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Biomedical subjects

B Jonson

Publications and source records attributed to B Jonson.

At least 19 recordsLinked to original sources
PubMed2001

Halo structure of (14)Be.

The two-neutron halo nucleus (14)Be has been investigated in a kinematically complete measurement of the fragments ((12)Be and neutrons) produced in dissociation at 35 MeV/nucleon on C and Pb targets. Two-neutron removal cross sections, neutron angular distributions, and invariant mass spectra were measured, and the contributions from electromagnetic dissociation (EMD) were deduced. Comparison with three-body model calculations suggests that the halo wave function contains a large nu(2s(1/2))(2) admixture. The EMD invariant mass spectrum exhibited enhanced strength near threshold consistent with a nonresonant soft-dipole excitation.

Journal Article↗
PubMed2000

Effects of NO inhalation on pulmonary leukocyte sequestration and blood volume in porcine endotoxaemia.

OBJECTIVE: Sequestration and migration of activated neutrophils plays a major role in the pulmonary injury typical of septic shock and the adult respiratory distress syndrome. Inhaled NO may counteract alveolar-capillary damage attributed to activated neutrophils. The present study describes a method to directly demonstrate the effects of NO inhalation on endotoxin-induced sequestration of 99mTc-labelled leukocytes [As(t)] in the lungs of pigs. DESIGN: Prospective controlled study. SETTING: Laboratory for experimental surgery at a university medical centre. SUBJECTS: Anaesthetised and ventilated pigs. INTERVENTIONS: To induce inflammatory shock 26 animals received a continuous endotoxin infusion. Thirteen animals inhaled NO from the start of the experiments, while 13 served as controls. In 13 animals from both groups, leukocytes were labelled in vitro and reinjected, while in the 13 others erythrocytes were labelled in vivo to provide corrections for changes in blood volume. MEASUREMENTS AND RESULTS: The pulmonary distribution of 99mTc-labelled leukocytes or erythrocytes was studied dynamically for 180 min. After correction for changes in pulmonary and heart blood volume (PBV, HBV), leukocyte sequestration curves were generated. Endotoxin induced pulmonary vasoconstriction, reduced PBV, impaired oxygenation, and caused a maximum increase in As(t) of 30% in the lungs. NO inhalation attenuated pulmonary vasoconstriction and the reduction in PBV. The maximum increase in As(t) was reduced to 15% of baseline. CONCLUSIONS: Inhaled NO exerts its main vascular effects in the pulmonary microvasculature, the primary site of physiological neutrophil margination and pathological adhesion of activated leukocytes. Early use of NO inhalation may offer protection against the development of more lasting pulmonary failure in septic shock by reducing leukocyte sequestration in the lungs.

Administration, Inhalation↗
PubMed2000

Surface active agents as enhancers of alveolar absorption.

PURPOSE: Small solutes which are deposited in the alveoli by aerosol inhalation will be absorbed across the alveolo-capillary barrier. Inhalation of dioctyl sodium sulfosuccinate (DOSS) enhances absorption while having little or no effect on lung function, suggesting that surface active agents may be used as enhancers of alveolar absorption of inhaled pharmaceuticals. The purpose of this study was to examine the effects of a selection of different surface active agents on alveolar absorption. METHODS: The absorption of 99mTc-diethylene triamine pentaacetate (99mTc-DTPA) from the lungs was studied in rabbits. We studied five different surface active agents: DOSS, sodium glycodioxycholate (GDCA), sodium lauryl sulphate (NaLS), lysophosphatidyl choline (LPC) and polyoxyethylene-23-laurylether (P23LE). RESULTS: DOSS and GDCA both dramatically enhanced the absorption of 99mTc-DTPA. There was a moderate effect of NaLS, no significant effect of LPC and P23LE reduced the rate of absorption. None of the compounds affected gas exchange or lung compliance. CONCLUSIONS: There is a wide spectrum of effects of inhaled surface active agents on the alveolar absorption of 99mTc-DTPA. Ionic compounds such as DOSS and GDCA have the greatest effect, and further studies of these classes of surface active agents for use as enhancers of alveolar absorption of pharmaceuticals seem warranted.

