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Respiratory Alkalosis- An Overview

Published on Nov 04, 2022 and last reviewed on May 18, 2023   -  6 min read


Respiratory alkalosis is a condition characterized by elevated blood pH due to various reasons. To know more about the condition, read the below content.


The normal pH of the blood ranges from 7.35 to 7.45, which means that the blood is slightly alkaline (basic). The body's pH balance is essential to maintain homeostasis and is also known as the acid-base balance. The lungs and kidneys play an important role in maintaining this balance. Any abnormalities or disease conditions affecting the lungs and the kidneys would result in a disturbance in the acid-base balance causing either acidosis or alkalosis. Both conditions need to be addressed earlier to prevent further complications.

What Is the Normal Physiology of Acid-Base Balance?

The physiological pH buffering is mediated by two main compounds, bicarbonate (HCO3) and carbon dioxide (CO2). Bicarbonate (HCO3) maintains the alkalinity of the blood, whereas carbon dioxide (CO2) maintains the acidic nature of the blood and the body fluids. The balance between both compounds is mandatory to keep the pH in balance and maintain homeostasis. The respiratory system is responsible for regulating the CO2 levels through a process called respiration, and the renal system is responsible for regulating the HCO3 levels through a process called reabsorption.

What Are the Types of Acid-Base Imbalances?

There are four types of acid-base imbalances that include:

  1. Metabolic Acidosis - It is characterized by the presence of excess acid in body fluids.

  2. Metabolic Alkalosis - It is characterized by an increase in serum bicarbonate levels.

  3. Respiratory Acidosis - This is a condition in which the lungs fail to eliminate the carbon dioxide produced by the body.

  4. Respiratory Alkalosis - It is characterized by a high level of carbon dioxide in the blood.

What Is Respiratory Alkalosis?

Respiratory alkalosis is characterized by the increase in the body's pH to a level greater than 7.45. It mainly occurs due to lung diseases or the disorder. Respiratory alkalosis is one of the four primary acid-base imbalances.

What Are the Types of Respiratory Alkalosis?

There are two types of respiratory alkalosis, it includes:

  1. Acute Respiratory Alkalosis: It is characterized by a sudden decline in serum CO2 levels.

  2. Chronic Respiratory Alkalosis: It is characterized by the sustained and slow decrease in the serum CO2 levels in the circulation.

What Is the Pathophysiology of Respiratory Alkalosis?

Respiratory alkalosis is caused as a result of decreased CO2 levels in the blood. This occurs mainly due to hyperventilation, where most of the carbon dioxide is breathed away. The above-discussed etiologies would induce hyperventilation, expelling more carbon dioxide from the circulation. This results in a disturbance in the chemical equilibrium, thereby stimulating the carbonic enzyme anhydrase to produce more CO2 to compensate for the deprivation. This, in turn, increases the circulating hydrogen ion concentration and results in respiratory alkalosis.

What Is Alkalemia?

Alkalemia is characterized by an arterial blood pH of more than 7.45.

What Is the Etiology of Respiratory Alkalosis?

The main cause of respiratory alkalosis is hyperventilation, the conditions which can cause hyperventilation that includes:

  • Stroke.

  • Head injury.

  • Stress.

  • Pain.

  • Fever.

  • Hyperthyroidism.

  • Anxiety-hyperventilation.

  • Salicylates (a plant-based chemical used in over-the-counter drugs such as Aspirin).

  • Various toxins.

  • Hypoxia (insufficiency of oxygen to maintain normal tissue homeostasis).

  • Pulmonary embolism.

  • Pneumothorax.

  • Pneumonia.

  • COPD (chronic obstructive pulmonary disease).

  • Asthma.

  • Intubated patients.

What Are the Symptoms of Respiratory Alkalosis?

The symptoms of the condition include:

  • Dizziness.

  • Anxiety.

  • Chest pain.

  • Fever.

  • Chills.

  • Trauma.

  • Confusion.

  • Wheezing.

  • Hemoptysis (coughing blood-filled mucus).

  • Weakness.

  • Orthopnea (shortness of breath while lying down).

