Respiratory Alkalosis: Causes, Symptoms, and Treatment

Respiratory alkalosis is an acid-base disorder caused by excessive alveolar ventilation, which lowers arterial carbon dioxide and raises blood pH. It occurs when a patient removes carbon dioxide faster than the body produces it.

Because carbon dioxide acts as an acid-forming substance in the blood, a low PaCO2 causes the blood to become more alkaline. Respiratory alkalosis may occur with anxiety, pain, fever, sepsis, hypoxemia, asthma, pneumonia, pulmonary edema, pulmonary embolism, or excessive mechanical ventilation.

Correct interpretation requires evaluating pH, PaCO2, bicarbonate, compensation, oxygenation, and the patient’s clinical condition.

What Is Respiratory Alkalosis?

Respiratory alkalosis is a primary respiratory acid-base disorder caused by hyperventilation. In this condition, the patient is breathing more than needed for the body’s carbon dioxide production. As a result, too much carbon dioxide is removed from the blood, PaCO2 falls below normal, and pH rises.

The normal PaCO2 range is 35 to 45 mmHg. When PaCO2 falls below 35 mmHg, the patient is hyperventilating. If the low PaCO2 is accompanied by a pH above 7.45, the patient has respiratory alkalosis.

The key concept is simple: respiratory acidosis occurs when ventilation is too low and carbon dioxide accumulates. Respiratory alkalosis occurs when ventilation is too high and carbon dioxide is removed excessively.

Respiratory alkalosis is sometimes described as alveolar hyperventilation because the main problem occurs at the level of alveolar ventilation. The lungs are eliminating carbon dioxide faster than it is being produced by metabolism.

Why Low Carbon Dioxide Raises pH

Carbon dioxide has a direct relationship with blood pH. In the blood, carbon dioxide combines with water to form carbonic acid. Carbonic acid can then separate into hydrogen ions and bicarbonate.

When carbon dioxide increases, more carbonic acid and hydrogen ions are produced, which lowers pH. This is why carbon dioxide retention causes respiratory acidosis.

When carbon dioxide decreases, less carbonic acid is present. Hydrogen ion concentration falls, and the pH rises. This is why excessive carbon dioxide removal causes respiratory alkalosis.

In other words, carbon dioxide behaves like an acid-forming gas in acid-base balance. When PaCO2 falls too low, the blood becomes more alkaline.

Normal Values Related to Respiratory Alkalosis

Understanding normal ABG values is essential for identifying respiratory alkalosis.

• Normal arterial pH is 7.35 to 7.45. A pH below 7.35 indicates acidemia, while a pH above 7.45 indicates alkalemia.
• Normal PaCO2 is 35 to 45 mmHg. A PaCO2 below 35 mmHg indicates alveolar hyperventilation and suggests respiratory alkalosis if the pH is elevated or leaning alkaline.
• Normal bicarbonate, or HCO3, is usually 22 to 26 mEq/L. Bicarbonate helps determine whether the respiratory alkalosis is acute, partially compensated, or chronic.
• Base excess may also be used to evaluate metabolic involvement. A negative base excess may appear during renal compensation for chronic respiratory alkalosis because the kidneys excrete bicarbonate.

Note: The basic ABG pattern for respiratory alkalosis is high pH with low PaCO2. The bicarbonate level helps determine the stage of compensation.

Main ABG Pattern

The classic ABG pattern in respiratory alkalosis is an increased pH and a decreased PaCO2.

In acute respiratory alkalosis, the pH is above 7.45, PaCO2 is below 35 mmHg, and bicarbonate is normal or only slightly decreased. This means the respiratory problem has occurred quickly, and the kidneys have not had enough time to compensate.

In chronic or compensated respiratory alkalosis, PaCO2 remains low, but bicarbonate is also decreased because the kidneys have excreted bicarbonate to help bring pH back toward normal. Therefore, respiratory alkalosis should not be interpreted from PaCO2 alone. The clinician must also consider the pH and bicarbonate level.

Acute Respiratory Alkalosis

Acute respiratory alkalosis occurs when PaCO2 drops suddenly due to hyperventilation. The pH rises above 7.45 because carbon dioxide is being removed too quickly.

In acute respiratory alkalosis, bicarbonate is often normal or only slightly decreased. This slight decrease can occur from the immediate chemical effect of the carbon dioxide hydration reaction. It does not mean the kidneys have fully compensated.

