36. Respiratory biophysics & physical examination Flashcards
What is Henry’s law?
At constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is proportional to the partial pressure of that gas
What is the capillary phenomenon?
capillary pressure difference sustained across the interface between 2 static liquids due to surface tension
Henry’s law equation
p = k * c
Capillary phenomenon equation
dp = 2gamma / R
p : pressure
gamma : surface tension
R : radius of curvature
What doe surface tension result from?
surface tension results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion), causing an inward force at the surface (like an elastic mb)
What is intrapulmonary pressure
Pressure exerted by gases within the alveoli
How does intrapulmonary pressure change in the respiratory cycle?
it decreases as lung volume increases (inspiration)
How does intrathoracic pressure change in the respiratory cycle?
It becomes more negative as the chest wall expands during inspiration
What is the transmural / transpulmonary pressure?
Pressure difference across the chest wall
How many dichotomic division are there
23-25
How many alveoli are there?
About 300 million
Total alveolar area
About 100m²
3 membranes separating the gas exchange surfaces
- Alveolar epithelium
- basal membrane
- Endothelial membrane
What are the 4 lung volumes?
- Tidal volume
- Expiratory reserve volume
- Inspiratory reserve volume
- Residual volume
What are the 4 lung capacities?
- Vital lung capacity
- Inspiratory capacity
- Functional residual capacity
- Total lung capacity
What is functional residual capacity?
Volume of air in the lung after passive expiration
What are the major mechanisms that drive pulmonary ventilation? (3)
- Atmospheric pressure
- Alveolar pressure
- Intra-pleural pressure
What is eupnoe?
Normal breathing (14-16 /min)
What is polypnoe / tachypnoe?
Number of breaths over 16/min
What is dyspnoe?
Shortness of breath
Compliance formula
C = V / P
What is surfactant
protein produced by alveolar cells, reduces surface tension and thus reduces the pressure needed to keep the alveoli open
Usual transmural pressure
0.7 kPa
Usual respiratory volume
0.5 L
Average work of the lungs (formula and value)
W = Ptm * V
0.35 J / inspiration (294J/h)
What is inspection?
Visual examination of the patient
What do you analyze with inspection?
Behavior, morphology, structure, color
What is the cause of ictarus, jaundice?
Hyperbilirubinemia
What is palpation?
Examining the patient by touching
What do we analyze with palpation?
shape, location, firmness, elasticity, viscosity…
What is distensibility?
Ability to be able to stretch and expand under pressure
What is viscous matter?
Matter that resists shear flow and strain linearly with time when a stress is applied
When does extension of the spring stop?
When the elastic spring force equals that of the external force
What do we examine with percussion
Content, shape, boundaries
What are the types of percussion sounds?
Flat, dull and resonating
What is auscultation?
Examining the patient by listening to sound
What is the 1st Korotkow’s sound?
Sharp thuds, starts at systolic pressure
What is the 2nd Korotkow’s sound?
Blowing sound, almost silent
What is the 3rd K sound?
crisp thud, quieter than phase 1
What is the 4th sound?
Muffled sound
What is the 5th K sound?
End of sound, diastolic pressure
What sound does aortic stenosis produce?
systolic murmur
What sound does mitral stenosis produce?
diastolic murmur
What are pleural rubs and what can they be caused by?
mechanical vibrations, pleural friction due to inflammation or tumor
What is lung wheezing?
mechanical resonance, obstruction of the air (athma)
What are lung crackles?
Bubbling fluid through ducts (penumonia, bronchitis)
What is crepitation in the lungs?
heart valves closing / opening
What is the respiratory work?
Average energy invested to inhale and exhale a breathing gas
What are the 3 types of lung sounds?
- Mechanical vibrations (rubs)
- Mechanical resonance (wheezing)
- Bubbling through fluid (crackles)
