Lecture 17: The Work of Breathing Flashcards
How is the pressure of gas related to its volume?
Inversely proportional
What is boyles law?
P = 1/V
What happens to pressure right before a breath?
The pressure outside the body and inside the lungs are equal so no air is moving
How does gas move?
From high pressure to low pressure
What happens as you inhale?
Your diaphragm drops while your rib cage expands
During inhalation what does the expansion of your chest do to pressure?
Lowers pressure
What happens to lung volume during inhalation?
It increases
What happens to pressure during inhalation?
Pressure inside the lungs decreases
What happens to air as a result of decreased pressure inside the lungs during inhalation?
Air rushes in
What happens to lung volume during exhalation?
It decreases
What happens to pressure during exhalation?
Pressure inside the lungs increases
What happens to air as a result of increased pressure inside the lungs during exhalation?
Air rushes out
What is the direction of airflow determined by?
A difference between atmospheric pressure and intrapulmonary pressure
What 2 opposing forces must be overcome to take a breath?
- Stiffness of the lungs
- Resistance of the airways to the lungs
What is lung stiffness related to?
Compliance
What is lung compliance?
Change in the lung volume produced by the given change in the pressure
What is a low lung compliance referred as?
Stiff lungs
What needs to happen for stiff lungs to expand?
More work to occur
What is pulmonary fibrosis?
Lung disease where lungs become too elastic resulting in a decreased compliance
What can cause scarring of the alveolar membranes?
Chronic inflammation or exposure to industrial chemicals
What happens to the compliance curve of lungs suffering from Pulmonary Fibrosis?
It lies lower and flatter on a graph
Alveoli are lined with fluid that does what?
Exerts surface tension
What enhances the effect of surface tension in Alveoli?
The walls of the alveoli are very thin
What must be overcome to expand the lungs?
Surface tension
What reduces the surface tension in alveoli?
Surfactant
What produces the surfactant used to reduce surface tension in alveoli?
Alveolar type II pneumocytes
What is the major constituent of surfactant used in Alveoli?
Phospholipids
What do phospholipids in surfactant do?
Reduce the attractive forces between fluid molecules lining alveoli making it easier to increase lung size
What does lack of surfactant/failure to produce adequate surfactant result in?
Stiff lungs
What does premature infants not producing surfactant result in?
Respiratory distress syndrome (RDS)
What is air conducted through?
The bronchi and bronchioles
What do the bronchi and bronchioles do to air moving through the respiratory tract?
Exert the force of friction that must be overcome
Where does most of the resistance to airflow occur as a result of a small cross sectional area?
In the Bronchi
How much resistance do the small airways (terminal and respiratory bronchioles) contribute to airway resistance?
Very little due to a high cross sectional area
What does a spirometer measure?
2
- Volume of air inhaled/exhaled
- How fast can you breathe
What is tidal volume?
The volume of air moved in and out during normal quiet breath
What is the typical tidal volume value?
500mL
What is inspiratory reserve volume (IRV)?
The extra volume that can be inhaled over and above the tidal volume
What is expiratory reserve volume (ERV)?
The extra volume that can be exhaled voluntarily after completion of a normal, quiet respiratory cycle
What is residual volume?
The volume remaining in lungs after maximal exhalation
What is minimal volume?
The volume remaining in lung if they collapsed
What is vital capacity?
The volume of air that can be moved in and out of your lungs
What is vital capacity a combination of?
Inspiratory reserve + Expiratory reserve + Tidal volume
What is total lung capacity?
Total volume in lungs when it is filled to max
What is total lung capacity a combination of?
Vital capacity + Residual volume
What is inspiratory capacity?
Total volume of air that can be inspired from rest (At the end of expiration)
What is inspiratory capacity a combination of?
Inspiratory reserve + Tidal volume
What is functional residual capacity?
Volume remaining in lung after normal exhalation
What is functional residual capacity a combination of?
Expiratory reserve + residual volume
What is forced expiratory volume in one second (FEV1)
How much of the forced vital capacity (FVC) comes out in the first second
What does disease do to FEV1?
It is reduced as there is an Increased resistance therefore reduced airflow
What is a normal FEV1/FVC ratio?
80%
What does an FEV1/FVC < 70% indicate?
airways are obstructed meaning an increased airway resistance
What can spirometry discern between?
Obstructive and restrictive issues
What is a result of a restrictive lung issue?
Reduced lung capacity
What is a result of a obstructive lung issue?
Increased resistance to airflow
What is an example of a restrictive lung issue?
Pulmonary fibrosis
What is an example of a obstructive lung issue?
Asthma, Chronic bronchitis
