An automated quantitative analysis of ventilation-perfusion lung scintigrams.

We have devised an automated computer analysis of ventilation (Kr-8 1m) and perfusion (Tc-99m) lung images that produces a graphical image of the distribution of ventilation and perfusion, and of ventilation-perfusion ratios. The analysis has overcome the following problems: the identification of the midline between two lungs and the lung boundaries, the exclusion of extrapulmonary radioactivity, the superimposition of lung images of different sizes, and the format for presentation of the data. Therefore, lung images of different sizes and shapes may be compared with each other. The analysis has been used to develop normal ranges from 55 volunteers. Comparison of younger and older age groups of men and women show small but significant differences in the distribution of ventilation and perfusion, but no differences in ventilation-perfusion ratios. Examples are presented to demonstrate that the technique can discriminate between normal and abnormal scintigrams. The analysis of serial images from one individual shows high reproducibility.

Hypomagnesaemia in diabetes.

The plasma magnesium (Mg) concentrations of 582 unselected diabetic outpatients and 140 control subjects were measured by atomic absorption spectrophotometry. Mean plasma Mg (+/-S.D.) was significantly lower in the diabetic patients (0.737 +/- 0.071 mmol/l) than in the control subjects (0.810 +/- 0.057 mmol/l), and 146 (25%) diabetics had values below those of all control subjects except one. Plasma Mg correlated best with clinic blood glucose concentration (r = -0.32, p less than 0.001) and other significant associations were observed with glycosuria, age, sex, insulin therapy and biguanide therapy. Although its significance is unclear, hypomagnesaemia could conceivably predispose to ischaemic heart disease in diabetes.

Comparison of elastolytic activity in lung lavage from current, ex- and non-smokers.

Cigarette smokers have an increased risk of developing a wide variety of lung diseases compared to non-smokers, and there have been many studies of the possible biochemical changes underlying this increased susceptibility. However, although epidemiological and physiological studies have shown that in the ex-smoker, the risk of smoking-related lung diseases falls between that of current and non-smokers, the biochemical and cellular mechanisms responsible for this intermediate status have not been investigated. In the present study, therefore, the extracellular elastolytic activities in lung lavage fluid from current, ex- and non-smokers have been compared. Elastolytic enzyme activity was investigated, since it is significantly elevated in lung lavage from smokers, and because it has been implicated in the development of pulmonary emphysema. In the subjects studied, extracellular elastolytic activities in lung lavage from ex-smokers were intermediate between those from current and non-smokers. There was no correlation between the time of abstinence from smoking, or the number of pack-years smoked and the extracellular elastolytic activities in ex-smokers' lung lavage. Elastolytic activity may remain elevated in ex-smokers' lungs for a number of reasons, including the persistence of particulate matter which may activate phagocytic cells on the lung surface. The possible significance of the raised elastolytic activity remains to be fully determined.

Lung scan abnormalities in asthma and their correlation with lung function.

We have used asthma as a model of airways disease to test how well an automated, quantitative method of analysis of lung scans correlates with physiological measurements of disturbed lung function and gas exchange. We studies 25 asthmatics (age 16-73) of widely differing severity (forced expiratory volume in 1-s (FEV1) 22%-123% of predicted value), who had airways tests, arterial blood gas analysis, and krypton-technetium lung scans within a short time of each other. In all patients with airways obstruction and in some with normal function during remission, scans showed the typical appearances of multiple defects of ventilation and perfusion. The severity of ventilation defects was computed from the posterior view of the krypton scan compared to an age- and sex-matched normal range to yield an underventilation score. This correlated closely with the severity of airways obstruction as measured by forced expiratory manoeuvres. Ventilation and perfusion defects were usually imperfectly matched; the severity of this was computed using a subtraction method applied to the counts on the posterior krypton and technetium scans. The degree of mismatch was inversely related to the arterial partial pressure of oxygen (r = -0.86). The results suggest that computer scan analysis can provide useful functional information about the lung in airways disease.

Computer analysis of ventilation-perfusion scans for detection and assessment of lung disease.

A previously reported computer analysis has been used to provide numerical ventilation-perfusion lung scan data, for comparison with tests of airways function and results of arterial blood gas analysis in 11 patients with pulmonary embolism, 18 with asthma, and 37 with chronic obstructive lung disease. In pulmonary embolism an index of underperfusion showed high sensitivity, and an index of ventilation-perfusion mismatching correlated well with severity (hypoxaemia). In asthma an index of underventilation was sensitive and correlated well with severity of airways obstruction. In chronic obstructive lung disease the same index was sensitive but correlated poorly with severity. This was attributed to heterogeneity of the lung disease (airways obstruction plus emphysema) in chronic obstructive lung disease. Ventilation-perfusion mismatching was frequently present in airways disease, and was often of great severity in chronic obstructive lung disease. Discrimination between pulmonary embolism and either type of airways disease was possible by using a combination of underfusion and underventilation indices. The technique offers the prospect of increasing the information derived from lung scans and of automating the reporting of scans.

