II. Indications
- Obstructive Sleep Apnea
- Loud continuous snoring
- Noninvasive positive airway pressure in respiratory distress (BIPAP offers similar respiratory support)
- See Acute Respiratory Failure
- Bridge to intubation in severe respiratory illness
- Adult Respiratory Distress Syndrome (ARDS)
- Refractory Hypoxemia
- Respiratory Failure in children and chronic airway disease
III. Contraindications
- See Non-Invasive Positive Pressure Ventilation
- See Advanced Airway Indications
- Central Sleep Apnea
- Respiratory Failure (requires intubation)
- Altered Level of Consciousness with increased aspiration risk
IV. Mechanism
-
Non-Invasive Positive Pressure Ventilation
- Used during spontaneous breathing (as with BIPAP)
- Pressure above atmospheric maintained at airway opening
- Maintained throughout respiratory cycle
- Acts as airway splint to prevent collapse of alveoli and Bronchioles
- Also decreases airway resistance by Splinting open inflamed or bronchospastic airways
- Overcomes anatomic airway resistance (e.g. Obstructive Sleep Apnea)
- Increases surface area for gas exchange
- Increases oxygen diffusion and improves Hypoxemia
- Decreases work of breathing
- Decreases pressure required on inspiration
- Same end-expiratory pressure as with PEEP
- Lower Inspiratory pressure excursion than with PEEP
- CPAP requires less pressure to open
- PEEP requires a greater work of breathing
V. Approach: Noninvasive positive airway pressure in respiratory distress
- See Acute Respiratory Failure
- Indications
- Hypoxemic Acute Respiratory Failure (inadequate tissue Oxygen Delivery)
- Not indicated for hypercarbic Acute Respiratory Failure
- CPAP only delivers Oxygen and increased end-expiratory pressure
- Only BiPap (increases Tidal Volume) or Mechanical Ventilation can correct Ventilatory failure
- Delivery mechanisms
- Technique CPAP Face Mask
- Target pressure range: 5-10 mmHg (continuous airway pressure)
- Contrast with the bi-level airway pressure of BIPAP (e.g. 15 mmHg inspiratory and 5 mmHg expiratory)
- CPAP pressure can be increased up to a maximum of 20 mmHg
- Pressure >20 mmHg exceeds lower esophageal sphincter pressure
- Start
- Set initial cpap pressure to 2-3 cm H2O
- Patient self-applies Face Mask
- Slowly increase the pressure
- Target pressure range: 5-10 mmHg (continuous airway pressure)
VI. Adverse Effects: Relates to decreased mask tolerance
- Nasal dryness or congestion
- Mask air leakage
- Claustrophobia
- Skin irritation or abrasions
- Conjunctivitis
VII. Efficacy: Noninvasive positive airway pressure in respiratory distress
- CPAP and BIPAP have similar outcomes in respiratory distress
- CPAP may be better tolerated in some cases (no need to synchronize their breaths with different inspiratory and expiratory pressure phases)
- Li (2013) Am J Emerg Med 31(9): 1322-7 [PubMed]
VIII. References
- Mallemat and Runde in Herbert (2015) EM:Rap 15(2): 7-8
- Marino (1991) ICU Book, Lea & Febiger, p. 379-80
- Martin and Hall (2015) Crit Dec Emerg Med 29(2): 11-8
- Olson (2012) Mayo POIM Conference, Rochester
- Bower (2000) Otolaryngol Clin North Am 33(1):49-75 [PubMed]
- Flemons (2002) N Engl J Med 347:498-504 [PubMed]
- Gozal (1998) Pediatrics 102:616-20 [PubMed]
- Owens (1998) Pediatrics 102:1178-84 [PubMed]
- Piccinillo (2000) JAMA 284:1492-4 [PubMed]
- Sliverberg (2002) Am Fam Physician 65(2):229-236 [PubMed]
- Victor (1999) Am Fam Physician 60(8):2279-86 [PubMed]
- Victor (2004) Am Fam Physician 561-74 [PubMed]
- Wickwire (2013) Chest 144:680-93 [PubMed]