Barium Enema

Excess oxygen can be harmful. Like many drugs, oxygen can be associated with toxicity and excess oxygen can be harmful to the lungs (pulmonary endothelium). The use of inspired oxygen greater than 60% should be avoided if possible. Decreasing the amount of supplemented oxygen at the earliest possible time should be routine practice.

1. Irrespective of the cause, hypoxia should be treated using a Ventimask which gives an appropriate dosage, to bring oxygen tension and saturation to near normal.

2. When acute ventilatory failure exists, indicated by CO2 retention, then O2 therapy is only indicated, if there is a concomitant hypoxia. Examples would be: CNS depression, Guillian-Barre syndrome and flail chest, all of which require treatment by IPPV if severe.

3. When chronic ventilatory failure and CO2 retention occur such as in chronic bronchitis and emphysema, patients rely on hypoxia to drive respiration. Excess Oxygen dosage in such patients will thus cause respiratory depression and narcosis. However, they will benefit from a small increase in inspired Oxygen. 24% and 28% Ventimasks are appropriate under these circumstances and will produce dramatic improvement in saturation and levels of consciousness.

4. Where there is excess shunting of venous blood without CO2 retention, as in infective pneumonia, direct lung trauma or contusion, shock lung, acid aspiration syndrome or chronic congestive cardiac failure, higher oxygen concentrations (35%-60%) are often required and can be administered safely. Monitoring of arterial oxygen while Ventimasks are in use will indicate whether the lungs are improving or deteriorating. When parenchymal lung failure is so severe that 60% inspired oxygen is not sufficient to achieve satisfactory blood oxygen levels, IPPV is indicated even if alveolar ventilation assessed by CO2 measurement is adequate. In the flow chart below, selection of the appropriate Ventimask is related to the various types of respiratory disorder.