A common expected pattern is high pH, low PaCO2, and normal or slightly low HCO3.

For example, an ABG with pH 7.57, PaCO2 23 mmHg, and HCO3 22 mEq/L indicates acute uncompensated respiratory alkalosis. The high pH shows alkalemia. The low PaCO2 identifies hyperventilation as the cause. The bicarbonate is near normal, so renal compensation has not meaningfully occurred.

Chronic Respiratory Alkalosis

Chronic respiratory alkalosis occurs when PaCO2 remains low over time. Because the problem is persistent, the kidneys begin to compensate by excreting bicarbonate in the urine.

This renal response lowers the blood bicarbonate level and helps move pH back toward normal. However, the underlying respiratory problem is still present because PaCO2 remains low.

A chronic compensated pattern includes low PaCO2, low HCO3, and a pH that has returned to the normal range. The pH usually remains on the alkaline side of normal, often between 7.41 and 7.45.

For example, an ABG with pH 7.44, PaCO2 26 mmHg, HCO3 17 mEq/L, and PaO2 53 mmHg suggests compensated respiratory alkalosis with hypoxemia. The low PaCO2 shows hyperventilation. The low bicarbonate shows renal compensation. The pH is normal but alkalemic-leaning, so the primary disorder is respiratory alkalosis, not metabolic acidosis.

Partial Compensation

Partially compensated respiratory alkalosis occurs when the kidneys have started to excrete bicarbonate, but the pH is still above 7.45.

This pattern includes high pH, low PaCO2, and low HCO3. The low bicarbonate shows that compensation has begun, but the pH remains alkalemic, so compensation is incomplete.

For example, if a patient has PaCO2 20 mmHg, pH 7.50, and HCO3 15 mEq/L, the low PaCO2 identifies the respiratory cause. The low bicarbonate shows renal compensation. Since pH is still high, the disorder is only partially compensated.

Why Compensation Matters

Compensation helps determine whether respiratory alkalosis is acute or chronic. This distinction matters because acute hyperventilation may represent a sudden clinical problem, while chronic respiratory alkalosis may be related to a persistent condition.

The kidneys compensate for respiratory alkalosis by excreting bicarbonate. This is sometimes called bicarbonate diuresis. By lowering bicarbonate, the kidneys reduce the blood’s base level and bring pH closer to normal.

Renal compensation is slow. It takes hours to days, so a patient with sudden respiratory alkalosis will not have full compensation right away.

Note: The body generally does not overcompensate. If respiratory alkalosis is the primary disorder, compensation may bring the pH toward normal, but it usually does not push the pH below 7.40.

Causes of Respiratory Alkalosis

Respiratory alkalosis can occur whenever ventilation exceeds the body’s carbon dioxide production. The causes may involve normal lungs, abnormal lungs, medical treatment, or ventilator settings.

Anxiety and Emotional Stress

Anxiety is a classic cause of acute respiratory alkalosis. Emotional stress can trigger rapid and deep breathing even when the lungs are structurally normal.

As the patient hyperventilates, PaCO2 falls and pH rises. Symptoms may include light-headedness, dizziness, tingling in the hands or around the mouth, and a feeling of breathlessness.

Anxiety may be the cause, but it should not be assumed too quickly. Other serious conditions can also cause hyperventilation, including hypoxemia, sepsis, pulmonary embolism, and asthma.

Pain, Fever, and Sepsis

Pain can stimulate ventilation and cause carbon dioxide levels to fall. Fever can increase respiratory drive and metabolic demand. Sepsis can also cause hyperventilation, often before obvious respiratory failure is present.

In these cases, respiratory alkalosis is a sign that the body is responding to stress or illness. Treatment should focus on the underlying cause rather than only the ABG number.

Central Nervous System Causes

Central nervous system lesions, inflammation, or injury may alter respiratory control and cause inappropriate hyperventilation. Stimulant drugs can also increase respiratory drive.

When the brain’s control of breathing is affected, the patient may ventilate excessively even without a primary lung problem. ABG interpretation helps identify the resulting low PaCO2 and high pH.

Hypoxemia

Hypoxemia is one of the most important causes of respiratory alkalosis in patients with lung disease. When PaO2 falls, the body responds by increasing ventilation. This helps improve oxygen intake but also removes too much carbon dioxide.

