48 一位28歲女性因為長時間杵狀指與肢端發紺到院求治。動脈血氣體分析為：pH 7.45，PaO2 50 mmHg，PaCO2 35 mmHg，HCO3􀀎􀀁24 mmol/L（未使用氧氣），血比容為65%。給予純氧呼吸30分鐘後，再分析動脈血氣體結果為：pH 7.4，PaO2 195 mmHg，PaCO2 39 mmHg，HCO3􀀎 24 mmol/L，胸部X光與肺功能檢驗都正常。最可能造成此病人低血氧的機制為何？

通氣不足 通氣灌流比異常 血液分流 肺部瀰散障礙

血液分流

SHUNTING!

肺部瀰散障礙: DIFFUSION PROBLEM

通氣不足 HYPOVENTILATION

通氣灌流比異常 V/Q MISMATCH

血比容:HEMATOCRIT

• Adult males: 42%-54%
  
  
• Adult women: 38%-46%

IN THIS PATIENT THE HEMATOCRIT IS ELEVATED. COMPENSATION TO HER CHRONIC LUNG PROBLEM

Elevated hematocrit

In cases of dengue fever, a high hematocrit is a danger sign of an increased risk of dengue shock syndrome.

Polycythemia vera (PV), a myeloproliferative disorder in which the bone marrow produces excessive numbers of red cells, is associated with elevated hematocrit.

Chronic obstructive pulmonary disease (COPD) and other pulmonary conditions associated with hypoxia may elicit an increased production of red blood cells. This increase is mediated by the increased levels of erythropoietin by the kidneys in response to hypoxia.

Professional athletes' hematocrit levels are measured as part of tests for blood doping or Erythropoietin (EPO) use; the level of hematocrit in a blood sample is compared with the long-term level for that athlete (to allow for individual variations in hematocrit level), and against an absolute permitted maximum (which is based on maximum expected levels within the population, and the hematocrit level that causes increased risk of blood clots resulting in strokes or heart attacks).

Anabolic Androgenic Steroid (AAS) use can also increase the amount of RBCs and, therefore, impact the hematocrit, in particular the compounds boldenone and oxymethelone.

If a patient is dehydrated, the hematocrit may be elevated.