ELRO FC280211 Bedienungsanleitung Seite 7

constant, the level of COHb in the blood will approach an equilibrium (saturation) state after several hours. However,
the rate at which the equilibrium is reached depends on many factors, e.g., lung ventilation rate (physical activity)
and alveolar capillary transfer, cardiac parameters, blood hemoglobin concentration, barometric pressure, oxygen,
and carbon dioxide concentration in the inhaled air, but the two most important factors in determining the COHb
level are the CO concentration and the duration of exposure.
The effects of different saturation blood COHb levels on healthy adults:
% COHb
0.3 - 0.7
0.7 - 2.9
2.9 - 4.5
4 - 6
7 - 10
10 - 20
20 - 30
30 - 40
40 - 50
60 - 70
Source: U.S. Environmental Protection Agency 1984
The relationship between the CO concentration and the duration of exposure can be calculated for a given %COHb,
by parameterizing the above factors.
7.2 Chronic effects on high-risk groups
Individuals with coronary artery disease exposed to low levels of CO show reduced ability to exercise and the time of
onset of exercise-induced angina pectoris in such patients exposed to low levels of CO is reduced. Carbon monoxide
readily crosses the placental barrier and may endanger the normal development of the foetus. Several high-risk
groups are particularly sensitive to the effects of CO because of various organ impairments or specific changes,
mainly:
a) those whose oxygen carrying capacity is decreased due to anemia or other hemoglobin disorders.
b) those with increased oxygen needs such as those encountered in fever, hyperthyroidism, or pregnancy.
c) those with systemic hypoxia due to respiratory insufficiency.
d) those with heart disease and any vascular insufficiency.
WHO guidance states that to protect non-smoking, middle-aged, and elderly population groups with documented or
latent coronary artery disease from acute ischemic heart attacks, and to protect the foetuses of non-smoking
pregnant women from untoward hypoxic effects, a COHb level of 2.5% should not be exceeded. The following WHO
guideline values and periods of time-weighted average exposures have been determined in such a way that the COHb
level of 2.5% is not exceeded, even when a normal subject engages in light or moderate exercise:
100 mg/m³ (90 ppm) for 15 min.
060 mg/m³ (50 ppm) for 30 min.
030 mg/m³ (25 ppm) for 1 h.
010 mg/m³ (10 ppm) for 8 h.
7.3 Normal COHb levels
Under normal conditions, humans typically have low levels of COHb of between 0.3% and 0.7% present within the
body. These levels are considered neither beneficial nor harmful.
7.4 Tobacco smoking
Tobacco smokers are exposed to significant concentrations of CO. In cigarette smokers, the COHb concentration
varies between 5%-9%, while heavy cigar smokers may exceed 10%.
WARNING! Exposure to high levels of carbon monoxide can be fatal or cause permanent damage and disabilities.
WARNING! The device may not prevent the chronic effects of carbon monoxide exposure, and that the device will
not fully safeguard individuals at special risk.
Effects
Normal range in non-smokers due to endogenous CO production
No proven physiological changes
Cardio-vascular changes in cardiac patients
Usual values observed in smokers, impairment in psychomotor tests
Cardio-vascular changes in non-cardiac patients (increased cardiac output and coronary blood flow)
Slight headache, weakness, potential burden on foetus
Severe headache, nausea, impairment in limb movements
Severe headache, irritability, confusion, impairment in visual acuity, nausea, muscular weakness,
dizziness
Convulsions and unconsciousness
Coma, collapse, death
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