respiratory alkalosis

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Respiratory alkalosis Respiratory alkalosis is a condition marked by low levels of carbon dioxide in the blood due to breathing excessively. See also: Alkalosis Causes Common causes include: Anxiety Fever Hyperventilation Any lung disease that leads to shortness of breath can also cause respiratory alkalosis. Symptoms The symptoms may include: Dizziness Light-headedness Numbness of the hands and feet Exams and Tests Arterial blood gas (measures levels of oxygen and carbon dioxide in the blood; in respiratory alkalosis, the level of carbon dioxide is too low)

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Page 1: Respiratory Alkalosis

Respiratory alkalosisRespiratory alkalosis is a condition marked by low levels of carbon dioxide in the blood due to breathing excessively.

See also: Alkalosis


Common causes include:

Anxiety Fever Hyperventilation

Any lung disease that leads to shortness of breath can also cause respiratory alkalosis.


The symptoms may include:

Dizziness Light-headedness Numbness of the hands and feet

Exams and Tests

Arterial blood gas (measures levels of oxygen and carbon dioxide in the blood; in respiratory alkalosis, the level of carbon dioxide is too low)

Chest x-ray Pulmonary function test

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Treatment is aimed at the condition that causes respiratory alkalosis. Breathing into a paper bag -- or using a mask that causes you to re-breathe carbon dioxide -- sometimes helps reduce symptoms.

Outlook (Prognosis)

What will happen depends on the condition that is causing the respiratory alkalosis.

Possible Complications

Seizures may occur if the alkalosis is extremely severe. This is very rare.

When to Contact a Medical Professional

Call your health care provider if you have any symptoms of lung disease, such as chronic cough or shortness of breath.

Alternative Names

Alkalosis - respiratory

Alternative NamesAlkalosis - respiratoryDefinition of Respiratory alkalosis:Respiratory alkalosis is a condition marked by low levels of carbon dioxide in the blood due to breathing excessively.See also: AlkalosisCauses, incidence, and risk factors:Common causes include:


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Fever Hyperventilation

Any lung disease that leads to shortness of breath can also cause respiratory alkalosis.

Respiratory system

Reviewed last on: 8/8/2009 David C. Dugdale, III, MD, Professor of Medicine, Division of

General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

ReferencesSeifter JL. Acid base disorders. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier. 2007: chap 119.Related Articles

Hyperventilation The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- 2010 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Respiratory Alkalosis

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(See also Approach to the Patient With Pulmonary Symptoms: Hyperventilation Syndrome.)

Respiratory alkalosis is a primary decrease in PCO2 with or without compensatory decrease in HCO3 −; pH may be high or near normal. Cause is an increase in respiratory rate or volume (hyperventilation) or both. Respiratory alkalosis can be acute or chronic. The chronic form is asymptomatic, but the acute form causes light-headedness, confusion, paresthesias, cramps, and syncope. Signs include

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hyperpnea or tachypnea and carpopedal spasms. Diagnosis is clinical and with ABG and serum electrolyte measurements. Treatment is directed at the cause.


Respiratory alkalosis is a primary decrease in PCO2(hypocapnia) from an increase in respiratory rate or volume (hyperventilation), or both. Ventilation increase occurs most often as a physiologic response to hypoxia, metabolic acidosis, and increased metabolic demands (eg, fever), and as such is present in many serious conditions. In addition, pain and anxiety and some CNS disorders can increase respirations without a physiologic need.


Respiratory alkalosis can be acute or chronic. Distinction is based on the degree of metabolic compensation; excess HCO3 − is buffered by extracellular hydrogen ion (H+) within minutes, but more significant compensation occurs over 2 to 3 days as the kidneys decrease H+ excretion.

