinal canal was reduced by around 40 mm2, corresponding to a 16% reduction of the initial area when the lumbar spines were moved both from flexion to extension and from distraction to compression. A corresponding reduction in the midsagittal diameter of the canal of 2 mm was found. During these motions, the ligamentum flavum did not appear to be a significant factor for the dynamic changes affecting the dimensions of the canal. This held true even after the disk had been excised in order to produce a total collapse of the disk space.

Humans↗
PubMed1979

Influence of an end inspiratory pause on pulmonary ventilation, gas distribution, and lung perfusion during artificial ventilation.

Using a constant tidal volume and ventilatory frequency, anesthetized piglets were ventilated with a new tidal volume ventilator. A short inspiratory time without a pause (10% of breathing cycle) was compared with a longer inspiratory time with a pause (33%) both with and without bronchial obstruction. Mechanics of ventilation, pulmonary ventilation, gas exchange, gas distribution, and lung perfusion were measured. The longer inspiratory time with a pause resulted in lower peak airway and end inspiratory pressures and a higher total compliance. Dead space/tidal volume ratio was reduced and the RQ was increased. While the cranial pulmonary fields were less well ventilated, the right caudal field was better ventilated. In the presence of bronchial obstruction, better alveolar ventilation was achieved when an end inspiratory pause was added. The results emphasize the importance of static end inspiratory tracheal conditions although the tidal volumes were kept unchanged.

Animals↗
PubMed1979

Experimental studies on artificial ventilation using a tidal volume ventilator. Mechanics and dynamics of ventilation.

In 24 piglets (2.7-24.5 kg b.w.), the mechanics of ventilation, the accuracy of dosage of respiratory volumes, and the influence of the ventilator's volume/pressure characteristics (Cvent, "internal compliance") on the dynamic course of insufflation were studied. A linear relationship was shown to exist between tidal volume and end-inspiratory tracheal pressure and between tidal volume and insufflation time. The insufflation time was reduced to about 50% of previously registered values. The error between set and registered tidal volume was found to be 6.0 +/- 2.7%. During the insufflation a linear relationship was found between the instant amount of delivered breathing gas and the corresponding endotracheal pressure change. The ventilator's Cvent did (and body size, total compliance and tidal volume did not) significantly influence the size of the direction coefficient for the linear instantaneous volume/pressure relationship, the magnitude of tracheal peak pressure and a short insufflation time, and vice versa. The use of greater power from the ventilator resulted in a significant shortening of the duration of insufflation and vice versa. The duration of insufflation is the parameter of choice in evaluating the efficiency of the ventilatory equipment. When the ventilator's performance is defined, measurements of the duration of insufflation may enable evaluation of conditions within the lungs.

Animals↗
PubMed1979

The circulatory response to specific ventilatory patterns using a tidal volume ventilator.

The circulatory response to different ventilatory patterns during artificial ventilation was examined in 17 sternotomized piglets. A constant CO2-tension level was maintained in all investigations by reference to analyses of the end-tidal infra-red CO2 fraction and arterial CO2-tension. The greatest variation in mean values for end-tidal CO2-tension was 0.2 kPa. Total compliance and lung compliance were lower at a ventilator volume/pressure quotient of 20 compared to those at 80 ml/kPa, and at f = 30 compared to f = 11 cycles/min. Higher cardiac output, lower pulmonary vascular resistance and systemic vascular resistance were measured at f = 11 (inspiration 20%) than at f = 30 (inspiration 50%). An increase in inspiration time by about 100% at the lower ventilatory frequency (f = 11) resulted in a significant but uncompensated decrease in cardiac output and stroke volume. These results demonstrate the value of a rapid insufflation in order to give longer expiration time per minute for the benefit of the venous return and cardiac output.

Animals↗
PubMed1979

Influence of ventilatory frequencies and ventilator volume/pressure quotients on pulmonary ventilation using a tidal volume ventilator.

The influence of ventilatory frequency and the ventilator's "internal state of gas compression" (Cvent) on mechanics of ventilation, pulmonary ventilation, gas distribution, gas exchange and lung perfusion was studied with free airway and experimental regional airway obstruction in 10 piglets (7-12 kg b. w. ), using a tidal volume ventilator. The VDphy/VTexp ratio was greater at f = 30 than at f = 10.3 cycles/min. This could be related to a significant increase in the VDanat/VTexp ratio at f = 30, while VDc/VTexp and VDlav/VTexp were unchanged at both frequencies. With regional ventilation and perfusion within the obstructed pulmonary field were reduced, compared to the values at f = 10.3 cycles/min. With Cvent 20 ml/kPa, the tidal volumes were insufflated in a shorter time and with a higher initial tracheal peak pressure than with Cvent 80 ml/kPa. Following bronchial obstruction, VA, RQ and Pao2 were greater with Cvent 20 than with Cvent 80 ml/kPa. With Cvent 20, the ventilation of the lung bases was reduced, which was compensated for by a large increase in ventilation within the apical areas of the lungs, while gas distribution within the unobstructed areas was more evenly distributed with Cvent 80. Ventilation at Cvent 20 showed no essential advantage over Cvent 80. Only in lungs extremely difficult to ventilate and with ventilatory frequencies over 50 cycles/min could possible indications for Cvent 20 be seen.

