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A study of the local surface velocity of the chest and abdomen as a function of the frequency of sinusoidal pressure waves introduced into the airways via the trachea, was made in 15 cats. The study confirmed and extended the observations DuBois, Brody, Lewis and Burgess had previously made in human beings and demonstrated that the effects seen were not produced by any part of the airway above the trachea. Comparison is made of this data with the averaged data obtained by using a plethysmograph to integrate the surface responses of the cat. The natural frequency (9.6, S.E. = 0.6 cps), damping factor (2.0, S.E. = 0.25), resistance ( k1 = 13.5, S.E. = 2.3 cm H2O/(l/sec.); k2 = 76, S.E. = 21 cm H2O/(l/sec.)2, and elastance (230, S.E. = 26 cm H2O/l.) were measured and the inertance (.09, S.E. = .008 cm H2O/(l/sec.2)) was calculated. The implications of these concepts and measurements for respiratory mechanics and ballistocardiography are discussed.

Sixteen comparisons (3 in females, 13 in males) were made of pulmonary function tests in the standing, seated and supine positions. The significant changes were an increase in tidal volume on standing from either the seated or supine positions, but no change on lying (supine) from the seated position; a progressive decrease in the expiratory reserve volume on going from the standing to the seated to the supine positions; an increase in the inspiratory capacity on lying supine from either seated or standing positions, but no significant change on standing from the seated position; and a suggestion of increased turbulence (k2 term) on passing from the seated to either of the other positions. The other functions tested (minute volume, vital capacity, maximal pressures, elastance, resistance, maximal flows) did not change significantly. The variation and progression of week-to-week changes are described for five paralyzed patients after poliomyelitis and three normal subjects studied over a 2–3 month period. The changes occurring in five normal subjects studied at about 9-month intervals for periods of 9–39 months are also described. Submitted on August 17, 1959