Pseudorespiratory alkalosis: Pseudorespiratory alkalosis is low arterial PCO2 and high pH in mechanically ventilated patients with severe metabolic acidosis from poor systemic perfusion (eg, cardiogenic shock, during CPR). Pseudorespiratory alkalosis occurs

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when mechanical ventilation (often hyperventilation) eliminates larger-than-normal amounts of alveolar CO2. Exhalation of large amounts of CO2 causes respiratory alkalosis in arterial blood (hence on ABG measurements), but poor systemic perfusion and cellular ischemia cause cellular acidosis, leading to acidosis of venous blood. Diagnosis is by demonstration of marked arteriovenous differences in PCO2 and pH and by elevated lactate levels; treatment is improvement of systemic hemodynamics.

Symptoms and Signs

Symptoms and signs depend on the rate and degree of fall in PCO2. Acute respiratory alkalosis causes light-headedness, confusion, peripheral and circumoral paresthesias, cramps, and syncope. Mechanism is thought to be change in cerebral blood flow and pH. Tachypnea or hyperpnea is often the only sign; carpopedal spasm may occur in severe cases. Chronic respiratory alkalosis is usually asymptomatic and has no distinctive signs.

Diagnosis ABG and serum electrolytes

If hypoxia present, cause vigorously pursued

Recognition of respiratory alkalosis and appropriate renal compensation discussed inAcid-Base Regulation and Disorders: Diagnosis requires ABG and serum

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electrolyte measurements. Minor hypophosphatemia and hypokalemia from intracellular shifts and decreased ionized Ca++ from an increase in protein binding may be present.

Presence of hypoxia or an increased alveolar-arterial (A-a) O2 gradient (inspired PO2 −[arterial PO2 + 5/4 arterial PCO2]) requires search for a cause. Other causes are often apparent on history and examination. However, because pulmonary embolism often presents without hypoxia (see Pulmonary Embolism), embolism must be strongly considered in a hyperventilating patient before ascribing the cause to anxiety.


Treatment is directed at the underlying cause. Respiratory alkalosis is not life threatening, so no interventions to lower pH are necessary. Increasing inspired CO2 through rebreathing (such as from a paper bag) is common practice but may be dangerous in at least some patients with CNS disorders in whom CSF pH may already be below normal.

Respiratory Alkalosis 

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DefinitionRespiratory alkalosis is a condition where the amount of carbon dioxide found in the blood drops to a level below normal range. This condition produces a shift in the body's pH balance and causes the body's system to become more alkaline (basic). This condition is brought on by rapid, deep breathing called hyperventilation.

DescriptionRespiratory alkalosis is an alkali imbalance in the body caused by a lower-than-normal level of carbon dioxide in the blood. In the lungs, oxygen from inhaled air is exchanged for carbon dioxide from the blood. This process takes place between the alveoli (tiny air pockets in the lungs) and the blood vessels that connect to them. When a person hyperventilates, this exchange of oxygen for carbon dioxide is speeded up, and the person exhales too much carbon dioxide. This lowered level of carbon dioxide causes the pH of the blood to increase, leading to alkalosis.

Causes and symptomsThe primary cause of respiratory alkalosis is hyperventilation. This rapid, deep breathing can be caused by conditions related to the lungs like pneumonia, lung disease, or asthma. More commonly, hyperventilation is associated with anxiety, fever, drug overdose, carbon monoxide poisoning, or serious infections. Tumors or swelling in the brain or nervous system can also cause this type of respiration. Other stresses to the body, including pregnancy, liver failure, high elevations, or metabolic acidosiscan also trigger hyperventilation leading to respiratory alkalosis.

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Hyperventilation, the primary cause of respiratory alkalosis, is also the primary symptom. This symptom is accompanied by dizziness, light headedness, agitation, and tingling or numbing around the mouth and in the fingers and hands. Muscle twitching, spasms, and weakness may be noted. Seizures, irregular heart beats, and tetany (muscle spasms so severe that the muscle locks in a rigid position) can result from severe respiratory alkalosis.

DiagnosisRespiratory alkalosis may be suspected based on symptoms. A blood sample to test for pH and arterial blood gases can be used to confirm the diagnosis. In this type of alkalosis, the pH will be elevated above 7.44. The pressure of carbon dioxide in the blood will be low, usually under 35 mmHg.

