Table 1 Characteristics of the biological effects of oxygen molecules

✓ Oxygenation

 • Increase in arterial oxygen content and hence systemic oxygen delivery

 • Variable efficacy depending on the type of hypoxia

✓ Circulation

 • Systemic vasoconstriction

  • Increase in systemic vascular resistance and hence systemic arterial pressure

  • Decrease in cardiac stroke volume and cardiac output

  • Possible decrease in tissue blood flow

 • Pulmonary vasodilation in affected area by inhaled oxygen

  • Decrease in pulmonary vascular resistance and hence pulmonary arterial pressure

  • Increase in pulmonary blood flow

  • Decrease in right-to-left intracardiac shunt flow, if it exists

 • Regional perfusion

  • Decrease in coronary blood flow

  • Aggravation of ischemic damage in myocardial infarction

✓ Cellular toxicity

 • Inflammation: Induction of pro-inflammatory cytokines

 • Production of reactive oxygen species

  • Enhanced neurological damage after ischemia reperfusion

  • Induced lung injury and possible dysfunction of other organs

✓ Others

 • Occurrence of resorption atelectasis

 • Impairment of mucociliary clearance in trachea/bronchus

 • Compromised innate immunity