Hyperventilation

Etiology

Hypoxemia-Induced Hyperventilation

Mechanism

  • Hypoxemia stimulation of Peripheral Chemoreceptors (in Carotid Bodies): however, the degree of hypoxemia-induced increase in VE is modulated by co-existing pCO2 and pH, mechanics of the lung and chest wall, genetic factors, and the overall duration of hypoxemia
    • Increase in Minute Ventilation (VE) in response to decrease in pO2 is non-linear: highest responses are seen with pO2 <60 mm Hg
    • Increase in Minute Ventilation (VE) in response to decreased SaO2 is relatively linear
    • Example: on Mount Everest (where pO2 is 27 mm Hg) -> pCO2 is decreased to 7.5 mm Hg [MEDLINE]

Examples

Lung Disease-Induced Hyperventilation

Mechanism

  • Stimulation of Mechanical and Chemical Bronchopulmonary Receptors: increased afferent vagal firing results in increase in respiratory drive (as well as cough and/or bronchoconstriction)
  • Stimulation of Chest Wall Receptors (due to Asthma, Pulmonary Fibrosis, and Chest Wall Disease): increase in respiratory drive (as well as dyspnea)

Examples

Cardiovascular Disease-Induced Hyperventilation

Mechanism

  • Pulmonary Congestion: results in stimulation of pulmonary vascular and interstitial receptors -> increased respiratory drive
  • Low Cardiac Output and Hypotension: results in stimulation of arterial baroreceptors -> increased respiratory drive
  • “Stagnant Hypoxia” of Carotid Body Chemoreceptors: results in increased respiratory drive

Examples

Metabolic Disorder-Induced Hyperventilation

Examples

  • Acidosis (see Metabolic Acidosis-Elevated Anion Gap, [[Metabolic Acidosis-Elevated Anion Gap]] and Metabolic Acidosis-Normal Anion Gap, [[Metabolic Acidosis-Normal Anion Gap]])): due to stimulation of peripheral and central chemoreceptors (and increased sensitivity of peripheral chemoreceptors to hypoxia) -> increased respiratory drive
  • Hyperthyroidism (see Hyperthyroidism, [[Hyperthyroidism]]): due to increased ventilatory chemoreflexes
  • End-Stage Liver Disease (ESLD) (see End-Stage Liver Disease, [[End-Stage Liver Disease]]): due to increased progesterone and VIP, increased brain ammonia and glutamine, and hypoxemia from the formation of small intrapulmonary shunts (ie: hepatopulmonary syndrome) -> increased respiratory drive

Neurologic/Psychogenic Disorder-Induced Hyperventilation

Examples

  • Psychogenic Hyperventilation: due to anxiety/stress (supported by the fact that this type of hyperventilation decreases during sleep)
  • Central Nervous System Infection: involvement of midbrain or hypothalamus -> increased respiratory drive
  • Head Trauma (see Head Trauma, [[Head Trauma]])
  • Intracerebral Hemorrhage (see Intracerebral Hemorrhage, [[Intracerebral Hemorrhage]]): due to RBC glycolysis and acidosis in CSF -> increased respiratory drive
  • Ischemic Cerebrovascular Accident (CVA) (see Ischemic Cerebrovascular Accident, [[Ischemic Cerebrovascular Accident]]): impairment of inhibition of cortex on brainstem respiratory centers
  • Brainstem Tumor: lactic acidosis by malignant cells in midbrain -> increased respiratory drive

Drug-Induced Hyperventilation

Mechanism

  • Stimulation of Peripheral and Central Chemoreceptors (or Direct Effect on Brainstem Respiratory Centers): results in increased respiratory drive
    • In the case of salicylates, secondary metabolic acidosis also drive respiration

Examples

Fever/Sepsis-Induced Hyperventilation

Mechanism

  • Fever-Related Stimulation of Hypothalamus or Carotid Bodies: occurs independent of hypotension and metabolic rate

Examples

  • Fever (see Fever, [[Fever]])
  • Sepsis (see Sepsis, [[Sepsis]])

Pain-Induced Hyperventilation

Mechanism

  • Adrenergic Stimulation of Peripheral and Central Chemoreceptors

Examples

  • Pain

Pregnancy (and Luteal Phase of Menstrual Cycle)-Induced Hyperventilation

Mechanism

  • Effect of Progesterone (and Other Hormones): stimulation of medullary respiratory centers

Examples

  • Ovulation
  • Pregnancy (see Pregnancy, [[Pregnancy]])

References

  • Pulmonary gas exchange on the summit of Mount Everest. J Appl Physiol Respir Environ Exerc Physiol. 1983 Sep;55(3):678-87 [MEDLINE]