A Practical Measure of the Maximum Ventilatory Capacity in Health and Disease

Abstract

The assessment of disability in dust diseases of the lung presents a problem of great practical importance.Available evidence indicates that disturbance of the alveolar respiratory component of pulmonary function is of importance in producing disability only in such diseases as pulmonary sarcoidosis and berylliosis (Ferris, Affeldt, Kriete, and Whitten berger, 1951) where there is a lesion of the alveolar epithelium. Much further work remains to be done before the importance of disturbance of the mixing component of pulmonary function in producing disability can be evaluated. Evidence is now available, however, that the principal cause of disability in dust diseases of the lung is disturbance of the ventilatory function (Baldwin, Cournand, and Richards, 1949; Gilson and HughJones, 1953). This is also true of asthma and to a large extent of emphysema.This paper is concerned with the assessment of the maximum ventilatory capacity, and presents a method of measuring this aspect of pulmonary function which has been used during the past three years in an out-patient clinic, and which has been found simple and practical.The oldest objective method for assessing the ventilatory capacity of a subject is the simple vital capacity measurement. This, however, is a static measure of volume and is an imperfect and often misleading index of the ventilatory function (Gilson and Hugh-Jones, 1949). To detect changes in the ventilatory capacity of individual subjects from day to day, and to detect differences between individuals, it is essential to measure the maximum ventilatory capacity. Since the work of f-Hermannsen (1933) It has been suggested (Kennedy, 1950) that a man's maximum voluntary ventilation or his maximum breathing capacity might be predictable from the analysis of his vital capacity tracings recorded on a fast-revolving kymograph. The remainder of this paper summarizes the development of this earlier work. APPARATUSA simple vital-capacity spirometer almost identical with that described by Gilson and Hugh-Jones (1949) has been used for recording the various respiratory tracings. The volume of the spirometer bell is roughly 6.5 litres. In order to minimize resistance to air-flow, a 2-in. diameter tube was used inside the spirometer and for the rubber connexion to the metal mouthpiece. The same electrical integrating device as described by Gilson and Hugh-Jones was used for measuring the volume of air breathed during voluntary hyperventilation. The spirometer bell was counterbalanced by means of a long, thin cylindrical weight which moved up and down within a hollow metal circular container. A small ink recording pen was fixed to this counter-weight so that movements of the spirometer bell could be recorded on a fastrevolving kymograph. Various speeds were tried, and it was found that a kymograph driven by an electric synchronous motor so that its drum periphery revolved at 1.24 cm. per second gave the most satisfactory result. The drum speed was checked by an electric time-marker, and was found to be uniform

The birth and development of the forced expiratory manoeuvre: a tribute to Robert Tiffeneau (1910-1961)

“…While the "timing of the VC" was progressively overcoming the MBC, much controversy remained about the most convenient time measurement; advocates of 0.75 s [55] or 2 s [56,57] could still be found. SNIDER et al [58] suggested that the 1 s VC was less sensitive than the MBC to demonstrate bronchodilator changes.…”

A Critical Discussion of the Recorded Form of the Fast Vital Capacity Record

“…record-or of some portion of it-with the M.V.C. Kennedy (1953) draws attention to the form of what he terms the E.V.S. tracing and comments that it is never uniform throughout its length, and may, except in certain types of abnormal patients, be divided into two fractions.…”

“…The position of the dividing point between the first and second fraction, i.e., where the tracing deviates from a straight line, has been termed the critical point (Kennedy, 1950 Clearly it is a matter of considerable importance, both for the theoretical implications and for the validation of any predictions which are to be made from such records, to decide which of these very different kinds of curve is correct, and, if possible, to explain the differences. Kennedy (1953) states that his records were made on a spirometer almost identical with that described by Gilson and Hugh-Jones (1949). From their description, which, unfortunately, is not detailed, it appears that their spirometer was physically similar to the conventional Knipping type of spirometer.…”

“…Recently much attention has been given to the possibility of using this record as a basis for the prediction of the maximum ventilatory capacity (M.V.C.) of the same individual, and a number of papers have appeared (Roche and Thivollet, 1949; Tiffeneau, Bousser and Drutel, 1949;Gaensler, 1951 ;Kennedy, 1953) in which attempts have been made to correlate the slope of the F.V.C. record-or of some portion of it-with the M.V.C.…”

“…Considering the first two of these possibilities, the Knipping spirometer is known to possess considerable errors for recording tidal ventilation at respiratory rates over 35 respirations per minute (Bernstein and Mendel, 1951) Kennedy (1953), record traced from a published paper, C, on the improved spirometer when the subject was the same individual as in A.…”