Respiratory alkalosis

Disease Description (Causes and Symptoms)

• Definition: A condition in which excessive alveolar ventilation decreases the partial pressure of arterial carbon dioxide (PaCO2), making the blood more alkaline (respiratory alkalosis).
• Main pathophysiology: Hyperventilation causes a decrease in PaCO2 → a decrease in blood hydrogen ions, resulting in an increase in pH. The more acute the condition, the more prominent the neurological and vascular symptoms due to rapid pH changes. When it becomes chronic, the kidneys excrete HCO3−, resulting in compensation.
• Common causes: Anxiety or panic-related hyperventilation, adaptation to high altitude, hypoxemia (such as pneumonia, pulmonary embolism, and pulmonary edema), central nervous system stimulation (the early stage of salicylate overdose, medications such as progesterone), and mechanical ventilation settings (hyperventilation).
• Main symptoms: Dizziness, fainting, tingling or numbness in the hands and feet (which may be caused by hypocalcemia), muscle cramps (spasms), tachypnea or a feeling of shortness of breath, chest pain, arrhythmia, altered consciousness, and seizures (in severe cases).
• Diagnosis: Arterial blood gas (ABG) — low PaCO2 and increased pH (with a possible decrease in HCO3− due to compensation). Clinical history, oxygen saturation, and evaluation of underlying diseases are also performed.

Treatment Methods

• Basic principles: Correct the cause and normalize breathing. Relief of acute symptoms and management of complications (such as hypocalcemia and arrhythmia) take priority.
• Nonpharmacological treatment: When anxiety or hyperventilation is the cause, stabilize the patient and provide breathing retraining (abdominal breathing). Rebreathing through a paper bag is contraindicated when hypoxemia is possible (when pulmonary embolism or hypoxemia is suspected).
• Pharmacological treatment: When severe anxiety or panic is present, an appropriate sedative (for example, a low-dose benzodiazepine) may be considered. For symptoms of hypocalcemia, intravenous calcium supplementation may be given (under medical judgment).
• Oxygen and mechanical ventilation: Apply oxygen therapy when hypoxemia is present. In patients using a ventilator, prevent hyperventilation by adjusting the respiratory rate and TV (tidal volume) (setting a target PaCO2).
• Treatment of underlying diseases: Appropriate antibiotics, anticoagulants, and other treatments for triggering diseases such as pneumonia and pulmonary embolism. If the cause is a medication, such as salicylate overdose, discontinue the medication and provide detoxification.
• Monitoring: Repeat ABG, electrocardiography (monitoring for arrhythmia), and electrolyte tests (especially calcium).
• Precautions:
  • Use paper-bag breathing only for a short period after hypoxemia has been ruled out.
  • Use sedatives with caution when there is a risk of reduced ventilation (for example, when combined with central nervous system depressants).
  • Treatment strategies and prognosis differ in patients with underlying heart or lung disease.

Checklist Before an Outpatient Visit (Items to Prepare and Example Questions)

• Items to prepare: A list of medications currently being taken (including prescriptions, OTC medications, and supplements), past medical history (heart, lung, and neurological diseases), recent test results (blood tests, oxygen saturation, and a copy of the ABG if available), records of when symptoms began and their triggers (anxiety, high altitude, exercise, medications, etc.), and notes on symptom frequency, duration, and presence or absence of symptoms such as fainting or seizures.
• Items to check before the visit: Current oxygen saturation, if possible; whether there have been any recent seizures or fainting episodes; whether there have been any changes in medications; and whether the patient is pregnant (which affects medication selection).
• Examples of useful information to provide to the doctor during the outpatient visit: A symptom diary (respiratory rate and symptoms before and after an episode), previous ABG or electrocardiogram results, and the timing and dosage of recently taken medications such as aspirin.

Examples of General Questions to Ask the Doctor

• "How should my ABG (or oxygen saturation) results be interpreted? What should the target PaCO2 and pH be during treatment?"
• "What appears to be the cause of this condition? Are additional tests (such as CT or pulmonary blood-flow studies) needed?"
• "Could any of the medications I am currently taking be causing a problem? Which medications should be stopped or replaced?"
• "What breathing-control techniques or lifestyle-management methods can I use at home?"
• "What preventive measures should I take to reduce recurrence?"

Examples of Customized Questions by Disease

• "I have repeated episodes of hyperventilation. How can we distinguish whether the cause is anxiety or panic from a lung or heart problem? What tests are needed?"
• "In a patient using a ventilator, the PaCO2 is too low. How should the ventilation settings be adjusted (recommended target value)?"