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Ventilation–perfusion coupling is the relationship between ventilation and perfusion processes, which take place in the respiratory system and the cardiovascular system. [1] Ventilation is the movement of gas during breathing, and perfusion is the process of pulmonary blood circulation , which delivers oxygen to body tissues. [ 2 ]
In respiratory physiology, the ventilation/perfusion ratio (V/Q ratio) is a ratio used to assess the efficiency and adequacy of the ventilation-perfusion coupling and thus the matching of two variables: V – ventilation – the air that reaches the alveoli; Q – perfusion – the blood that reaches the alveoli via the capillaries
The ventilation/perfusion ratio (V/Q ratio) is higher in zone #1 (the apex of lung) when a person is standing than it is in zone #3 (the base of lung) because perfusion is nearly absent. However, ventilation and perfusion are highest in base of the lung, resulting in a comparatively lower V/Q ratio.
Exchange of gases in the lung occurs by ventilation and perfusion. [1] Ventilation refers to the in-and-out movement of air of the lungs and perfusion is the circulation of blood in the pulmonary capillaries. [1] In mammals, physiological respiration involves respiratory cycles of inhaled and exhaled breaths.
The control of ventilation is the physiological mechanisms involved in the control of breathing, which is the movement of air into and out of the lungs. Ventilation facilitates respiration. Respiration refers to the utilization of oxygen and balancing of carbon dioxide by the body as a whole, or by individual cells in cellular respiration. [1]
The volume of air that moves in or out (at the nose or mouth) during a single breathing cycle is called the tidal volume. In a resting adult human, it is about 500 ml per breath. At the end of exhalation, the airways contain about 150 ml of alveolar air which is the first air that is breathed back into the alveoli during inhalation.
Lung volumes and lung capacities refer to the volume of air in the lungs at different phases of the respiratory cycle. The average total lung capacity of an adult human male is about 6 litres of air. [1] Tidal breathing is normal, resting breathing; the tidal volume is the volume of air that is inhaled or exhaled in only a single such breath.
Pulmonary function testing is a safe procedure; however, there is cause for concern regarding untoward reactions and the value of the test data should be weighed against potential hazards. Some complications include dizziness, shortness of breath, coughing, pneumothorax, and inducing an asthma attack.