PL2 Flashcards
Static vs dynamic lung vol.?
Static – lung vol. when no air is flowing (measured in L)
Dynamic –> Dependent on the rate of air flow (Measured against time –> L/min)
What are gas flow measurement devices called?
Pneumotachometers
Spirometer?
ANy device used to measure lung vol.
Define the following + write their volumes:
- Tidal vol.
- Inspiratory reserve vol.
- Expiratory reserve vol.
- Residual vol.
- Tidal vol. :: Vol of air moving in and out of the lungs under normal resting conditions = 0.5L
- Inspiratory reserve vol. :: Max. vol of air that can be inhaled above the tidal vol. = 3.1L
- Expiratory reserve vol. :: Max vol. of air that can be exhaled below tidal vol. = 1.2 L
- Residual vol. :: Vol. of air that remains in the lungs even after full expiration = 1.2 L
- Vital capacity
Max. vol. of air that can be inhaled and exhaled
VC = 4.8 L
(= tidal vol.+ IRV+ ERV = 0.5+3.1+1.2 = 4.8 L)
- Inspiratory capacity
Max. volume of air that can be inhaled
IC = Tidal vol. + IRV = 0.5 + 3.1 = 3.6 L)
- Functional residual capacity
Vol. of air that remains in the lungs during normal respiration
FRC = ERV + residual vol. = 1.2+1.2 = 2.4 L
- Total lung capacity
Total vol. of air that the lungs can hold
– sum of all volumes
= 6L
Define the following:
PIF
PEF
FVC
FEV1
%FVC in 1 sec.
What principle do bellow/bell/water spirometers work on?
Volume displacement
explain how inspiration and expiration affect the wokring of the following:
– Water bell spirometer
– Bellows spirometer
– Water bell spirometer::
Expiration – pressure inside bell rises above atm. P. causing bell to rise
Inspiration – pressure inside bell decreases below atm. P. causing bell to drop
– Bellows spirometer::
Expiration – air exhaled causes bellow to inflate
Inspiration – air inhaled causes bellow to collapse
Results from both these machines are plotted – kymography
What would the highest point on a volume time graph represent?
The forced vital capacity (FVC)
What is a good indicator of:
- Lung function
- Airway resistance
- Lung function:: FEV1/FVC (should be about 70-80%)
- Airway resistance:: FEF 25-75. (forced expiratory flow from 25-75% of airway resistance)
Give examples of and explain how obstructive and restrictive diseases would affect the following:
- Elasticity
- Compliance
- FEV1
- FVC
- FEV1/FVC
- FEF (20-75)
Obstructive – COPD (chronic bronchitis, emphysema), asthma – arent able to exhale air due to decreased elastic recoil
- Elasticity: decreases
- Compliance: increases
- FEV1: decreases
- FVC: decreases but less than FEV1
- FEV1/FVC : decrease (below 80% - normal)
- FEF (20-75): Decreases
Restrictive – Pulmonary fibrosis, RIGID TB – due to decreased compliance - arent able to inhale a large vol. of air
- Elasticity: increases
- Compliance: Decreases
- FEV1: Decreases (but proportionally – as a result of not being able to inhale a large vol. of air - only able to exhale what they’ve inhaled)
- FVC: Decreases (not able to inhale large vol. of air and thus cant exhale a large vol either - overall lung capacity decreases)
- FEV1/FVC: Remains about the same (as there’s a decrease in both variables)
- FEF (20-75): Slightly decreases
What difference does a pneumotachometer measure?
A difference in air-flow pressure before and after passing thru a resistance screen
Flow-volume loops tells us whether _______________________
Flow-volume loops tells us whether airflow
is appropriate for a particular lung volume
When does max inspiratory flow (peak inspiratory flow - PIF) occur on a flow-volume loop?
Occurs halfway between Total lung capacity (TLC) and Residual volume (RV)
Max insp flow occurs half-way between TLC & RV
Why does PIF occur at this point?
The following factors are involved:
a) force generated by inspiratory muscles as lung volume
b) lung recoil as volume
c) airway resistance
a – force generated decreases as lung vol increases
b – Lung recoil increases as vol increases
c – airway resistance decreases
What law is whole body plethysmography based on? Can you measure true lung vol. thru this?
Boyle’s law
P1V1 = P2V2
Yes you can.
Ideal Peak flow meter readings for a young male?
approx. 580L/min for a young male
Importance of FRC at rest
- Index of ________
- If chest muscles weak FRC _______
- If airway is obstructed FRC ______
- Index of elastic recoil (decreased elastic recoil and increased compliance – increased volume left in lungs)
- If chest muscles weak FRC decreases
- If airway is obstructed FRC increases (more air left in lungs)
Can FRC be measured using spirometry?
no
Techniques to measure FRC
- Helium dilution method ::: He is insoluble in blood
-Nitrogen washout ::: done by breathing in 100% O2
Relationship between alveolar ventilation and PCO2?
How do hyperventilation and hypoventilation affect PCO2 levels?
How are V(e) and V(a) – Total minute ventilation and alveolar ventilation different? Which one is more?
Ve = tidal volume – includes both deadspace and alveolar space (involved in gas exchange)
Va = Only respresents the air involved in gas exchange (excludes the deadspace)
Thus Ve would be more
Respiratory pressures are expressed relative to ___________
Respiratory pressures are expressed relative to atmospheric pressure
Pleurisy
Pleural effusion
Pleurisy:: inflammation of the pleural lining of the lungs
Pleural effusion: acumulation of fluid in the pleural cavity
What are the following pressure at rest:
- Intrapleural p.
- Intra-alveolar P.
- Transpulmonary P.
- Transthoracic P.
