Breathing Quantified

Question 1

Identify static lung volume and capacities on a spirogram.

Given lung volumes calculate lung capacities.

Answer 1

4 static lung volumes, measurable, used to calculate capacities.

tidal volume (TV): how much you breathe normally

vital capacity (VC): max inspiration –> max expiration

functional residual capacity (FRC): end of normal breathe, could still breathe out

CANNOT measure RV, TLC, and FRC

TLC: all air, including what can’t exhale

Question 2

2.  Outline 3 factors that affect lung volumes in a healthy person.

Answer 2

height: taller = larger lung volume
gender: males larger lung volume
age: lung volume increases until age 20-25. aging increases RV & FRC; VC decreases resulting in gas trapping
ethnicity: diff body build. Asian volume lower 10%/ Inuit-increased volume. black-decreased volume

Question 3

Describe and compare the effect of obstructive and restrictive
respiratory diseases on static lung volumes and the FEV1 to
FVC ratio.

Answer 3

Restrictive diseases: difficulty inspiring (PF, spondylitis)
Obstructive: limit air flow during expiration (COPD, asthma, bronchitis, emphysema)

healthy: FEV1/FVC = 75% or more. within 1 sec of esp. fev is 75% of total air u could breathe

Obstructive: FEV1/FVC <70%

Restrictive: FEV1/FVC >70% or normal

Question 4

distinguish between minute, alveolar, and dead space
ventilation and be able to calculate them given tidal volume,
breathing frequency and anatomic dead space. Outline how
pattern of breathing impacts alveolar ventilation.

Answer 4

minute ventilation (VE): tidal volume (VT) x breathing frequency= 6 L/min

alveolar ventilation (VA)= Va x breathing frequency = 4.2 L/min

dead space ventilation (VD)= Vds x frequency = 1.8 L/min

breathing shallow/fast- no air to alveoli
deep/slow- substantial air to alveoli. less dead

exercise: increases TV and frequency (combo of shallow/fast and deep/slow)

Question 5

Compare the partial pressure of gases in an ideal alveolus to
those in extremes of ventilation/perfusion mismatch

Answer 5

alveolar ventilation: in steady state, end pulmonary capillary blood reflects alveolar PCO2 and O2.
ideally- O2=100, CO2=40. V(ventilation)/Q(perfusion)=1

if obstructive blood flow. alveolar dead space = V/Q= 1/0 = infinity. alveolar pO2 increases, alveolar CO2 decreases (matches inspired)

Question 6

Describe the homeostatic mechanisms in place for matching of
ventilation and perfusion at alveolar level.

Answer 6

small bf = low CO2 in area= bronchoconstriction = constrict local airway = increase RAW = decrease airflow

small bf = increase O2 in area = relax smooth muscle = dilation = decrease raw = increase bf

(opposite if perfusion is greater than airflow)- shunt like i.e. mucus plug. gases just go past V/Q=0

Question 7

alveolar dead space

Answer 7

portion of breathing that reaches alveoli. doesn’t participate in gas exchange bc inadequate perfusion. insignificant in healthy lungs