Hypoxic Vasoconstriction in Pneumonia

HPV appears to be ineffective in pneumonia. Light et al. measured blood flow with microspheres to the left lower lobe of the dog before and 3 days after inoculating the left lower lobe with Streptococcus pneumoniae (20). Using radiographs, they confirmed the presence of pneumonia confined to the left lower lobe. Perfusion to the left lower lobe showed a variable and nonsignificant decrease that was not affected by 02 breathing. Utilizing blood samples from the lobar veins at terminal thoracotomy, they measured QS/QT through the left lower lobe with pneumonia as 0.69 compared to 0.08 through the control right lower lobe. Alveolar ventilation approached zero in some of the pneumonia lungs.

They concluded that HPV was ineffectual in pneumonia so that the magnitude of shunt and low V/Q perfusion was increased causing marked hypoxemia. Other authors with other models (27) have reached similar conclusions and Sostman et al. have shown that perfusion scans in consolidated pneumonia cases in humans may be normal (40).

Pulmonary Hypertension

Figure 5. Control arterial blood gases and H+ in 27 subjects before and the maximum change in arterial blood gases after the sublingual administration of 0.6 mg nitroglycerin. Individual values for Pa02 and group mean values (means±SE) for Pa02 (•), PaC02 (o), and H+ (x) are shown. The decrease in Pa02 in subjects with small airways disease was significant at P<0.001 and in the normal subjects at P=0.05 (Reprinted from Ref. 12).

Figure 5. Control arterial blood gases and H+ in 27 subjects before and the maximum change in arterial blood gases after the sublingual administration of 0.6 mg nitroglycerin. Individual values for Pa02 and group mean values (means±SE) for Pa02 (•), PaC02 (o), and H+ (x) are shown. The decrease in Pa02 in subjects with small airways disease was significant at P<0.001 and in the normal subjects at P=0.05 (Reprinted from Ref. 12).

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