ABGs are based on normals for healthy adults at sea level. Newborns have a lower PaO2, as do older adults. From ages 60-90, an older adult’s PaO2 decreases 10 mmHg per decade. Pts w/ chronic lung dxs may have a PaO2 of 60 mmHg and a PaCO2 of 50 mmHg as baseline. Attempts to return to ‘normal’ would be catastrophic for these clients. For an individual receiving oxygen therapy, the PaO2 should rise approximately 50 mmHg for each 10 percent rise in oxygen concentration.
Less than 35, alkalosis. Causes: Alveolar hyperventilation, hypoxia, anxiety, PE, pregnancy, hyperventilation with mechanical ventilator, compensatory mechanism to metabolic acidosis, head injury, fever, fear, pain Acidosis acute causes: alveolar hypoventilation, respiratory depression, oversedation, drug overdose, head injury, decreased ventilation, respiratory muscle fatigue, neuromuscular disease, mechanical ventilation w/ underventilation, altered diffusion / ventilation – perfusion mismatch from pulmonary edema, severe atelectasis, pneumonia, severe bronchospasm. Chronic acidosis causes usually COPD
Carbon dioxide is considered an acid because it combines w/ water to form carbonic acid
pH is key to determining extent of compensation.
UGI tract losses include vomitting and NG suctioning
If pt is severely anemic, O2 levels will drop
Bases bind free hydrogen ions in solution. Bases are hydrogen acceptors that reduce the amount of free hydrogen ions in solution. HCO3 is a weak base and HCO3 ions in the body prevent major changes in pH.
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