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Biomedical subjects

B Jonson

Publications and source records attributed to B Jonson.

At least 109 records · Page 6Linked to original sources
PubMed1986

On-line measurement of gas-exchange during cardiac surgery.

This paper describes an on-line system for continuously monitoring expired CO2 during controlled ventilation. Signals from a Servo ventilator 900B or C and a CO2 Analyzer 930 are processed and corrected by the computer to produce a CO2 single breath test (SBT-CO2). This is the tracing of expired CO2 concentration or fraction against expired volume, from which the computer calculates the airway deadspace (VDaw). If a value for arterial PCO2 is supplied, the computer will calculate the physiological deadspace (VDphys) and the alveolar deadspace (VDalv) for each breath. The system was used to make measurements at four stages during coronary artery by-pass grafting in 13 male patients. When the sternum was opened there was a 32% increase in VDaw, and the physiological deadspace fraction therefore increased. There were reductions in VDaw after extra-corporeal circulation and again after sternal suture. By the end of surgery, the alveolar deadspace fraction had increased significantly. VDaw at this stage was smaller than pre-operatively, and so there was no net change in the physiological deadspace fraction at the end of surgery. Arterial PO2 was, however, reduced at this stage.

Aged↗
PubMed1986

Pulmonary clearance of inhaled 99mTc-DTPA: effect of surfactant depletion in rabbits.

We examined the effect of surfactant depletion on the rate of pulmonary clearance of inhaled 99mTc-diethyl-triamino-penta-acetate (DTPA). 99mTc-DTPA was administered as a fine aerosol to four control animals and to four animals after wash-out of pulmonary surfactant. Care was taken to minimize structural damage to the lavaged lungs. Clearance of 99mTc-DTPA was measured over the right lung by external counting. The clearance rate was substantially increased in the lavaged animals compared to the control animals. We conclude that the pulmonary surfactant system is a rate-limiting factor for the absorption of inhaled 99mTc-DTPA. Measurement of the pulmonary clearance of 99mTc-DTPA may provide a new means for studying the pathogenetic role of the surfactant system in a variety of lung diseases.

Absorption↗
PubMed1986

Measurement of pulmonary density by means of X-ray computerized tomography. Relation to pulmonary mechanics in normal subjects.

We examined the relationship between pulmonary density, measured with computerized tomography, and pulmonary mechanics (static pulmonary volume; pulmonary resistance) in 39 normal subjects (20 nonsmokers and 19 smokers). Pulmonary density decreased with increasing static elastic recoil pressure, and smokers consistently showed higher pulmonary density than nonsmokers. Pulmonary density, measured at full inspiration, correlated inversely with total lung capacity. Pulmonary density showed a ventrodorsal gradient, which was greater at low elastic recoil pressure than at high recoil pressure. The study shows that pulmonary density is related to the mechanical properties of the lung in normal subjects. Increased pulmonary density appears to be a sensitive indicator of pulmonary damage induced by smoking. Further studies of the relationship between pulmonary density and pulmonary mechanics in disease seem warranted.

Aged↗
PubMed1985

Measurement of functional residual capacity by sulfur hexafluoride washout.

Measurement of functional residual capacity (FRC) by the open-circuit multiple breath tracer gas washout technique is an established method. A system based upon washout of sulfur hexafluoride (SF6) during mechanical ventilation is described. The central unit in the system is a sensitive and rapid-response infrared SF6 analyzer. SF6 is washed in until the alveolar concentration of SF6 is 0.5%, a concentration so low that the supply of other gases is hardly influenced. During washout, the flow of SF6 from the lungs is calculated by a computer every 10 ms from signals representing expiratory flow and SF6 concentration. The total volume of SF6, washed out, is calculated by integration of SF6 flow. Since the alveolar concentration at the end of washin is known, the lung volume may be obtained. The measurement procedure is highly automated and the result is presented by the computer immediately after washout. Accurate and reproducible results in model lung tests were obtained during air and N2O/O2 ventilation. Comparison with body plethysmography (FRCBOX) in eight sitting healthy subjects gave the following: FRCSF6 = 7 ml + 0.98 X FRCBOX, r = 0.99. Comparison with nitrogen washout (FRCN2) in five postoperative patients gave the following: FRCSF6 = 59 ml + 0.97 X FRCN2, r = 0.97. FRCSF6 during N2O/O2 ventilation was the same as during air/O2 ventilation in a group of paralyzed patients. The measurement system has not been tested in patients with obstructive lung disease.

