Figure 2 – Common modes of oxygen administration. a and b) Nasal cannulae (‘prongs’), which allow control of oxygen flow rate but not inspired concentration. c–e) Venturi masks, which allow precise control of inspired oxygen concentration: the flow of oxygen through a nozzle entrains air via holes around the nozzle; increasing the oxygen flow entrains more air so that, within certain limits, the percentage oxygen the patient breathes remains constant. A larger orifice in the nozzle gives a higher oxygen concentration, here colour-coded from 24% to 60% (compared with 21% in room air). f) An oxygen concentrator suitable for home use. Figure 2a credit: istockphoto/Beano5.
See the entire Principles of respiratory therapy Chapter