Page 275 - Industrial Ventilation Design Guidebook

236 CHAPTER 5 PHYSIOLOGICAL AND TOXICOLOGICAL CONSIDERATIONS

Distal: In the airways, positioned relatively further from the nares.
Donnan equilibrium: Both concentration gradients and charge gradients
contribute to the distribution of ions on either side of a membrane.
Consequently, if there is a concentration gradient of an impermeable
charged solute (e.g., protein) across a semipermeable membrane, then
concentrations of permeable ions on either side of the membrane will
not be equal.
Dose-dependent: Response to applied stimuli directly proportional to con-
centration of stimuli.
Edema: Excessive accumulation of fluid in cells, interstitial spaces, or tissues.
Eddy currents: Vortices that characterize turbulent flow.
End-expiratory: Airstream conditions measured when expiration ceases and
just prior to initiating inspiration.
Endogenous ammonia: Byproduct of metabolism and bacterial catabolism
that diffuses into the airway lumen. Highest concentrations are found in
the oral cavity.
Endothelium: Layer of flat cells lining blood vessels.
Entrance flow: Flow within the inlet region of a conduit that has not devel-
oped a parabolic velocity profile. Airflows within the respiratory tract are
not fully developed (parabolic) because of the relatively short tube lengths
and irregular geometry.
Epiglottis: Leaf-shaped cartilage which closes larynx during swallowing.
Epiphase: Airway surface liquid gel layer composed of mucins in the form
of droplets, sheets, or blankets.
Epithelium: Cellular layer interfacing with external environment which con-
tains no blood vessels. In the airway, the epithelium lines the airway lumen.
Expiratory reserve volume (ERV): Maximum additional volume one can
expire from end-tidal expiration.
Extrapulmonary airways: All airways not involved in gas exchange. These
include the extrathoracic airways and the tracheobronchial tree down to
the terminal bronchioles.
Extrathoracic airways: The portion of the human conducting airways prox-
imal to and including the larynx. Also called the upper airways.
Fibroelastic: Fibrous material possessing elastic properties. In the airway, fi-
broelastic tissue throughout the lung contributes to its overall elasticity,
generating a positive recoil force at the functional residual capacity, or
resting state of the lungs.
Flow distortion: Nonuniform airstream velocity profile due to asymmetric
shear, as in inspiratory bronchial airflow distal to a bifurcation.
Flow separation: Formation of turbulent eddies away from boundary as
flow streamlines diverge.
Forced expired volume (FEV f): Gas volume forcibly expired within the time
interval t (typically t = 1.0 seconds).
Forced vital capacity (FVC): Maximum forced expired volume following a
maximum inspiratory effort.
Fully conditioned airstream: Inspired airstream which has been warmed
and humidified to approximate alveolar conditions (theoretically 37 °C,
100% relative humidity).