Absorption↗
PubMed2000

Partitioning of dead space--a method and reference values in the awake human.

Although dead space is often increased in disease, it is not frequently measured in the clinic. This may reflect that an adequate method as well as reference values are missing. Healthy males and females, n=38, age 20-61 yrs, were connected to a pneumotachograph and a fast CO2 analyser after radial artery catheterization. The physiological dead space was partitioned into airway and alveolar dead space using a delineation principle denoted the pre-interface expirate. Physiological dead space was 201+/-41 mL in males and 150+/-34 mL in females. Dead space values were depending upon parameters reflecting lung size (predicted total lung capacity), breathing pattern and age. After multiple correlation the variation decreased and differences between males and females disappeared. The residual SD was then for physiological dead space 18.9 mL. The clinical use of the new method for determination of dead space can be based upon reference values, with a more narrow range than previous data.

Adult↗
PubMed2000

Elastic pressure-volume curves indicate derecruitment after a single deep expiration in anaesthetised and muscle-relaxed healthy man.

BACKGROUND: In acute respiratory distress syndrome, lung volume is lost immediately after positive end-expiratory pressure (PEEP) is removed and is not immediately regained when PEEP is restored to its original value. The aim of this study was to investigate whether the same phenomenon also occurs in cardiopulmonary healthy individuals during anaesthesia and muscle relaxation. METHODS: In 13 anaesthetised and muscle-relaxed patients, inspiratory elastic pressure-volume (Pel-V) curves were, after lung recruitment, obtained from zero end-expiratory airway pressure (ZEEP) and from a PEEP of 5 cmH2O. The curves were aligned on a common volume axis. Differences in lung volumes and compliance (Crs) were calculated at the different airway pressures. RESULTS: At comparable pressures the ZEEP curve showed significantly lower volumes up to an airway pressure of 25 cmH2O. Maximum Crs was similar on the curves obtained from ZEEP and PEEP. However, the lower segments of the curve recorded from PEEP showed lower Crs compared to the curve recorded from ZEEP. CONCLUSION: During anaesthesia and muscle paralysis, the Pel-V relations change immediately when 5 cmH2O of PEEP is removed. This phenomenon is probably mainly caused by closure of small airways and only in a minor part, if any, by formation of atelectasis. This study indicates that under these conditions lung volume might easily be normalised by a large breath producing an airway pressure of 20 cmH2O.

Adult↗
PubMed2000

Efficient lung scintigraphy.

Lung scintigraphy is a first-choice method to diagnose lung embolism. The clinical routine in most centres is a perfusion study complemented with a ventilation study when judged necessary. We describe a routine with ventilation scintigraphy preceding perfusion scintigraphy, which is completed within one hour. Furthermore, the data acquired allow the determination of lung clearance of the tracer 99mTc-DTPA (diethylene triamine penta-acetate) used for the ventilation scintigraphy. An aerosol generator charged once a day with 99mTc-DTPA solution is used for all inhalations during the day. Inhalation is monitored with a counter and interrupted when the count rate corresponds to about 20 MBq. The ventilation imaging starts and ends with posterior projections. This allows calculation of lung clearance of 99mTc-DTPA. Perfusion scintigraphy is performed in a standard fashion with 100 MBq of 99mTc-MAA (macro-aggregated albumin). The ventilation study was considered to give some diagnostic information in the majority of the patients. The clearance determination allows detection of inflammatory lung disease. The background activity caused by the ventilation study comprised only 13% of the activity in the perfusion scintigraphy and did not significantly interfere with interpretation of the perfusion scan. The cost for the investigation is low because of the rational system for aerosol administration and the short time for a complete study.

Humans↗
PubMed2000

One year follow-up of lung clearance of 99mTc-diethylene triamine penta-acetic acid and disease activity in sarcoidosis.

