Lecture 3.1: Lung Ventilation Flashcards
(38 cards)
How much oxygen should blood pick up in the lungs at rest?
5 liters of blood must pick up 12 mmol of oxygen per minute
How many alveoli do we have?
300 million alveoli (each surrounded by a capillary)
What is the order of sub-divisions in the lung airways?
• Trachea branches
• Main bronchi (right and left)
• Lobar bronchi (3 on right 2 on left)
• Segmental bronchi
• Sub-segmental bronchi
• Bronchioles
• Terminal bronchioles
• Respiratory bronchioles
• Alveolar ducts
• Alveoli
What is the difference between the walls of bronchi and bronchioles?
• Bronchi have cartilage in walls
• Bronchioles do not but do have more
smooth muscle
What is the importance of the hydrostatic pressure gradient?
Drives fluid from the pulmonary microcirculation into the interstitium
What is the importance of the oncotic pressure (colloidal osmotic pressure)?
Gradient favours movement of fluid in the opposite direction
How does ‘alveolar air’ have a different composition to the atmosphere?
• Less Oxygen
• More Carbon Dioxide
• As gas exchange removes oxygen from and
adds carbon dioxide to alveolar air
Mixed Venous Blood: pO2? pCO2?
• Returns to the lungs from the body
• pO2 typically 6.0 kPa
• pCO2 typically 6.5 kPa
• This varies with metabolism
Alveolar Air: pO2? pCO2?
• pO2 normally 13.3 kPa
• pCO2 normally 5.3 kPa
What are the 3 factors that affect Diffusion?
1) Area: Large (exchange area in normal lung
70m2)
2) Gradients: Large
3) Diffusion Resistance
Diffusion Barrier
• Diffusion through gas to alveolar wall
• Epithelial cell of alveolus
• Tissue Fluid
• Endothelial Cell of Capillary
• Plasma
• Red Cell Membrane
What machine is used to measure ventilation?
Spirometer
How to use a Spirometer?
• Subject breathes from a closed chamber
over water
• Whose volume changes with ventilation
What is Tidal Volume?
• Volume in and out with each breath
• In males: 0.5L
• In females: 0.5L
What is Inspiratory Reserve Volume?
• Extra volume that can be breathed in over
that at rest
• In males: 3.3L
• In females: 1.9L
What is Expiratory Reserve Volume?
• Extra volume that can be breathed out
over that at rest
• In males: 1.1L
• In females: 0.7L
What is Residual Volume? How to measure it?
• Volume left in lungs at maximal expiration
(0.8L)
• Volume does not change
• Cannot be measured by spirometer
• Use helium dilution
Lung Capacities vs Lung Volumes
• Lung volumes change with breathing pattern
• Capacities do not change
• Because measured from fixed points in breathing cycle
What are the 4 measured Lung Capacities?
- Vital capacity (VC) (can be measured by spirometers)
- Total lung capacity (TLC)
- Inspiratory capacity (IC) (can be measured by spirometers)
- Functional residual capacity (FRC)
What is Vital Capacity?
• Measured from max inspiration to max expiration
• Often changes in disease
• Typically 5L
• Total Lung Capacity = Vital Capacity + Reserve Volume
What is Inspiratory Capacity?
• Biggest breath that can be taken from resting expiratory level
• Typically 3.8L
What is Functional Residual Capacity?
• Volume of air in lungs at resting expiratory level
• Typically 2L
• Functional Residual Capacity = Expiratory Reserve Volume + Residual Volume
What is Ventilation Rate?
The amount of air moved into and out of a space per minute product of:
1) Volume moved per breath
2) Respiratory Rate
What is Pulmonary Ventilation Rate?
• Tidal volume x respiratory rate
• Typically 8l.min-1 at rest
• Can exceed 80 l.min-1 in exercise
