Airway_resistance

Airway resistance

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 ventilate the lungs.

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

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

Ohm's law

$R = \frac {\Delta P}{\dot V} = \frac {P_{\mathrm{mouth}} - P_{\mathrm{alveoli}}}{\dot V}$

$R$ = resistance
$P$ = pressure
$\dot V$ = airflow (the dot over the letter is used to denote rate in respiratory physiology.)

Poiseuille's law

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

(rewrite)

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

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

References

External links

v • d • e Respiratory system, physiology: respiratory physiology

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

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

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

Interactions	ventilation/perfusion ratio (V/Q) and scan - zones of the lung - gas exchange - pulmonary gas pressures - alveolar gas equation - alveolar-arterial gradient - 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)

Insufficiency	high altitude - oxygen toxicity - hypoxia

Contents

Ohm's law

Poiseuille's law

See also

References

External links