This is why respiratory alkalosis is common in acute oxygenation problems such as asthma, pneumonia, pulmonary embolism, pulmonary edema, pneumothorax, postoperative atelectasis, and ARDS.

A patient with hypoxemia and respiratory alkalosis may not be “just anxious.” The hyperventilation may be the body’s response to low oxygen levels.

Asthma

In early or moderate asthma exacerbations, patients often hyperventilate due to airway obstruction, anxiety, increased work of breathing, and hypoxemia. The ABG may show high pH, low PaCO2, and low PaO2.

This pattern indicates respiratory alkalosis with hypoxemia.

A major warning occurs when a severe asthma patient’s PaCO2 begins to rise toward normal. This may not mean improvement. It may mean the patient is tiring and can no longer maintain hyperventilation. This can signal impending ventilatory failure and progression toward respiratory acidosis.

Pneumonia

Pneumonia can cause hypoxemia by impairing gas exchange. In response, the patient may breathe faster and deeper. This can lower PaCO2 and produce respiratory alkalosis.

A patient with pneumonia may therefore have both an oxygenation problem and an acid-base disturbance. The low PaO2 should be interpreted separately from the low PaCO2.

Pulmonary Edema and Heart Failure

Pulmonary edema and acute heart failure can impair oxygenation and increase the work of breathing. Patients often present with dyspnea, crackles, hypoxemia, and rapid breathing.

ABG results may show hypoxemia with respiratory alkalosis. The alkalosis occurs because the patient is hyperventilating in response to impaired gas exchange and respiratory distress.

Pulmonary Embolism and Pulmonary Vascular Disease

Pulmonary embolism and other pulmonary vascular problems can cause ventilation-perfusion mismatch and hypoxemia. The body may respond with hyperventilation, producing low PaCO2 and respiratory alkalosis.

A low PaCO2 in a dyspneic patient should therefore be interpreted with the full clinical picture. It may reflect a serious cardiopulmonary process.

Iatrogenic Respiratory Alkalosis

Respiratory alkalosis can be caused by medical treatment. This is called iatrogenic respiratory alkalosis.

The most common example is excessive mechanical ventilation. If the ventilator delivers too much minute ventilation, the patient may blow off too much CO2. PaCO2 falls, and pH rises. This may occur when the respiratory rate is too high, tidal volume is too large, pressure support is excessive, or the patient is breathing rapidly on top of ventilator settings.

Note: Aggressive deep-breathing or lung-expansion therapy may also contribute to hyperventilation in some situations.

Respiratory Alkalosis During Mechanical Ventilation

In mechanically ventilated patients, respiratory alkalosis usually means the patient is receiving or generating too much ventilation.

If PaCO2 is too low and pH is too high, the clinician should evaluate minute ventilation, respiratory rate, tidal volume, pressure support, patient effort, anxiety, pain, and ventilator synchrony.

If the tidal volume is appropriate, decreasing the ventilator rate may help PaCO2 rise toward normal. If pressure support is excessive, reducing support may be appropriate. If agitation is causing the patient to overbreathe the ventilator, pain control, sedation adjustment, or a different ventilator mode may be needed, depending on the clinical situation.

Note: The goal is not simply to increase PaCO2. The goal is to correct excessive ventilation safely while maintaining adequate oxygenation and patient comfort.

Signs and Symptoms of Respiratory Alkalosis

Respiratory alkalosis can produce symptoms related to low PaCO2 and alkalemia.

An early symptom is paresthesia, which means numbness or tingling. This may occur in the fingers, hands, feet, or around the mouth. Patients may also report dizziness, light-headedness, chest tightness, or feeling faint.

Low PaCO2 can constrict cerebral blood vessels, reducing blood flow to the brain and contributing to dizziness or light-headedness. Severe hyperventilation may cause hyperactive reflexes or tetany, which involves intermittent muscle spasms.

Note: The clinical presentation depends on the cause. A patient with anxiety may look very different from a patient with pneumonia, sepsis, pulmonary embolism, or excessive ventilator support.

Respiratory Alkalosis and Oxygenation

Oxygenation must always be assessed separately from acid-base status. Respiratory alkalosis tells us the patient is blowing off too much carbon dioxide, but it does not automatically tell us whether oxygenation is normal.