Adolescent↗
PubMed1985

Lung function in progressive systemic sclerosis is dominated by poorly compliant lungs and stiff airways.

Pulmonary function was investigated in 24 patients with progressive systemic sclerosis. The lung volumes were measured by a body plethysmograph. Bronchial and parenchymal properties were studied by relating pulmonary resistance and lung volume to pulmonary elastic recoil pressure. Pulmonary mechanics and arterial blood gases were studied during graded exercise on a bicycle ergometer. The most fundamental abnormality was a less compliant lung parenchyma together with lowered TLC, VC and ventilatory capacity. A mild intrinsic bronchial obstruction was found, irrespective of smoking habits. In 7 patients, resistance did not, however, increase towards residual volume as it does in normal subjects. This phenomenon is interpreted as stiff airways withstanding compression. Blood gas values at rest, and during work, were remarkably normal. There was no correlation between fibrosis judged from static lung compliance and from chest roentgenograms.

Adult↗
PubMed1984

Deadspace and the single breath test for carbon dioxide during anaesthesia and artificial ventilation. Effects of tidal volume and frequency of respiration.

Using the single breath test for carbon dioxide (SBT-CO2), the components of physiological deadspace were investigated during anaesthesia with IPPV in 58 patients. A square-wave inspiratory flow and an end-inspiratory pause (25% and 10% of cycle time, respectively) were used. At tidal volumes of 0.45 litre (f = 17 b.p.m.), and 0.75 litre (f = 9 b.p.m.), median values for VDphys/VT were 0.44 and 0.31. Increasing VT and decreasing f did not change airway deadspace (VDaw) so that the fraction VDaw/VT was decreased (P less than 0.001). The alveolar deadspace fraction, VDalv/VTalv, was decreased in 93% of patients (P less than 0.001). These improvements with increasing VT can be attributed to beneficial effects on gas distribution and diffusion time. Patients with large alveolar deadspaces had steeply sloping SBT-CO2 phase III, and increased expiratory time constants of the respiratory system. The median arterial--end-tidal PCO2 difference, (PaCO2-PE'CO2), was 0.6 kPa at small and 0.3 kPa at large tidal volumes (P less than 0.001). Three patients had zero and four had negative (PaCO2-PE'CO2) values at large tidal volumes. When phase III slopes steeply, negative (PaCO2-PE'CO2) values may be observed in the presence of alveolar deadspace.

Adolescent↗
PubMed1984

Vasoactive drugs and elastic properties of human arteries in vivo, with special reference to the action of nitroglycerine.

Pulsatile changes in the volume of an arm segment were recorded with an air-filled plethysmograph and related to intra-arterial blood pressure. Alterations in transmural arterial pressure were obtained by changing the pressure in a large chamber surrounding the entire arm. Arterial compliance values were calculated in late diastole when pressure and volume changes were slow. Compliance varied with transmural arterial pressure in a hyperbolic manner, rising steeply at low pressure. Noradrenaline and hypertensin did not change the arterial compliance values, while dihydroergotamine reduced them. Nitroglycerine caused a pronounced increase in compliance values in doses that did not change cardiac output and arterial pressure.

Adult↗
PubMed1984

Early changes in oesophageal function in progressive systemic sclerosis: a comparison of manometry and radiology.

The characteristics of oesophageal dysfunction were studied with manometry and cine radiography in a recumbent position in 21 patients with typical progressive systemic sclerosis (PSS). Manometry was also performed in a matched control group. Only one patient had a completely normal manometry. Mean resting pressure in both the upper and lower oesophageal sphincters were significantly decreased in PSS. Twelve patients had no detectable peristalsis in the lower oesophagus. In the upper oesophagus, the mean pressure amplitude of the peristalitic wave was found to be lower than normal in all patients with detectable peristalsis. In some patients, the only feature of oesophageal dysfunction observed was an increased speed of the peristaltic wave in the middle and lower oesophagus. This is interpreted as an impaired coordination of the propulsive peristalsis. Neuromuscular dysfunction of the oesophagus in its full length was thus clearly demonstrated. At cine radiography, three patients were judged as normal, and 13 patients had severe impairment of the peristaltic function in the distal two-thirds of oesophagus. Oesophageal scoring based on manometry correlated well to scoring based on radiography. Cine radiography of the recumbent patient gives adequate information for clinical purposes. Detection of early changes in the amplitude and speed of the propagation wave requires manometry.