- Intrapleural p. = -4
- Intra-alveolar P. = 0
- Transpulmonary P. = +4
- Transthoracic P. = -4 (same as intrapleural P)
How are the following calculated:
- Transpulmonary P.
- Transthoracic P.
- Trans respiratory P.
- ALveolar P.
- Transpulmonary P. = P(alv) - P(IP)
- Transthoracic P. = P(ip) - P(atm). –> same as P(ip)
- Trans respiratory P. = P(Transpulm.) + P(transthoracic)
- ALveolar P. = P (intraPl) + P (elastic recoil of lung)
Why is the intrapleural P. negative?
- The surface tension of the alveolar fluid (Alveolar fluid within has surface tension – they have the tendency to collapse)
- Elasticity of lungs (Elastic tissue in lungs tends to recoil and pull lungs inwards)
- Elasticity of the thoracic wall (Elastic tissue of the thoracic cavity tends to pull away from the lungs in the opposite direction of the lungs and alveoli)
— All these 3 factors tend to increase volume of the pleural cavity and thus in accordance to Boyle’s law – this would correspond with a decrease in pressure.
The -ve intrapleural P thus helps prevent the lungs from collapsing.
Which pressure is always:
-ve
+ve
Intrapleural
Transpulmonary (Palv - Pi)
How do the following change during inspiration and expiration:
- Intrapleural p.
- Intra-alveolar P.
- Transpulmonary P.
- Transthoracic P.
Inspiration:
- Intrapleural p. –> Becomes more -ve (-6)
- Intra-alveolar P. –> decreases and then goes back to 0 as it equilibrates with atm. P. (from 0–> -1—> 0)
- Transpulmonary P. –> +5 mmHg
- Transthoracic P. –> same as intrapleural (-6)
Expiration:
- Intrapleural p. –> Becomes less -ve (-3)
- Intra-alveolar P. –> increases and then goes back to 0 as it equilibrates with atm. P. (from 0–> +1—> 0)
- Transpulmonary P. –> +4 mmHg
- Transthoracic P. –> same as intrapleural (-3)
What is the alveolar Pressure at start of and at peak inspiration and expiration
At the start of:
– Inspiration:: -1 mmHg
– Expiration:: +1 mmHg
Peak:
0 mmHg (for both)
(As pressure equilibrates with atm. Pressure)
How do we measure intrapleural pressure?
oesophageal manometry
Which pressure represents the following:
1. – responsible for the actual flow of gas into and out of the alveoli during breathing.
- represents the total pressure required to expand or contract the lungs and chest wall
- responsible for maintaining alveolar inflation.
- Transrespiratory gradient
- Transthoracic P
- Transpulmonary P.
is tidal vol. constant or does it vary from breath to breath AT REST?
not constant - slightly varies from breath to breath even at rest
Can spirometry be used to measure the following:
- Tot. lung capacity
- Residual vol.
No it cant be used to measure either.
How can Total lung capacity and Residual vol. be measured?
Via whole body plethysmography
How do volume-flow loops vary in disease (obstructive vs restrictive)
What would the value of absolute pressure in pulm. resp. physiology be the same as?
In pulmonary physiology, absolute pressure refers to atmospheric pressure and thus would have a value of 760mmHg
Is transpulmonary P always -ve or +ve?
When could this change?
Transpulmonary P = Palv - Pip
– It is always +ve
– This can change in pneumothorax which refers to the puncture of the lungs – air in pleural cavity.
– If this occurs, the Palv and Pip pressures equalise and it can lead to lung collapse.
Is transpulmonary P always -ve or +ve?
When could this change?
Transpulmonary P = Palv - Pip
– It is always +ve
– This can change in pneumothorax which refers to the puncture of the lungs – air in pleural cavity.
– If this occurs, the Palv and Pip pressures equalise and it can lead to lung collapse.
Explain Boyle’s law
Boyles law:: Explains the relationship between Volume and pressure.
—> States that Pressure is inversely related to Volume at a constant temperature. (P = 1/V)
–> Also states that at a given temp the product of pressure x gas is constant (P1V1=P2V2 at constant temp. )
Explain Boyle’s law in relation to::
– Intralveolar P. / Intrapulmonary P
Boyle’s law states that P=1/V
– Intralveolar P is = 0 at rest
– Inspiration:: Alveoli expand and thus volume increases causing a drop in P. within the alveoli in accordance w/ boyles law.
– Thus inspiration P = -1
– Air rushes in down its P. gradient and causes pressure to go back to 0.
– Expiration:: Alveoli shrink causing a decrease in vol. however air still in alveoli now exert a greater pressure due to drop in vol. according to boyles law.
– Thus expiration P = +1
– Air flows out down its P gradient causing pressure to go back to 0.
Explain Boyle’s law in relation to::
– Intrapleural P.
Intrapleural P. is always -ve due to::
- The surface tension of the alveolar fluid (Alveolar fluid within has surface tension – they have the tendency to collapse)
- Elasticity of lungs (Elastic tissue in lungs tends to recoil and pull lungs inwards)
- Elasticity of the thoracic wall (Elastic tissue of the thoracic cavity tends to pull away from the lungs in the opposite direction of the lungs and alveoli)
— All these 3 factors tend to increase volume of the pleural cavity and thus in accordance to Boyle’s law – this would correspond with a decrease in pressure.
The -ve intrapleural P thus helps prevent the lungs from collapsing.
How does intrapleural P. change during inspiration vs expiration?
Normally at rest intrapleural P = -ve mmHg
Inspiration – thoracic cavity expands and the pleural cavity space slightly increases.
Thus slightly decreasing Intrapleural P. (becomes more -ve)
Expiration – Returns back to its normal Pressure = -4 mmHg.
What are the different respiratory pressure gradients? How are they calculated?
What are the different respiratory pressure gradients? How are they calculated?
