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31.O.04 Aerosol dispersion in human airways during one breathing cycle: The dependence of the aerosol penetration
J. Aerosol Sci., Vol. 25, Suppl. I, pp. $553-$554, 1994 Copyright~1994 Elsevier Science Ltd
Pergamon
31 0
04
'° ° "
0021-8502/94 $7.00 + 0.00
AEROSOL DISPERSION IN HUMAN AIRWAYS DURING ONE BREATHING CYCLE:
THE DEPENDENCE OF THE AEROSOL P E N E T R A T I O N
G. SCHEUCH and W. STAHLHOFEN GSF - Forschungszentrum for Umwelt und Gesundheit Institut far Biophysikalische Strahlenforschung Paul-Ehrlich Strasse 20, D-60596 Frankfurt am Main, Germany
KEYWORDS Aerosol Dispersion, Inhalation, Health Effects, Aerosol Inhalation, Aerosol Bolus
The dispersion of small aerosol boluses in the human lungs has been studied in healthy subjects. The dispersion of the aerosol is related to the volumetric lung depth, V L, to which it had been penetrated into the respiratory system (Muir et al., 1971). Most of the results that were published until now measured dispersion when the aerosol boluses penetrated to V L > 100 cm 3. In this study dispersion was measured in much shallower lung depth (V L = 20 - 100 cm3), additionally. It can be shown that the dispersion mechanisms in the conducting airways are entirely different from that in the peripheral lung. With an aerosol inhalation device (Scheuch et al., 1989) small volumes of aerosols ("boluses") were injected by a fast operating valve system during the inhalation of a single breath of clean air. The valve system was computer controlled and could deliver a bolus of aerosol into the inhaled airstream at any preselected volume. In this way penetration of the boluses into the human lungs could be varied. The aerosol concentration was measured with a laser photometer directly in front of the mouth during inhalation and exhalation. The respired volumes were determined by integrating the respired flow rates measured with Fleisch manometers. Aerosol dispersions in the human lungs during a breathing cycle were investigated by measuring the broadening of the bolus in the exhaled air. To minimize particle losses by diffusion and by inertial forces monodisperse sebacate aerosols were used with droplets in the aerodynamic size range between dae = 0.8 - 1.1 lam. To minimize aerosol dispersion in the mouth cavity an individually shaped mouthpiece filled at least 50 cm 3 of the subject's mouth. The subject inhaled and exhaled with a constant flow rate of 250 cm3/s. The volumetric half widths of the inhaled boluses were VHWin = 15 (__.4)cm3. Two measures for bolus dispersion were used: i) the standard deviation of the expired aerosol concentration distribution (a5) ii) the volumetric half-width of the expired bolus (VHw). Both measures were corrected by the volume of the inhaled bolus. VHw = ( VHWex2 _ Vrtwin 2 )1/2 Where the indexes (in and ex) represent inhalation and exhalation, respectively. The effect of the physical motion of the heart on these measurements has been investigated by increasing the heart rate of a subject by exercise by more than a factor of 2. It was shown that the motion of the heart did not considerably affect dispersion of the inspired $553
$554
G. SCHEUCH and W. STAHLHOFEN
and expired bolus in shallow lung depths but it was found an increase of dispersion for boluses penetrated to more peripheral lung depths (Scheuch and Stahlhofen, 1991). 1000
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11111
• Volumetric Haft Width
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• Standarddevlation
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100
200
300
400
500
600
VOLUMETRIC
700
LUNG DEPTH, crns
Fig. 1: Bolus dispersion of the expired aerosol boluses as function of the volumetric lung depths. The increasing dispersion of the aerosol boluses as they were drawn deeper into the lung is illustrated in Figure 1. Both o 5 and Vnw plotted as function of V L showed a similar tendency. The increase in dispersion during the first 150 cm 3 is much steeper as in the deeper lung regions. This shows clearly that dispersion mechanisms in the airways are different from the aerosol dispersion in the peripheral lung. The branching of the airways might play an important role on these effects. Experiments with realistic airway casts and theoretical studies are necessary to explain these results.
ACKNOWLEDGMENT This study was partially supported by the CEC under Contract F13PCT920064A. REFERENCES
MUIR, D.C.F., K. SWEETLAND, R.G. LOVE, (1971). Inhaled aerosol boluses in man. in: Inhaled Particles III, Ed. W.H. WALTON. Unwin Brothers Ltd., Surrey, 81-90. SCHEUCH, G., J. GEBHART, G. HEIGWER, W. STAHLHOFEN, (1989). A New Device for Human Inhalation Studies with small Aerosol Boluses. J. Aerosol Sci. 20, 1293-1296. SCHEUCH, G., and W. STAHLHOFEN, (1991). Effect of Heart Rate on Aerosol Recovery and Dispersion in Human Conducting Airways After Periods of Breathholding. Experimental Lung Research 17, 763-787.
