– Pulmonary ventilation is commonly referred to as breathing. It is the process of air flowing into the lungs during inspiration (inhalation) and out of the lungs during expiration (exhalation). Air flows because of pressure differences between the atmosphere and the gases inside the lungs.
– The body needs a way to get oxygen in and carbon dioxide out, which is through diffusion
– The carbon dioxide moves from the blood to the alveoli, where it can be exhaled through the lungs.
– Gas exchange is the delivery of oxygen from the lungs to the bloodstream, and the elimination of carbon dioxide from the bloodstream to the lungs. It occurs in the lungs between the alveoli and a network of tiny blood vessels called capillaries, which are located in the walls of the alveoli.
Blood Gas transport
– Oxygen is transported in the blood in two ways: A small amount of O 2 (1.5 percent) is carried in the plasma as a dissolved gas. Most oxygen (98.5 percent) carried in the blood is bound to the protein hemoglobin in red blood cells. A fully saturated oxyhemoglobin (HbO 2) has four O 2 molecules attached.
– Also deals with CO2 which has important effects on acid base balance
– Your blood needs the right balance of acidic and basic (alkaline) compounds to function properly. This is called the acid-base balance. Your kidneys and lungs work to maintain the acid-base balance.
Control of Ventilation
– The control of ventilation refers to the physiological mechanisms involved in the control of breathing, which is the movement of air into and out of the lungs.
Weibel Model of Airways
– The Weibel “A” model, developed in 1963, treats the lung as a single unit with regular, symmetric bifurcations although it is known that in the right lung the first generation airway produces three second generation airways while the left lung only gives rise to two second generation airways.
– The terminal bronchiole is the most distal segment of the conducting zone. It branches off the lesser bronchioles. Each of the terminal bronchioles divides to form respiratory bronchioles which contain a small number of alveoli. Terminal bronchioles are lined with simple cuboidal epithelium containing club cells.
Anatomic Dead Space
– Anatomic dead space is the total volume of the conducting airways from the nose or mouth down to the level of the terminal bronchioles, and is about 150 ml on the average in humans. The anatomic dead space fills with inspired air at the end of each inspiration, but this air is exhaled unchanged.
– Tidal volume (symbol VT or TV) is the lung volume representing the normal volume of air displaced between normal inhalation and exhalation when extra effort is not applied. In a healthy, young human adult, tidal volume is approximately 500 mL per inspiration or 7 mL/kg of body mass.
– Alveolar ventilation is the exchange of gas between the alveoli and the external environment. It is the process by which oxygen is brought into the lungs from the atmosphere and by which the carbon dioxide carried into the lungs in the mixed venous blood is expelled from the body.
– A spirometer is an apparatus for measuring the volume of air inspired and expired by the lungs. A spirometer measures ventilation, the movement of air into and out of the lungs. The spirogram will identify two different types of abnormal ventilation patterns, obstructive and restrictive.
– Residual volume is the amount of air that remains in a person’s lungs after fully exhaling. Doctors use tests to measure a person’s residual air volume to help check how well the lungs are functioning.
– Vital capacity is the maximum amount of air a person can expel from the lungs after a maximum inhalation. It is equal to the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume. A person’s vital capacity can be measured by a wet or regular spirometer.
Total Lung Capacity
– The volume of air contained in the lungs at the end of a maximal inspiration.
Functional Residual Capacity
– Functional Residual Capacity is the volume of air present in the lungs at the end of passive expiration. At FRC, the opposing elastic recoil forces of the lungs and chest wall are in equilibrium and there is no exertion by the diaphragm or other respiratory muscles.
Helium Dilution Technique
– The helium dilution technique is the way of measuring the functional residual capacity of the lungs. This technique is a closed-circuit system where a spirometer is filled with a mixture of helium and oxygen. The amount of He in the spirometer is known at the beginning of the test.
– A plethysmograph is an instrument for measuring changes in volume within an organ or whole body (usually resulting from fluctuations in the amount of blood or air it contains).
– Boyle’s law, most often referred to as the Boyle–Mariotte law, or Mariotte’s law, is an experimental gas law that describes how the pressure of a gas tends to increase as the volume of the container decreases.
– Dead space is the volume of air that is inhaled that does not take part in the gas exchange, because it either remains in the conducting airways or reaches alveoli that are not perfused or poorly perfused. In other words, not all the air in each breath is available for the exchange of oxygen and carbon dioxide.