Respiratory Flashcards
(33 cards)
What is external respiration?
The sequence of events that lead to the exchange of carbon dioxide and oxygen between the external environment and the cells of the body
What are the 4 steps of external respiration?
1/ Ventilation/gas exchange between the atmosphere and the alveoli 2/ Exchange of oxygen and carbon dioxide between the alveoli and the blood. 3/ transport of oxygen and carbon dioxide between the lungs and tissues 4 exchange of carbon dioxide and oxygen between the blood and tissues
What is Boyles Law
At any constant temperature, the pressure exerted by a gas varies inversely with the volume of the gas
What 3 pressures are important in ventilation?
Atmospheric. Intra-alveolar. Interpleural
What gives the lungs recoil during expiration? Which is more important?
Elastic connective tissue. Alveolar surface tension - more important
What is intracellular fluid cohesiveness?
The attraction of water molecules for each other in the intrapleural fluid. This causes resistance to then being pulled apart
What is the negative intrapleural pressure?
the sub atmospheric intracellular pressure creates a transmural pressure gradient across the lung wall and across the chest wall. Causes lungs to expand outwards while the chest is forces to squeeze inwards.
What three pressures are important in ventilation?
Atmospheric pressure, intra-alveolar pressure and intrapleural pressure
what happens to the ribs when the external intercostal muscles contract?
The ribs lift and the sternum moves out - bucket handle mechanism
Is inspiration an active or passive process?
Active
Is normal expiration a passive or active process?
Passive - brought by relaxation of inspiratory muscles
what is La Place’s Law
The inward directed collapsing pressure is proportional to the surface tension and inversely proportional to the radius
What is the function of type 2 pneumocytes?
surfactant production
What is alveolar interdependence and what does it do?
Helps keep alveoli open. If an alveolus starts to collapse, the site surrounding alveoli are stretched and then recoil exerting expanding forces in the collapsing alveolus to open it.
Name the 3 forces keeping alveoli open?
Transmural pressure gradient. Pulmonary surfactant ( opposes surface tension). alveolar interdependence.
Name the 2 forces promoting alveolar collapse?
elasticity of stretched pulmonary connective tissue fibres. Alveolar surface tension.
What is FVC?
the maximum volume that can be forcibly expelled from the lungs following a maximum inspiration.
In obstructive disease, the FEV1, FVC and FEV1/FVC ratio are generally what, compared to normal lungs?
FEV1 - reduced. FVC- normal. Think obstructive : something stopping air coming out as quickly. Ratio is lower
In restrictive disease, the FEV1, FVC and FEV1/FVC ratio are generally what, compared to normal lungs?
FEV1 and FVC reduced. Think restrictive : something stopping lungs filling. Less volume in lungs means less can come out as quickly. Ratio is normal as both are reduced.
What is the primary determinant of airway resistance?
Radius of conducting airways
During inspiration, intrapleural pressure increase/decreases?
Decreases - as lungs fill, pressure gradient falls.
During expiration, intrapleural pressure increase/decreases?
Increases - pressure gradient forces air out of lungs
pulmonary compliance
The measure of effort that has to go into stretching pr distending the lungs. The less compliant the more work requires to produce a given degree of inflation.
What disease state/s is/are there decreased compliance?
pulmonary fibrosis/oedema/ pneumothorax, pneumonia, absence of surfactant
