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Airflow, pressure, and resistance
Alveolar gas equation
Breathing cycle and regulation
Diffusion-limited and perfusion-limited gas exchange
Fick's laws of diffusion
Gas exchange in the lungs, blood and tissues
Ideal (general) gas law
Reading a chest X-ray
Respiratory system anatomy and physiology
Alveolar surface tension and surfactant
Combined pressure-volume curves for the lung and chest wall
Compliance of lungs and chest wall
Carbon dioxide transport in blood
Oxygen binding capacity and oxygen content
Oxygen-hemoglobin dissociation curve
Anatomic and physiologic dead space
Lung volumes and capacities
Pulmonary changes at high altitude and altitude sickness
Pulmonary changes during exercise
Pulmonary chemoreceptors and mechanoreceptors
Regulation of pulmonary blood flow
Ventilation-perfusion ratios and V/Q mismatch
Zones of pulmonary blood flow
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The main job of the lungs is gas exchange, pulling oxygen into the body and getting rid of carbon dioxide.
Normally, during an inhale - the diaphragm and chest muscles contract to pull open the chest and suck in air like a vacuum cleaner, and then during an exhale - the muscles relax, allowing the lungs to spring back to their normal size pushing that air out.
Ventilation rates measure the volumes of air moving in and out of the lungs, over a period of time.
During normal quiet breathing, each breath of air that enters and leaves the lungs is about half a liter, which is called the tidal volume.
The respiratory rate is the number breath a person takes per minute. In an adult this is normally around 15 breath per minute at rest.
So the minute ventilation is the amount of air moved in and out of the lungs in a minute. So minute ventilation is given by
Minute Ventilation = (Tidal Volume) X (Respiratory Rate)
In a normal healthy adult, this means 500 ml per breath times 15 breaths per minute, or about 7.5 litres per minute.
However, not all the air that we breathe in reaches the alveoli, where gas exchange actually takes place.
Some air is trapped in the airways - an area called the anatomical dead space.
Also, some of the alveoli may be defective and can’t even participate in gas exchange.
When you add the volume of air lost in these malfunctioning alveoli to the anatomical dead space, you get the physiological dead space.
So to calculate alveolar ventilation, it’s the tidal volume minus the physiologic dead space and that volume gets multiplied by the respiratory rate:
Ventilation refers to the process of moving air in and out of the lungs. Alveolar ventilation refers to the amount of air that reaches the alveoli in the lungs for gas exchange. This determines the amount of oxygen that is available for the body to use, and the amount of carbon dioxide that is eliminated from the body.
Alveolar ventilation is determined by the tidal volume and the amount of dead space in the respiratory system. The formula for alveolar ventilation is (tidal volume - physiological dead space) x respiratory rate. Tidal volume is the amount of air that enters or leaves the lungs during a single normal breath; and physiological dead space refers to the portion of the respiratory system where air exchange does not occur, resulting in wasted ventilation.
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