Airway resistance

From Wikipedia, the free encyclopedia

Airway resistance is a concept used in respiratory physiology to describe mechanical factors which limit the access of inspired air to the pulmonary alveoli, and thus determine airflow.

Resistance is greatest at the bronchi of intermediate size, in between the fourth and eighth bifurcation.^[1]

Because airway resistance is dictated by the diameter of the airways and by the density of the inspired gas, the low density of heliox reduces airway resistance, and makes it easier to ventilage the lungs.

Resistance can be calculated using Ohm's law^[2] or Poiseuille's law.^[3]

Contents

1 Ohm's law
2 Poiseuille's law
3 See also
4 References
5 External links

$R = \frac {\Delta P}{V^*} = \frac {P_{mouth} - P_{alveoli}}{V^*}$

R = resistance
P = pressure
V* = airflow (the asterisk should be read as a dot over the letter, which is used to denote rate in respiratory physiology.)

$R = \frac{8nl}{\pi r^{4}}$

(rewrite)

R = resistance
n = viscosity
l = length
r = radius

Because of the fourth power in the denominator, resistance increases rapidly as diameter decreases.

v • d • e

Respiratory system, physiology: respiratory physiology

Volumes:

lung volumes - vital capacity - functional residual capacity - respiratory minute volume - dead space - spirometry - body plethysmography - peak flow meter

ventilation (V) (positive pressure) breath (inhalation, exhalation) - respiratory rate - respirometer - pulmonary surfactant - compliance - hysteresivity - airway resistance

pulmonary circulation - perfusion (Q) - hypoxic pulmonary vasoconstriction - pulmonary shunt

ventilation/perfusion ratio (V/Q) and scan - zones of the lung - gas exchange - pulmonary gas pressures - alveolar gas equation - hemoglobin - oxygen-haemoglobin dissociation curve (2,3-DPG, Bohr effect, Haldane effect) - carbonic anhydrase (chloride shift) - oxyhemoglobin - respiratory quotient - arterial blood gas - diffusion capacity - Dlco

control of respiration: pons (pneumotaxic center, apneustic center) - medulla (dorsal respiratory group, ventral respiratory group) - chemoreceptors (central, peripheral) - pulmonary stretch receptors - Hering-Breuer reflex

high altitude - oxygen toxicity - hypoxia

Retrieved from "http://en.wikipedia.org../../../a/i/r/Airway_resistance.html"

Category: Respiration

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