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Geometry of airways and diffusive gas mixing in the lung
194
Abstracts MECHAMCAL CONSIDERATIONS IN THE COORDINATION OF SEQUENTIAL JOINT ACTIONS
C. A. PUTNAM (Biomechanics Laboratory, Department of Physical Education, University of Iowa, Iowa City, Iowa) The purposes of this investigation were : (1) to describe in detail the mechanical characteristics of two general, twosegment motions in which a definite sequencing of the segmental actions occur, and (2) to investigate the effects that changes in selected aspects of the segment motions have on the resulting performance. The mechanical descriptions were focused on the interaction between the two segments in terms of the forces and torques acting on each segment, the movement kinematics and angular momentum relations of the two segments. A series of motions were mathematically simulated to determine how the system might function within kinetic and kinematic constraints normally imposed on its motion. The results revealed several specific aspects of the timing of segmental actions which were critical to a high level of performance. LIFE IN A VELOCITY GRADIENT STEVEN VOGEL
(Department of Zoology, Duke University, Durham, NC 27706)
Fluids flowing across a surface do not “slip”at the surface ; instead there exists a region in the fluid adjacent to the surface within which the speed offlow gradually approaches the speed of the undisturbed fluid well away from the surface. This gradient region is a source of perils and opportunities to organisms attached to a surface. By the organisms’ efforts it may become depleted in food or dissolved gases, but it provides shielding from the full drag forces of the wind or current. Gametes, spores, or seeds, to be effectively dispersed by the flow, must not be released deep within the gradient region; but it constitutes a potential gradient from which energy may be extracted for a rich diversity of functions. ANALYSIS OF REGIONAL FILLING AND EMPTYING IN THE LUNG
W. R. Scorr and D. B. TAULBEE (Department of Engineering Science, State University of New York at Buffalo, Buffalo, NY 14214) Nonuniform distribution of gases inspired into the lung has been experimentally observed using radioactive tracer gases and external counters. These differences in the ventilation pattern have been theorized to be caused by regional differences in static transpulmonary pressure, which are related to gravity. A geometrical model was chosen to approximate the shape of the lung, and the transpulmonary pressure distribution and tissue displacements are computed using a simple hydrostatic equation, which equates the vertical transpulmonary pressure gradient to the local density of the lung tissue.The distribution of an inspired bolus of tracer gas and the ensuing washout are simulated. Close agreement with the measurements infer the plausibility of the assumptions. GEOMEITtY OF AIRWAYS AND H. D. VAN
LIES and K. R.
MURRAY
DIFFUSiVE GASMDUNG IN THE LUNG (State University of New York at Buffalo, But&lo, New York)
The lung is constructed to maximize diffusive mixing. We used Weibel’s morphometric data to calculate “diffusive time constants” from summed volume of each generation of airways, airway length, summed crosssectional area, and gas-phase diffusivity ; the V,LJDA, values were less than 0.1 set for all but the uppermost airways, whereas duration of a breath is several seconds. Factors that curtail diffusion such as short time (exercise),decrease of d8usivity (hyperbaric environments), and deterioration of airway geometry (disease) will increase the amount of inspired gas that remains unmixed in uppermost airways, but since upper airway volumes are small, there is minimal consequence to gas exchange. RELATIONSHIPS BEIWEEN TETHERED AND FREE SWIMMING THE FRONT CRAWL STROKE ALBERT
B. CRUG, JR. and WILLIAM F. BOOMER(Department of Physiology, School of Medicine and Dentistry, and Division of Sports and Recreation, University of Rochester, Rochester, NY 14642)
The maximal velocity of free swimming (u max.), the maximal force which could be developed when completely tethered (F,), and the velocities (uwt.) which could be obtained with a series of different retarding forces (DA) were measured for each subject. All of these tests demanded maximal effort for 5-6 sec. One group of 12 males and 26 females were nationally ranked swimmers who attended a camp at the US. Olympic Development Center. The others were 9 males and 9 females from the University of Rochester swimming teams. During the partially tethered swimming experiments the u wt. increased as the DA was decreased and the relationship could be described by v wt. = A(D,) + B. The calculated velocity when DA = 0 correlated well with the v max, and the calculated DA when u wt. = 0 correlated with Fr Thus the three independent tests were related. From the
