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Biomedical subjects

B Jonson

Publications and source records attributed to B Jonson.

At least 19 recordsLinked to original sources
PubMed1992

Effect of inhaled terbutaline sulphate in relation to its deposition in the lungs.

We studied the effects of inhaled terbutaline on FEV1 and gas exchange, and the pattern of deposition within the lungs. To document this and to estimate the dose of terbutaline administered to the lungs, [99mTc]DTPA was added to nebulised terbutaline solution. The aerosol was deposited preferentially in large or small airways by using aerosols with different particle mass median diameters (1.5 and 4.8 microns) and different inhalation flow rates (0.25 and 1.0 l/s). The patients inhaled placebo and then three increasing doses of terbutaline (0.006, 0.02 and 0.08 mg to the lungs). Finally, 2 mg terbutaline was inhaled from a metered dose inhaler via a spacer. After each inhalation FEV1, PaO2 and PaCO2 was measured. The inhalation of small particles at a low flow resulted in a fairly uniform lung deposition, while larger particles at a higher flow resulted in heavy central deposition. Penetration index for small and large particles were 1.3 +/- 0.2 and 0.8 +/- 0.3 (P less than 0.001), respectively. In both groups FEV1 increased similarly with each dose, and at 0.02 and 0.08 mg the increase was significant (P less than 0.01). After eight metered doses of terbutaline sulphate (0.25 mg per dose) inhaled via a spacer, there was a further increase in FEV1 (P less than 0.001). Gas exchange did not differ between the two groups but if they were combined the DA-aO2 was significantly lower after metered doses than control (P less than 0.05). Thus, it appears that the site of deposition is not important for the bronchodilator effect of terbutaline, and gas exchange tended to improve with both modes of administration.

Adult↗
PubMed1991

Lung mechanics and gas exchange during exercise in pulmonary sarcoidosis.

To clarify how lung function at exercise is affected in sarcoidosis, and to analyze how exercise studies compare to testing measurements, 63 patients with pulmonary sarcoidosis were examined with lung mechanics and arterial blood gases during exercise. These findings were compared with simultaneously obtained, but previously reported results of the static lung pressure/volume curve and the lung resistance/static lung pressure curve. While mechanical variables at maximal exercise were as sensitive as those determined by measuring the PstL/V and RL/PstL curves, mechanics during spontaneous breathing at rest was less sensitive. The derangement of mechanics was more evident than that of arterial blood gases. No measurement at rest was a good predictor of working capacity or of arterial PaO2. A comprehensive exercise examination may be an alternative to resting investigations, which are either more elaborate or less sensitive.

Adult↗
PubMed1991

Lung mechanics and gas exchange in steroid treated pulmonary sarcoidosis. A seven year follow-up.

Fifteen patients with pulmonary sarcoidosis, representing the functionally most severely affected quartile of referred patients, were prescribed steroids during one year. During this period and after 7 years on average, measurements were made of lung volumes, the static elastic pressure/volume (PstL/V) curve and lung resistance (RL). Lung mechanics and arterial blood gases were studied at exercise. Within months static compliance (CstL) and the arterial partial pressure of oxygen improved along with radiography. A modest positive trend continued throughout the follow-up. The vital capacity followed CstL changes closer than did the total lung capacity, which remained low. Though CstL improved, transpulmonary pressure at maximal inspiration increased and the upper part of the PstL/V curve became flatter. RL remained moderately increased. The course of the physiologic findings may be explained by fairly stable parenchymal and peribronchial fibrosis after cessation of active inflammation, and by regress of reflex inhibition of inspiration. Thus most subjects showed modest improvement during and after treatment. The initial study of lung function provided important prognostic information. The study does not allow conclusive evidence with respect to long term benefit of treatment, but encourages continued use of steroids under the guidance of function tests.

Adult↗
PubMed1990

Quantitative SPECT by attenuation correction of the projection set using transmission data: evaluation of a method.

A method for measuring attenuation coefficients in single-photon emission tomography (SPECT) is described and evaluated, together with a method for attenuation correction using these measured attenuation coefficients. Build-up, caused by scattered photons, is corrected for by a simple substitution in the algorithms. Transmission studies are performed with a 99mTc- or 57Co flood source, and emission phantom studies with 99mTc line sources. The method is evaluated with variable but well-defined phantoms. The result is accurate attenuation coefficients for different densities, dimensions and geometries, and an accuracy of corrected emission activities of better than +/- 10% in most cases. The present limitations of the method for attenuation correction are discussed.

