Ventilation (physiology)

In respiratory physiology, ventilation is the movement of air between the environment and the lungs via inhalation and exhalation. Thus, for organisms with lungs, it is synonymous with breathing. Ventilation usually happens in a rhythmic pattern, and the frequency of that pattern is called the ventilation rate (or, by long-standing convention, the respiratory rate, although in precise usage ventilation is a hyponym, not a synonym, of respiration).

Ventilation volumes and rates are categorized under the following definitions:

Measurement	Symbol	Equation	Description
Minute ventilation	${\dot {V}}_{E}$	= tidal volume * respiratory rate^[1]^[2]	the total volume of gas entering the lungs per minute.
Alveolar ventilation	${\dot {V}}_{A}$	= (tidal volume - dead space) * respiratory rate ^[1]	the volume of gas per unit time that reaches the alveoli, the respiratory portions of the lungs where gas exchange occurs.
Dead space ventilation	${\dot {V}}_{D}$	= dead space * respiratory rate^[3]	is the volume of gas per unit time that does not reach these respiratory portions, but instead remains in the airways (trachea, bronchi, etc.).

Sample values

Measure	Sample value at rest	Sample value moderate exercise^[4]
Tidal volume	0.5 L	3.0 L
Respiratory rate	12 breaths/minute	30 breaths/minute
Minute ventilation	6.0 L/min	90 L/min
Dead space	0.15 L	0.15 L
Dead space ventilation	1.8 L/min	4.5 L/min
Alveolar ventilation	4.2 L/min	85.5 L/min
Functional residual capacity (FRC)	2.5 L	2.5 L
Specific Ventilation (Tidal volume / FRC)	0.2

Pulmonary ventilation may be evaluated using a breathing tube or spirometer, measuring the movement of the chest and abdominal walls using respiratory inductance plethysmography or by isolating the subject in an enclosed metabolic chamber (body plethysmography).

1 2 Respiratory Physiology: Ventilation
↑ Respiratory Physiology (page 2)
↑ Physiology: 4/4ch3/s4ch3_16 - Essentials of Human Physiology
↑ Int Panis, L (2010). "Exposure to particulate matter in traffic: A comparison of cyclists and car passengers". Atmospheric Environment. 44: 2263–2270. doi:10.1016/j.atmosenv.2010.04.028.

Respiratory physiology

Respiration	breath inhalation exhalation respiratory rate respirometer pulmonary surfactant compliance elastic recoil hysteresivity airway resistance bronchial hyperresponsiveness constriction dilatation mechanical ventilation

Control	pons pneumotaxic center apneustic center medulla dorsal respiratory group ventral respiratory group chemoreceptors central peripheral pulmonary stretch receptors Hering–Breuer reflex

Lung volumes	VC FRC Vt dead space CC PEF calculations respiratory minute volume FEV1/FVC ratio Lung function tests spirometry body plethysmography peak flow meter nitrogen washout

Circulation	pulmonary circulation hypoxic pulmonary vasoconstriction pulmonary shunt

Interactions	ventilation (V) Perfusion (Q) V/Q scan zones of the lung gas exchange pulmonary gas pressures alveolar gas equation alveolar–arterial gradient hemoglobin oxygen–haemoglobin dissociation curve (Oxygen saturation 2,3-BPG Bohr effect Haldane effect) carbonic anhydrase (chloride shift) oxyhemoglobin respiratory quotient arterial blood gas diffusion capacity (DLCO)

Insufficiency	high altitude oxygen toxicity hypoxia

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