BACKGROUND AND AIM OF THE WORK: In interstitial lung disease lung clearance of 99mTc-diethylenetriaminepentaacetic acid (DTPA) reflects alterations in the alveolar capillary barrier. Our objective was to describe changes in lung clearance during one year in sarcoidosis, and to relate clearance to other data of lung function and disease activity. METHODS: Twenty-three newly diagnosed patients were studied with respect to lung DTPA clearance, spirometry, 67Ga scintigraphy and serum angiotensin converting enzyme (SACE). Lung mechanics and arterial PO2 at rest and exercise were studied in patients with radiological parenchymal changes. Six of these patients were prescribed peroral steroids. RESULTS: At inclusion lung DTPA clearance measured over 30 minutes was 53 +/- 16 minutes and at follow-up 59 +/- 20 minutes (p > 0.05). The number of pathological clearance curves at inclusion was 10 and at follow-up 6. In treated patients lung DTPA clearance improved as did lung 67Ga score and SACE. However, lung clearance did not correlate significantly with changes in lung function or other activity parameters. CONCLUSIONS: Lung DTPA clearance reflects lung function from an aspect different from that of other methods. It seems sensitive to pathology reversed by steroids and may, in some cases, help in the evaluation of disease activity.

Adult↗
PubMed1999

Aspiration of dead space allows normocapnic ventilation at low tidal volumes in man.

OBJECTIVE: Aspiration of dead space (ASPIDS) improves carbon dioxide (CO2) elimination by replacing dead space air rich in CO2 with fresh gas during expiration. The hypothesis was that ASPIDS allows normocapnia to be maintained at low tidal volumes (VT). DESIGN: Prospective study. SETTING: Adult intensive care unit in a university hospital. PATIENTS: Seven patients ventilated for neurological reasons were studied. All patients were clinically and haemodynamically stable and monitored according to clinical needs. INTERVENTIONS: ASPIDS implies that, during expiration, gas is aspirated through a catheter inserted in the tracheal tube. Simultaneously, a compensatory flow of fresh gas is injected into the inspiratory line. ASPIDS was achieved with a computer/ventilator system controlling two solenoid valves for aspiration and injection. RESULTS: At the basal respiratory rate of 12.6 breaths min-1, with ASPIDS VT decreased from 602 to 456 ml, as did the airway pressures to a corresponding degree. PaCO2 and PaO2 remained stable. At a frequency of 20 breaths min-1, with ASPIDS VT was further reduced to 305 ml with preserved normocapnia. ASPIDS did not interfere with the positive end-expiratory pressure (PEEP) level. No intrinsic PEEP developed. All patients remained stable. No haemodynamic or other side effects of ASPIDS were noticed. CONCLUSION: The results of this study suggest that ASPIDS may be a useful and safe modality of mechanical ventilation that limits alveolar pressure and minute ventilation requirements while keeping PaCO2 constant.

Adult↗
PubMed1999

Elastic pressure-volume curves of the respiratory system reveal a high tendency to lung collapse in young pigs.

OBJECTIVE: To study pressure-volume (P/V) curves over a wide pressure and volume range in pigs. DESIGN: Dynamic and static P/V curves (P(dyn)/V and P(st)/V) and compliance of the respiratory system were studied. The effects of recruitment, positive end-expiratory pressure (PEEP) and body position were analysed. SETTING: Research animal laboratory. MATERIALS: Seven anaesthetised, paralysed and ventilated healthy pigs of 21 kg. MEASUREMENTS: P/V curves up to a pressure of about 40 cmH(2)O were recorded with a computer-controlled ventilator. P(st)/V curves were obtained with the static occlusion method and P(dyn)/V curves during an insufflation at a low, constant flow rate. RESULTS: P(dyn)/V recording showed a complex pattern. During the insufflation compliance increased, fell, increased and fell again. A 2nd P(dyn)/V recording immediately following the 1st one was displaced towards higher volumes and showed only one maximum of compliance. The difference between the two curves reflected: (1) lung collapse during a period of 5 min of ventilation at zero end-expiratory pressure (ZEEP) following a recruitment manoeuvre, (2) recruitment during the measurement of the 1st P(dyn)/V curve. These observations were similar in the supine and in the left lateral position. After ventilation at PEEP, 4 cmH(2)O, the signs of collapse and recruitment were reduced. It was confirmed that PEEP offers a partial protection against collapse. P(st)/V curves showed higher volumes and higher compliance values compared to P(dyn)/V curves. This reflects the influence of viscoelastance on P(dyn)/V curves. CONCLUSION: The study demonstrates a particularly strong tendency to lung collapse in pigs.

