Respiratory Acidosis, and Respiratory Alkalosis (carbonic acid deficit)

Respiratory Acidosis

Definition: respiratory acidosis is a clinical disorder in which the pH is less than 7.35 and the Pco2 is greater than 42mmHg

It may be either:

  • Acute respiratory acidosis
  • Chronic respiratory acidosis

Respiratory acidosis is always due to inadequate excretion of Co2 with inadequate ventilation, resulting in elevated plasma Co2 levels and thus elevated carbonic acid (H2CO3) levels (Epstein and singh 2001)

Acute respiratory acidosis occurs in emergency situations such as acute pulmonary edema, aspiration of foreign object, atelectasis, pneumothorax, over dose of sedatives, sleep apnea syndrome

Reparatory acidosis can also occur in disease that impair respiratory muscles such as: muscular dystrophy, myasthenia gravis and gullian-ballian syndrome

Clinical manifestation

  • Clinical manifestations in acute and chronic respiratory acidosis vary sudden hypercapnia (PaCO2) can cause increased pulse rate
  • Increased respiratory rate
  • Increased blood pressure
  • Mental cloudiness
  • Feeling of fullness in the head
  • An elevated PaCO2
  • Cerebrovascular vasodilatation
  • Increased cerebral blood flow particularly when it is higher than 60mmHg
  • Ventricular fibrillation may be the first sign of respiratory acidosis
  • If respiratory acidosis is severe, intra cranial pressure may increase, resulting in palpation and dilated conjuctival blood vessels
  • Chronic respiratory acidosis occurs with pulmonary disease such as:
  • Chronic emphysema and bronchitis, obstructive sleep apnea and obesity
  • Cyanosis, ICP, tachypnea, COPD

Assessment and Diagnostic Findings

  • Arterial blood gas (ABG’s) evaluation reveals a pH less than 7.35 a PaCO2 greater than 42mmHg and variation in the bicarbonate level
  • Depending on the duration and cause of the acidosis in acute respiratory acidosis
  • ECG

Medical management

  • Treatment is directed at improving ventilation
  • Pharmacological agents are used as indicated e.g bronchodilators, to relieve spasm Antibiotics for infection
  • Thrombolytics or anti coagulants are used for pulmonary emboli Adequate hydration
  • Mechanical ventilation use appropriately may improve pulmonary ventilation

Respiratory Alkalosis (carbonic acid deficit)

 Definition: respiratory alkalosis is a clinical condition in which the arterial pH is greater than 7.45 and the PaCO2 is less than 38mmHg

  • As like respiratory acidosis acute and chronic condition can occur
  • Respiratory alkalosis is always due to hyperventilation which cause excessive blowing off of CO2 and hence a decrease in the plasma carbonic acid concentration
  • Causes can include”
  • Extreme anxiety
  • Hypoxemia
  • Inappropriate ventilator setting
  • Chronic respiratory alkalosis results from chronic hypocapnia and decreased serum bicarbonate levels
  • Chronic liver insufficiency
  • Cerebral tumors are predisposing factors

Clinical Manifestation

  • Light headedness – due to vasoconstriction and decreased cerebral blood flow
  • Inability to concentrate
  • Numbness
  • Tingling due to decreased calcium
  • Tinnitus and at time loss of consciousness
  • Tachycardia
  • Arterial dysthermias


  • ABG’s assist in the diagnosis of respiratory alkalosis
  • In acute state pH is elevated above normal as result of low PaCO2 and normal bicarbonate level
  • Serum electrolytes analysis decreased Ca+ level
  • Patient with chronic respiratory alkalosis are usually asymptomatic

Medical Management

  • Treatment depends on the underlying cause of respiratory alkalosis
  • If the cause is anxiety – the patient instructed to breath slowly to allow CO2 to accumulate
  • A sedative may be required to relieve hyperventilation in vary anxious patients
  • To correct underlying problem