Fifty years ago: Pulmonary function tests in asbestos workers

In established asbestosis, examination reveals crepitations at the lung bases, clubbing of the fingers and cyanosis. The clubbing and cyanosis are late and inconstant features, but basal crepitations are nearly always present. To begin with they are fine and are heard at the end of inspiration when the lungs are fully expanded, but as the disease progresses, they become coarser and are audible at lower lung volumes, eventually being heard throughout inspiration. Characteristically they appear first in the axillary basal region but eventually spread throughout the lung. They are heard first at the lung bases because of the effect of gravity. When a patient is examined lying on one side, the crepitations often disappear from the upper lung and are heard only in the lower lung, and this phenomenon is repeated when the patient turns on to the other side. They are heard at the back when the patient is supine and at the front when he is prone. A probable reason for the variations in timing of the crepitations is that the diseased part of the lung is less compliant than the rest and is the last to expand on inspiration, hence delaying the crepitations until the end of inspiration. The postural effects are clinical expressions of the principle that the lowermost part of the lung collapses furthest on expiration and expands most on inspiration (Milic-Emili, Henderson, Dolovich, Trop and Kaneko, 1966). Early in the disease, the crepitations are intermittent, but can sometimes be brought to light by examining the lower lung in a patient lying on one side, or by examining the back of the patient who is supine. The angle between the seat and the head-rest of a hospital examination couch affords a gap through which the back of a supine patient can be reached. Although crepitations are usually present in asbestosis, they are not invariable and a few patients have been seen in whom they were absent despite a positive diagnosis by lung biopsy. In figure 3, the time at which basal crepitations were first heard is indicated by a thickening of the lines, continuous when they were invariably present, interrupted when they were intermittent. This sign was present in five of the subjects and in all of them it was first noted before the diffusing capacity had dropped significantly. Crepitations were not present, however, in two of the cases with a low diffusing capacity, an experience similar to that of Williams and Hugh-Jones (1960). Other measurements made in these 12 subjects showed small and inconsistent changes over the years. Compliance rose on average by 26%, while vital capacity fell by 7–8% during the period of observation.

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