This series of illustrations shows how respiratory alkalosis develops at the cellular level.

1. When pulmonary ventilation increases above the amount needed to maintain normal carbon dioxide (CO₂) levels, excessive amounts of CO₂ are exhaled. Hypo capnia (a fall in PaCO₂) leads to a reduction in carbonic acid (H₂CO₃) production, a loss of hydrogen ions (H⁺) and bicarbonate ions (HCO₃^-), and a subsequent rise in pH. Look for a pH above 7.45, a PaCO₂ below 35 mm Hg, and an HCO₃^- below 22 mEq/L.
   
2. In defense against the rising pH, H⁺ is pulled out of the cells and into the blood in exchange for potassium ions (K). The H⁺ entering the blood combines with HCO₃^- to form H₂CO₃, which lowers pH. Look for a further decrease in HCO₃^- levels, a fall in pH, and a fall in serum potassium levels (hypokalemia).
   
3. Hypocapnia stimulates the carotid and aortic bodies and the medulla, which causes an increase in heart rate without an increase in blood pressure. Monitor for angina, electrocardiogram (ECG) changes, restlessness, and anxiety.
   
4. Simultaneously, hypocapnia produces cerebral vasoconstriction, which prompts a reduction in cerebral blood flow. Hypocapnia also overexcites the medulla, pons, and other parts of the autonomic nervous system. Monitor for increasing anxiety, fear, diaphoresis, dyspnea, alternating periods of apnea and hyperventilation, dizziness, and tingling in the fingers or toes.
   
5. When hypocapnia lasts more than 6 hours, the kidneys increase secretion of HCO₃^- and reduce excretion of H⁺. Periods of apnea may result if the pH remains high and the PaCO₂ remains low. Look for slowed respiratory rate, hypoventilation, and Cheyne-Stokes respirations.
   
6. Continued low PaCO₂ increases cerebral and peripheral hypoxia from vasoconstriction. Severe alkalosis inhibits calcium (Ca) ionization, which in turn causes increased nerve excitability and muscle contractions. Eventually, the alkalosis overwhelms the CNS and the heart. Look for decreasing LOC, hyperreflexia, carpopedal spasm, tetany, arrhythmias, seizures, and coma.