Observations on the mechanism of hypoxaemia in acute minor pulmonary embolism.

An automated computer analysis of ventilation-perfusion lung scans was used to derive graphical data from lung scans of 11 patients with acute minor pulmonary embolism, free of pre-existing cardiorespiratory disease, and with no evidence of intrapulmonary complication or pleural effusion. In each case the analysis showed the presence of areas of lung, remote from those affected by the pulmonary embolism, that had a pathological disturbance of ventilation-perfusion matching with relative overperfusion. Such a disturbance would cause hypoxaemia. When the extent of the mismatching was calculated in terms of relative blood flow and alveolar ventilation it correlated well with the degree of arterial hypoxaemia. It is proposed that in acute minor pulmonary embolism the development of ventilation-perfusion mismatching in areas of lung unaffected by the embolic event may be an important mechanism of hypoxaemia.

Acid-stable low molecular mass proteinase inhibitors in human lung lavage.

An acid-stable, low molecular mass proteinase inhibitor, bronchial mucus proteinase inhibitor (BMPI), has been isolated from sputum and partially characterised. A single band with a modal molecular mass of 18 700 was observed following SDS-polyacrylamide gel electrophoresis. BMPI inhibited human leukocyte elastase, cathepsin G, trypsin and chymotrypsin, but not porcine pancreatic elastase. Although BMPI had a molecular mass close to the similarly isolated inhibitor of Girard et al. (Girard, F., Tournier, J.M., Polu, J.M. & Sadoul, P. (1980), Bull. Eur. Physiopathol. Respir. 16 (Suppl.) 237-245), and although it showed immunological cross reactivity to the low molecular mass inhibitor of Kramps et al. (Kramps, J.A., Franken, C., Meyer, C.J.L.M. & Dijkman, J.H. (1981) J. Histochem. Cytochem. 29, 712-719), it was found to have an amino-acid profile different to any previously described inhibitor. BMPI was detectable in bronchoalveolar lavage fluid collected from healthy and diseased human lungs. The median molar ratio of BMPI/alpha 1-proteinase inhibitor (alpha 1 PI) observed in these lavage samples was 0.7, which is generally higher than those derived from the data of other authors. This suggests that BMPI is a different protein to those previously described, although its exact relationship to other low molecular mass proteinase inhibitors remains to be determined.

Extracellular elastolytic activity in human lung lavage: a comparative study between smokers and non-smokers.

Unrestrained proteolysis in the lung is believed to initiate emphysema, a disease common among tobacco smokers. However, few studies have found extracellular protease activity in human lung lavage. In this investigation, elastase and serine protease activities were measured in bronchoalveolar lavage supernatants (BAL) from patients undergoing routine investigations. Significantly more elastolytic activity (against insoluble [3H]-elastin) was recovered in the lavage of smokers than that of non-smokers. However, no significant difference was found when the levels of serine proteolytic activity (against N-succinyl-L-trialanyl-p-nitroanilide) were compared. The elastolytic component of the protease activity rose from 5% in non-smokers' BAL to over 30% in that of smokers, suggesting that elastase activity is selectively enhanced by smoking. In lavages from most smokers, 80% or more of the elastase activity was serine-dependent, whereas lavages from non-smokers contained variable proportions of serine elastase. Both alpha 1-proteinase inhibitor (alpha 1-PI) and a low molecular weight antiprotease, bronchial mucus proteinase inhibitor (BMPI) were detectable in the lavage samples, the latter contributing up to 76% of the total antiprotease quantified in the lavage. Functional antiprotease was detected in 85% of the lavages. Since there were no differences in either antiprotease levels or functional inhibitory capacities between lavages from smokers and controls, it is concluded that the imbalance in the protease/antiprotease profile of the smokers' lung results from an enhancement of proteases, specifically of elastolytic activity, rather than a reduction in inhibitory capacity.

Effects of cigarette smoking and drugs on respiratory tract proteases and antiproteases.

