Pulmonary ventilation Flashcards
Function of the respiratory system?
Supply tissues with oxygen
Remove excess carbon dioxide
How are hypo/hyper ventilation defined?
By amounts of CO2 in blood
Why is hypo/hyperventilstion not based on O2 stats
Acid-base balance
Oxygen exchange is non inear due to haemolglobin
total ventilation equation
V=Vt X f
Total ventilation = tidal volume(mL) X frequency
What is the tidal volume
Volume of air inhaled in each breath
Why does the respiratory system not completely empty even at forced maximum expiration?
Air is required to occupy airways
so alveoli do not completely collapse
This is known as the anatomical dead space
Equation for Alveolar ventilation
Va = (Vt-Vd) x f
Alveolar minute volume = tidal volume - dead space volume x frequency
What is Vt-Vd
The amount of fresh air entering the alveoli in each breath
What is boyles law ?
Boyle’s law describes the relationship between pressure, volune and molar quantity (number of gas molecules present)
Boyle’s law states that the volume of gas is inversely proportional to pressure (when temperature is constant).
P ∝n/v
If the temperature is ke[pt constant how can we change the pressure?
By changing the volume
Why does air move from atmosphere into lungs?
Alveolar pressure falls below atmospheric
Therefore air moves down pressure gradient
How are the lungs and chest walls seperated ?
Pleural cavity
The visceral pleura lines each lung; what does the parietal pleura line?
The thoracic cavity surrounding the chest, diaphragm and mediastinum
The chest walls recoils outwards and the lungs recoil inwards. This decreases the pressure within the pleural cavity. Why?
Same number or molecules with larger volume. the pleural cavity is sealed. it is filled with liquid.
Is the pressure in the pleural cavity positive or negative
The pressure is naturally sub-atmospheric. This is known as negative pressure.
Why is the system in equilibrium at the end of expiration?
Force pulling viscreal pluera inwards = Force pulling parietal pleura outwards
Explain the process of inspiration
Contraction of respiratory muscles
Generates enough force to pull parietal pleura outwards
This stretches pleural cavity, decreasing intrapleural pressure
As the intrapleural pressure becomes more negative the force pulling the pleurae together increases.
When the force becomes larger than the force of the elastic recoil of the lungs, the visceral pleura will be pulled outwards expanding the lungs
Air will be pulled in
Explain the process of passive expiration:
Relaxation of inspiratory respiratory muscles
Decreased outwards force of parietal pleura
Increases intrapleural pressure
Cannot overcome elastic recoil of lung
So visceral pleura is pulled inward.
This decreases lung volume
Which extra muscles are used in forced expiration?
THE ABDOMINALS
They actively contract to compress volume of thoracic cavity
The muscle contraction generates inward force on parietal pressure, compressing pleural cavity
Increases intrapleural pressure
Cannot overcome elastic recoil of lung
What is a pneumothorax
Air entering the pleual space
What can cause a rupture to the pleura?
Trauma, bleb formation, disease
Why is pnemothorax a problem?
Air will enter the pleural space
This causes an increase in volume until intrapleural pressure = atmospheric pressure
This causes the lung to collapse