  • Dyspnea (shortness of breath, also called air hunger).

  • Tachycardia (increased heart rate).

  • Tachypnea (decreased heart rate).

  • Numbness.

  • Abdominal pain.

  • Nausea.

  • Vomiting.

  • Cardiac murmur.

  • Arrhythmia.

  • Tinnitus.

  • Weight loss.

  • Trousseau sign (a carpopedal spasm caused due to ischemia following inflation of the sphygmomanometer cuff).

  • Chvostek sign (twitching of the ipsilateral facial muscles on percussion over the branches of facial nerves).

  • Jaundice (characterized by the yellowish discoloration of the skin and mucous membranes).

  • Hematochezia (the passage of fresh blood through the anus).

  • Hepatosplenomegaly (the inflammation of the spleen and the liver).

  • Melena (characterized by the passage of black-colored stool).

How Is Respiratory Alkalosis Diagnosed?

1. History: A thorough medical history would help in understanding the symptoms of the disease and provide a clue in diagnosing the condition. The patient should be enquired about the history of breathlessness and difficulty in breathing, asthma, COPD, dizziness, chest pain, etc.

2. Physical Examination: Careful examination of the patient to check for the signs of hyperventilation and alkalosis such as respiratory rate, heart rate, temperature, blood pressure, cardiac murmur, arrhythmias, jaundice, Trousseau sign, and Chvostek sign. It would help in diagnosis and treatment planning.

3. Arterial Blood Gas: This is a type of blood test in which a blood sample from an artery is collected to measure the oxygen and carbon dioxide levels in the blood and also measures the acid-base balance in the blood. In the case of patients with respiratory alkalosis, the carbon dioxide levels in the blood would be reduced with pH increased by more than 7.5.

4. A-a Gradients: It is the alveolar-arterial gradient that measures the difference between the oxygen concentration in the alveoli and the arterial system. These values help in identifying the cause of respiratory alkalosis. The values of the A-a gradient are increased in case of pulmonary embolism, COPD, etc.,

5. Blood Test:

  • Serum Electrolyte Levels - The levels of electrolytes in the blood, such as sodium, potassium, calcium, magnesium, phosphate, etc., should be monitored to rule out further complications.

6. Pulmonary Function Test: It is done to check the functioning capacity of the lungs in the case of patients with respiratory disorders.

7. Chest X-Ray: This would help to rule out the infectious cause and the presence of pulmonary edema in patients with respiratory alkalosis.

8. Computed Tomography (CT) and Magnetic Resonance Imaging (MRI): CT and MRI of the head would help to find out whether the underlying cause of the disease is a neurological insult or head injury.

How Is Respiratory Alkalosis Managed?

The main aim of management is to treat the underlying cause of the condition and address it as early as possible. The steps in management are as follows:

  • Anxiolytics - These are a group of drugs given to treat anxiety in patients with this condition.

  • Antibiotics - Are given to patients with infection as the underlying cause. Appropriate antibiotics should be chosen based on the culture reports.

  • Anticoagulants - Are given to patients with a history of embolism.

  • Ventilator Support - This is necessary for patients with asthma, respiratory failure, COPD, etc., to regularize their breathing patterns.

  • Infusing Acidic Agents - In patients with severe respiratory alkalosis, acidic agents can be directly infused into the blood to balance the pH values.

What Is the Differential Diagnosis of Respiratory Alkalosis?

  • Asthma Exacerbation - It is characterized by swollen and inflamed airways, causing difficulty breathing, wheezing, etc.,

  • Atrial Tachycardia - This is a type of supraventricular tachycardia resulting in an increased heart rate.

  • Metabolic Alkalosis - It is characterized by the primary increase in bicarbonate levels.


Though respiratory alkalosis is not a life-threatening condition, it can lead to serious complications if not addressed early. As many conditions would result in respiratory alkalosis, the management of the condition needs the coordinated work of an interprofessional team. The prognosis of the condition depends on the cause of respiratory alkalosis; hence, it is always important to diagnose the etiology and treat the primary factor.

Last reviewed at:
18 May 2023  -  6 min read




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