Some patients with respiratory alkalosis have normal or even elevated PaO2 because hyperventilation increases alveolar oxygen levels. Other patients have respiratory alkalosis because they are hypoxemic and breathing rapidly in response.

For example, a patient with anxiety-induced hyperventilation may have normal oxygenation. A patient with pneumonia may have low PaO2 with low PaCO2 because hypoxemia is driving hyperventilation.

Note: This is why ABG interpretation should include both acid-base analysis and oxygenation assessment.

Common ABG Examples

ABG examples help reinforce how respiratory alkalosis appears in practice.

Uncompensated Respiratory Alkalosis

• pH 7.57
• PaCO2 23 mmHg
• HCO3 22 mEq/L

Note: The pH is high, showing alkalemia. The PaCO2 is low, showing hyperventilation. The bicarbonate is near normal, so there is no meaningful renal compensation. This is acute uncompensated respiratory alkalosis.

Respiratory Alkalosis With Hypoxemia

• pH 7.53
• PaCO2 27 mmHg
• PaO2 53 mmHg
• HCO3 22 mEq/L

Note: The high pH and low PaCO2 indicate respiratory alkalosis. The low PaO2 indicates moderate hypoxemia. This pattern may be seen in asthma, pneumonia, pulmonary embolism, or another condition causing hypoxemia and reflex hyperventilation.

Compensated Respiratory Alkalosis

• pH 7.44
• PaCO2 25 mmHg
• HCO3 17 mEq/L
• BE -7 mEq/L

Note: The PaCO2 is low, indicating respiratory alkalosis. The bicarbonate and base excess are low, showing renal compensation. The pH is within the normal range but on the alkaline side, so this is compensated respiratory alkalosis.

Iatrogenic Respiratory Alkalosis

A mechanically ventilated patient has pH 7.52 and PaCO2 28 mmHg after a ventilator rate increase.

This suggests excessive ventilation. If tidal volume is appropriate and oxygenation is stable, decreasing the ventilator rate may help correct the low PaCO2.

Treatment of Respiratory Alkalosis

Treatment focuses on correcting the cause of hyperventilation. Respiratory alkalosis is not treated by chasing the ABG number alone.

Treat Hypoxemia

If hypoxemia is causing hyperventilation, oxygen therapy and treatment of the underlying lung problem are needed. This may include oxygen, bronchodilators, airway clearance, CPAP, PEEP, antibiotics, diuretics, anticoagulation, or other therapies depending on the diagnosis.

The key is that the patient is hyperventilating because oxygenation is impaired. Correcting oxygenation often helps reduce the ventilatory drive and improves the alkalosis.

Address Anxiety, Pain, or Fever

If anxiety, pain, or fever is the cause, treatment should address that stimulus. This may include reassurance, coaching, pain control, fever management, or additional evaluation if symptoms do not match a simple anxiety picture.

The clinician should avoid assuming anxiety when the patient may have hypoxemia, pulmonary embolism, sepsis, asthma, or another acute condition.

Adjust Mechanical Ventilation

If the patient is being overventilated mechanically, ventilator settings may need adjustment. This may involve reducing respiratory rate, tidal volume, pressure support, or minute ventilation, depending on the mode and patient condition.

If the patient is overbreathing due to agitation or discomfort, the cause should be addressed. Options may include improving comfort, treating pain, adjusting sedation, or changing the ventilator mode.

Respiratory Alkalosis for Exam Preparation

For respiratory therapy exams, respiratory alkalosis is usually recognized by low PaCO2. The next step is to look at pH and bicarbonate.

• If PaCO2 is below 35 mmHg and pH is above 7.45, the disorder is acute or uncompensated respiratory alkalosis if bicarbonate is normal.
• If PaCO2 is low, pH is normal or near-normal, and bicarbonate or base excess is decreased, the disorder is compensated respiratory alkalosis.

Always evaluate oxygenation separately. A patient may have respiratory alkalosis with normal oxygenation, or they may have respiratory alkalosis because hypoxemia is stimulating hyperventilation.

A common exam clue is acute asthma, pneumonia, pulmonary embolism, or pulmonary edema with high pH and low PaCO2. This often indicates respiratory alkalosis caused by hypoxemia or respiratory distress.

Note: Another key exam point is severe asthma. If a patient with asthma goes from low PaCO2 to normal PaCO2 while still in distress, this may indicate fatigue and impending ventilatory failure.

