AMBIENT OXYGEN THERAPY EQUIPMENT
Classifying Oxygen Therapy Equipment
Oxygen given alone or in a gas can be mixed with air as a partial supplement to patients’ tidal or minute volume or serve as the entire source of the inspired volume. This approach provides the basis for classifying devices or systems according to their ability to provide adequate flow levels and range of fraction of inspired oxygen (Fio2). Other considerations in selecting therapy include patient compliance, the presence and type of artificial air-way, and the need for humidification or an aerosol delivery system.
Oxygen (usually 100%) is supplied at a fixed flow that is only a portion of inspired gas. Such devices are usually intended for patients with stable breathing patterns. As ventilatory demands change, variable amounts of room air will dilute the oxygen flow. Low-flow systems are adequate for patients with
· Minute ventilation less than ∼8–10 L/min
· Breathing frequencies less than ∼20 breaths/min
· Tidal volumes (VT) less than ∼0.8 L
· Normal inspiratory flow (10–30 L/min).
Inspired gas at a preset Fio2 is supplied continuously at high flow or by providing a sufficiently large reser-voir of premixed gas. Ideally, the delivered Fio2 is not affected by variations in ventilatory level or breath-ing pattern. Profoundly dyspneic and hypoxemic patients may need flows of 100% oxygen in excess of 100 L/min. High-flow systems are indicated for patients who require
· Consistent Fio2
· Large inspiratory flows of gas (>40 L/min).
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