Age Factors↗
PubMed1999

Regional VA/Q ratios in man using 133Xe and single photon emission computed tomography (SPECT) corrected for attenuation.

We describe a technique to obtain non-invasively regional pulmonary ventilation-perfusion ratios (VA/Q) using single photon emission computed tomography (SPECT) and continuous infusion of 133Xe. Single photon transmission tomography was used for attenuation correction, for delineation of the lungs and for VA/Q calculations. Data are presented for six normal subjects and compared to those for two patients with moderate chronic obstructive pulmonary disease (COPD). The mean VA/Q for the whole lung of the normal subjects ranged from 0.49 to 0.65, group mean 0.56 +/- 0.07 (1 SD), and there was no significant difference between the right and left lung. The consistently too low VA/Q values are related to the inability to measure regional blood volume and the low resolution of the scintillation camera, giving an under-estimation of tracer input. For the normal subjects, the dispersion of VA/Q, as defined by the standard deviation of the individual distribution functions, ranged from 0.12 to 0.19. One of the patients was characterized by a low mean VA/Q of 0.35, and the other patient had a wide dispersion (SD) of VA/Q of 0.37. In the normal subjects, a consistent VA/Q gradient was found only in the ventrodorsal direction. 133Xe and SPECT can be used to obtain meaningful biological information regarding ventilation/perfusion relationships of potential clinical value.

Adult↗
PubMed1999

Aspiration of airway dead space. A new method to enhance CO2 elimination.

Alveolar ventilation and CO2 elimination during mechanical ventilation can be enhanced by reducing dead-space ventilation. Aspiration of gas from the dead space (ASPIDS) is a new principle, according to which gas rich in CO2 during late expiration is aspirated through a channel ending at the distal end of the tracheal tube. Simultaneously, fresh gas injected into the inspiratory line fills the airway down to the same site. We hypothesized that ASPIDS would allow a reduction of tidal volume (VT) and airway pressure (Paw). To test our hypothesis we studied six anaesthetized and mechanically ventilated pigs (24 +/- 4 kg). The intention was to decrease VT while keeping PaCO2 constant by using ASPIDS. VT was reduced by decreasing the minute ventilation (V E) in two steps, of 1.8 L/min (VE - 1.8) and 2.2 L/min (VE - 2.2), respectively, and by increasing respiratory rate (RR) from 20 to 46 breaths/min. At ASPIDS, peak Paw was reduced by 35% at VE - 1.8 and at VE - 2.2 (p < 0.001), and by 20% at an RR of 46 (p < 0.01). PaCO2 was maintained or reduced at ASPIDS. No intrinsic positive end-expiratory pressure developed. Arterial blood pressure and heart rate were unaffected. The results show that ASPIDS allows a reduction in VT and Paw while PaCO2 is kept constant. ASPIDS does not lead to problems associated with jet streams of gas or with gas humidification, and can be developed as a safe technique.

Airway Resistance↗
PubMed1999

Pressure-volume curves and compliance in acute lung injury: evidence of recruitment above the lower inflection point.

