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J Grønlund

Publications and source records attributed to J Grønlund.

At least 19 recordsLinked to original sources
PubMed2004

Hypoxaemia after cardiac surgery: clinical application of a model of pulmonary gas exchange.

BACKGROUND AND OBJECTIVE: To investigate the clinical application of a mathematical model of pulmonary gas exchange, which ascribes hypoxaemia to shunt and ventilation/perfusion mismatch. Ventilation/perfusion mismatch is quantified by deltaPO2, which is the drop in oxygen pressure from alveoli to lung capillaries. Shunt and deltaPO2 were used to describe changes in oxygenation after coronary artery bypass grafting. METHODS: Fourteen patients were studied 2-4 h after surgery and on postoperative days 2, 3 and 7. On each occasion inspired oxygen fraction was changed in four to six steps to obtain arterial oxygen saturation (SaO2) in the range of 90-100%, enabling construction of FEO2/SaO2 curves. Measurements of ventilation, circulation and oxygenation were entered in a previously described mathematical model of pulmonary gas exchange. RESULTS: We found that oxygenation was most impaired 3 days after surgery. By fitting the mathematical model to the FEO2/SaO2 curve, we found that shunt remained constant throughout the study period. However, deltaPO2 increased from 0.5 kPa (median, range 0-3.8) 2-4 h after surgery, to 3.2 kPa (range 1.2-6.4, P < 0.05) on day 2, and to 4.0 kPa (range 1.2-8.3) on day 3. On day 7, deltaPO2 decreased to 2.2 kPa (range 0-3.5, P < 0.05). CONCLUSIONS: Ventilation/perfusion mismatch (deltaPO2), rather than shunt, explains the changes in postoperative oxygenation. The model of pulmonary gas exchange may serve as a useful and potentially non-invasive clinical tool for monitoring patients at risk of postoperative hypoxaemia.

Aged↗
PubMed2001

Purification and characterization of beta-methylaspartase from Fusobacterium varium.

Beta-methylaspartase (EC 4.3.1.2) was purified 20-fold in 35% yield from Fusobacterium varium, an obligate anaerobe. The purification steps included heat treatment, fractional precipitation with ammonium sulfate and ethanol, gel filtration, and ion exchange chromatography on DEAE-Sepharose. The enzyme is dimeric, consisting of two identical 46 kDa subunits, and requires Mg2+ (Km = 0.27+/-0.01 mM) and K+ (Km = 3.3+/-0.8 mM) for maximum activity. Beta-methylaspartase-catalyzed addition of ammonia to mesaconate yielded two diastereomeric amino acids, identified by HPLC as (2S,3S)-3-methylaspartate (major product) and (2S,3R)-3-methylaspartate (minor product). Optimal activity for the deamination of (2S,3S)-3-methylaspartate (Km = 0.51+/-0.04 mM) was observed at pH 9.7. The N-terminal protein sequence (30 residues) of the F. varium enzyme is 83% identical to the corresponding sequence of the clostridial enzyme.

Amino Acid Sequence↗
PubMed1994

Precision and accuracy of a noninvasive inert gas washin method for determination of cardiac output in men.

Stout et al. (J. Appl. Physiol. 38:913-918, 1975) suggested an open-circuit multibreath (MB) inert gas method for determining pulmonary capillary blood flow (Qc) in anesthetized dogs receiving artificial ventilation. In the present work we investigated the accuracy and reproducibility of the MB method in nine healthy human subjects at spontaneous ventilation, and we compared the MB method with the inert gas rebreathing (RB) method. Qc was calculated at rest and during exercise at 50 or 100 W, and experimental errors were evaluated in computer simulations of a two-alveoli lung model. The calculated mean Qc values of the MB method were 5.56 +/- 1.23 (SD), 10.02 +/- 0.78, and 13.2 +/- 0.84 l/min, and the mean difference (MB Qc - RB Qc) was not significantly different (P > 0.05). The variation in Qc of the MB method was found to be significantly larger than that in Qc of the RB method (P < 0.01). Random measurement errors and uneven distribution of ventilation contributed to the experimental errors. We conclude that the MB method is inferior to the RB method but that the MB method may be useful under exercise conditions.

Adult↗
PubMed1994

A modified photo- and magnetoacoustic multigas analyzer applied in gas exchange measurements.

