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Biomedical subjects

J Grønlund

Publications and source records attributed to J Grønlund.

At least 19 recordsLinked to original sources
PubMed1991

Measurement of transcutaneous PO2, PCO2 and skin blood flow at different probe temperatures using mass spectrometry.

Transcutaneously measured partial pressures of oxygen and carbon dioxide (PtcO2, PtcCO2) approximate the corresponding arterial values at a probe temperature of 44 degrees C. The temperature-dependent increase of PtcO2 and PtcCO2 is caused by an increased skin perfusion, a decrease in the mean diffusion path, a change of skin metabolism, a decrease of tissue solubility of oxygen and carbon dioxide and a right shift of the oxygen and carbon dioxide binding curves of blood. Seven healthy volunteer test subjects participated in the study. A transcutaneous probe connected to a mass spectrometer was placed on the earlobe of the test subject. Four measurements of the transcutaneous PO2, PCO2 and skin blood flow (from the washout kinetics of argon) were determined on each test subject. The first measurement was made with a transcutaneous probe temperature of 37 degrees C. The probe temperature was then increased to 44 degrees C before the next determination. Finally, two determinations were made at 37 degrees C, separated by a time interval of 1 h. The PtcO2 and skin blood flow increased when the probe temperature increased from 37 degrees C to 44 degrees C. However, when the probe temperature was decreased again from 44 degrees C to 37 degrees C, the estimated skin blood flow returned to the initial value while the PtcO2 remained unchanged. It required a further 1 h before the PtcO2 returned to the initial value at 37 degrees C. The most likely explanation of the experimental results is that heating of the skin to 44 degrees C causes a reversible decrease in the skin metabolism.

Adult↗
PubMed1990

Effects of variation in systemic blood pressure on intraosseous pressure, PO2, and PCO2.

Several regulatory mechanisms have been shown to influence the intraosseous circulation. The influence of general hypovolemia on bone circulation and possible regulatory effects were investigated by recording the intraosseous pressure and PO2 and PCO2 continuously by mass spectrometry in rabbits. Hypovolemia was induced by repeated bleedings. The intraosseous and arterial pressures were found to be linearly related. The intraosseous PO2 already decreased after the first step of bleeding and decreased more than 50% of the initial value after an average blood loss of 40 ml. The intraosseous PCO2 showed an opposite pattern. The experimental PO2 vs. arterial pressure curves were similar to curves obtained by a computer simulation that assumes the blood flow to be proportional to the intraosseous pressure.

Animals↗
PubMed1990

Repeatability of the acetylene rebreathing method in measuring cardiac output: influence of acetylene concentration.

The acetylene rebreathing method is a reliable noninvasive method for estimation of cardiac output. However, the method is not commonly used for clinical purposes. This is due mainly to the fact that acetylene is explosive at concentrations above 2% and that acetylene at concentrations above 0.5% has an unpleasant taste. In the present study we have investigated whether it is possible to reduce the concentration of acetylene to 0.3% in the rebreathing bag without degrading the repeatability of the estimated cardiac output. The problem was elucidated theoretically and experimentally. A theoretical investigation was carried out by producing an acetylene rebreathing curve from a single alveolus lung model. The theoretical study showed that the random noise arising from the gas analyzer gives rise to less than 10% of the total variation of the estimated cardiac output. The results of the experimental study showed that it is possible to reduce the acetylene concentration to 0.3% without decreasing the reproducibility of the acetylene rebreathing method.

Acetylene↗
PubMed1989

[Demonstration of urogenital Chlamydia infection by means of the Chlamydiazyme test].

Abbott's recently introduced Chlamydiazyme test which is based on the Elisa principal and cell culture technique was employed with the object of demonstrating urogenital infection with Chlamydia trachomatis in 150 persons. Neither of the methods were optimal. The Chlamydiazyme test had a lower sensitivity and specificity than the cell culture method.

Chlamydia Infections↗
PubMed1989

Estimation of blood flow distribution in skeletal muscle from inert gas washout.

A new method is evaluated for the estimation of blood flow-to-volume distribution in skeletal muscle from inert gas washout kinetics. Acetylene washout from the isolated, blood-perfused canine gracilis muscle was measured continuously with a blood gas catheter in combination with a mass spectrometer. The washout curves were transformed to flow-to-volume ratio distributions by means of a 50-compartment model. The algorithm fits the expression for the washout curve derived from the model by a least-squares method with enforced smoothing. The algorithm was evaluated using computer simulations in which artificial washout curves were generated by a multicompartment model with a known flow distribution. A wide range of given flow distributions could be recovered from the simulated data. The data were also analyzed using a linear programming technique. Analysis of the experimental data with the least-squares method showed that there is considerable heterogeneity in the distribution of perfusion in resting gracilis muscle. The distribution is characterized by at least two modes and a single compartment with a very low perfusion-to-volume ratio. Experimental noise made it impossible to obtain feasible flow distributions by means of linear programming.

Acetylene↗
PubMed1989

Nonlinear curve fitting improves noise sensitivity of the single-breath method for estimation of cardiac output.

In a recent theoretical study, Srinivasan (10) presented a new nonlinear curve fitting algorithm for computing pulmonary blood flow by the single-breath method. The results obtained with the new algorithm showed a considerably lower sensitivity of the estimated pulmonary blood flow to experimental noise than with the linear curve fitting technique reported previously by Grønlund (5). In the present study, we have compared the linear and the nonlinear algorithms using computer simulations and experimental single-breath data. The results showed only a small difference between the two methods. Further, we showed that the difference between the noise sensitivities obtained by Grønlund (5) and Srinivasan (10) can be explained almost entirely by a difference between the models used to simulate experimental noise.

