Respiratory Physiology-ventilation and perfusion

Question 1

Pip(intra pleural pressure)

Answer 1

-already negative due to counter recoil of chest wall and alveoli and slight ‘suction’ of excess fluid into lymphatic channels

Question 2

transpulmonary pressure

Answer 2

Ptp is synonymous with alveolar wall distension-the larger the Pip-The greater the alveolar wall distension

Question 3

pneumothorax

Answer 3

pleural seal broken, with pathway either:
-inwards towards lung tissie
-outwards through chest wall
negative pressure cannot be generated->ventilation ineffective
-natural tendency of lung to collapse now unopposed

Question 4

Compliance

Answer 4

expandability of lung and chest wall
high compliance-good
value varies as lung inflates

Question 5

emphysema

Answer 5

destruction of alveolar walls->large air spaces that are not cleared of air on exhalation

• barrel chest
• emphysema and chronic bronchitis are the two principle causes of COPD

Question 6

surfactant

Answer 6

a lipoprotein secreted by type ii alveolar cells
lowers surface tension
-increases compliance
-improves work of breathing
clinically
-infant respiratory distress syndrome and acute respiratory distress syndrome
IRDS-surfactant not produced until four months gestation and not sufficiently until 7 months gestation or later

Question 7

SHUNT

Answer 7

no ventilation:pulmonary arterial blood from this area is not oxygenated

Question 8

alveolar dead space

Answer 8

no perfusion:alveolar gas is the same as room air, containing no CO2

Question 9

henry’s law

Answer 9

quantity of gas dissolved in a liquid is directly proportional to:
-partial pressure of gas
-solubility of gas
the higher the partial pressure and the higher the solubility of the gas=>more gas will stay in the solution

Question 10

the Bohr effect

Answer 10

in tissues that need more O2,the local environment moves Hb-O2 curve to the right, aiding unloading of O2

Question 11

Haldane effect:works in tandem with the Bohr effect to enhance CO2 transport

Answer 11

tissues;
-Hb gives up O2
-Affinity for CO2 increases
-Greater CO2 carriage
lungs:
-Hb binds O2
-Affinity for CO2 decreases
-Hb gives up CO2