Respiratory Alkalosis Practice Questions

1. What is respiratory alkalosis?
Respiratory alkalosis is an acid-base disorder caused by excessive alveolar ventilation, which lowers PaCO2 and raises blood pH.

2. What is the primary cause of respiratory alkalosis?
The primary cause of respiratory alkalosis is alveolar hyperventilation.

3. What happens to PaCO2 in respiratory alkalosis?
PaCO2 decreases because the patient is eliminating carbon dioxide faster than the body produces it.

4. What PaCO2 value indicates alveolar hyperventilation?
A PaCO2 less than 35 mmHg indicates alveolar hyperventilation.

5. What pH value indicates alkalemia?
A pH above 7.45 indicates alkalemia.

6. What ABG pattern identifies acute respiratory alkalosis?
Acute respiratory alkalosis is identified by a high pH and a low PaCO2.

7. Why does low PaCO2 raise blood pH?
Low PaCO2 reduces carbonic acid and hydrogen ion concentration, which raises blood pH.

8. What is hypocapnia?
Hypocapnia is an abnormally low level of carbon dioxide in the blood.

9. Why is hypocapnia associated with respiratory alkalosis?
Hypocapnia is associated with respiratory alkalosis because low carbon dioxide removes acid from the blood and increases pH.

10. What is the normal PaCO2 range?
The normal PaCO2 range is 35–45 mmHg.

11. What is the normal arterial pH range?
The normal arterial pH range is 7.35–7.45.

12. What is the normal bicarbonate range?
The normal bicarbonate range is approximately 22–26 mEq/L.

13. What is acute respiratory alkalosis?
Acute respiratory alkalosis is a sudden decrease in PaCO2 with an elevated pH and little or no renal compensation.

14. What is another term for acute respiratory alkalosis?
Acute respiratory alkalosis is also called acute alveolar hyperventilation.

15. What ABG pattern is expected in acute respiratory alkalosis?
Acute respiratory alkalosis usually shows high pH, low PaCO2, and normal or slightly decreased HCO3.

16. Why is bicarbonate usually normal or only slightly decreased in acute respiratory alkalosis?
Bicarbonate is usually normal or only slightly decreased because the kidneys have not had enough time to compensate.

17. What does a slight bicarbonate decrease in acute respiratory alkalosis usually represent?
A slight bicarbonate decrease usually reflects the immediate chemical effect of reduced CO2 rather than full renal compensation.

18. What is chronic respiratory alkalosis?
Chronic respiratory alkalosis is long-term low PaCO2 with renal bicarbonate excretion that helps bring pH back toward normal.

19. What ABG pattern is expected in compensated respiratory alkalosis?
Compensated respiratory alkalosis usually shows low PaCO2, low HCO3, and a normal or high-normal pH.

20. Why does bicarbonate decrease in chronic respiratory alkalosis?
Bicarbonate decreases because the kidneys excrete bicarbonate to compensate for the alkalemia caused by low PaCO2.

21. How long does renal compensation for respiratory alkalosis take?
Renal compensation takes hours to days because the kidneys adjust bicarbonate slowly.

22. What does fully compensated respiratory alkalosis mean?
Fully compensated respiratory alkalosis means PaCO2 and HCO3 are low, but the pH has returned to the normal range.

23. Where does the pH usually fall in fully compensated respiratory alkalosis?
The pH usually remains on the alkaline side of normal, often around 7.41–7.45.

24. What does partially compensated respiratory alkalosis mean?
Partially compensated respiratory alkalosis means PaCO2 and HCO3 are low, but the pH remains above 7.45.

25. Why does a normal pH not rule out respiratory alkalosis?
A normal pH does not rule it out because renal compensation may have lowered bicarbonate while PaCO2 remains below normal.

26. What is the main difference between acute and chronic respiratory alkalosis?
Acute respiratory alkalosis develops suddenly with little renal compensation, while chronic respiratory alkalosis persists long enough for the kidneys to excrete bicarbonate.

27. What does a low PaCO2 with a high pH suggest?
A low PaCO2 with a high pH suggests acute or uncompensated respiratory alkalosis.

28. What does a low PaCO2 with a normal alkaline-leaning pH suggest?
A low PaCO2 with a normal alkaline-leaning pH suggests compensated respiratory alkalosis.

29. What does a decreased HCO3 indicate in respiratory alkalosis?
A decreased HCO3 indicates renal compensation for chronic or partially compensated respiratory alkalosis.

