Mechanics of ventilation 2 Flashcards
(37 cards)
tidal volume - TV
amount of air inhaled or exhaled during normal quiet breathing w/o effort
inspiratory reserve volume - IRV
The maximum amount of air that can be inhaled after a quiet inhale
expiratory reserve volume - ERV
the amount of air that can be exhaled with maximum effort after normal inhalation
residual volume - RV
the amount of air remaining in the lungs after maximum exhalation
inspiratory capacity
maximum amount of air that can be inhaled - IRV
after quiet inhalation - TV
TV + IRV
Functional residual capacity
the amount of air remaining in the lungs - RV after quiet exhalation - ERV
Total lung capacity
RV + ERV + TV + IRV
Vital capacity
amount of air that can be exhaled w/ max effort - ERV after maximum inhalation - TV + IRV
cane be forced FVC or slow
FEV1 - Forced Expiratory Volume
amount of air that is exhaled during 1st second of forced exhalation after full inhalation
normal FEV1/FVC ratio
70-80%
low FEV1/FVC ratio indicates
increased lung resistance
how is inspiratory restrictive disease evident in spirometers
reduced lung compliance - limited lung expansion during inhalation
significant decrease in IRV and TV only
example of restrictive inspiratory disease
fibrosis -
how is expiratory restrictive disease evident in spirometers
weakness of accessory muscles in deep exhalation
decreased lung volumes - ERV,
and TLC
Signs of obstruction in spirometer
increased lung resistance, making it harder and slower to breath out - causes increased residual lung volume
normal vital capacity
reduced FVC
helium dilution technique
spirometer - V1 contains a measured conc of helium - C1
patient starts breathing in normal outside air in normal tidal volume
when the patient is at the functional residual capacity patient begins to inhale helium/air mixture until the air mixture has reached equilibrium with the tank and the patients lungs - FRC = V2 - V1
V2 = FRC + V1
volume of lungs - V2
Helium conc in lungs = C2
Initial amount of helium calculation
conc of helium = C1
Volume of spirometer = V1
C1 X V1
Final amount of helium calculation
C2 (V2 + FRC)
FRC calculation using the helium dilution method
C1 x V1 = C2 x V2
V2 = V1 + FRC
C1 x V1 = C2 x (V1 + FRC)
FRC = (C1 x V1)/C2 – V1
Process of body plethysmography
Patients sits in a “body box” (airtight chamber) and breathes through a mouthpiece
At FRC, the mouthpiece is closed
Patient tries to breathe in
consequences of body plethysmography
- Chest and lungs expand, pressure in lungs drop as volume increases
- Expanding chest compresses the air inside the chamber, air volume in chamber decreases, pressure in chamber increases
key principle in body plethysmography
Boyles law
P1V1 = P2V2
how can Boyle’s law to find ∆V
Change in lung volume: trying to find FRC and therefore ∆V
FRC = FRC + ∆V
Change of air volume in box:
V1 = V1 - ∆V
Change of pressure in box:
P1 = P1 + ∆P
P1 x V1 = (P1 + ∆P) x (V1 - ∆V) [Boyle’s Law]
- P1 x V1 = P1 V1 + ∆P V1 - ∆V P1 - ∆P ∆V
- ∆V = ∆P V1/ (P1+ ∆P)
how can Boyles law be used to find FRC in body plethysmography
P1 x FRC = (P1 - ∆P) x (FRC + ∆V) [Boyle’s Law]
FRC = ∆V(P1- ∆P)/ ∆P
