Respiratory system 9

The alveolar PO2 is

• 159 mmHg
• 149 mmHg
• 100 mmHg
• 40 mmHg

The arterial PO2 is less than alveolar PO2 as

• The lungs use O2
• venous blood from the myocardium drain directly into the left heart
• Some portions of lung are better ventilated than others
• Some portions of lung are better perfused than others

Th amount of O2 carried in blood in dissolved form is

• 0.03 ml
• 0.3 ml
• 3 ml
• more than 3 ml

Saturation of oxygen in arterial and venous blood is

• 100% & 75%
• 100% & 50%
• 97% & 75%
• 50% & 50%

Shift of Oxygen haemoglobin dissociation curve (ODC) to right indicates

• Increased affinity of O2
• Decreased affinity of O2
• Cannot be commented
• Increased O2 carrying capacity of blood

Right shift of oxygen dissociation curve (ODC) is not found in

• rise of temperature
• fetal blood replaced with adult blood
• rise of CO2
• in pulmonary capillaries

Coefficient of oxygen utilisation normally is

• 1.0
• 0.75
• 0.50
• 0.25

Physiological significance of plateau phase of Oxygen dissociation curve is

• causes more release of oxygen from Hb when PO2 falls
• Shifting to right makes this portion steeper
• amount of O2 carried with Hb does not change considerably in reduced PO2
• Uptake of O2 by body decreases at high altitude

Normal value of P50 is

• 20 mmHg
• 27 mmHg
• 37 mmHg
• 40 mmHg

A 12 yrs old boy has severe asthmatic attack. he has rapid breathing and becomes cyanotic. His arterial Po2 is 60 mmHg and pCO2 is 30 mmHg. Which statement correlates well with the case?

• FEV1/FVC is increased
• V/Q ratio is increased in affected areas of lung
• His arterial PO2 is less than normal because as hypoxemia is causing him to hyperventilate
• RV would be decreased