Measuring elastic pressure-volume (Pel-V) curves of the respiratory system and the volume recruited by a positive end-expiratory pressure (PEEP) allows one to study the pressure range over which recruitment occurs in acute lung injury (ALI), and to explain how recruitment affects the compliance. Pel-V curves were measured with the low flow inflation technique in 11 patients mechanically ventilated for ALI. Curve I was recorded during inflation from the volume attained after a prolonged expiration (6 s) at PEEP (9.0 +/- 2.2 cm H2O), and Curve II after expiration to the elastic equilibrium volume at zero end-expiratory pressure (ZEEP). By using the end-expiratory volume of the breaths, the curves were aligned on a common volume axis to determine the effect of a single complete expiration. In each patient, Curve II (from ZEEP) was shifted toward lower volumes than Curve I. The volume shift, probably due to derecruitment, was 205 +/- 100 ml at 15 cm H2O (p < 0.01) and 78 +/- 93 ml at 30 cm H2O (p < 0.01); thus, during inflation from ZEEP, the volume deficit was successively regained over a pressure range up to at least 30 cm H2O. At any pressure, compliance was higher on the curve from ZEEP than from PEEP, by 10.0 +/- 8.7 ml/cm H2O at 15 cm H2O (p < 0.01), and by 5.4 +/- 5.5 at 30 cm H2O (p < 0.01). It is concluded that in ALI, a single expiration to ZEEP leads to lung collapse. High compliance during insufflation from ZEEP indicates that lung recruitment happens far above the lower inflection point of the Pel-V curve.

Adolescent↗
PubMed1998

Diagnosis of pulmonary embolism by measurement of alveolar dead space.

OBJECTIVE: Pulmonary embolism (PE) gives rise to alveolar dead space, which can be measured with a single breath test for CO2 (SBT-CO2). The characteristics of the SBT-CO2 are different in PE and other common conditions giving rise to alveolar dead space, notably airways disease. An analysis of alveolar dead space focusing on the late part of the breath (fDlate) has been suggested as a method for diagnosis of PE. Our aim was to evaluate this technique by comparison with lung scintigraphy. METHODS: We randomly selected patients with clinical suspicion of PE. SBT-CO2 and lung scintigraphy were performed on the same day. The scintigraphies were reviewed and classified as high, intermediate and low probability of PE. RESULTS: Out of 223 patients able to be evaluated, there were 20 of the high, 29 of the intermediate and 174 of the low probability category. There were large differences between the means of fDlate in the high and the intermediate and in the high and the low categories. We obtained a sensitivity of 85% and a specificity of 93% for diagnosis of PE, based on high and low probability categories. If a patient with previous PE, but no scintigraphic evidence of current PE, is excluded the sensitivity increases to 90%. CONCLUSIONS: This study provides further support for the measurement of fDlate by the SBT-CO2 as a diagnostic test in patients with suspicion of PE. The test should be especially useful in small hospitals without access to pulmonary scintigraphy or pulmonary angiography.

Adult↗
PubMed1998

The effects of nitric oxide inhalation on respiratory mechanics and gas exchange during endotoxaemia in the pig.

BACKGROUND: In the adult respiratory distress syndrome, nitric oxide (NO) inhalation improves oxygenation through reducing ventilation-perfusion mismatching, but detailed information on the pulmonary effects of NO inhalation in septic shock is scarce. The present study investigated the effects of inhaled NO on alveolar dead space (Vdalv) and venous admixture as well as on respiratory system compliance (Crs) and respiratory system resistance (Rrs) in a porcine model of septic shock. Protective effects of NO are discussed. METHODS: Thirteen anaesthetised and ventilated pigs were given an infusion of endotoxin for an observation time of 220 min to induce acute lung injury (ALI). In the NO-early group (n=6), an inhalation of 60 ppm NO was started simultaneously with the endotoxin infusion and continued for 190 min. In 7 control/NO-late animals, 60 ppm NO was administered for 30 min following 190 min of endotoxin infusion. Haemodynamics, single-breath CO2-, pressure-, and flow signals were recorded. RESULTS: Endotoxin induced haemoconcentration, pulmonary vasoconstriction, and a decrease in Crs, while venous admixture, Vdalv, and Rrs increased. In the NO-early group, the pulmonary vasoconstriction was attenuated, no increase in pulmonary venous admixture or in Vdalv was seen before cessation of NO, and the improvements in oxygenation outlasted the NO inhalation. In the control/NO-late group, the NO inhalation reversed the changes in dead space and venous admixture. NO had no effect on the changes in respiratory mechanics. CONCLUSION: In porcine ALI, 60 ppm NO diminishes pulmonary vasoconstriction and improves gas exchange by reducing pulmonary venous admixture and alveolar dead space, but does not prevent a fall in Crs. NO inhalation may help prevent long-lasting pulmonary failure.