Pergamon
31 0
04
'° ° "
0021-8502/94 $7.00 + 0.00
AEROSOL DISPERSION IN HUMAN AIRWAYS DURING ONE BREATHING CYCLE:
THE DEPENDENCE OF THE AEROSOL P E N E T R A T I O N
G. SCHEUCH and W. STAHLHOFEN GSF - Forschungszentrum for Umwelt und Gesundheit Institut far Biophysikalische Strahlenforschung Paul-Ehrlich Strasse 20, D-60596 Frankfurt am Main, Germany
KEYWORDS Aerosol Dispersion, Inhalation, Health Effects, Aerosol Inhalation, Aerosol Bolus
The dispersion of small aerosol boluses in the human lungs has been studied in healthy subjects. The dispersion of the aerosol is related to the volumetric lung depth, V L, to which it had been penetrated into the respiratory system (Muir et al., 1971). Most of the results that were published until now measured dispersion when the aerosol boluses penetrated to V L > 100 cm 3. In this study dispersion was measured in much shallower lung depth (V L = 20 - 100 cm3), additionally. It can be shown that the dispersion mechanisms in the conducting airways are entirely different from that in the peripheral lung. With an aerosol inhalation device (Scheuch et al., 1989) small volumes of aerosols ("boluses") were injected by a fast operating valve system during the inhalation of a single breath of clean air. The valve system was computer controlled and could deliver a bolus of aerosol into the inhaled airstream at any preselected volume. In this way penetration of the boluses into the human lungs could be varied. The aerosol concentration was measured with a laser photometer directly in front of the mouth during inhalation and exhalation. The respired volumes were determined by integrating the respired flow rates measured with Fleisch manometers. Aerosol dispersions in the human lungs during a breathing cycle were investigated by measuring the broadening of the bolus in the exhaled air. To minimize particle losses by diffusion and by inertial forces monodisperse sebacate aerosols were used with droplets in the aerodynamic size range between dae = 0.8 - 1.1 lam. To minimize aerosol dispersion in the mouth cavity an individually shaped mouthpiece filled at least 50 cm 3 of the subject's mouth. The subject inhaled and exhaled with a constant flow rate of 250 cm3/s. The volumetric half widths of the inhaled boluses were VHWin = 15 (__.4)cm3. Two measures for bolus dispersion were used: i) the standard deviation of the expired aerosol concentration distribution (a5) ii) the volumetric half-width of the expired bolus (VHw). Both measures were corrected by the volume of the inhaled bolus. VHw = ( VHWex2 _ Vrtwin 2 )1/2 Where the indexes (in and ex) represent inhalation and exhalation, respectively. The effect of the physical motion of the heart on these measurements has been investigated by increasing the heart rate of a subject by exercise by more than a factor of 2. It was shown that the motion of the heart did not considerably affect dispersion of the inspired $553
$554
G. SCHEUCH and W. STAHLHOFEN
and expired bolus in shallow lung depths but it was found an increase of dispersion for boluses penetrated to more peripheral lung depths (Scheuch and Stahlhofen, 1991). 1000
IL.IIIII..
Z 0 uJ O.
.
I
.
.
...iiiiiii ...... i .. i ii. i.iii,
....
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
. ....... .
.
.
.
.
.
.
. .. .
.
.
.
.
.
.
................
.
.
.
:.~..-~.:.:.T"
. . . . . . . . . .
11111
• Volumetric Haft Width
10 0
• Standarddevlation
[
I
I
I
l
1
100
200
300
400
500
600
VOLUMETRIC
700
LUNG DEPTH, crns
Fig. 1: Bolus dispersion of the expired aerosol boluses as function of the volumetric lung depths. The increasing dispersion of the aerosol boluses as they were drawn deeper into the lung is illustrated in Figure 1. Both o 5 and Vnw plotted as function of V L showed a similar tendency. The increase in dispersion during the first 150 cm 3 is much steeper as in the deeper lung regions. This shows clearly that dispersion mechanisms in the airways are different from the aerosol dispersion in the peripheral lung. The branching of the airways might play an important role on these effects. Experiments with realistic airway casts and theoretical studies are necessary to explain these results.
ACKNOWLEDGMENT This study was partially supported by the CEC under Contract F13PCT920064A. REFERENCES
MUIR, D.C.F., K. SWEETLAND, R.G. LOVE, (1971). Inhaled aerosol boluses in man. in: Inhaled Particles III, Ed. W.H. WALTON. Unwin Brothers Ltd., Surrey, 81-90. SCHEUCH, G., J. GEBHART, G. HEIGWER, W. STAHLHOFEN, (1989). A New Device for Human Inhalation Studies with small Aerosol Boluses. J. Aerosol Sci. 20, 1293-1296. SCHEUCH, G., and W. STAHLHOFEN, (1991). Effect of Heart Rate on Aerosol Recovery and Dispersion in Human Conducting Airways After Periods of Breathholding. Experimental Lung Research 17, 763-787.