Increased pulmonary proteolytic (elastolytic) activity is thought to be the primary cause of emphysema and may also play a rôle in the pathology of bronchitis. These diseases are common amongst tobacco smokers. Serum-derived alpha 1-proteinase inhibitor (alpha 1PI) and locally produced protease inhibitors normally protect the pulmonary epithelium from proteolytic attack, but tobacco smoke can inactivate these antiproteases by oxidative and non-oxidative mechanisms. Bronchoalveolar lavage fluid (BALF) samples lung surface components and most studies show that there is elevated elastolytic activity in smokers' BALF. Whether antiproteolytic capacity is reduced in these samples remains debatable. A selective lavage technique is described which independently samples central and peripheral epithelium from the same subject. Analysis demonstrates a protease-antiprotease imbalance which can differ in central and peripheral lavage and which could be significant in the development of obstructive airways disease. Therapeutic approaches include augmenting antiprotease potential using genetically engineered, oxidant-resistant alpha 1PI or synthetic peptide inhibitors.

Comparison of human lung surface protein profiles from the central and peripheral airways sampled using two regional lavage techniques.

This study describes two new techniques of lung lavage which selectively remove material from the central airways, or from the lung below the seventh generation. Bronchograms confirmed that discrete regions of the lung were washed by central lavage (CL; maximum airway diameter approximately 6.5 mm) and peripheral lavage (PL; maximum airway diameter approximately 1.3 mm), and that both could be clearly distinguished from conventional bronchoalveolar lavage (BAL). These techniques were used to establish whether or not large-airway proteins made a major contribution to the protein profile of BAL. Twenty consecutive patients undergoing routine fibreoptic bronchoscopy were investigated. More bronchial mucus proteinase inhibitor per unit albumin and per unit total measured antiproteinase was present in CL than PL or BAL. In contrast alpha 1-proteinase inhibitor per unit albumin and as a percentage of total measured antiproteinase was lower in CL than in other lavage types. There were no differences in elastase activity, irrespective of the way in which the data were expressed. As no differences were found between BAL and PL for any of the variables measured, it was concluded that in the subjects studied the contribution of CL proteins to BAL was minimal.

The elastase: anti-elastase profile in lung lavage from sarcoidosis patients.

One feature of pulmonary sarcoidosis is an increase of lymphocyte numbers in bronchoalveolar lavage fluid (BALF). In some patients the number of polymorphonuclear neutrophils (PMN) also rises. It has been suggested that the prognosis for the latter subjects is likely to be worse than that for the former, but the damaging agent (or agents) released by the PMN have not yet been identified. Therefore, in the current study, the activity of one neutrophilic enzyme, elastase, which is known to damage the pulmonary interstitium, has been assessed in sarcoid BALF and compared to BALF from subjects matched for age, sex and smoking status. As BALF also contains locally-produced and serum-derived inhibitors of elastase, levels of which may change in subjects with sarcoidosis, the serine protease inhibitory capacity and the levels of three anti-elastases have been measured in the samples. Levels of the serum-derived antiproteases, alpha 1 proteinase inhibitor (alpha 1PI) and alpha 2 macroglobulin (alpha 2M) were found to be significantly increased. However, alpha 1PI/albumin and alpha 2M/albumin ratios were unchanged, suggesting that the increased levels were due to an increased permeability of the alveolar-capillary barrier. The total protease inhibitory capacity was elevated and this could be entirely explained by the raised levels of alpha 1PI and alpha 2M. Levels of the locally-produced inhibitor were unaltered. The elastolytic capacity of sarcoid BALF was unchanged. Thus, the elastase: anti-elastase balance was shifted against elastolytic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

The acute effect of cigarette smoking on the neutrophil elastase inhibitory capacity of peripheral lung lavage from asymptomatic volunteers.

Cigarette smoke-induced emphysema is thought to involve reduction of antielastolytic capacity, resulting in elevated elastase activity and lung tissue damage. Peripheral lavage collected from ten asymptomatic subjects immediately before and 20 min after smoking two high tar cigarettes was analysed for neutrophil elastase (NE) inhibitory capacity (IC), alpha 1-proteinase inhibitor (PI) function, elastolytic activity and immunoreactive levels of PI and bronchial inhibitor (BI). The only change found was a small fall in mol immunoreactive PI/mol albumin after smoking (approximately 17%, p less than 0.05) which did not affect NEIC, since PI contributed less than 50% of the NEIC. There was often more NEIC than mol BI + functional PI, suggesting the presence of other NE inhibitors. Thoracic computerized tomography scans of eight of these subjects highlighted two with emphysematous regions of lung; lavage from these two subjects contained either undetectable BI or inactive BI and this suggests a protective role for BI in emphysema.