Regional Pulmonary Function Studied With Xenon133 in Patients With Bronchial Asthma*

Abstract

It has been known for some years that there may be impairment in the distribution of an inert gas in the lungs of patients with bronchial asthma at a time when the disease appears to be in remission (1, 2). Maximal ventilatory air flow may also be reduced in the absence of symptoms (2).A recently described technique for the study of regional distribution of pulmonary ventilation and perfusion using xenon'33 (3) appeared to be suitable for the study of zonal variations in function in these patients. METHODSSelection of patients. One of us (B.R.) selected twelve asthmatic patients in remission, eight men and four women, ranging in age from 17 to 46 years, with an average age of 31 years. All patients had been observed over the course of several years and gave an average 10-year history (3 to 26 years) of recurrent, typical attacks. Between attacks, all patients were free from cough and dyspnea, and this, together with the nature of the attacks of spasmodic asthma, clearly distinguished them from patients with chronic bronchitis and emphysema. Two patients were on no treatment at the time of the study, while the remainder were receiving vaccine injections at varying intervals, and small doses of steroids, or conventional bronchodilators, or both.Routine pulmonary function tests in ten patients immediately followed the xenon1" study; in two subjects, the tests preceded the study by a variable interval, but airflow measurements at the time of the xenon study agreed with those recorded earlier, indicating that the clinical condition of the patients had not changed. The tests included the study of the total lung capacity and its subdivisions, maximal mid-expiratory flow rate, forced expiratory volume, mixing efficiency, and steady-state resting diffusing capacity of the lung for carbon monoxide (end-tidal sample). Details of these techniques and prediction tables have been reported elsewhere (4-7).For maximal mid-expiratory flow rates, the prediction formulas for men had to be used, owing to the lack of prediction data for women.* Supported by a grant from The John A. Hartford Foundation, Inc.Xenon"' technique. A technique using xenon3 to measure regional lung function has recently been reported from this laboratory (3). Six scintillation counters were placed over the chest posteriorly, in standard positions in relation to a 6-foot posteroanterior chest film. Pulses from each counter were fed through amplifying and discriminating circuits, recorded on a multichannel magnetic tape recorder, and displayed through counting-rate meters onto a 4-channel direct writer. The zonal distribution of ventilation was studied by recording the count-rate plateaus after the subject took a normal and a full inspiration from a spirometer containing xenon1" in air. The zonal distribution of pulmonary blood flow was determined by rapid intravenous injection of xenon1" dissolved in saline, followed immediately by a breathholding maneuver in full inspiration. Since approximately 95% of the injected xenon"' is discharged into the alveoli dur...

Regional lung function in patients with bronchial asthma

“…This underperfusion was not entirely effective from a gas exchange point of view since VA/Q was relatively low in hypoventilated regions; if there had been no change in perfusion distribution, however, over-all gas exchange obviously would have been more inefficient. The normal blood flow distribution found in patients with asthma in a previous study (2) probably was due to their upright posture; since blood flow distribution in the erect normal subject is uneven (9), abnormalities are difficult to detect. Since it is likely that the lung parenchyma was morphologically normal in these patients, regional decreases in flow probably were functional in origin.…”

“…Studies with 133xenon (133Xe) in this laboratory (2) showed hypoventilation of lung regions in symptom-free patients with asthma, and it was concluded that these regions probably had low ventilation/perfusion ratios (VA/Q). This conclusion was supported by the findings of Ledbetter, Bruck, and Farhi (3), who measured nitrogen tension in both alveolar gas and arterial blood in patients with asthma and found lung units with abnormally low alveolar VA/Q.…”

“…The aims were to document further the phenomenon of regional hypoventilation and to correlate it with tests of over-all pulmonary function; to detect regions with low VA/Q; to assess regional blood flow distribution; and, since most of these patients had been studied previously with 133Xe (2), to record changes in regional function. METHODS Selection of patients.…”

Simple Method for Determination of Perfusion and Ventilation-Perfusion Ratio of the Underventilated Elements (the Slow Compartment) of the Lung*

“…If it is assumed that the same equilibrium existed under control conditions, Cao a(PB -47) FAo 760 [6] and It is also possible to obtain the relative ventilation-perfusion ratio of the slow compartment (i.e., the value of that ratio for this compartment in respect to that of the whole lung, as expressed in Equation 7) by dividing FA/FAo by Ca/Cao measured at the same time during the washout.…”

“…Some are based on injection or inhalation of radioactive materials (3)(4)(5)(6), but are too complicated or too costly for general use. Finley (7) has reported a method of estimating perfusion of poorly ventilated alveoli that requires simultaneous recording of alveolar CO2 and N2 (from which alveolar 02 is calculated) and arterial 02 tension.…”