2010B07 List the physical properties of oxygen. Discuss the potential adverse
effects associated with oxygen administration.

Definition

·  8th element on periodic table

·  MW 32. Diatomic form

·  Ubiquitous clear, colourless, odourless gas

·  Essential in mammals

Numbers

·  Boiling point -180°C

·  Critical temperature -118°C

·  Critical pressure 50 atm

Production

·  Fractional distillation of air

·  Oxygen concentrator

·  Electrolysis of water

Storage

·  Vacuum-insulated evaporator (VIE)

·  Cylinder manifold

Pathophysiology

·  ↑O₂ indices:

o ↑↑PAO2, ↑↑PaO2

o ↑CaO2 only 0.003mL/100mL/mmHg O2 due to shape of OHDC

o Minimal change CvO₂

·  ↑Formation of reactive oxygen species (ROS)

o Substance with unpaired outer shell electron (e.g. O2-)

o Reacts with and causes damage to enzymes, DNA, lipid membranes

o Damage especially if antioxidants exhausted (e.g. superoxide dismutase)

Neurological

·  Anxiety, nausea, tinnitus, confusion, seizures

·  Threshold immediately: 3atm

·  Threshold at 24 hours: 1.5 atm

·  No toxicity at 1 atm

Respiratory

·  ↓Ventilatory drive via carotid body chemoreceptors

·  ↓HPV -> ↑VQ mismatch in susceptible patients e.g. COPD

·  Alveolar collapse, atelectasis, ↓FRC

·  A few hours 1atm: tracheobronchial irritation, chest pain, cough

·  24 hours 1atm: alveolar membrane lipid peroxidation

Cardiovascular

·  Coronary vasoconstriction

Worsen ischaemic injury

·  Post-MI: ↑ROS damage

·  Post-stroke: ↑ROS damage

·  Post-arrest: ↑ROS damage

Neonate-specific

·  Retinopathy of prematurity

·  Bronchopulmonary dysplasia

·  Necrotising enterocolitis