Hypoxemia, effects on the pulmonary vascular bed

A kinetic study of lung DNA-synthesis during simulated chronic high altitude hypoxia

Rats were exposed to crhonic hypobaric hypoxia at a simulated altitude of 4250 m for 3, 6, 9, 12, 20, and 35 days. The in-vitro incorporation of 3H-thymidine into the DNA of lung tissue was measured and compared with that of normoxic controls: the obtained time course study showed a maximum increase of 345% on the ninth day of hypoxia, indicating a marked stimulation of cellular proliferation. Between the 12th and 20th day of hypoxia, the lung DNA-synthesis reached control values. No significant change in the DNA-concentration of the lungs was registered. The response to hypoxia was less impressive in rat livers used as controls.

Quantitation of thick-walled peripheral lung vessels in chronic airways obstruction

The number of thick-walled peripheral lung vessels (defined as vessels of less than 100 mu diameter with two distinct elastic laminae) was calculated in 50 postmortem lungs. The size of the right ventricle, the amount and type of emphysema, and the proportion of small airways lumen in the lung were also quantitated. Eighteen patients had died as a result of chronic airways obstruction, 17 had symptoms of chronic chest disease but died from some unrelated cause, and 15 had no symptoms related to the respiratory system. The mean number of thick-walled peripheral lung vessels (TWPV) was found to be significantly greater in the fatal disease group than in both of the other groups. No significant difference was found between the mean values of the symptomatic and asymptomatic groups. The mean number of TWPV was significantly greater in cases with a right ventricular weight of more than 80 g than in those with a weight of less than 65 g. Positive correlations were found between the number of TWPV and right ventricular weight, total amount of emphysema in the lung, and the amounts of centrilobular and panlobular emphysema. Significant negative correlations were found between the number of TWPV and both the ratio of the weight of the left ventricle to the right ventricle and the proportion of small airways lumen in the lung.