Algorithms↗
PubMed1990

Treatment of drug-induced agranulocytosis with recombinant GM-CSF.

A 53-year male patient, treated for rheumatoid arthritis with sulphasalazine, developed a total agranulocytosis. When this state had prevailed for at least 10 d no bone marrow granulocyte progenitor cells were detectable. Intravenous GM-CSF treatment was initiated 5 d later, and the patient recovered within the next 6 d. GM-CSF treatment for severe agranulocytosis deserves further investigation.

Agranulocytosis↗
PubMed1990

Pulmonary clearance of inhaled [99Tcm]DTPA: effects of ventilation pattern.

While a rise in lung volume is known to increase the pulmonary clearance of technetium-99m-labelled dietylene triamine pentaacetate ([99Tcm]DTPA), little interest has been focused on the effects of changes in ventilation frequency, tidal volume and airway pressure. We studied adult, anaesthetized and intubated rabbits during three ventilation patterns (VP) using pressure controlled ventilation (ServoVentilator 900C). VP was either deep slow (f = 20 min-1, tidal volume (VT) = 30 +/- 4 ml kg-1 and positive end-expiratory pressure (PEEP) = 0.2 kPa [VP 20/0.2, n = 8]) or rapid shallow (f = 80 min-1, VT = 11 +/- 2 ml kg-1 and PEEP = 0.2 or 0.4 kPa [VP 80/0.2, n = 6 and VP 80/0.4, n = 6]). The mean airway pressure was similar at VP 20/0.2 and VP 80/0.4. During administration of [99Tcm]DTPA aerosol all animals were ventilated under the same conditions (f = 40 min-1 and PEEP = 0.2 kPa). The pulmonary clearance rate expressed as the half-life time (T1/2) of [99Tcm]DTPA was at VP 80/0.2 = 113 +/- 31 min, at VP 80/0.4 = 70 +/- 24 min (P less than 0.01 compared to VP 80/0.2) and at VP 20/0.2 = 36 +/- 18 min (P less than 0.001 compared to VP 80/0.2 and P less than 0.01 compared to VP 80/0.4). We conclude that the pulmonary clearance of [99Tcm]DTPA increases (1) during rapid shallow ventilation when PEEP is increased from 0.2 to 0.4 kPa; (2) during deep slow ventilation relative to rapid shallow ventilation even when the mean airway pressure is similar.

Animals↗
PubMed1990

Expiratory flushing of airways: a method to reduce deadspace ventilation.

A jet of fresh gas entering the trachea during the last part of expiration, expiratory flushing of airways (EFA), may during mechanical ventilation bring the fresh gas interface into the trachea to reduce deadspace. EFA, delivered in a variety of modes, was tested in healthy dogs. EFA allowed tidal volume, peak and mean airway pressure to be reduced by about 25%. EFA was administered in the form of pulses with frequencies 2-8 Hz, and as a continuous flow. The mode was of little importance. EFA was found to be efficient and should be clinically tested.

Animals↗
PubMed1989

Potential of early chest roentgen examination in ventilator treated newborn infants to predict future lung function and disease.

The potentially of early chest X-ray to predict the risk of lung function abnormalities was studied prospectively in 40 preterm ventilator treated infants in a 8-10-year follow-up investigation. According to the findings at chest X-ray 3 to 10 days after completed ventilator treatment the infants were divided into 3 groups considered to represent increasing risk and severity of lung damage: 1) normal findings, 2) interstitial parenchymal abnormalities exclusively or 3) in combination with local or general hyperinflation. Lung function tests and chest x-ray were performed at the age of 8 to 10 years. A correlation was found between the findings at the early chest roentgen examination and the risk of abnormal lung function at the follow-up. Occurrence of focal or general hyperinflation or both were associated with a greater risk of airway obstruction. Infants with only interstitial abnormalities were, however, at a higher risk than those with normal chest examination to develop general hyperinflation and increased air way obstruction.

Bronchopulmonary Dysplasia↗
PubMed1989

Lung function in patients with systemic lupus erythematosus and persistent chest symptoms.

Twelve consecutive patients with systemic lupus erythematosus (SLE) and chest symptoms of at least 3 months' duration were investigated with spirometry, lung mechanics at rest and exercise, diffusion capacity and right heart catheterization. Vital capacity (88% of predicted, p less than 0.05), and FEV1 (84%, p less than 0.01) were decreased in the study group, but spirometric and diffusion capacity abnormalities were moderate compared with previous studies. The single breath CO2 test showed, in six patients, ventilation-perfusion mismatch with patterns typical for either bronchial obstruction or vascular disease. Non-respiratory factors were responsible for reduction of working capacity (on average 68% of predicted normal values (p less than 0.001]. Two patients with pulmonary hypertension were identified by right heart catheterization. One of them had overlap features with the CREST syndrome. Both these patients had abnormal SBT-CO2 test and diffusion capacity, along with diffuse perfusion defects on perfusion scintigraphy. The low frequency of pulmonary function abnormalities in this study suggests that irreversible pulmonary damage is uncommon in SLE.