30. What does a negative base excess suggest in compensated respiratory alkalosis?
A negative base excess suggests bicarbonate loss from renal compensation.

31. What type of respiratory alkalosis is suggested by pH 7.57, PaCO2 23 mmHg, and HCO3 22 mEq/L?
This ABG suggests acute uncompensated respiratory alkalosis.

32. What type of respiratory alkalosis is suggested by pH 7.44, PaCO2 26 mmHg, and HCO3 17 mEq/L?
This ABG suggests compensated respiratory alkalosis.

33. What type of respiratory alkalosis is suggested by pH 7.50, PaCO2 20 mmHg, and HCO3 15 mEq/L?
This ABG suggests partially compensated respiratory alkalosis.

34. What is the most common cause of hyperventilation in patients with pulmonary disease?
Hypoxemia is a common cause of hyperventilation in patients with pulmonary disease.

35. Why can hypoxemia cause respiratory alkalosis?
Hypoxemia can stimulate the patient to breathe faster and deeper, which lowers PaCO2 and raises pH.

36. What lung conditions can cause respiratory alkalosis through hypoxemia?
Asthma, pneumonia, pulmonary embolism, pulmonary edema, pneumothorax, postoperative atelectasis, and ARDS can cause respiratory alkalosis through hypoxemia.

37. Why can anxiety cause respiratory alkalosis?
Anxiety can trigger rapid, deep breathing that removes too much carbon dioxide from the blood.

38. How can pain contribute to respiratory alkalosis?
Pain can stimulate ventilation, causing excessive CO2 elimination and a rise in pH.

39. How can fever contribute to respiratory alkalosis?
Fever can increase respiratory drive and cause hyperventilation, lowering PaCO2.

40. How can sepsis cause respiratory alkalosis?
Sepsis can stimulate ventilation and cause a low PaCO2, especially early in the illness.

41. How can central nervous system lesions cause respiratory alkalosis?
Central nervous system lesions can alter respiratory control and trigger inappropriate hyperventilation.

42. How can stimulant drugs contribute to respiratory alkalosis?
Stimulant drugs can increase respiratory drive, causing excessive ventilation and low PaCO2.

43. Why should respiratory alkalosis not automatically be blamed on anxiety?
Respiratory alkalosis should not automatically be blamed on anxiety because hypoxemia, sepsis, pulmonary embolism, asthma, and other serious conditions can also cause hyperventilation.

44. What is iatrogenic respiratory alkalosis?
Iatrogenic respiratory alkalosis is respiratory alkalosis caused by medical treatment, most commonly excessive mechanical ventilation.

45. How can mechanical ventilation cause respiratory alkalosis?
Mechanical ventilation can cause respiratory alkalosis if it delivers too much minute ventilation and removes too much CO2.

46. What ventilator settings may contribute to respiratory alkalosis?
A high respiratory rate, large tidal volume, excessive pressure support, or excessive minute ventilation may contribute to respiratory alkalosis.

47. What ventilator adjustment may help correct respiratory alkalosis when tidal volume is appropriate?
Decreasing the ventilator rate may help raise PaCO2 and correct respiratory alkalosis when tidal volume is appropriate.

48. Why would increasing the respiratory rate worsen respiratory alkalosis?
Increasing the respiratory rate would remove more CO2, further lowering PaCO2 and raising pH.

49. How can patient anxiety on a ventilator contribute to respiratory alkalosis?
Anxiety can cause the patient to overbreathe the ventilator, increasing minute ventilation and lowering PaCO2.

50. What should be assessed if a ventilated patient develops respiratory alkalosis?
The clinician should assess respiratory rate, tidal volume, minute ventilation, pressure support, patient effort, pain, anxiety, sedation, and ventilator synchrony.

51. What are common symptoms of respiratory alkalosis?
Common symptoms include dizziness, light-headedness, tingling, numbness, chest tightness, and feeling faint.

52. What is paresthesia?
Paresthesia is numbness or tingling, often felt in the fingers, hands, feet, or around the mouth.

53. Why can respiratory alkalosis cause dizziness?
Respiratory alkalosis can cause dizziness because low PaCO2 may constrict cerebral blood vessels and reduce blood flow to the brain.