Key termsHyperventilation — Rapid, deep breathing, possibly exceeding 40 breaths/minute. The most common cause is anxiety, although fever, aspirin overdose, serious infections, stroke, or other diseases of the brain or nervous system.

pH — A measurement of acid or alkali (base) of a solution based on the amount of hydrogen ions available. Based on a scale of 14, a pH of 7.0 is neutral. A pH below 7.0 is an acid; the lower the number, the stronger the acid. A pH above 7.0 is a base; the higher the number, the stronger the base. Blood pH is slightly alkali with a normal range of 7.36-7.44.

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TreatmentTreatment focuses on correcting the underlying condition that caused the alkalosis. Hyperventilation due to anxiety may be relieved by having the patient breath into a paper bag. By rebreathing the air that was exhaled, the patient will inhale a higher amount of carbon dioxide than he or she would normally. Antibiotics may be used to treat pneumonia or other infections. Other medications may be required to treat fever, seizures, or irregular heart beats. If the alkalosis is related to a drug overdose, the patient may require treatment for poisoning. Use of mechanical ventilation like a respirator may be necessary. If the respiratory alkalosis has triggered the body to compensate by developing metabolic acidosis, symptoms of that condition may need to be treated, as well.

PrognosisIf the underlying condition that caused the respiratory alkalosis is treated and corrected, there may be no long-term effects. In severe cases of respiratory alkalosis, the patient may experience seizures or heart beat irregularities that may be serious and life threatening.


Books"Fluid, Electrolyte, and Acid-Base Disorders." In Family Medicine Principles and Practices. 5th ed. New York: Springer-Verlag, 1998.

Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

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alkalosis /al·ka·lo·sis/ (al″kah-lo´sis) a pathologic condition due to accumulation of base in, or loss of acid from, the body. Cf. acidosis. alkalot´ic

altitude alkalosis  increased alkalinity in blood and tissues due to exposure to high altitudes.

compensated alkalosis  a form in which compensatory mechanisms have returned the pH toward normal.

hypochloremic alkalosis  metabolic alkalosis marked by hypochloremia together with hyponatremia and hypokalemia, resulting from the loss of sodium chloride and hydrochloric acid due to prolonged vomiting.

hypokalemic alkalosis  metabolic alkalosis associated with a low serum potassium level.

metabolic alkalosis  a disturbance in which the acid-base status shifts toward the alkaline side because of retention of base or loss of noncarbonic, or fixed (nonvolatile), acids.

respiratory alkalosis  a state due to excess loss of carbon dioxide from the body, usually as a result of hyperventilation.

Dorland's Medical Dictionary for Health Consumers. © 2007 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

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respiratory alkalosis


Alkalosis resulting from abnormal loss of carbon dioxide due to hyperventilation.

The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

respiratory alkalosis,

an abnormal condition characterized by a high plasma pH resulting from increased alveolar ventilation. The consequent acceleration of carbon dioxide excretion lowers the plasma level of carbonic acid, thus raising plasma pH. The hyperventilation may be caused by pulmonary and nonpulmonary problems. Some pulmonary causes are acute asthma, pulmonary vascular disease, and pneumonia. Some nonpulmonary causes are aspirin toxicity, anxiety, fever, metabolic acidosis, inflammation of the central nervous system, gram-negative septicemia, and hepatic failure. Compare metabolic alkalosis. See also metabolic acidosis, respiratory acidosis.

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observations Deep and rapid breathing at rates as high as 40 breaths per minute is a major sign of respiratory alkalosis. Other symptoms are lightheadedness, dizziness, peripheral paresthesia, tingling of the hands and feet, muscle weakness, tetany, and cardiac arrhythmia. Confirming diagnosis is often based on a PaCO2below 35 mm Hg and a pH greater than 7.45. PaO2 may be higher than 100. In the acute stage, blood pH rises in proportion to the fall in PaCO2, but in the chronic stage it remains within the normal range of 7.35 to 7.45. The carbonic acid concentration is normal in the acute stage of this condition but below normal in the chronic stage.

interventions Treatment of respiratory alkalosis concentrates on removing the underlying causes. Severe cases, especially those caused by extreme anxiety, may be treated by having the patient breathe into a paper bag and inhale exhaled carbon dioxide to compensate for the deficit being created by hyperventilation. Sedatives may also be administered to decrease the ventilation rate.

nursing considerations The nurse monitors neurologic, neuromuscular, and cardiovascular functions, arterial blood gases, and serum electrolyte levels. The patient benefits from explanations of laboratory tests and treatment.