Adult↗
PubMed1989

Setting and monitoring of high-frequency jet ventilation in severe respiratory distress syndrome.

High-frequency jet ventilation (HFJV) is used in respiratory distress syndrome (RDS) to avoid high airway pressures and barotrauma. This study was designed to find rational strategies to regulate oxygenation and alveolar ventilation at HFJV and to determine appropriate monitoring methods. Seven dogs were subjected to total lung lavage with saline to induce RDS. PEEP was increased at conventional intermittent positive-pressure ventilation until re-expansion was indicated by a PaO2 of 300 torr at an FIO2 of 1.0 HFJV at 4 and 15 Hz was each tried at 0 and 10 cm H2O PEEP. Intermittent low-frequency inflations were also added to HFJV at 0 PEEP. Lung expansion was maintained without circulatory depression by adjustment of minute ventilation (VE) delivered by the HFJ ventilator; external PEEP was a useful complement. PaCO2 was controlled by frequency adjustment. HFJV at 4 Hz resulted in hypocapnia; intermittent low-frequency inflations had no effect. VE monitoring, CO2 elimination monitoring, and PEEP adjustment was done with a standard ventilator during HFJV. This study illustrates that HFJV is efficient in RDS; VE and external PEEP strongly influence oxygenation and may be used to regulate this factor, and frequency affects CO2 elimination, thus suggesting a method of PaCO2 control.

Alkalosis, Respiratory↗
PubMed1989

Volume-controlled ventilation with superimposed high frequency ventilation during expiration in healthy and surfactant-depleted pig lungs.

In the healthy and surfactant-depleted lungs of five pigs the influence of different forms of high frequency ventilation superimposed on conventional mechanical ventilation during the expiratory phase of the ventilatory cycle (SHFVE) on gas exchange and cardiocirculatory parameters was investigated. Subsequently the effects of end-expiratory flushing (EF), i.e. cleaning the large airways and connecting tubes from the ventilator free from end-expiratory CO2, with a volume greater than the dead space of the large airways and connecting tubes was investigated. SHFVE and EF resulted in a significant improvement in CO2 elimination in both healthy and surfactant-depleted lungs. Furthermore, in stiff lungs, at a certain level of oxygenation and CO2 elimination, SHFVE produced the lowest peak and mean airway pressure without any additional depression of cardiocirculatory parameters.

Animals↗
PubMed1989

Monitoring of physiological parameters during high frequency ventilation (HFV).

Non-biological descriptors such as jet feeding pressure and oscillator stroke volume are often used to describe HFV. This results in confusion and hinders acceptance of HFV. The goal of this paper is to show how physiological parameters which are valid during HFV can be monitored. Airway pressure measured in narrow tubes with high linear flow rates is underestimated. A relevant airway pressure must be measured well below the tracheal tube. Pressure measured higher up should be validated against peripheral pressure measurements. Minute ventilation and expired CO2 concentration can be determined with a ServoVentilator and a CO2 analyzer arranged at its exit port. Minute ventilation and CO2 elimination can thereby be continuously monitored during high frequency jet ventilation or so-called "combined high frequency jet ventilation" to prevent undetected disturbance of ventilation and perfusion. Physiological dead space can be studied for optimization of ventilatory pattern. The principle of gas analysis at the exit port of the ventilator may be used for FRC determinations with sulfur-hexafluoride.

Animals↗
PubMed1989

Measurement of ventilation and respiratory mechanics during continuous positive airway pressure (CPAP) treatment in infants.

A new method has been evaluated for measuring ventilation and lung mechanics in spontaneously breathing infants by means of a face chamber. Airway flow is measured with a pneumotachograph inserted between the face chamber and a stable pressure source. Oesophageal pressure is measured via a water-filled oesophageal catheter. The method is suitable for use in conjunction with continuous positive airway pressure (CPAP) treatment in neonatal intensive care. A flat frequency response curve up to 15 Hz for the two measuring systems (i.e., airway flow and oesophageal pressure), and a time shift between the two respective signals of less than 2 msec are prerequisites for correct evaluation of respiratory mechanics. In preterm infants with chest distortion, the inhomogeneity of pleural pressure affects the significance of resistance and compliance values, as calculated from oesophageal pressure. Supra-diaphragmatic pressure variations reflect the resistive and elastic load on the diaphragm exerted by the lungs and thorax. Thus, oesophageal pressure is still useful in studies of respiratory mechanics in preterm infants.