Abstracts MECHAMCAL CONSIDERATIONS IN THE COORDINATION OF SEQUENTIAL JOINT ACTIONS
C. A. PUTNAM (Biomechanics Laboratory, Department of Physical Education, University of Iowa, Iowa City, Iowa) The purposes of this investigation were : (1) to describe in detail the mechanical characteristics of two general, twosegment motions in which a definite sequencing of the segmental actions occur, and (2) to investigate the effects that changes in selected aspects of the segment motions have on the resulting performance. The mechanical descriptions were focused on the interaction between the two segments in terms of the forces and torques acting on each segment, the movement kinematics and angular momentum relations of the two segments. A series of motions were mathematically simulated to determine how the system might function within kinetic and kinematic constraints normally imposed on its motion. The results revealed several specific aspects of the timing of segmental actions which were critical to a high level of performance. LIFE IN A VELOCITY GRADIENT STEVEN VOGEL
(Department of Zoology, Duke University, Durham, NC 27706)
Fluids flowing across a surface do not “slip”at the surface ; instead there exists a region in the fluid adjacent to the surface within which the speed offlow gradually approaches the speed of the undisturbed fluid well away from the surface. This gradient region is a source of perils and opportunities to organisms attached to a surface. By the organisms’ efforts it may become depleted in food or dissolved gases, but it provides shielding from the full drag forces of the wind or current. Gametes, spores, or seeds, to be effectively dispersed by the flow, must not be released deep within the gradient region; but it constitutes a potential gradient from which energy may be extracted for a rich diversity of functions. ANALYSIS OF REGIONAL FILLING AND EMPTYING IN THE LUNG
W. R. Scorr and D. B. TAULBEE (Department of Engineering Science, State University of New York at Buffalo, Buffalo, NY 14214) Nonuniform distribution of gases inspired into the lung has been experimentally observed using radioactive tracer gases and external counters. These differences in the ventilation pattern have been theorized to be caused by regional differences in static transpulmonary pressure, which are related to gravity. A geometrical model was chosen to approximate the shape of the lung, and the transpulmonary pressure distribution and tissue displacements are computed using a simple hydrostatic equation, which equates the vertical transpulmonary pressure gradient to the local density of the lung tissue.The distribution of an inspired bolus of tracer gas and the ensuing washout are simulated. Close agreement with the measurements infer the plausibility of the assumptions. GEOMEITtY OF AIRWAYS AND H. D. VAN
LIES and K. R.
MURRAY
DIFFUSiVE GASMDUNG IN THE LUNG (State University of New York at Buffalo, But&lo, New York)
The lung is constructed to maximize diffusive mixing. We used Weibel’s morphometric data to calculate “diffusive time constants” from summed volume of each generation of airways, airway length, summed crosssectional area, and gas-phase diffusivity ; the V,LJDA, values were less than 0.1 set for all but the uppermost airways, whereas duration of a breath is several seconds. Factors that curtail diffusion such as short time (exercise),decrease of d8usivity (hyperbaric environments), and deterioration of airway geometry (disease) will increase the amount of inspired gas that remains unmixed in uppermost airways, but since upper airway volumes are small, there is minimal consequence to gas exchange. RELATIONSHIPS BEIWEEN TETHERED AND FREE SWIMMING THE FRONT CRAWL STROKE ALBERT
B. CRUG, JR. and WILLIAM F. BOOMER(Department of Physiology, School of Medicine and Dentistry, and Division of Sports and Recreation, University of Rochester, Rochester, NY 14642)
The maximal velocity of free swimming (u max.), the maximal force which could be developed when completely tethered (F,), and the velocities (uwt.) which could be obtained with a series of different retarding forces (DA) were measured for each subject. All of these tests demanded maximal effort for 5-6 sec. One group of 12 males and 26 females were nationally ranked swimmers who attended a camp at the US. Olympic Development Center. The others were 9 males and 9 females from the University of Rochester swimming teams. During the partially tethered swimming experiments the u wt. increased as the DA was decreased and the relationship could be described by v wt. = A(D,) + B. The calculated velocity when DA = 0 correlated well with the v max, and the calculated DA when u wt. = 0 correlated with Fr Thus the three independent tests were related. From the