Adult↗
PubMed1983

Factors limiting exercise performance in progressive systemic sclerosis.

In order to evaluate to which extent various organs limit physical performance in PSS, maximal working capacity was studied in 22 patients. Special attention was given to cardiac and pulmonary function, joint mobility, and muscular strength. A model for scoring these parameters is given. Working capacity was on the average 51% of the predicted normal value. Ventilation at maximal workload was high despite normal arterial blood gases and presumably normal physiologic dead space. This can be explained by an increased demand on ventilation from an increased muscle metabolism. This may be due to impeded mobility of respiratory and locomotive organs. The maximal heart rate was low and patients with low physical capacity had only a small decrease in base excess. One third of the patients developed arrhythmia during exercise, which contributed to a low performance. Other myocardial involvement was common, seen in the Q-waves, low voltage, left axis deviation, and increased heart volume. In PSS, these ECG changes probably reflect myocardial fibrosis that has developed without clinically manifest infarction. Special attention must be given to arrhythmias at work, which are overlooked in a resting ECG. Ventricular tachycardia plays an important role in sudden death, which, when it occurs, almost always does so within the first years after the onset of PSS. There was no close linkage between cardiac dysfunction and pulmonary fibrosis or joint-muscle impairment. The scoring system showed an equal distribution in reduction of working capacity as to circulation, pulmonary function, and locomotive function.+2

Adult↗
PubMed1983

Sources of error and their correction in the measurement of carbon dioxide elimination using the Siemens-Elema CO2 Analyzer.

The Siemens-Elema CO2 Analyzer 930 allows calculation of carbon dioxide elimination from the instantaneous measurement of expired gas flow (VE) and carbon dioxide fraction (FECO2). VE is measured in the ventilator and FECO2 at the Y-piece. The most important source of error in the measurement of carbon dioxide elimination is rebreathing, which corresponds to about 24 ml of end-expiratory gas per breath with the standard Y-piece and tubing. This problem may be decreased by the use of non-return valves in the Y-piece. Allowance must be made for the effects of intermolecular interaction between carbon dioxide and the carrier gas, as the reading is about 20% greater with nitrous oxide than with oxygen. This problem can be largely circumvented by calibration with appropriate gas mixtures. Errors resulting from analyser delay are small, and are eliminated completely by the inclusion of fast electronic components. Carbon dioxide analysis is linear with air as carrier gas, but slightly alinear with nitrous oxide in oxygen mixtures. This error can be minimized by using calibration gases with a carbon dioxide content close to that of expired gas. The expiratory flow meter is linear if kept in good condition. Variations in temperature and water content of expired gas cause overestimation of mean expired carbon dioxide fraction (FECO2) by a factor of 1.01-1.02. Compressed gas in the tubing causes a small error which may be neglected at normal airway pressures with tubing of low compliance. Carbon dioxide measurement is slightly affected by barometric pressure. During mechanical ventilation of the lungs in 10 patients with air, FECO2 obtained after corrections for known errors agreed well with Scholander analysis of mixed expired gas.

Carbon Dioxide↗
PubMed1983

Lung function and bronchial reactivity in six patients with immotile cilia syndrome.

Previous studies of immotile cilia syndrome have shown airway obstruction. The aim of this study was to analyse lung function in such patients before severe chronic obstruction had occurred. Spirometry, lung volumes, pulmonary resistance and static pressure volume diagram were studied in six patients (ages 21-43 years). Closing capacity, the volume of trapped gas and the slope of the alveolar plateau were determined with N2 wash-out tests. Regional ventilation was studied with a gamma camera after inhalation of 99Tcm-tagged dry aerosol. Arterial blood gases were determined at rest and during exercise. Bronchial reactivity was studied with FEV1 before and after inhalation of methacholine aerosol. Five of six patients showed a rather uniform pattern, dominated by signs of "small airway disease" seen in e.g. volumes of trapped gas and closing capacity. Those five patients had uneven ventilation scintiscans and bronchial hyperreactivity. Spirometric findings and lung mechanics were influenced by lung resection, scoliosis and by the lability of bronchial tone. Five patients had normal arterial blood gases at maximum work load. Working capacity was essentially normal in all but one patient, who had a high degree of obstruction. Immotile cilia syndrome is thus compatible with a comparatively well preserved lung function and a normal working capacity far into adult life.

Adult↗