Breathing Flashcards
Creating pressure gradient
As you inhale your diaphragm drops while your rib cage expands. This increases the volume in your chest, which lowers the pressure
Atmosphere pressure is zero - difference relative to atmospheric pressure is what we refer to when we talk about pressure in and out of our lungs
Inhalation in pressure gradient
Lung volume is increasing, pressure inside lungs decreasing, pressure outside lung is greater than inside so air rushes in
Exhalation in pressure gradient
Lung volume is decreasing, pressure inside lungs increasing, pressure outside lung is lower than inside so air rushes out
Direction of airflow
Direction of airflow is determined by difference between atmospheric pressure and intrapulmonary pressure (pressure inside the lungs)
What two opposing forces need to be overcome to take a breath?
Stiffness : Amount of elastic tissue in lungs (more elastic tissue, low stretching, low compliance), Lungs expand to take in air, How compliant the lungs are, Surface tension holds lungs in place
Resistance : Need to move air from outside to alveoli, How much resistance the respiratory tract is putting on the movement of air
Compliance in lung stiffness
Defined as the magnitude of the change in lung volume produced by the given change in the pressure C=V/P
Low compliance in lungs
Low compliance means stiff lungs hence need to do more work to expand. Lungs very resistant to stretching, high amount of pressure required to change volume. Thickening and scarring of the alveolar membranes. Shallow breathes but occur more rapidly. Can arise from chronic inflammation or exposure to industrial chemicals
Surface tension in the lungs
Surface tension - tendency of a fluid surface to occupy the smallest possible surface area
Alveoli are lined with fluid that exert surface tension. Walls of alveoli are very thin, enhancing this effect, must overcome surface tension to expand the lungs. Surface tension creates a very stiff lung and causes the lung itself to collapse
What is surfactant?
Surfactant reduces surface tension in alveoli - makes them easier to expand and stops attractive forces pulling molecules together (lungs don’t collapse)
Where is surfactant produced?
Produced by alveolar type II pneumocytes, major constituent is phospholipids. Lowers surface tension, reduces attractive forces between fluid molecules lining alveoli and easier to increase lung size (increased compliance)
What happens if you have a lack of surfactant?
Lack of surfactant/failure to produce adequate surface means stiff lungs (compliance reduced). Premature infants do not produce surfactant, results in respiratory distress syndrome (RDS)
Airway resistance through respiratory tract
Need to move air from outside to the alveoli. Air is conducted through the bronchi and bronchioles. Exert force (friction) on the air that must be overcome. The small airways (terminal and respiratory bronchioles) contribute very little to airway resistance due to high CSA, most resistance comes from bronchi
What is a spirometer?
Spirometer measures volume inspired/exhaled. Common, simple test and can measure how much and how fast you breathe
What are the five spirometry trace volumes?
Tidal volume: volume of air moved in and out during normal quiet breath
Inspiratory reserve volume: extra volume that can be inhaled over and above the tidal volume
Expiratory reserve volume: extra volume that can be exhaled voluntarily after completion of a normal, quiet respiratory cycle
Residual volume: volume remaining in lungs after maximal exhalation
Minimal volume: volume remaining in lungs if they collapse
What are the four spirometry trace capacities?
Vital capacity: volume of air that can be moved in and out of your lungs (IRV + ERV + VT)
Total lung capacity: total volume in lungs when it is filled to max (Vital capacity + residual volume)
Inspiratory capacity: total volume of air that can be inspired from rest (IRV + VT)
Functional residual capacity: volume remaining in lungs after normal exhalation (ERV + residual volume)
