If the atmospheric pressure is 101 kPa, what is the partial pressure of oxygen in dry inhaled air:
Dalton's law states that when two or more gases, which do not react chemically, are present in the same container, the total pressure is the sum of the partial pressures of each gas.
In the atmosphere, the partial pressure of a gas is the contribution to barometric pressure exerted by that gas. The total pressure exerted by the atmosphere at sea level is 760 mmHg (101 kPa).
The partial pressure of each gas is determined by the fractional concentration of that gas. Dried air contains 21% oxygen, 78.1% nitrogen and 0.9% inert gases such as helium and argon. The small amount of CO2 in air (< 0.04 %) is usually ignored.
Therefore the partial pressure of oxygen in dry inhaled air = 0.21 x 760 (101) = 159 mmHg (21.2 kPa) and the partial pressure of nitrogen = 0.78 x 760 (101) = 593 mmHg (78.8 kPa).
At altitude, the oxygen fraction is unaltered but the barometric pressure and thus partial pressure of oxygen is reduced.
Typical values for a resting young healthy male (in kPa) are shown below:
If a gas is exposed to a liquid to which it does not react, gas particles will move into that liquid. Henry's law states that the number of molecules dissolving into the liquid is directly proportional to the partial pressure at the surface of the gas.
The constant of proportionality is the solubility of the gas in the liquid, and it is determined by the gas, the liquid and the temperature:
Content of dissolved gas X in liquid Y = (Solubility of X in Y) x (Partial pressure of X at surface)
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Biochemistry | Normal Value |
---|---|
Sodium | 135 – 145 mmol/l |
Potassium | 3.0 – 4.5 mmol/l |
Urea | 2.5 – 7.5 mmol/l |
Glucose | 3.5 – 5.0 mmol/l |
Creatinine | 35 – 135 μmol/l |
Alanine Aminotransferase (ALT) | 5 – 35 U/l |
Gamma-glutamyl Transferase (GGT) | < 65 U/l |
Alkaline Phosphatase (ALP) | 30 – 135 U/l |
Aspartate Aminotransferase (AST) | < 40 U/l |
Total Protein | 60 – 80 g/l |
Albumin | 35 – 50 g/l |
Globulin | 2.4 – 3.5 g/dl |
Amylase | < 70 U/l |
Total Bilirubin | 3 – 17 μmol/l |
Calcium | 2.1 – 2.5 mmol/l |
Chloride | 95 – 105 mmol/l |
Phosphate | 0.8 – 1.4 mmol/l |
Haematology | Normal Value |
---|---|
Haemoglobin | 11.5 – 16.6 g/dl |
White Blood Cells | 4.0 – 11.0 x 109/l |
Platelets | 150 – 450 x 109/l |
MCV | 80 – 96 fl |
MCHC | 32 – 36 g/dl |
Neutrophils | 2.0 – 7.5 x 109/l |
Lymphocytes | 1.5 – 4.0 x 109/l |
Monocytes | 0.3 – 1.0 x 109/l |
Eosinophils | 0.1 – 0.5 x 109/l |
Basophils | < 0.2 x 109/l |
Reticulocytes | < 2% |
Haematocrit | 0.35 – 0.49 |
Red Cell Distribution Width | 11 – 15% |
Blood Gases | Normal Value |
---|---|
pH | 7.35 – 7.45 |
pO2 | 11 – 14 kPa |
pCO2 | 4.5 – 6.0 kPa |
Base Excess | -2 – +2 mmol/l |
Bicarbonate | 24 – 30 mmol/l |
Lactate | < 2 mmol/l |