Use of radioactive xenon for studies of regional lung function. A comparison with oxygen-15

The validity of different methods of analysis of 133Xe washout curves for the determination of lung function

The influence of different mathematical methods on the analysis of 133Xe washout data, used in the assessment of lung function in the pig, were investigated. When the data were fitted using a bi-exponential or a bi-exponential plus a constant type equation, neither the two clearance rate constants nor the overall 50% clearance time were found totally appropriate for the study of lung function. A new two compartmental model for the in vivo clearance of 133Xe is proposed. The model assumes the whole blood as one compartment and the lung, including the pulmonary blood, as the second compartment. This suggests that the curvature of the xenon clearance curve is the result of recording the summation of the activities from the alveoli and the pulmonary blood and not, as previously described, due to the existence of two different sub-populations of alveoli.

Scintigraphic evaluation of regional pulmonary ventilation

Radioactive gases are useful for evaluating pulmonary ventilation because they allow assessment of regional lung function in a physiologic, noninvasive manner. The most widely used radioactive gases are Xe-133, Xe-127, and Kr-81m. These gases provide visual and/or quantitative assessments of regional ventilation or ventilation-perfusion matching in obstructive airways disease, and aid the scintigraphic diagnosis of pulmonary embolism. The precision of ventilation scintigraphy is limited by detector resolution, signal distortion at depth, poor counting statistics, and respiratory motion.

The radiospirometric flow-volume diagram recording technique and comparative study with conventional spirometry

The spirometric flow-volume diagram recorded for a forced expiration gives information which is used in assessing obstructive or restrictive pulmonary diseases. Regional data of the same kind can be achieved using a simple radiospirometric technique and scintillation camera. A series of images during inspiration and expiration are defined and a time-activity curve with an integration time constant of about 100-200 ms is obtained from the images during the forced expiration phase. The equivalent of the flow-volume diagram, i.e., the time derivative of the activity vs. activity is computed. There were 21 subjects studied in this series. Normal subjects or patients with various diseases underwent classical spirometry, so that the global radioactive diagram could then be compared to the spirometric flow-volume diagram and its parameters expressed in terms of volumes and flow: vital capacity, peak flow, mean flow, flow at mean volume. The correlation with classical spirometry is highly significant. Similarly regional data are consistent with the pulmonary results.

The measurement of regional ventilation during tidal breathing: a comparison of two methods in healthy subjects, and patients with chronic obstructive lung disease

Regional ventilation has been measured in 17 healthy volunteers, and 24 patients with chronic obstructive lung disease during tidal breathing using 133-Xe. The wash-in and wash-out of 133-Xe were recorded by a gamma camera interfaced to a small digital computer. Regional ventilation was calculated as the distribution of tidal volume per unit lung volume-a measure of relative ventilation--and from the wash-out curves as the fractional exchange of air per second. Determination of the regional fractional exchange of air showed a significant difference between the patients with chronic obstructive lung disease and normal subjects for all regions. The distribution of tidal volume per unit lung volume did not effect such a clear separation. Significant correlations were found between the whole-lung fractional exchange of air in the patients with chronic obstructive lung disease and their FEV1 r equal 0-70, MMFR r equal 0-70, FVC r equal 0-56 and FEV1/FVC r equal 0-57. It is suggested that measurement of regional ventilation as the fractional exchange of air is more realistic than methods that determine relative ventilation or only make use of the early part of the wash-out 133-Xe.

Regional lung function in scoliosis

Radioactive xenon-133 was used to study the pattern of regional lung function in 35 scoliotic patients and 10 normal subjects in the sitting posture. The scoliotic curves were classified into three anatomical sites: high, if the apical vertebra was located between Th1 and Th5; mid, between Th6 and Th10; and low, between Th11 and L4; only the primary curve was considered and in 70% of the patients this measured more than 60°.

The mean pattern of perfusion in patients with low and mid curves was not significantly different from that of the normals, nor was there any significant difference between the convex and concave lungs in these two groups. Patients with high curves showed three distinct patterns: [List: see text]

The mean pattern of ventilation in the three groups of scoliotic patients was not significantly different from that of the normals although there was wide individual variation. The only patients to show a significantly abnormal ventilation/perfusion ratio were the high group.

Regional lung volumes calculated from the equilibration scan indicated that in a majority of scoliotics the lung on the convex side of the curvature was larger than that on the concave side.

Our results suggest that both the anatomical site and the angle of the scoliotic curvature have an effect on regional lung function but that this effect falls equally on the convex and concave lungs.

Correlation of hemodynamic data and pulmonary angiography in mitral stenosis

The abnormalities of pulmonary arterial blood supply in mitral stenosis, consisting primarily of constriction of lower lobe vessels with resultant upper lobe preferential flow, was assessed by means of pulmonary angiography in 30 patients with mitral stenosis uncomplicated by other cardiac diseases. The abnormalities in blood flow correlated best with both the pulmonay artery pressure and the pulmonary arteriolar resistance, and only reasonably well with the area of the mitral valve and the pulmonary capillary wedge pressure. It is suggested that the reversal of the normal lower lung field preferential blood flow in mitral stenosis is primarily a function of pulmonary artery hypertension due to increased pulmonary arteriolar resistance.

Similarly, the width of the right main pulmonary artery as measured on pulmonary angiograms correlated well with both the pulmonary artery pressure and pulmonary arteriolar resistance and less well with the area of the mitral valve. Pulmonary artery size in mitral stenosis is most likely a function of the severity of the pulmonary arteriolar resistance as reflected in the pulmonary artery pressure.