Animals↗
PubMed1979

Artificial ventilation in children during anaesthesia using a tidal volume ventilator.

Standards for artificial pulmonary ventilation at ventilatory frequencies of 15 and 20 cycles per min, (PETCO2 4 +/- 0.5 kPa), were defined in 16 children with healthy lungs and body weights between 2.6 and 22.6 kg. A tidal volume ventilator and balanced anaesthesia were used during abdominal surgery. At f = 20 cycles/min an approximately direct proportionality existed between tidal volume and body weight (VTpat = 12.3 . kg b.w.--2.1, r = 0.99). The mean value VTpat per kg b.w. was 12.1 +/- 1.4 ml/kg. At f = 15 cycles/min, a linear relationship between tidal volume and kg b.w. was recorded (VTpat = 14.6 . kg b.w. + 16, r = 0.97). The mean value VTpat per kg b.w. was 15.9 +/- 1.5 ml/kg. A significant decrease in total compliance was recorded during the initial part of the surgical procedure. A rectilinear relationship existed between total compliance and kg b.w. (CTOT = 11.2 . kg b.w.--12.5, r = 0.95). The mean value CTOT per kg b.w. was 9.7 +/- 0.54 ml/kPa/kg at f = 20. The endotracheal peak pressure maintained a fairly constant pressure level independent of the initial pressure within the ventilator, the tidal volume and the body weight, a phenomenon explained by the hypothesis that the proportional increase in total lung volume and functional residual capacity in the older children compensated for the higher pressures.

Abdomen↗
PubMed1977

On the mechanism of sodium- and potassium-activated adenosine triphosphatase. Time course of intermediary steps examined by computer simulation of transient kinetics.

In order to learn whether the kinetics of transient phosphorylation of sodium plus potassium ion transport adenosine triphosphatase was compatible with the hydrolysis of ATP, computer simulation of experimental data was studied. The enzyme mechanism was described in terms of first order and pseudo-first order reactions. The resulting system of linear first order differential equations was solved by a Runge-Kutta method. Phosphorylation kinetics was studied by means of a rapid mixing apparatus at 21 degrees in the presence of 100 micron ATP, 3 mM MgCl2, 120 mM NaCl, and 10 mM KCl. Computer simulation gave a close fit to experimental data with a model of the reaction mechanism which included a sequence of two dephospho forms and two phospho forms of the enzyme. With this model, rate constants obtained by computer simulation were in agreement with constants which had been determined in separate phosphorylation and dephosphorylation experiments. Within experimental limits, the net flux of reaction in each partial step was compatible with the (Na+,K+)-stimulated hydrolysis of ATP (about 324 and 300 nmol-mg-1-min-1, respectively).

Adenosine Triphosphatases↗
PubMed1975

Human renal carbonic anhydrase. Purification and properties.

Carbonic ahyndrase was isolated from fresh human donor kidneys which had been thoroughly perfused free from blood. The isolation procedure involved biospecific affinity chromatography on a sulfanilamide-agarose column and yielded one soluble form of the enzyme, which was homogenous with respect to sedimentation in the ultracentrifuge, electrophoresis, isoelectric focusing and immunodiffusion. The renal enzyme had an amino acid composition and beahved chromatographically, electrophoretically, and immunochemically like the erythrocyte form human carbonic anhydrase C, isolated by the same technique. The kinetic behaviour of the renal enzyme was similar to that of human carbonic anhydrase C when compared by the stopped-flow pH-indicator technique. The results therefore suggest that the cytoplasmic carbonic anhydrase of the human kidney is very similar, if not identical, to the high-activity erythrocyte form of human carbonic anhydrase C.

Amino Acids↗
PubMedDate not supplied

Computed tomography of intraorbital foreign bodies.

Computed tomography (CT) has been shown to be an important diagnostic tool in the evaluation of intraorbital foreign bodies (IOFB). In order to further analyze the capacity and limitations of CT in this respect, 55 cases with IOFB (intraocular and extraocular) detected at CT were retrospectively analyzed. It was shown that CT was an excellent diagnostic modality in detecting and localizing IOFB of different material and superior to ultrasonography in this respect. Still, even with high resolution CT, there are some limitations of this modality that are discussed. CT is recommended as the primary diagnostic tool in the detection and localization of intraocular and extraocular foreign bodies.

Adolescent↗