Thorax: first published as 10.1136/thx.28.1.89 on 1 January 1973. Downloaded from Thorax (1973), 28, 89. Lung volume and its subdivisions in normal and asthmatic males MARGARET I. BLACKHALL and R. S. JONES1 Institute of Child Health, University of Liverpool, Alder Hey Children's Hospital, Eaton Road, Liverpool 12 Measurements of lung volume and its subdivisions were made in 89 asthmatic children and adults and 58 normal subjects. The asthmatics were divided into three groups according to the classifica- tion of Jones (1966). In this the FEV1 is used as an index of airways resistance which is divided into labile and fixed components. The compartment of lung volume showing the largest increase was the residual volume in subjects with a predominantly fixed increase of airways resistance (group 3) and this was true of both the children and adults. This compartment was also signifi- cantly enlarged in the labile subjects (groups 1 and 2). Significant increases in functional residual capacity were demonstrated in all three groups, especially in the children. Total lung capacity was significantly increased in the two labile groups of children but not in the adults. Even a low level of lability (group 1) may be associated with highly significant abnormalities in lung volume compartments which may be more evident in the child than in the adult. copyright. There has been little attempt in the past to TABLE I correlate the severity of asthma with change in CLASSIFICATION lung volume and its subdivisions. Kraepelien, Group Max. FEV1 Lability % Engstrom, and Karlberg (1958) made measure- 1 N 15-30 ments in children classified on clinical grounds 2 N > 30 http://thorax.bmj.com/ as mild, moderate, and severe, and found func- 3 <N Variable tional residual capacity (FRC), residual volume Normal N < 20 (RV), and total lung capacity (TLC) to be sig- Fall in of LabilityLabilitindex= FEV1 (litres)+rise FEVY (litres) Xx 1000 most severe Predicted normal FEYV nificantly higher than normal. The In the normal subject, the FEV1 at rest replaces the predicted normal group showed the most marked changes, but FEVY. Fall in FEV,=fall from resting level after 8 minutes' exercise. since some children in each group gave normal Rise in FEVY=rise from resting level after bronchodilator drug+ values they considered that lung function and exercise for 1 minute. Group 1: mild asthma, low lability index clinical classification do not always coincide. Group 2: more severe asthma, high lability index The arbitrary level separating groups 1 and 2 is 30% lability. on September 26, 2021 by guest. Protected Palmer and Diament (1969) studied lung volume Group 3: lability varies, because of fixed component of airways and its compartments in adult asthmatics in acute resistance. Maximum FEVY (that is, after bronchodilator drug+ attacks and found that severity correlated with exercise for 1 minute) below normal. degree of hyperinflation and that the best index of this is the ratio RV/TLC. of airway resistance. In this paper asthma is Changes in lung volume compartments clearly defined as an abnormal degree of lability of the reflect changes in airway resistance. It has been bronchial tree (lability index>20%) since this shown that the latter is made up of fixed and has proved to be more reliable that arbitrary labile components (Jones, 1966). The clinical pre- clinical definitions in both the child and adult sentation and course of the disease vary with the (Blackhall, 1970a; Blackhall, 1970b). Subjects with relative contributions of these components. More- bronchitis were thus excluded by reason of a over, their relative importance changes with in- normal lability index. creasing age. The lung volume changes in child- The lability index and lung volume compart- hood and adult asthma have therefore been ments were also measured in normal subjects examined in terms of a classification (Table I) since reports of the effect of age on TLC, RV, and based upon indices of labile and fixed components FRC are somewhat conflicting. There is general ICorrespondence to R. S. Jones agreement on the fact that RV increases with age. 89 Thorax: first published as 10.1136/thx.28.1.89 on 1 January 1973. Downloaded from 90 Margaret 1. Blackhall and R. S. Jones Kaltreider, Fray, and Hyde (1938) found a de- Asthmatic subjects were chosen from those who crease with age in TLC and an increase in FRC. had well-documented histories over long periods, so Needham, Rogan, and McDonald (1954) agreed that the severity of their asthma could be assessed that TLC decreased with age but found little with reasonable accuracy. In this way, subjects who alteration in FRC. Boren, Kory, and Syner (1966) had been stable over a considerable number of years were