L18-Airway resistance & flow Flashcards
(33 cards)
Where in the respiratory system is the main site of resistance?
At arterioles just before the gas exchange area and the capillaries
How is airway resistance controlled?
pathological and physiological control, other conditions like asthma-where we have a change in resistance and makes it harder to breathe.
-smooth muscle tone, mucus production, inflammation, autonomic nervous system, mechanical factors, external influences.
what is the impact of airway resistance changing?
-increased breathing resistance > more effort to move air into the lungs, asthma
-👇sed resistance > allows air to flow in more easily, beneficial during physical activity.
-impact on gas exchange >high resistance can lead to uneven ventilation.
-compensation mechanisms>breathing more deeply can lead to fatigue.
-chronic increases in airway resistance in COPD can lead to hyperinflation(trapped air in the lungs)
How might I measure the effect of changing airway resistance?
-Spirometry – This test measures lung function, including forced expiratory volume (FEV1) and forced vital capacity (FVC). A decrease in FEV1 or the FEV1/FVC ratio can indicate increased airway resistance.
-Plethysmography (Body Box Test) – This measures airway resistance (Raw) directly by analyzing pressure changes as a person breathes inside an enclosed chamber.
What are the components of resistance to airflow?
- lung tissue viscous resistance(10-20%)> inertia to get the lungs moving.
-airway resistance(80-90%)> resistance to flow exists in tubes
What is the equation with flow, resistance and pressure gradient? What can you conclude from the equation?
Flow = pressure gradient/resistance
-pressure gradient>can control it, In CV system it’s the heart pumping to generate pressure gradient & cardiac cycle.
-resistance> can control it, high resistance to flow, inhibits the flow.
Equation to measure airway resistance
Rate of change of flow /FLOW = flow between the biometric pressure and the alveolar
pressure divided by airway resistance.
- you have to rearrange this equation to make the airway resistance the subject
What is the air pressure at sea level? What do we use to measure the atmospheric pressure?
100KPa, use a manometer to measure the atmospheric pressure
What is a plethysmograph used for?
to measure the constant pressure of all the alveoli.
What to use to measure airflow ? and what else can we measure ?
spirometer in a closed box, can measure the change in air pressure inside the box
Why do we need to calibrate with a calibration syringe for pressure changes?
When you breathe in air, the lungs expand. As the lungs expand, the pressure inside the box is changing.
Why do we use centimetres of water as a measure of pressure sometimes?
Bc there are relatively(very low) low pressures in the respiratory system.
Why do we use millimetres of mercury as a measure of pressure sometimes?
To measure much bigger units like arterial blood pressure
Do we have resistance at the larger or the smaller end?
Larger end(larger airways) of the CV system
What is 90mmHg is almost equaivalent to?
13KPa
What does the longer Pascal complies to?
We can get similar amounts of fluid movements for much smaller pressure gradients.
How does the pulmonary circulation links to Cardiac output?
As the pulmonary circulation goes down the lungs, where the blood pressure is much lower, the cardiac output will be at lower pressure too. Because circulation has a much lower resistance.
Define “resistance in series”
When you go through resistance from the 1st generation then to the 2nd generation and so on. This is because each generation is in parallel.
Smaller radius gives….(higher/lower resistance)
higher resistance
How does the radius change when moving down the generations and their effect on resistance?
- 1st couple of generations, resistance is increasing because the airway is getting smaller in diameter. Only a couple of them(too little) in parallel. dominant effect of them getting smaller.
- A lot of resistance through the terminates[humidify the air]when reached the trachea.
- After the 1st few generations, airway number increases in parallel eventhough the airway is getting smaller. domino’s effect
- So then the overall resistance 👇 ses as we move further down.
-Then from here the diameter of the airways changes and so does the resistance.
What does the larger airways have a constant of ?
larger airways have a relatively constant radius therefore a constant resistance.
What does airways in series contribute to?
Airways in series contribute to both constant(upper) & variable(lower) resistances.
what does the cartilage acts as in the 1st generation?
It acts as a scaffold and holding the trachea open.
What happens if the pressure outside the airways is greater than the pressure inside the airways ?
The airway system and the lung will collapse.
