Physio Flashcards

Question

Causes of surfactant deficiency

Answer 1

① Respiratory distress syndrome • in premature infant →↓ Surfactant →↑ surface tension → lung collapse ②Long term inhalation of 100% 02 or use of pump oxygenator in cardiac surgery ③ Obstruction of branch of pulmonary artery ④ Heavy smokers ⑤ Hypothyroidism ⑥ Hypocorticism ⑦ Hyperinsulinsm:

Answer 2

Physical factors: negative intrapleural pressure: During inspiration → more negative intrapleural pressure → more airways distention →↓ airway resistance. Lateral tension: During inspiration as alveoli expand → exerts lateral traction on small airways →↓ airway resistance. Nervous: sympathetic and parasympathetic Chemical factors: cause bronchoconstriction like hitamine

Answer 3

Part of respiratory system that doesn’t take part in gas exchange ❶ Anatomical Dead Space: volume of air in the conducting zone = 150 ml ❷ Physiological dead space = anatomical dead space + alveolar dead space. in normal both are the same Significance: ❶ Difference in composition between inspired, alveolar and expired air: Alveolar air contain less PO2 and more CO2 than inspired/expired ❷ Differences in alveolar ventilation in various breathing patterns: in shallow rapid there is low ventilation causing hypoxia. In deep becomes high alveolar ventilation Protective function: humification and warming of inspired air. Removal of foreign particles from air.

Answer 4

VA/Q = 0.8. Both alveolar ventilation and perfusion ↓ from lung base toward apex At apex, perfusion is poor compared to ventilation At base, perfusion is high compared to ventilation Cause of the regional difference: Under the effect of its weight, the lung drop → widen pleural space more at lung apex Intra pleural pressure is more negative at apex than base Cause of regional difference in perfusion is due to the effect of gravity.

Answer 5

At ideal ventilation and perfusion: Arterial PO2 slightly < alveolar PO2 due to venous admixture At normal perfusion, no ventilation (in bronchial obstruction): VA/Q is 0, capillaries can't be oxygenated, PO2 in veins=arteries At normal ventilation, no perfusion (pulmonary embolism) VA/Q is infinite. No gas exchange (no CO2 is extracted or O2 is added)

Answer 6

Relationship between PO2 and % HbO2 saturation is S shaped Plateau part: PO2 from 100 to 60 mmHg the saturation is relatively constant, doesn't go below 90%. Importance at high altitudes allow easy saturation even if O2 tension is low Steep part: At 60 mmHg, desaturation is very rapid. At 40 mmHg 27% of O2 is taken by tissue. At 20 mmHg curve becomes vertical.

Answer 7

Means ↓ Hb affinity to O2 = less O2 bound to Hb ↑ temperature ↑ PCO2 ↑ H+ (↓PH) muscular exercise ↑ (2.3 DBG)

Answer 8

Means ↑ Hb affinity to O2 = more O2 bound to Hb ❶ ↓ temperature ❷ ↓ PCO2 ❸ ↓ H+ (↑ PH) ❹ ↓ 2,3 DBG ❺ Carbon monoxide ❻ fetal hemoglobin

Answer 9

At tissues; CO2 diffuse from tissue to blood according to pressure gradient. Inside the RBCs, CO2 gets converted into HCO3- which causes an electric charge and acidity. Some of the HCO3- moved from RBCs to plasma by binding to Na+ to decrease acidity. Chloride diffuses from plasma to RBCs so it can neutralize the change in electrical charge. At the lungs: Low CO2 tension, HCO3 shifted from plasma to RBC's and Chloride returns to plasma.

Answer 10

Two groups of respiratory centers: Medullary and Pontine respiratory center. Medullary center can maintain automatic, irregular respiration, modified by pontine center Medullary has 2 centers: Dorsal respiratory group and ventral respiratory group. Dorsal respiratory group is responsible for inspiration and get excited by apneustic center and inhibited by pneumotaxic center. Ventral respiratory group ( turned on during respiration) mainly responsible for expiration, works in case of hyperventilation. receive stimulus from dorsal respiratory group. Apneustic center: in lower pons, stimulate DRG and pneumotaxic and turn on inspiration Pneumotaxic center: in upper pons, inhibitory to DRG apneustic and switch of inspiration.

Answer 11

Site: under ventral surface of medulla Stimulus: ↑H+ (primary stimulus)  H+ in CSF & brain interstitial fluid: the only direct stimulus  H+ in blood: has no effect on stimulating central chemoreceptor b) ↑ PCO2 in blood  indirect effect as CO2 crosses BBB  CO2+H2O → H2CO3→ HCO3- + H+ (acidifying CSF)  Small change in arterial PCO2→ results in large changes in CSF pH

Answer 12

Site: carotid bodies and aortic bodies They monitor only PO2 Stimulus: ↓ Oxygen tension (hypoxia) most potent stimulus. At PO2 60 doubles ventilation, PO2 100 no effect on ventilation and at 20 inhibit RC. H+ concentration: Metabolic acidosis: stimulate ventilation Metabolic alkalosis: inhibit ventilation CO2 tension: when increase it stimulates ventilation

Answer 13

↓ PO2 from 100-60 mmHg has a minimal effect on Hb O2 saturation Stimulatory effect of ↓ PO2 from 100 to 60 mmHg → not affect ventilation ↓ PO2 has Stimulatory effect on peripheral chemoreceptors & inhibitory effects on RC

Answer 14

Hypoxia is O2 deficiency at tissue due to low O2 supply or utilization Hypoxic hypoxia: due to inadequate oxygenation of arterial blood. ❶ ↓PO2 in inspired air : e.g. high altitude ❷ Shunting of venous into arterial blood ❸ pulmonary disorders: impaired ventilation: RC depression Impaired diffusion: edema ventilation perfusion imbalance characteristics: ↓ PO2, O2 content, % Hb sat. in arterial blood and cyanosis Anemic hypoxia: due to low Hb ❶ ↓ Hb (anemia) ❷ Abnormal Hb: e.g. Characteristics pf anemic hypoxia: Normal PO2, % Hb sat., ↓ 02 content in arterial blood. No cyanosis