obtained. Children with asthma formed a cross- found TLC and FRC to be correlated with height section of those attending the asthma clinic at Alder but unrelated to age, whereas RV correlated with Hey Children's Hospital. Since few children with both height and age; the correlation coefficient mild asthma are referred to the clinic, this group was, however, poor for all these. was a small one. The majority of children attending In asthmatic subjects between attacks, Lukas the hospital belong to the moderately severe group, (1951) found an increase in RV and Bates (1952) and a smaller number to the severe group. an increase in FRC in young subjects. Herschfus, Adults with asthma from childhood came from Bresnick, and Segal (1953) found in adult subjects three sources. The majority had attended the asthma a reduced vital capacity and an increase in the clinic at one of the Liverpool City hospitals, and case histories dating from childhood were available. ratio RV/TLC. Beale, Fowler, and Comroe (1952) Another group consisted of those who in childhood reported an increase in FRC and RV but noted had attended the asthma clinic at Alder Hey Child- great variability. ren's Hospital. A few older subjects with asthma came from general practitioners. MATERIAL AND METHODS METHODS The lability index (Jones, 1966) was used In the first instance, 58 normal and 89 asthmatic to classify the asthmatic patients into three groups subjects were studied. These were divided into (Table I). This classification is based upon measure- children aged 6 to 16 years, young adults aged 17 ments of lability made between attacks when the sub- to 32 years, and older adults aged 33 to 53 years. ject is clinically 'well' and all measurements reported The childhood group consisted of 19 normal subjects here were made under these conditions. Group 1 and 44 asthmatics; the young adult group was com- asthmatics are only a little more labile than the nor-copyright. posed of 21 normal subjects and 34 asthmatics; mal subjects. Group 2 are highly labile and in Group while the older group contained 18 normals and 11 3, the fixed component of airways resistance (AR) asthmatics. predominates. It should be noted that a high lability index is not synonymous with severe asthma; the SUBJECTS STUDIED Normal adults were members of subject may not have clinical asthma at all. It des- the hospital staff-doctors, students, and laboratory cribes the degree to which the bronchioles constricthttp://thorax.bmj.com/ technicians. Normal children were the sons of staff and dilate in response to specific stimuli. and their friends. They were accepted only if they were Since the results for normal subjects (Table III) entirely free of respiratory symptoms and had no showed a definite effect of age on lung volume com- history suggestive of chronic respiratory disease. partments, which became apparent in the group aged Although they were by no means a random sample 17 to 32 years, a further 15 normal men were added of the population, the results obtained from the to this group so that the age effect could be studied group were very similar to those found by other more accurately. The total of 36 subjects were then workers (Engstrim, Karlberg, and Kraepelien, 1956). divided into two groups aged 17 to 24 years and Thus it was considered justifiable to use them as a 25 to 32 years, each containing 18 subjects. control group and these data were used to predict Measurement of lung volume and its subdivisions on September 26, 2021 by guest. Protected normal values for the asthmatic subjects of com- was made with the subject in the sitting position and parable age. The lability indices were measured on after resting for 15 minutes. The FRC was deter- all normal subjects and it will be seen (Table II) that mined by a closed-circuit helium dilution technique the results are within normal limits. (Gilson and Hugh Jones, 1949). Oxygen was fed in manually through a small rotameter to replace that TABLE II being used by the patient, thus keeping the resting IN NORMAL CONTROLS expiratory level constant. The oxygen content of the LABILITY INDEX circuit gases was kept at approximately 210%. When Age (yr) Lability Index % the subject had reached equilibrium with the mixture helium in the the 8-16 Mean 10 3 of air and spirometer, expiratory Range 2-20 reserve volume (ERV) was measured, followed by SD 5 the inspiratory reserve volume (IRV). Two attempts 17-32 Mean 9.9 at each were made and the larger figure for each was Range 5-19 used in calculating the vital capacity (VC). SD 3 5 Duplicate estimations on 12 subjects gave a mean 33-53 Mean 8-6 change between first and second estimations in FRC Range 3-19 SD 4 of 0-013±0-117, in RV of 0-051±0-068, and in TLC of 0035±0-102.