Apnea↗
PubMed1989

Lung function eight years after neonatal ventilation.

Forty children who had had artificial ventilation during the neonatal period were studied at the age of 8-10 years with spirometry, the nitrogen washout test, bicycle exercise test, pulse oximetry, electrocardiogram, vectorcardiogram, and chest radiography. The median gestational age at birth was 29 weeks, and the median birth weight was 1310 g. Hyaline membrane disease was the indication for neonatal ventilation in 25 children. Bronchopulmonary dysplasia was diagnosed from radiographs in 11 infants (27%). Airway obstruction was observed in 10 of 11 children who had had bronchopulmonary dysplasia and in nine of 29 children who had not. After inhalation of terbutaline, the forced expiratory volume in one second (FEV1) was significantly increased. General hyperinflation was found in 16 of 17 children with abnormal chest radiographs (eight who had had bronchopulmonary dysplasia and nine who had not). Functional residual capacity was significantly higher in children with abnormal radiographs. Each child had a normal maximum working capacity and a normal electrocardiogram, and all but two had normal vectorcardiograms. Oxygen saturation at maximum work load decreased significantly in both groups of children. The risk of future respiratory problems calls for further follow up of lung function and chest radiography.

Electrocardiography↗
PubMed1989

Viscoelastic behavior of lung and chest wall in dogs determined by flow interruption.

Pulmonary and chest wall mechanics were studied in six anesthetized paralyzed dogs, by use of the technique of rapid airway occlusion during constant flow inflation. Analysis of the pressure changes after flow interruption allowed us to partition the overall resistance of the lung (Rl) and chest wall (Rw) and total respiratory system (Rrs) into two components, one (Rinit) reflecting in the lung airway resistance (Raw), the other (delta R) reflecting primarily the viscoelastic properties of the pulmonary and chest wall tissues. The effects of varying inspiratory flow and inflation volume were interpreted in terms of frequency dependence of resistance, by using a spring-and-dashpot model previously proposed and substantiated by Bates et al. (Proc. 9th Annu. Conf. IEEE Med. Biol. Soc., 1987, vol. 3, p. 1802-1803). We observed that 1) Raw and Rw,init were nearly equal and small relative to Rl and Rw (both were unaffected by flow); 2) Rrs,init decreased slightly with increasing volume; 3) both delta Rl and delta Rw decreased with increasing flow and increased with increasing lung volume. These changes were manifestations of frequency dependence of delta R, as it is predicted by the model; 4) Rrs, Rl, and Rw followed the same trends as delta R. These results corroborate data previously reported in the literature with the use of different techniques to measure airways and pulmonary tissue resistances and confirm that the use of Rl to assess bronchial reactivity is problematic. The interrupter techniques provides a convenient way to obtain Raw values, as well as analogs of lung and chest wall tissue resistances in intact dogs.

Airway Resistance↗
PubMed1989

Diagnosis of pulmonary embolism based upon alveolar dead space analysis.

Pulmonary embolism (PE) leads to an abnormal alveolar deadspace that is expired in synchrony with gas from normally perfused alveoli. This feature of PE separates it from pulmonary diseases affecting the airways, which are characterized by nonsynchronous emptying of compartments with an uneven ventilation/perfusion relationship. An analysis of the single breath test (SBT) for CO2, SBT-CO2, focusing on the late tidal expirate, was made in order to evaluate the feasibility to use the SBT-CO2 for the diagnosis of PE. The test was evaluated in 38 patients with suspected PE where pulmonary angiography showed that nine had PE and 29 did not. It was also tested in a reference population consisting of patients with normal lung function, obstructive lung disease and interstitial lung disease. Previously suggested gas exchange measurements for the diagnosis of PE, ie, the physiologic deadspace fraction, VDphys/VT, and the arterial-to-end-tidal CO2 gradient, P(a-E')CO2, were also evaluated in the groups. SBT-CO2 achieved a nearly complete separation between the patients with PE and those without. The other measurements, however, showed a substantial overlap between patients with PE and those with obstructive or interstitial lung disease. The SBT-CO2 is simple and potentially widely available and warrants further study as a routine technique for the diagnosis of PE.

Angiography↗