54. What is tetany?
Tetany is intermittent muscle spasm that may occur with severe alkalosis or marked hyperventilation.

55. Why can severe hyperventilation cause muscle spasms?
Severe hyperventilation can alter blood chemistry and increase neuromuscular irritability, which may contribute to muscle spasms.

56. Why must oxygenation be assessed separately in respiratory alkalosis?
Oxygenation must be assessed separately because respiratory alkalosis may occur with either normal oxygenation or significant hypoxemia.

57. What does respiratory alkalosis with normal PaO2 often suggest?
Respiratory alkalosis with normal PaO2 may suggest anxiety, pain, fever, stimulant drugs, or another non-hypoxemic cause of hyperventilation.

58. What does respiratory alkalosis with low PaO2 often suggest?
Respiratory alkalosis with low PaO2 often suggests that hypoxemia is stimulating the patient to hyperventilate.

59. What ABG pattern may occur early in an acute asthma attack?
Early acute asthma may show high pH, low PaCO2, and low PaO2 due to hyperventilation with hypoxemia.

60. Why is a normalizing PaCO2 concerning in severe asthma?
A normalizing PaCO2 in severe asthma may indicate fatigue and impending ventilatory failure rather than improvement.

61. What ABG trend may indicate worsening asthma and fatigue?
A rising PaCO2 with falling pH in a distressed asthma patient may indicate worsening ventilation and possible respiratory failure.

62. How can pneumonia lead to respiratory alkalosis?
Pneumonia can impair gas exchange, causing hypoxemia that stimulates hyperventilation and lowers PaCO2.

63. How can pulmonary edema cause respiratory alkalosis?
Pulmonary edema can impair oxygenation and increase work of breathing, leading to rapid breathing and excessive CO2 elimination.

64. How can pulmonary embolism cause respiratory alkalosis?
Pulmonary embolism can cause ventilation-perfusion mismatch and hypoxemia, which may trigger hyperventilation and low PaCO2.

65. How can postoperative atelectasis contribute to respiratory alkalosis?
Postoperative atelectasis can cause hypoxemia, which may stimulate increased ventilation and reduce PaCO2.

66. What is a common ABG pattern in acute hypoxemic conditions?
A common pattern is respiratory alkalosis with low PaCO2 and low PaO2.

67. What does pH 7.53, PaCO2 27 mmHg, and PaO2 53 mmHg suggest?
This pattern suggests uncompensated respiratory alkalosis with moderate hypoxemia.

68. What does pH 7.57, PaCO2 20 mmHg, HCO3 24 mEq/L, and normal oxygenation suggest?
This pattern suggests uncompensated respiratory alkalosis with normal oxygenation.

69. What does pH 7.45, PaCO2 22 mmHg, HCO3 16 mEq/L, and BE -6 suggest?
This pattern suggests compensated respiratory alkalosis.

70. Why is low HCO3 not always metabolic acidosis?
Low HCO3 is not always metabolic acidosis because it may represent renal compensation for chronic respiratory alkalosis.

71. How can pH help distinguish compensated respiratory alkalosis from compensated metabolic acidosis?
If the pH is above 7.40, compensated respiratory alkalosis is more likely; if it is below 7.40, compensated metabolic acidosis is more likely.

72. What does base excess less than -2 suggest during respiratory alkalosis?
Base excess less than -2 may suggest renal compensation through bicarbonate loss.

73. What is bicarbonate diuresis?
Bicarbonate diuresis is renal excretion of bicarbonate to compensate for respiratory alkalosis.

74. Why do the kidneys excrete bicarbonate during respiratory alkalosis?
The kidneys excrete bicarbonate to reduce alkalinity and help move pH back toward normal.

75. Why does renal compensation not occur immediately in respiratory alkalosis?
Renal compensation does not occur immediately because the kidneys require hours to days to adjust bicarbonate levels.

76. What is the main treatment goal for respiratory alkalosis?
The main treatment goal is to identify and correct the cause of hyperventilation.

77. Why should respiratory alkalosis not be treated by only changing the ABG number?
Respiratory alkalosis should not be treated by only changing the ABG number because the underlying cause of hyperventilation must be corrected.

78. What should be done if hypoxemia is causing respiratory alkalosis?
If hypoxemia is causing respiratory alkalosis, oxygenation should be improved and the underlying lung problem should be treated.

