L7 - Relationship between CVS & RS (heart&lungs)

Question 1

What causes the enlargement of the right side of the heart?

Answer 1

• High BP in the pulmonary blood vessels, usually causes by chronic lung disease

Question 2

Hypertrophic heart disease

Answer 2

• Hypertrophic cardiomyopathy (HCM) is a condition affecting the left ventricle, the main pumping chamber of the heart.
• The walls of the left ventricle become thick and stiff.
• Enlarged heart muscle
• Over time, the heart can’t take in or pump out enough blood during each heartbeat to supply the body’s needs.

Question 3

Ventilation(V) : Perfusion (Q) Matching

Answer 3

• Ventilation rate (V) - volume of gas inhaled + exhaled at given time (min).
• V = tidal volume x respiratory rate
• Perfusion (Q) - total volume of blood reaching pulmonary capillaries at given time
• Ideal V/Q ratio = 1 – but varies depending on the part of lung concerned

Question 4

Ventilation-Perfusion Mismatch

Answer 4

• Decreased ventilation – decreased V/Q.
• Result => pO2 falls and pCO2 rises
• Response => hypoxic vasoconstriction causes diversion of blood to better ventilated parts of lung but haemoglobin already saturated so unable to bind to additional O2 to increase pO2. Therefore, pO2 level remains low - causing hyperventilation — resulting in normal/low CO2 levels (decreasing pCO2) — V/Q ratio maintained.

Question 5

What is the effect of PO2 o haemoglobin saturation?

Answer 5

• Oxygen-heamoglobin dissociation curve
• Steep slope portion of curve at 60mmHg down to 20mmHg - ideal for unloading oxygen in tissues - small decrease in pO2
• In arterial blood, pO2 = 100mmHg and haemoglobin = 98.5% saturated
• In venous blood, pO2 = 40mmHg and haemoglobin = 75% saturated

Question 6

Effect of O2 affinity on Oxygen-heamoglobin dissociation curve

Answer 6

• Shift to right (decreased affinity) = less loading of O2 and less unloading into tissues
• Shift to left (increased affinity) = more loading of O2 but less unloading into tissues

Question 7

Effect of temperature on Oxygen-heamoglobin dissociation curve

Answer 7

• 37oC = optimal temperature
• 20oC = increased affinity
• 43oC = decreased affinity – active tissues so more O2 delivery + unloading in tissues

Question 8

Effect of pH on Oxygen-heamoglobin dissociation curve

Answer 8

• pH = 7.4 =>optimal pH level
• pH = 7.2 (decreased affinity) => Bohr effect – increases O2 unloading into tissues
• pH = 7.6 (increased affinity) => active tissues so produce more acid (decreased pH in tissues) causing a shift to right — result: more O2 unloading to tissues.

Question 9

Effect of PCO2 on Oxygen-heamoglobin dissociation curve

Answer 9

• Increased pCO2 => increased CO2 loading => decreased haemoglobin’s affinity for O2 => decreased O2 unloading
• Decreased pCO2 => increased CO2 unloading => increased haemoglobin’s affinity for O2 => increased O2 loading