Oxygen therapy is most useful in
(Arterial hypoxia) (75-77-A yadav 4th)Hypoxic hypoxia responds best to oxygen therapy while there is no benefit to oxygen therapy in histotoxic cyanoidpoisoning) hypoxiaClinical presentation of hypoxia is cyanosis, which is produced if reduced Hb level is more than 5g/dl (which roughly corresponds to O2 saturation) < 85 to 90% or pO2 < 50 mmHg) methaemoglobin > 1.5g/dL and sulphaemoglobin >0.5 g/dLCharacteristic features of diffeent types of HvpoxiaFeaturesHypoxic hypoxiaAnemic hypoxiaStagnant hypoxiaHistotoxic hypoxia1. CO2 in arterial bloodReducedNormalNormalNormal2. O2 carrying capacity of bloodNormalReducedNormalNormal3. Rate of blood flowNormalNormalReducedNormal4. Utilization of O2 by tissue100%75%50%Not usefulOXYGEN TOXICITY - toxic radicals of oxygen damage the capillary membrane increasing capillary permeability and ARDS like picture, Abnormality in ciliary transport, absorption atelectasis** and tracheobronchitis, decreased pulmonary compliance**In neonates pulmonary toxicity manifests as bronchopulmonary dysplasia**, Retrolental fibroplasia** (premature neonates (<36 weeks) are greatest risk.* Acute oxygen toxicity may manifest as convulsions this is called as paulbert effectHYPER BARIC OXYGEN : USESA.Poisonings- CO, cyanoid poisoningB.Gas bubble disease- Decompression sickness, Air embolismC.Ischaemia- Crush injury, Ischemic ulcer, Radiation necrosisD.Infections- Clostridial, Mucormycosis, Refractory osteomyelitisE.Others- Oxygen support during lung lavage, Bums cerebral edemaHeliox (80% helium + 20% oxygen) is used for upper air way obstruction like tracheal stenosis
Arterial hypoxia
Stagnent hypoxia
Anemic hypoxia
Cyanide hypoxia
Miscellaneous