Ventilation and Lung Mechanics Flashcards
What walls(position) does the diaphragm arise from?
Lateral and posterior of the body cavity
What is the diaphragm?
Dome shaped muscle which lungs rest on
What happens to muscles during inspiration?
diaphragm and muscles contract and ribs elevate
What happens to muscles during expiration?
muscles relax and elastic properties of lungs allow it to relax
For air flow in the lungs where does there have to be a pressure difference?
between internal enviroment of lungs and external enviroment - similiar to flow of fluids
How can the flow rate be measured?
Pressure at point 1 minus pressure at point 2 divided by resistance to flow
What is the pressure in the alveoli described as?
When the pressure of gas is inversely proportional to the volume (when one increases other decreases, always constant)
How can pressure in alveoli be measured?
Pressure is the number of moles of gas x gas constant x absolute temp / volume
What are the 2 reasons lungs would collapse?
Elastic recoil - elastic properties of alveolar walls
Surface tension - droplets forming in the alveoli cause alveolar membranes to be drawn together
What prevents collapse of the lung?
Surfactant and intrapleural pressure
Where is surfactant created?
From the alveolar epithelium and contains a mixture of lipoproteins
With surfactant what is the force produced by surface tension? what would it be without surfactant?
4mm Hg, 20-30mm HG
During expiration what pressure will the intrapleural pressure drop to?
2mm Hg below atmospheric pressure
What is atmospheric pressure?
760mm Hg
Elastic recoil prevents lung collapse by balancing what?
Negative intrapleural pressure
What is the compliance of the lungs and thorax referred to as?
the ability to expand
How is compliance measured?
Increased lung volume per unit of change in intrapulmonary pressure
What is compliance expressed as?
Litres per cm of water L/cm
What is the normal compliance of the lungs and thorax?
0.13L/cm
What pressure needs to increase for lung volume to increase by 0.13L?
1cm increase in intrapulmonary pressure
What tool can measure the flow of air in and out of lungs?
Spirometer
What is air flow examined by?
The pulmonary volumes and capacities
What are the pulmonary volumes a measure of?
Tidal volume, Inspiratory reserve volume, Expiratory reserve volume and Residual volume
What is the tidal volume?
volume of air passes in and out of lungs during normal inspiration and expiration 500ml
What is inspiratory reserve volume?
Amount of air that can be inspired on top of the tidal volume 3000ml
What is the expiratory reserve volume?
Volume of air that can be exhaled forcefully 1100ml
What is the residual volume?
volume of air still remaining in lungs after forcible expiration 1200ml
What is the pulmonary capacities a measure of?
2 or more pulmonary volumes combined
What is the inspiratory capacity?
normally 3500ml
What is the functional residual capacity?
measure of total air left in lungs after normal expiration 2300ml
What is the vital capacity?
total amount of air that can be exhaled after maximum inspiration 4600ml
What is the total lung capacity?
Most air you can inspire in your lungs
What is the minute respiratory volume?
total volume of air that passes through the respiratory system per minute usually 6L
What is the dead air space?
region of respiratory system where gas exchange does not occur
What can dead air space be divided into
Anatomical and physiological dead air spaces
Where is the anatomical dead space?
Volume taken up by nasal cavities to terminal bronchioles 150ml
What is the physiological dead air space?
anatomical dead air space and volume of non-functional alveoli
what is the alveolar ventilation rate how is it calculated?
volume of air available for gas exchange per minute
Respiratory rate x (tital volume - dead air space)
