respiratory physio 2 Flashcards
spirometer
-measures volumes of the lungs (breathing out)
what is tidal volume? expiratory and inspiratory reserve volume? Vital capacity? total lung capacity?
- tidal vol- normal inspiration and expiration curve for a person at rest
- expiratory and inspiratory reserve volume- when you ask the patient to breathe out and breathe in as much as they can
- vital capacity- aka forced vital capacity is when pt is the full inspiratory reserve to expiratory reserve
functional residual capacity? residual capacity
- where everything is balanced, no inspiration or expiration
- at bottom of tidal volume expiration
- functional residual capacity- the amount of air left in your lungs after expiration- CANNOT BE MEASURED BY SPIROMETRY
how does the inspiratory reserve volume (IRV), Vt, ERV, and RV change with restrictive lung disease? obstructive?
restrictive- everything decreases as there is a restriction in expansion of the lungs
obstructive- you can get better breath in more than out which causes air to get trapped in- COPD and asthma
forced vital capacity -
Fev 1-
what does the FEV1/FVC ratio mean? what does a higher value mean?
- total volume of air that can be FORCIBLY expired following maximal inspiration
- tell patient to breath out as hard and as fast as they can-
-Fev1- air vol that is forcibly expired in the first second
- FEV1/FVC- the fraction of total FVC that can be expelled during the first second = REFLECTS THE RESISTANCE TO AIRFLOW
- the higher the value of the fraction, the less resistance
- normal: 0.75-0.8
describe the flow-volume curve and its values.
- has a peak inspiratory flow (at bottom of curve)-reflection
- peak lung capacity at top of curve and decreasing volume FEF 25, 50, 75% of exhaled vital capacity that ends in FVC (forced lung capacity)
in terms of expiration, what are large airways responsible for? small?
large- the beginning part of expiration to the peak
small airways- from peak and down as the airflow begins to decline
how does the flow-volume curve change with obstructive lung disease?
upper airway obstruction?
restrictive lung disease?
obstructive lung disease- expiration peak is decreased and the peak volume is also decreased (shifted to left) with steeper slope post peak
upper airway obstruction- looks like a square, don’t reach peak inspiration or expiration flows
restrictive lung disease- no obstruction just decreased airflow and thus more volume required (shift to right)- mini normal curve
what is the normal Fev1/FVC ratio? what does that mean?
how is that different in an obstructive lung disease pt?
restrictive lung disease pt?
- normal ration is 0.8 - this means that in a normal patient, the patient should be allowed to forcibly expire about 80% of the vital capacity in the first second)
- In obstructive lung disease, this ratio is decreased- both FVC and FEV1 are decreased but FEV1 is decreased MORE than FVC (which makes sense because there is a prob with expiration not inspiration) is causing the ratio to be under 0.7
- in restrictive lung diseases like fibrosis you get a decrease in both FEV1 and FVC but FEV1 is decreased LESS than FVC is causing the ratio to go higher
what is physiological dead space and how do you calculate it?
- physiological dead space(Vd) is the total volume of the lungs not used to participate in gas exchange
- Vd = anatomic dead space + functional dead space
- anatomic dead space is not pathologic- just the generation 1-16 bronchioles etc
- functional dead space is always pathologic- alveoli that do not participate in gas exchange (ventilated but not perfused)
how do you calculate minute ventilation and what is it
-total rate of air movement into and out of the lungs
minute ventilation - Vt x RR
vt= tidal volume and RR is respiratory rate
how do you calculate alveolar ventilation RATE? what is it?
- rate at which new air reaches the gas exchange areas of the lungs
Va = RR x (Vt -Vd)
Vt = tidal volume, Vd = dead space, RR respiration rate in breaths per min
what does the alveolar ventilation equation tell us? what is the equation?
- it describes the INVERSE VOLUME relationship between alveolar ventilation and alveolar pCO2
Va = [Vco2 x K]/ PaCO2
Va= alveolar ventilation- amount of air reaching the alveoli per min
PaCO2- Alveolar Pco2
Vco2= rate of CO2 production
K = constant 863 mmHg
what happens with PAco2 if CO2 production is constant
- it is determined by Va b/c
Va = [Vco2 x K]/ PaCO2
what happens to PaCO2 and Va if VaCO2 were increased
PaCO2 would increase too but Va would decrease (inversely proportional)