79. How can oxygen therapy help respiratory alkalosis caused by hypoxemia?
Oxygen therapy can reduce the hypoxemic stimulus for hyperventilation, which may help PaCO2 and pH move toward normal.

80. What should be done if anxiety is causing respiratory alkalosis?
If anxiety is causing respiratory alkalosis, the patient may need reassurance, coaching, and assessment to rule out other serious causes.

81. What should be done if pain is causing respiratory alkalosis?
If pain is causing respiratory alkalosis, pain control may help reduce excessive ventilation.

82. What should be done if fever is causing respiratory alkalosis?
If fever is causing respiratory alkalosis, fever management and treatment of the underlying cause may help reduce hyperventilation.

83. What should be done if sepsis is suspected in respiratory alkalosis?
If sepsis is suspected, the patient needs prompt evaluation and treatment of the infection or systemic illness causing hyperventilation.

84. How should iatrogenic respiratory alkalosis from mechanical ventilation be corrected?
Iatrogenic respiratory alkalosis may be corrected by reducing excessive minute ventilation and adjusting ventilator settings appropriately.

85. What ventilator change may be appropriate if respiratory alkalosis is caused by an excessive rate?
Decreasing the ventilator rate may be appropriate if an excessive respiratory rate is causing low PaCO2.

86. What ventilator change may be appropriate if pressure support is excessive?
Reducing pressure support may be appropriate if excessive support is causing overventilation and low PaCO2.

87. Why might adding dead space be considered in ventilator-related respiratory alkalosis?
Adding dead space may be considered in select situations to help increase PaCO2 when the patient is being overventilated.

88. Why might sedation adjustment be considered in ventilator-related respiratory alkalosis?
Sedation adjustment may be considered if agitation or anxiety is causing the patient to overbreathe the ventilator.

89. Why is patient comfort important when managing ventilator-related respiratory alkalosis?
Patient comfort is important because pain, anxiety, and poor synchrony can increase breathing effort and worsen hyperventilation.

90. What is the relationship between respiratory alkalosis and minute ventilation?
Respiratory alkalosis occurs when minute ventilation is excessive relative to the body’s carbon dioxide production.

91. What happens to PaCO2 when minute ventilation increases too much?
PaCO2 decreases when minute ventilation increases too much.

92. What happens to pH when PaCO2 decreases?
The pH increases when PaCO2 decreases.

93. Why can aggressive deep-breathing therapy contribute to respiratory alkalosis?
Aggressive deep-breathing therapy can increase ventilation enough to remove excessive carbon dioxide in some patients.

94. Why is respiratory alkalosis common in acute pulmonary disease?
Respiratory alkalosis is common in acute pulmonary disease because hypoxemia and respiratory distress often stimulate hyperventilation.

95. What is the main ABG clue for respiratory alkalosis?
The main ABG clue is a PaCO2 below 35 mmHg.

96. What confirms acute respiratory alkalosis when PaCO2 is low?
A pH above 7.45 with low PaCO2 confirms acute respiratory alkalosis.

97. What confirms compensated respiratory alkalosis when PaCO2 is low?
A low PaCO2 with low HCO3 or negative base excess and a normal alkaline-leaning pH confirms compensated respiratory alkalosis.

98. Why should PaO2 be reviewed in every case of respiratory alkalosis?
PaO2 should be reviewed because respiratory alkalosis may be caused by hypoxemia that requires oxygenation support.

99. What is a key exam warning about asthma and respiratory alkalosis?
A key exam warning is that early asthma may cause respiratory alkalosis, but a rising PaCO2 in a distressed patient may indicate fatigue and impending respiratory failure.

100. What is the main clinical priority in respiratory alkalosis?
The main clinical priority is to treat the cause of hyperventilation while maintaining adequate oxygenation and ventilation.

Final Thoughts

Respiratory alkalosis is caused by excessive alveolar ventilation that lowers PaCO2 and raises blood pH. It may occur with anxiety, pain, fever, sepsis, hypoxemia, asthma, pneumonia, pulmonary edema, pulmonary embolism, or excessive mechanical ventilation.

Acute respiratory alkalosis usually shows high pH, low PaCO2, and normal or slightly decreased bicarbonate. Chronic or compensated respiratory alkalosis shows low PaCO2 with decreased bicarbonate and a pH closer to normal.

Accurate interpretation requires assessing ABG values with oxygenation status and the patient’s clinical condition, then treating the cause of hyperventilation.