Flashcards in Ventilation and Lung Volumes Deck (37):
What effect does increasing lung compliance have on FRC?
It increases FRC
-not able to expel as much air
What happens to lung compliance with age?
What is total lung capacity? What is the normal value?
max volume of gas that the lungs can contain
What is the tidal volume? What is the normal value?
Volume of gas which flows into and then out with each breath
How can tidal volume be increased?
can tidal volume be measured by a spirometer?
What is inspiratory reserve volume?
max volume of gas that can be inhaled from end-tidal inspiratory position
What is expiratory reserve volume?
-volume of gas that can be exhaled from end-tidal expiratory position
What is residual volume?
volume of gas contained in the lungs after max force of expiration
-can't be exhaled
What is vital capacity?
-max volume of gas that can be exhaled after normal inspiration
What is inspiratory reserve capacity? (IC)
max volume of gas that can be inhaled from resting expiratory position
What is the formula for vital capacity ?
VC= IRV +Vt + ERV = TLC- RV
What is the formula for IC?
IC= VT+IRV = TLC - FRC
What is functional residual capacity?
Volume of gas in the lungs after normal expiration
-when diaphragm and chest muscles are relaxed
Can FRC be measured by a spirometer?
NO - it includes RV
What is the ultimate goal of using a N2 washout?
You want to measure FRC
- can't measure with a spirometer
-this value is a good indicator of obstructive or restrictive diseases
What are the steps involved in N2 washout ?
1. subject breathes normal air
-N2 fraction is measured
2. at the end of eupneic breathing - lung is at FRC and subject breathes in 100% O2
-for at least 7 minutes
-washes out all N2 from the lung
3. expired gas is collected in spirometer
What is the issue with using N2 washout to record FRC?
- if there are regions in the lung with trapped air, this volume won't be measured
-FRC is underestimated
do we have to know the FRC equation for N2 washout, or the pletysmograph equation ????
not sure, making this flash card to remind us to memorize them if need be
What is a plethysmograph?
a gas-tight chamber in which a patient sits in and breathes through a tube leading to outside
-used to measure FRC
As a patient expires against a pressure transducer with a closed valve in a pletysmograph, what happens to their lung volume and P?
-the volume of the lung is compressed
-the P of the lung is raised
Since the chamber is gas tight, what happens to the air in the box outside the subject's body as they breathe air to the outside?
-the air will expand
-this change in volume is exactly equal to the amount of compression of air in the lungs
What is the amount of dead space in mL approximated as ?
equal to the subject's weight in pounds
What is total ventilation equal to?
Dead space ventilation plus alveolar ventilation
Hypoventilation results in what two consequences?
1. alveolar hypercapnea - inc PACO2
2. hypoxia - dec PAO2
Hyperventilation results in what two consequences?
1. alveolar hypocapnea - dec PACO2
2. hyperoxia - inc PAO2
Increasing oxygen consumption, has what effect on alveolar oxygen?
What does R mean in the equation:
-ratio of O2 consumption to production
Vt is about what percentage of TLC?
only about 10%
-volume of air going into and out of the lung with each breath = small fraction of air in the lung
About by how much do the PO2 and PCO2 oscillate by in alveoli during eupnea?
Why does the PO2 first decrease when you first inspire?
O2 is going into blood when air is going through the dead space
What is a single breath analysis of dead space?
-subject inspires air containing neglible CO2 and then exhales into a spirometer
-fraction of CO2 is measured
(contains CO2 from the body)
As the subject exhales, what does the FECO2 rise to and plateau at?
Why when the patient first exhale, does the first gas contain negligibly low CO2?
gas comes from the anatomic dead space
What does the time of the midpoint of the rise of FECO2 correspond to?
the time at which all of the dead space air would be expired
-if there was a sharp boundary btwn dead space gas and alveolar gas
What does the alveolar ventilation equation predict?
It describes the dependence of alveolar and arterial Pco2 on alveolar ventilation