11-24-2007, 05:01 AM
A 63-year-old man has pneumococcal pneumonia
with extensive air-space consolidation in the left upper
and left lower lobes. He complains of extreme shortness
of breath when positioned with his left side down. An
arterial blood sample drawn in this position shows a PO2
of 6.2 kPa (46 mmHg); 10 min earlier, an arterial blood
sample drawn while his right side was dependent had revealed a P of 8.2 kPa (66 mmHg). The most likely ex- O2
planation for the drop in P when the man was lying on O2
his left side is
(A) increased blood flow to the dependent lung
(B) reduced ventilation to the dependent lung
© increased airway resistance in the dependent lung
(D) accumulation of interstitial edema in the dependent
lung
(E) increased stiffness of the chest wall on the dependent
side
with extensive air-space consolidation in the left upper
and left lower lobes. He complains of extreme shortness
of breath when positioned with his left side down. An
arterial blood sample drawn in this position shows a PO2
of 6.2 kPa (46 mmHg); 10 min earlier, an arterial blood
sample drawn while his right side was dependent had revealed a P of 8.2 kPa (66 mmHg). The most likely ex- O2
planation for the drop in P when the man was lying on O2
his left side is
(A) increased blood flow to the dependent lung
(B) reduced ventilation to the dependent lung
© increased airway resistance in the dependent lung
(D) accumulation of interstitial edema in the dependent
lung
(E) increased stiffness of the chest wall on the dependent
side