Respiratory - Flow of air Flashcards
In emphysema, what happens to the lungs? How does this affect breathing?
Elastic fibres are lost fro the alveolar walls resulting in increased lung compliance. This means that the lungs becomes limp and soft so that the elastic recoil of the lungs is reduced making it harder to expire
How does expiration in an emphysema patient and healthy patient differ?
Emphysema: the patient exhales using intercostal muscles to depress ribcage raising the intrapleural pressure which raises the alveolar air pressure pushing air out of the lungs (i.e. the chest presses down on the lungs to push air out)
Healthy patient: Elastic recoil of the lung tissue plus the rib cage inwards and the diaphragm upwards raisin alveolar air pressure but creating sub-atmosphereic pressure it the intrapleural space (i.e. lungs pulls chest inwards to push air out)
What is this graph showing?
The intrapleural pressure
What is this graph showing?
The alveolar pressure
What is this graph showing?
The air flow
What is this graph showing? What is the respiratory rate of this diagram
The tidal volume where the rate is 15 breaths min-1
What is the pressure in the lungs relative to?
They are given relative to the atmospheric pressure (i.e. at the mouth/nose)
What are the factors that affect the airflow?
Muscular efforts and lung characteristic
What are the lung characteristics that affect air flow?
compliance, Resistance, dead-space and diffusion
What is the muscular effort?
The force generated by the diaphragm and intercostal muscles
What is compliance describing?
The elasticity of the lung tissue (change of V (volume) per change of P (pressure), i.e. the more change in V per change in P the more the compliance)
What is the inverse of compliance?
Stiffness (i.e. lower compliance = greater stiffness)
What is resistance?
Change of P (pressure) per change of F (flow) (i.e. the more that P needed per change in F, the more resistance)
What is the inverse of resistance?
Conductance (i.e. the greater the resistance the lower the conductance)
What is a greatly increased compliance characteristic of? What is happening to the lungs?
Emphysema due to a loss of elastic fibres
What are the two different fluids filling the lungs in each graph? Why are they different?
When filled with air there is an air-water surface tension that has to be overcome which makes the lungs less compliant when filled with air while in water this air-water barrier is eliminated so it is
In the Pressure-Volume of lungs being filled with air, why are the inflation and deflation loops different? What is this loop called
This is a hysterisis loop
At low volume the lungs are very compliant because most of the alveoli have collapsed so a large pressure is required to over come surface tension (hence the plateau at the start). The deflation curve is different because the
What are the contributors to airway resistance?
Cross-sectional area and air flow rate
How is air resistance proportional to the radius of the airway?
Resistance proportional to the radius^4
What is the relative air resistance in the alveoli relative to the resistance in the mouth and nose? Why?
The air resistance is much lower in the alveoli because the smallest branches are arranged in parallel. This means that the total cross-sectional area of all the airways is the radius used to calculate air resistance and it is much larger than the mouth and nose area
What is the characteristic that causes asthma? Why does it cause asthma
Sporadic broncho-constriction causes increased airway resistance
What is anatomic dead-space?
The volume of the conduction airways (i.e. no gas exchange)
What is the volume of the conduction airways?
150ml (FYI makes up only 3% of the lungs 5L volume)
What is the consequence of the dead-space?
It means that for every breath taken, the air that was in the dead-space and is not fresh get re-inhaled and some of the fresh air that was inhaled is stuck in the dead space ‘diluting’ the fresh air
How does the dead-space change as your breath size changes? Why?
It doesn’t, it is a constant 150ml as that is the volume of conduction airways and doesn’t change regardless of breath size
What is the rate of gas exchange across a membrane proportional to?
(P_Agas [partial pressure of gas in the alveoli] - P_Cgas [partial pressure of gas in capillaries])
The surface area of gas exchange
Inversely proportional to the thickness of the membrane wall
The square root of the molecular weight of the gas
What is law of the square root of the molecular weight of the gas?
Graham’s law
What some conditions caused when the function of the lungs are compromised?
Respiratory Distress Syndrome
Emphysema
Asthma
Pulmonary oedema
Who gets respiratory distress syndrome? What is not functioning properly?
Premature babies who haven’t developed their pulmonary surfactant yet
Why does the absence of pulmonary surfactant affect breathing/chances of survival in premature babies?
Without the pulmonary sufactant there is a higher air-water surface tension which means that a greater interpleural pressure is required to inflate the lungs require greater muscular effort which they don’t have resulting in distress/fatigue
What is the physiological cause of emphysema?
Destruction of inter-alveolar and inter alveolar tissue
What do the inter-alveolar and inter alveolar tissue do?
Hold the smallest bronchioles open during expiration
How does emphysema impact breathing?
Lung compliance decreases therefore less air can be expired per breath increasing the functional residual breath. This results in a lower tidal volume as if less air can get out, less air can get in
What is pulmonary oedema?
Where there is water on the lungs
How does pulmonary oedema affect breathing?
Water on the lung increases the distance which the oxygen has to travel across therefore decreasing gas exchange
