CHAPTER 47 Oxygen Delivery Devices
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Oxygen therapy forms a major part of an anesthesiologist’s premise and is also a basic skill for all other specialties. The indications for oxygen therapy are as follows:
Cardiac and respiratory arrest.
Hypoxemia defined by SpO2 < 90% or PaO2 < 60 mm Hg.
In patients with limited oxygen-carrying capacity—severe anemia, hypotension or shock, very low ejection fraction, and metabolic acidosis.
Respiratory distress due to any other reason.
After partial recovery from anesthesia.
Patients with shivering.
Severe cardiorespiratory disease.
In all these situations, the primary reason for the indication has to be identified and treated appropriately while oxygen is being given.
The oxygen delivery devices can be classified as follows:
Low-flow devices: Nasal prongs, face mask.
High-flow devices: Venturi mask, high-flow nasal cannula.
Low-flow devices deliver oxygen at a flow rate less than the patient’s inspiratory flow rate, leading to air entrainment. The FiO2 depends on the patient’s inspiratory flow rate. It is of two types: nasal cannula and face mask.
It consists of two soft prongs that arise from the oxygen supply tubing, which are inserted into the nares of the patient, and tubing is secured to the face by an adjustable strap (Fig. 47.1). The nasopharynx acts as an anatomical reservoir, and the FiO2 depends on the flow rate, patient’s minute ventilation, inspiratory flow, and volume of the nasopharynx. Approximate FiO2 with different flow rates are as follows:
1 L/min: 24%.
2 L/min: 28%.
3 L/min: 32%.
4 L/min: 36%.
5 L/min: 40%.
Higher flow rates can cause irritation of the nasal mucosa and can result in bleeding and headache. Increased patient compliance and the ability to speak, eat, and drink are the advantages. Inability to control the FiO2 and easier displacement are the disadvantages.
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