The feasibility of replacing a conventional mass spectrometer (MS) with a specially modified multicomponent (O2, CO2, Freon 22, and SF6) acoustic infrared and paramagnetic (IR/PM) gas analyzer in inert gas-rebreathing and metabolic gas exchange measurements has been investigated. Rebreathing variables were determined simultaneously with the MS and IR/PM analyzers in duplicate measurements at rest and during submaximal exercise in 10 subjects. The differences (means +/- SD, IR/PM - MS) were 0.028 +/- 0.048 liters [functional residual capacity (FRC)], 0.18 +/- 0.38 l/min [cardiac output (Qc)], -0.006 +/- 0.030 l/min [O2 consumption (VO2)], and -33 +/- 108 ml [combined lung tissue and capillary blood volume (Vti,c)]. The coefficients of variation on repeated estimates were 5.8% (FRC), 5.4% (Qc), 6.2% (VO2), and 17% (Vti,c) with the IR/PM analyzer and 5.9% (FRC), 4.2% (Qc), 5.0% (VO2), and 9.8% (Vti,c) with the MS. The differences (IR/PM - MS) obtained in mixed-expirate measurements were -0.006 +/- 0.020 l/min (VO2) and 0.020 +/- 0.021 l/min (CO2 production). Breath-by-breath estimates of VO2 and CO2 production with the IR/PM analyzer were, on average, 2.4 and 4.4% higher than the MS estimates, respectively. Our results demonstrate that the IR/PM gas analyzer, when appropriately modified, can substitute for a complex MS in a variety of noninvasive pulmonary gas exchange measurements.

Adult↗
PubMed1993

[Intrathoracic perforation of stomach ulcer in a massive hiatal hernia].

A case of intrathoracic perforation of a chronic gastric ulcer in a hiatus hernia is presented. A 67-year-old woman had suffered from interscapular pain and epigastric discomfort following large meals for four years. During the week before admission, the epigastric and interscapular pain increased, reaching a crescendo in the 24 hours before the patient's arrival in the emergency room. Chest and abdominal x-ray showed free gas and a large hiatus hernia with an intrathoracic stomach. At laparotomy, the stomach was gently returned to the abdominal cavity, and a perforated chronic gastric ulcer was found on the greater curvature. The ulcer was excised, and the diaphragmatic crura were approximated. Apart from wound dehiscence, the postoperative course was uneventful.

Aged↗
PubMed1993

In vivo quantitation of carbonic anhydrase and band 3 protein contributions to pulmonary gas exchange.

The contributions to pulmonary gas exchange of red blood cell (RBC) membrane band 3 protein HCO3(-)-Cl- exchange and carbonic anhydrase- (CA) catalyzed HCO3- dehydration have never been determined directly in the whole animal. We utilized an experimental and model approach to measure these by analysis of phase III exhaled CO2 and O2 profiles in anesthetized dogs. In this method, we inhibit RBC membrane band 3 protein and cytoplasmic CA in RBCs passing the pulmonary capillaries and lung vascular luminal membrane-bound CA during a single ventilatory cycle. This is achieved with appropriately timed right atrial infusions of 4,4'-dinitrostilbene-2,2'-disulfonate (DNDS) to inhibit band 3 protein, ethoxzolamide (a lipophilic CA inhibitor with rapid membrane penetrance) to inhibit RBC and lung tissue CA, and benzolamide (an extremely hydrophilic CA inhibitor with virtually no penetrance into RBC cytoplasm) to inhibit only lung vascular luminal membrane CA. DNDS caused a 15% reduction in CO2 production (VCO2) without any change in O2 consumption (VO2). The addition of benzolamide to DNDS did not cause any further decrease in VCO2. Inhibition of RBC CA by ethoxzolamide caused a 67% reduction in VCO2 and a 11.5% reduction in VO2. Inhibition of lung vascular CA by benzolamide alone caused no statistically significant changes in either VCO2 or VO2. These results are in general agreement with in vitro data and model calculations. The only exceptions are the higher than predicted effect of RBC CA inhibition on VO2 (Bohr effect) and the lack of any contribution to CO2 transfer in the dog by lung vascular CA with access to plasma as a possible consequence of an endogenous plasma CA inhibitor.

Acetylene↗
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↗