Breathing of half-micron aerosols. I. Experimental.

Aerosol Deposition in the Human Lung at Variable Tidal Volumes: Calculation of Fractional Deposition

“…Hence, demonstration of wash-in is harder than demonstration of wash-out . Wash-out was demonstrated over more than six breaths for several subjects (Heyder and Davies, 1971;Davies et al, 1972), whereas wash-in was only demonstrated for the first four breaths (Heyder and Davies, 1971;Davies et al, 1972). Heyder and Davies (1971) concluded that failure to demonstrate experimentally the validity of Eq.…”

“…The inhalation apparatus used differs from that used by Davies et al (1972) in that flow was measured continuously by a Fleisch pneumatachograph. Smoothed signals from the photomultiplier tube and the flow transducer were electronically transformed to display the product of 1. the addition of a voltstat (A) (smoothw these signals, whose integral represents the transformer) to stabilize the heating cur-quantity of aerosol inhaled or exhaled.…”

“…As discussed by Davies et al (1972) and Heyder et al (1973a), the main difficulty in calculating the fractional deposition D is that the volume exhaled T$ and the volume inhaled y are rarely equal. If the quantity exhaled is less than that inhaled, the recovery of aerosol is reduced.…”

“…Plots of recovery against the ratio T/,/K will therefore show a systematic trend, low recovery correlating with T/,/K V, 1. Interpolation from such plots will yield the steady state deposition (at T/,/K = I), even if the subject never satisfies the criterion V, = K 10% suggested by Davies et al (1972). If air at ambient humidity is breathed in, the air will take up moisture in the lungs, and this will cause it to expand.…”

“…Davies proposed a method of calculation applicable to trained subjects using any type of apparatus in whch inhaled and exhaled concentrations are measured continuously (Davies 1964(Davies , 1972Davies et al, 1972Davies et al, , 1977Heyder et al, 1973aHeyder et al, , 1973bHeyder et al, , 1975Heyder et al, , 1978, breathng at fixed frequency without respiratory pauses, and with tidal volume held constant to $1096.…”