• Oxygen delivery systems
• Nasal cannula, simple face masks, ventimasks
• Partial rebreathing
• Non-rebreathing
• most common
• all expired gas is vented
• BiPAP
• Complications of Oxygen Therapy

Nasal cannula

• F_iO₂ factors
• Inspiratory flow and pattern
• Respiratory rate, exhalation time
• O₂ flow rate
• Mouth breathing
• Anatomic reservoir
• Nasopharyngeal volume (50ml)
• Typically; F_iO₂ increases 0.03 for each l/m
• Max F_iO₂ 0.50
• 1 L = 0.24
• 2 L = 0.28
• 3 L = 0.32
• 4 L = 0.36
• 5 L = 0.40
• 6 L = 0.44
• Tissue desiccation; pain from higher flows

Simple face masks

• No valves or reservoirs
• F_iO₂ 0.35-0.60 @ 6-10 l/m flow rates
• Rebreathing is minimized
• Gas flow rate > MV
• <5 l/m CO₂ accumulation
• 5-6 L = 0.40
• 6-7 L = 0.50
• 7-8 L = 0.60
• Augmented reservoir volume via mask around nose and mouth (in addition to nasopharyngeal volume of ~50ml)
• Nothing gained at higher flow rates
• Lower flow rates (2-4 l/m)
• similar to nasal cannula

Partial rebreathing masks

• Higher F_iO₂ possible
• 0.70-0.85
• 6 L = 0.60
• 7 L = 0.70
• 8 L = 0.80
• 9 L = 0.80+
• 10 L = 0.80+
• Oxygen reservoir bag from which pt. gets inspired gas
• No exhalation valve to prevent CO₂ into reservoir
• > 8 l/m ; reservoir kept full
• initial vs terminal expired gas: inital exhaled gas (from anatomic deadspace, therefore with no CO₂) goes into reservoir while terminal gas is exhaled. This should minimize rebreathing.
• Uses less oxygen than other masks
• Transport uses

Non-rebreathing systems

• High flow (fixed performance)
• Exceed peak inspiratory flow rates
• All inspired gas supplied by delivery system
• Stable FiO2 possible

• Low flow (variable performance)
• Most common systems

• Highest F_iO₂ possible
• 0.80-0.95
• 10 L = 0.80+
• 15 L = 0.90+
• nidirectional valves each side
• vent expired tidal volume
• prevent inspiration of room air
• 3^rd valve at reservoir
• prevents expired gas going into reservoir
• Reservoir should be inflated during entire cycle
• Snug fit
• If mask fits too snug and fresh gas flow rate is too low, inhalation impossible
• Backup: Remove one of the mask valves to allow entrainment of room air if flows too low

Ventimasks; Air entrainment masks

• High-flow devices with no valves or reservoirs
• Bernoulli principle and jet-mixing
• Color coded adaptors;specific flows

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Complications

• Suppressed ventilatory drive
• Desiccation of airways
• Absorption atelectasis
• Pulmonary oxygen toxicity

BiPAP

• Bi-level positive airway pressure ventilation
• Nasal mask plus strap
• Full face mask if nasal mask not tolerated
• IPAP, EPAP, Flow rate
• Estimated V_t
• Estimated leak

• Noninvasive ventilation: experience at a community teaching hospital

Intens Care Med 1999;25:458-63.
• Use of a ventilatory support system(BiPAP) for acute respiratory failure in the emergency department Chest 1999;116:166-71.
• Effect of bi-level positive airway pressure(BiPAP) nasal ventilation on the postoperative pulmonary restrictive syndrome in obese patients undergoing gastroplasty Chest 1997;111:665-70.
• All patients post-op
• decreased FVC, FEV₁, PEFR, S_pO₂
• BiPAP 12/4 (insp, exp) for 24hrs improved all except PEFR compared to no BiPAP