Physiology: biomechanics of breathing Flashcards
Does the pulmonary circulation have low pressure and low resistance?
Yes
Differentiate bulk flow, Boyle’s law, Dalton’s law, and Henry’s law
Differentiate atmospheric pressure, intrapulmonary (alveolar) pressure, intrapleural pressure, transpulmonary pressure
Inhalation
- What happens to diaphragm and external intercostal muscles (relaxation/contraction, direction of movement)? What happens to thoracic volume?
- What does negative intrapleural do to the lung volume?
- Consequence of this on lung pressure vs atmospheric pressure?
- Consequence on air flow?
- When does air flow stop?
Both contract. Diaphragm goes down, external intercostal muscles moves ribcage up and out
Thoracic volume increases
Stretches lungs with the thoracic cavity borders - increasing lung volume.
Decreases lung pressure.
Air flows into lungs until lung pressure = air pressure
Exhalation
- What happens to diaphragm and external intercostal muscles (relaxation/contraction)? What happens to thoracic volume?
- What causes the lungs to decrease in volume?
- Consequence of this on lung pressure vs atmospheric pressure?
- Consequence on air flow?
- When does air flow stop?
Contract, decreases.
Elastic recoil ofthe lungs.
Increases lung pressure; air flows out of lungs until alveolar pressure = air pressure
Compliance:
- What does it measure?
- What is its equation?
When you change the pressure, how easily the volume changes
C = ∆V/∆P
Low compliance: small changes in pressure causes a ______ change in volume
High compliance: small changes in pressure causes a ___ change in volume
small, large
Do elastic fibres increase or decrease compliance?
They increase compliance (easier to blow up elastic balloon than collagen balloon!)
Does surface tension increase or decrease compliance?
Decreases compliance
What is the effect of surfactant on surface tension and thus compliance?
Surfactant decreases the surface tension of the alveoli, thus increasing the compliance of the lungs. Thus preventing lung collapse.
Distinguish compliance and elastance.
Which one relates to inhaling, which one relates to exhaling?
Compliance: how easy the lungs are to inflate (inhaling).
Elastance: how easily the lungs recoil (exhaling)
Compliance and elastance are inversely proportional to each other
In COPD, what happens to
- Compliance (and impact on the lung’s ability to inflate)
- Elastance (and impact on the lung’s ability to deflate)
Increased compliance - easier to inhale.
Decreased elastance - more difficult to exhale. Air (CO2) gets trapped in lungs.
In fibrosis, what happens to
- Compliance (and impact on the lung’s ability to inflate)
- Elastance (and impact on the lung’s ability to deflate)
Decreases - more difficult to inhale
Increases - easier to exhale
In fibrosis, what happens to
- Compliance (and impact on the lung’s ability to inflate)
- Elastance (and impact on the lung’s ability to deflate)
Decreases - more difficult to inhale
Increases - easier to exhale
Thus - how would the size of a COPD (obstructive) vs fibrosis (restrictive) lung compare?
COPD lung would be larger - air can’t get out of lungs
Fibrosis lung would be smaller - air can’t get into the lungs
Define: functional residual capacity
Lung volume when the elastic recoil of the lung is balanced by the intrapleural pressure (tendency of chest wall to spring out)
Define minute ventilation
Formula?
The total volume of gas that is inhaled/exhaled in 1 minute, under resting conditions
Define anatomical dead space
The amount of inspired air that doesn’t reach the alveoli (remains in conducting zones) and therefore isn’t involved in gas exchange.
Define: alveolar ventilation rate
Equation?
Define: physiological dead space
Resistance
- Relationship to flow?
- Relationship to radius of tube?
Airway resistance
- Where is it highest?
- Where is it lowest? Why?
Medium sized bronchi
At the smallest airways (paradoxical as radius is very small; BUT has high surface area)
What is the calculation for work of breathing?
- Example of breathing pattern that would involve low/high work?
Work of breathing = ∆ volume x ∆ pressure
Fast, shallow breaths - low work of breathing
Slow, deep breaths - high work of breathing
