DSA Lung volume and capacities Flashcards
what is the Physiological unit of the lung
Alveolar-Capillary Unit
what is Tidal Volume (Vt)
Is the amount of air inspired or expired in a single breath
- Varies under circumstances
- increased during workout
- Normal resting = 500 mL
what is Residual Volume
Volume of air that cannot be forced out no matter how hard one tries
- getting wind knocked out of you, you are forced into residual volume
- cannot be determined by spirometry
what is Inspiratory Reserve Volume (IRV)
Additional volume that can be inhaled greater than the tidal volume
-the gab between inspiration during tidal volume and maximal inspiration
what is Expiratory Reserve Volume (ERV)
additional volume that can be exhaled greater than tidal volume
- this does not include residual volume
- requires activation of expiratory muscles (active respiration)
what is Total lung capacity (TLC)
Maximal volume to which lungs can be expanded with greatest effort
TLC = IC +FRC
TLC = VC + RV
TLC = ERV + RV + IRV + Vt
cannot be measured by spirometry
Functional residual Capacity (FRC)
amount of air that remains in the lungs following a normal expiration
FRC = ERV + RV
cannot be determined by spirometry
Helps prevent collapse of lungs, reduces workload, dilutes toxic inhaled gases
what is Vital Capacity (VC)
Amount of air that can be maximally inspired following a maximal expiration
VC = IRV + Vt + ERV
VC influenced by posture, abillity of diaphragm to contract/relax, strength of respiratory muscles, thoracic wall expansibillity, resistance to air flow, lung elascity, disease
what is Inspiratory capacity (IC)
capacity of air that can be maximally inspired following a normal exhale
IC = Vt + IRV
what is shown on a Spirometry
IRV Vt ERV IC VC
what plays an influence on lung volumes
Body Size
AGE: FVC, FRC, and RV all increase with age
Posture: reduced FRC when supine
Sex
Ethnicity
Obesity: besides tidal volume, obesity causes a reduction in all static lung volumes, particularly ERV, and FRC
other pulmonary diseases
Measuring Residual Volumes: Helium dilution
Inhalation of a known concentration of helium (C1) which is insoluble in blood, from a known volume (V1)
the change in concentration (C2) allows for determination of V2 = FRC
C1 x V1 = C2 x (V1 + V2)
FRC = V2= V1 x (C1-C2)/C2
Measuring Residual Volumes: Body Plethysmography
Enclosed rigid box
Breath against a shutter
-Pressure in lungs change
-Pressure in box changes proportionally in opposite direction
Boyle’s Law (P1xV1 = P2xV2)
Measuring Residual Volumes: Nitrogen Washout Technique
Determines FRC
Individual breaths 100 percent )2 through one way valve, all expired gas is collected monitored until N2 reaches zero
Total volume of all gas expired is determined and multiplied by % of N2 in mixed expired air (80 %)