Mosby's Medical Dictionary, 8th edition. © 2009, Elsevier.

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alkalosis (alk lō´sis),

n a disturbance of acid-base balance and water balance, characterized by an excess of alkali or a deficiency of acids.

alkalosis, compensated,

n a condition in which the blood bicarbonate is usually higher than normal but compensatory mechanisms have kept the pH level within normal range. See also alkalosis, uncompensated.

alkalosis, hypochloremic,

n a metabolic abnormality caused by an increase in blood bicarbonate after significant chloride loss.

alkalosis, respiratory,

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n alkalemia produced by hypoventilation. Plasma bicarbonate is therefore decreased in respiratory alkalosis but raised in metabolic alkalosis.

alkalosis, uncompensated,

n alkalemia usually accompanied by an increased blood bicarbonate.

Mosby's Dental Dictionary, 2nd edition. © 2008 Elsevier, Inc. All rights reserved.


a pathological condition resulting from accumulation of base, or from loss of acid without comparable loss of base in the body fluids, and characterized by decrease in hydrogen ion concentration (increase in pH). Alkalosis is the opposite of acidosis. See also acid-base balance.

compensated alkalosis

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a condition in which compensatory mechanisms have returned the pH toward normal.

concentration alkalosis

associated with deficit in free body water, hypotonic fluid losses or increased sodium levels.

gastric alkalosis

alkalosis due to loss of gastric fluid because of persistent vomiting. See also hypochloremic alkalosis (below).

hypochloremic alkalosis

a metabolic alkalosis in which gastric losses of chloride are disproportionately greater than sodium loss because of corresponding increase in potassium loss.

hypokalemic alkalosis

a metabolic alkalosis associated with a low serum potassium level; retention of alkali or loss of acid occurs in the extracellular (but not intracellular) fluid compartment; although the pH of the intracellular fluid may be below normal.

metabolic alkalosis

a disturbance in which the acid-base status shifts toward the alkaline because of uncompensated loss of acids, ingestion or retention of excess base, or potassium depletion. The condition can occur with vomiting or accompany treatment with diuretics.

respiratory alkalosis

reduced carbon dioxide tension in the extracellular fluid caused by excessive excretion of carbon dioxide through the lungs

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(hyperventilation). Conditions commonly associated with respiratory alkalosis include pain, hypoxia, fever, high environmental temperature, poisoning, early pulmonary edema, pulmonary embolism and central nervous system disease.

Saunders Comprehensive Veterinary Dictionary, 3 ed. © 2007 Elsevier, Inc. All rights reserved

respiratory alkalosis

Metabolism A condition characterized by ↑ pH due to excess CO2 excretion Etiology Hyperventilation–eg, due to anxiety, pain, panic attacks, psychosis, CVA, fever, encephalitis, meningitis, tumor, trauma, hypoxemia–severe anemia, high altitude, right-to-left shunt, drugs–progesterone, methylxanthines, salicylates, catecholamines, nicotine, hyperthyroidism, pregnancy, ↑ ambient temperature, lung disease–pneumo/hemothorax, pneumonia, pulmonary edema, PE, aspiration, interstitial lung disease, etc–sepsis, liver failure, mechanical ventilation, heat exhaustion, recovery from metabolic acidosis DiffDx Asthma, A Fib, flutter and tachycardia, heatstroke, metabolic acidosis or alkalosis, acute MI, and other causes of RA Clinical Hyperventilation, paresthesia, twitching–positive Chvostek and Trousseau signs, N&V, focal neurologic signs, depressed consciousness, or coma Lab pH > 7.42, HCO3- < 22 mEq/L–if compensating, PaCO2 < 35 mmHg. See Metabolic acidosis, Metabolic alkalosis, Respiratory acidosis.

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