2) respiration - ventilation and perfusion

Question 1

what is total ventilation

Answer 1

volume of air moved out of the lungs per unit of time

Question 2

under normal conditions what is tidal vol, breathing freq and total ventilation

Answer 2

tidal. vol = 0.5L
breathing freq = 12 per min
total ventilation. = 0.5 L x 12 = 6L

Question 3

what is the first portion of air that enters the respiratory zone

Answer 3

stale air present in conducting zone (anatomical dead space ~0.15L)

Question 4

what is alveolar ventilation

Answer 4

volume of fresh air reaching the respiratory zone

Question 5

equation for alveolar ventilation

Answer 5

alveolar ventilation - tidal vol - dead space vol (0.5-1.5 = 0.35L)

Question 6

how much CO2 is made by metabolism per minute

Answer 6

200ml

Question 7

how is C02 removed

Answer 7

alveolar ventilation

Question 8

effect of hyperventilation on alveolar composition

Answer 8

doubles breathing rate
alveolar ventilation goes from 4.2 to 8.4 L per minute
same (200ml) CO2 made, diluted in larger alveolar ventilation
over time CO2 in blood drops to balance alveoli, get. respiratory alkylosis

Question 9

effect of slowing breathing

Answer 9

alveolar ventilation decreases, same amount of CO2. therefore mmHg increases
blood CO2 increases causing respiratory acidosis

Question 10

effect of increasing rate of gas turnover on oxygen conc in alveoli

Answer 10

increases

Question 11

where is ventilation greatest in the lung

Answer 11

base, due to starting vol of alveoli and gravity

alveoli at apex start at larger volume therefore need greater pressure change to make a bigger vol change

Question 12

how to position in lung effect ventilation

Answer 12

posture and gravity

Question 13

starting vol and compliance of apex and base

Answer 13

apex = larger starting vol = lower compliance
base = smaller starting vol = greater compliance

Question 14

when is pulmonary resistance lowest

Answer 14

when lungs are at functional residual capacity

Question 15

what are alveolar vessels

Answer 15

capillaries and slightly larger vessels surrounded on all sides by alveoli

Question 16

what is the resistance in alveolar vessels linked to ?

Answer 16

transmural pressure. and lung volume.

alveoli expand, stretch capillaries, lumen of vessel s narrow, resistance increases

Question 17

what are extra-alveolar vessels

Answer 17

vessels not surrounded by alveoli

Question 18

what is the resistance in extra-alveolar vessels linked to ?

Answer 18

sensitive to changes in intrapleural pressure - more negative intrapleural pressure then blood vessels expand, resistance decreases

Question 19

what occurs in extra-alveolar vessels when breath in

Answer 19

resistance decreases due to a more negative intrapleural pressure
however when breath out, resistance increases due to intrapleural pressure becoming more positive

Question 20

where is the reference point for pulmonary circulation pressure

Answer 20

outside the heart at the level of the left atrium

Question 21

what is Ppa

Answer 21

pressure in pulmonary arterioles. mean of 15mmHg = 20cmH20

Question 22

Ppv

Answer 22

pressure in pulmonary vessels

mean of 8mmHg - 10cmH20

Question 23

PA

Answer 23

alveolar pressure

Question 24

Ptm

Answer 24

transmural pressure gradient across the wall of a vessel

Question 25

gradients in region above heart

Answer 25

profusion pressure is 3cmH20 on side and -7 on the other
have gradient so capillary is partly open and partly reduced
closer to heart pressure increases so compression only at end of capillaries

Question 26

level of heart

Answer 26

expansion of capillaries as go through alveolar beds, as pressure in capillaries is greater than that of alveoli
effect is increased when go down the lungs, so does perfusion rate

Question 27

base of lungs

Answer 27

linked to Extra-Alveolar and alveolar vessles
EA is due to most positive intrpleural pressure, compression effect on blood supply through A system. explains drop off of max perfusion at base of lungs

Question 28

factors that alter perfusion

Answer 28

decrease in oxygen = constriction of blood vessels in pulmonary circultation

increase in CO2 = constriction in blood vessels due to sensing pap of gas in alveoli

Question 29

what does a shunt do

Answer 29

local reduction of ventilation
as gas can’t be removed from area, composition becomes the same as mixed venous blood
Ventilation/perfusion ratio becomes 0
compensation - air redirected to other areas of the lung, hypoxic pulmonary vasoconstriction

Question 30

effect of pulmonary embolism

Answer 30

local reduction of perfusion
no exchange of gas in affected alveoli, composition the same as inspired air. Vent/perf rate becomes infinite
compensation - blood redirected to other areas, bronchiolar constriction, reduction in surfactant production