Oxygen Delivery Systems

Quick Answer

Oxygen delivery systems provide supplemental oxygen to patients with varying degrees of efficiency and control. Variable performance devices (nasal cannula, simple mask): Delivered FiO2 depends on patient's inspiratory flow rate and tidal volume; nasal cannula 1-6 L/min (24-44% FiO2), simple mask 5-10 L/min (40-60% FiO2), non-rebreather mask with reservoir 10-15 L/min (60-80% FiO2 if tight seal). Fixed performance devices (Venturi mask, high-flow nasal cannula): Deliver precise FiO2 independent of patient's breathing pattern; Venturi mask uses Bernoulli principle (air entrainment) to deliver 24-60% FiO2; high-flow nasal cannula (HFNC) delivers heated, humidified oxygen up to 60-70 L/min (up to 100% FiO2) with CPAP effect (2-6 cm H2O). High-flow nasal cannula advantages: Heated humidification (improves comfort, reduces airway drying), CPAP effect (reduces work of breathing, recruits alveoli), washout of nasopharyngeal dead space, precise FiO2 delivery, better tolerated than mask. Preoxygenation: 100% oxygen via face mask for 3-5 minutes (denitrogenation of FRC) extends safe apnoea time from 2 minutes to 8-10 minutes in healthy adults; head-up position improves FRC and extends time; obese and pregnant patients have shorter safe apnoea times (60-90 seconds). Apnoeic oxygenation: Nasal cannula 15 L/min during laryngoscopy (diffusion of oxygen into alveoli) extends safe apnoea time by 2-3 minutes; effective in obese patients and difficult airways. Oxygen toxicity: Prolonged high FiO2 (>60% for >24 hours) causes absorption atelectasis, tracheobronchitis, ARDS; aim for lowest FiO2 to maintain SpO2 >92% (PaO2 >60 mmHg). Fire risk: Surgical fires with laser/electrocautery; minimum FiO2 needed (<30% if possible), draping precautions, fire extinguisher available. [1-10]