Administration, Inhalation↗
PubMed1998

Effects of recruitment of collapsed lung units on the elastic pressure-volume relationship in anaesthetised healthy adults.

BACKGROUND: The elastic pressure-volume (Pel-V) curve of the respiratory system can be used as a guide for improved ventilator management. The understanding of curves recorded for sick patients can be improved with better knowledge of the Pel-V relationship observed in healthy humans. Dynamic Pel-V curves were determined over an extended volume range in 15 anaesthetised and muscle-relaxed healthy humans. The influence of a recruitment manoeuvre was studied. METHODS: Dynamic Pel-V curves were determined during a single prolonged insufflation before and after the recruitment manoeuvre. A mathematical three-segment model of the curve including a linear intermediate segment, delineated by the lower (LIP) and upper (UIP) inflection points, was used for characterisation of the recorded curves. RESULTS: The model gave an adequate description of the recorded Pel-V curves. Before the recruitment manoeuvre, compliance increased until the LIP was reached at 20 cm H2O (1.9 L). Then followed a long linear segment. After the recruitment manoeuvre, compliance increased during insufflation until a LIP was reached at 13 cm H2O (1.2 L). Above the LIP followed a shorter linear segment (compliance = 140 mL/cm H2O) and then an upper segment with decreasing compliance. CONCLUSION: Pel-V curves recorded before and after the recruitment manoeuvre show that large lung compartments close during anaesthesia and that high pressures are needed to achieve recruitment even in the normal lung. Accordingly, the LIP does not define the end of recruitment during insufflation.

Adult↗
PubMed1997

Anaphylactic bronchoconstriction in immunized guinea pigs provoked by inhalation and intravenous administration of hexahydrophthalic anhydride and methyltetrahydrophthalic anhydride.

We established a guinea-pig model of anaphylactic bronchoconstriction provoked in immunized animals by inhalation and intravenous administration of 4,4-methyltetrahydrophthalic anhydride (MTHPA) and hexahydrophthalic anhydride (HHPA). Guinea pigs were immunized intradermally with either MTHPA (n = 8) or HHPA (n = 8) suspended in olive oil. Control animals (n = 8) were injected with olive oil alone. After 4 weeks, the animals were challenged during mechanical ventilation by inhalation or intravenous administration of MTHPA or HHPA conjugated with guinea-pig serum albumin (GPSA). Airway flow, and airway and esophageal pressures were measured. Resistance (R) and static compliance (Cst) of the respiratory system (rs), lung (1), and chest wall were studied with the flow-interruption technique. After challenge with MTHPA-GPSA or HHPA-GPSA, R,rs and R,1 increased dramatically while Cst,rs and Cst,1 decreased, and severe arterial hypoxia developed. The reaction occurred at a well-defined dose of anhydride and lasted about 30 min. When the same dose was repeated after 30 min, the response was much attenuated. MTHPA and HHPA can induce asthma in guinea pigs. The dose-response curve at antigen challenge is steep. Once a threshold dose is reached, a severe reaction occurs. The reactivity is then exhausted. This model may be suitable for assessing occupational asthma caused by acid anhydrides and possibly by other low-molecular-weight chemicals.

Administration, Inhalation↗