W11- Lecture 54- Ventilation and lung mechanics Flashcards
what is the equation for flow rate F
HINT PRESSURES
The flow rate F = (P1-P2)/R
P1 = the pressure at point P1 P2 = The pressure at point P2 R = The resistance to flow.
what is to Boyle’s law,
(volume and pressure relationship )
+ equation
that the pressure of a gas is inversely proportional to the volume.
PV = nRT
Where
P = Pressure n = Number of moles of gas R = Gas constant T = Absolute temperature (Degrees Kelvin) V = Volume
what are two reasons for collapse of the lung ?
1) Elastic recoil, this is based upon the elastic properties of the alveolar walls.
2) Surface tension. Formation of droplets in the alveoli can cause the alveolar membranes to be drawn together resulting in alveolar collapse.
describe how the collapse of the lung is prevented (by anatomy )
surfactant and intrapleural pressure
surfactant =mixture of lipoproteins
surface tension is about 4mm Hg. Without surfactant 20 - 30 mm H
intrapleural pressure
during expiration the intrapleural pressure will drop to about 2 mm Hg below atmospheric pressure
this is balanced with elastic recoil
describe the compliance (ability to expand ) of the lungs and thorax
what does this mean ?
about 0.13L/cm.
1cm increase in intrapulmonary pressure, the lungs volume will increase by 0.13L.
define Tidal volume Inspiratory reserve volume Expiratory reserve volume Residual volume
which one of these cant we measure directly ?
how can it be
why is this volume important
1) Tidal volume. The volume of air that passes into and out of the lungs during normal inspiration and expiration. (500ml).
2) Inspiratory reserve volume. The amount of air that can be inspired on top of the tidal volume. (3000ml).
3) Expiratory reserve volume. The volume of air that can be exhaled forcefully (1100ml).
4) Residual volume. (1200ml). The amount of air that remains in the alveoli after a forceful exhilation
We cant measure residual volume directly
So we breath in labelled nitrogen at a known conc
Nitrogen will mix with the residule volume + know quantities by ratios
enables us to calculate t lung capacity
define + how they are calculated
1) The inspiratory capacity- normally about 3500ml.(tidal v + inspiratory reserve )
2) The functional residual capacity provides a measure of the total amount of air left in the lungs after a normal expiration (2300ml).(expiratory v + residual v )
3) The vital capacity - the total amount of air that can be exhaled after a maximal inspiration (4600ml).(inspiratory reserve +tidal v+expiratory reserve)
4) The total lung capacity(vital capacity +residual v )
what is Minute respiratory volume?
normal V at rest ?
a measure of the total volume of air that passes through the respiratory system per minute.
about 6L
how can be split up the respiratory dead airspace ?
e.g
divided into the anatomical and physiological dead air spaces
The anatomical dead air space is the volume taken up by the nasal cavities to the terminal bronchioles
The physiological dead air space is the anatomical dead air space and the volume of non-functional alveoli
what is the equation for the alveolar ventilation rate
AVR = RR(TV - DAS)
Where
RR = Respiratory Rate (Breaths/Min) TV = Tidal Volume (ml/respiration) DAS = Dead air space (ml/Respiration)