Algorithms↗
PubMed1989

Improved method to estimate oxygen consumption, diffusing capacity and blood flow of synovial membrane.

The joint cartilage is depending on the oxygen diffusing from the capillaries of the synovial membrane through the synovial tissue and synovial fluid. In the present study we describe a new method to calculate the diffusing capacity (DO2), oxygen consumption (VO2) and blood flow of the synovial membrane. The principle of the method is to perfuse the joint cavity with two saline solutions, one with high and one with low oxygen and nitrogen partial pressures and to measure the oxygen and nitrogen partial pressures in the perfusate flowing out of the joint. Using a model of gas exchange between the joint and the membrane a set of equations was derived expressing the relationship between the blood flow, diffusing capacity and oxygen consumption and the oxygen and nitrogen flowing to and from the joint in the two different perfusion situations. In 12 rabbit knee joints we found a blood flow of 0.388 ml/min (SEM 0.027), VO2 of 0.495 microliters/min (SEM 0.196) and DO2 of 0.024 microliter/min/Torr SEM 0.003 (mean).

Animals↗
PubMed1988

Subchondral pO2, pCO2, pressure, pH, and lactate in human osteoarthritis of the hip.

The pathogenesis of primary human osteoarthritis is unknown. It has been suggested that hypoxia caused by reduced subchondral blood flow plays a central role in the development of tissue damages in osteoarthritis. This hypothesis was investigated using an in situ technique based on mass spectrometry to measure subchondral pO2 and pCO2 in both femoral heads of patients with late stage unilateral osteoarthritis and the normal opposite hip. Intraosseous pressure was recorded and lactate concentrations and pH were measured in blood samples obtained from the two femoral heads. The subchondral pO2 in the diseased hip was significantly lower than pO2 in the normal hip (43 torr versus 63 torr). The intraosseous pressure was significantly higher in the diseased than in the normal hip. The lactate concentration showed a 50% increase in the diseased hip. There were no differences in pCO2 and pH between the two locations.

Aged↗
PubMed1987

Contribution of continuing gas exchange to phase III exhaled PCO2 and PO2 profiles.

Changes in PCO2 and PO2 during expiration have been ascribed to simultaneous gas exchange, but other factors such as ventilation-perfusion inhomogeneity in combination with sequential emptying may also contribute. An experimental and model approach was used to study the relationship between gas exchange and changes in expired PCO2 and PO2 in anesthetized dogs during prolonged high tidal volume expirations. Changes in PCO2 and PO2 were quantified by taking the area bounded by the sloping exhalation curve and a line drawn horizontally from a point where the Fowler dead space plus 250 ml had been expired. This procedure is similar to using the slope of the exhalation curve but it circumvents problems caused by nonlinearity of the PCO2 and PO2 curves. The gas exchange components of the CO2 and O2 areas were calculated using a single-alveolus lung model whose input parameters were measured in connection with each prolonged expiration. The relationship between changes in experimental CO2 areas caused by sudden reductions in mixed venous PCO2 (produced by right atrial infusions of NaOH) and those calculated by the model was also studied. In seven dogs, calculated CO2 and O2 areas were 13% higher and 25% lower than the respective experimental areas, but interindividual variations were large. Changes in experimental CO2 areas caused by step changes in mixed venous PCO2 were almost identical to changes in the calculated areas. We conclude that the changes in PCO2 and PO2 during expiration cannot be explained solely by gas exchange. However, the single-alveolus lung model accurately predicts changes in the CO2 exhalation curve caused by alterations in the alveolar CO2 flow.

Animals↗
PubMed1987

Arterial hypoxia does not affect subchondral pressure and regional blood flow.

The influence of arterial hypoxia on bone marrow pressure, regional blood flow and oxygen and carbon dioxide tensions was investigated by simultaneous and continuous measurements in the femoral condyles of 8 rabbits. Arterial hypoxia was obtained by hypoventilation. The subchondral gas tensions and regional blood flow were measured by a previously described technique based on mass spectrometry. Arterial hypoxia caused a significant decrease in subchondral oxygen tension and an increase in subchondral carbon dioxide tension. There was no significant change in bone marrow pressure and regional blood flow.

Animals↗
PubMed1987

Single-breath method for estimating pulmonary blood flow: data reduction based on nonlinear curve fitting.

The single-breath method of Kim et al. for noninvasive estimation of pulmonary blood flow utilizes the PCO2 vs. PO2 curve recorded during a prolonged expiration. The calculation of pulmonary blood flow is complicated by the nonlinearity of the expression for the PCO2 vs. PO2 curve. In previous studies of the single-breath method, this problem has been solved by using a data reduction procedure which includes transformation of the nonlinear expression into a linear plot. The disadvantage of this data reduction procedure is that the transformation utilizes the first derivative of the PCO2 vs. PO2 curve, which is very sensitive to experimental noise. In the present study, we have examined an alternative data reduction procedure in which the nonlinear expression was fitted directly to the experimental curve. At an expiration length of 15 s, the two data reduction procedures gave almost identical standard deviations of 0.57 L.min-1 on repeated determinations of the pulmonary blood flow. However, the linear data reduction procedure was much more sensitive to omission of the PCO2 vs. PO2 curve segments obtained in the last part of the prolonged expiration.

Adult↗