This document discusses various oxygen delivery devices and their indications. It describes low flow devices like nasal cannulas and masks that can deliver oxygen concentrations from 24-44% depending on flow rate. High flow devices like venturi masks and bag valve masks can deliver fixed high concentrations from 35-100%. Key factors in choosing a device include the needed oxygen level, humidification needs, patient comfort and breathing pattern. The document provides details on how each device works and guidelines for safe operation.