Equipment | Techniques | Candidates | Indications | Contraindications | Complications

Equipment

• It inivolves the use of a mechanical ventilator connected by tubing to an interface (full-face or nasal mask or mouthpiece with headstraps) that directs airflow into the nose or the nose & mouth.                 

Techniques

• Continuous Positive Airway Pressure (CPAP)
  It delivers a continuous positive pressure throughout the respiratory cycle & is effective only if the patient is breathing spontaneously.  It cannot provide ventilation if the patient becomes apneic.
• Bilevel Positive Airway Pressure (Bi-PAP)
  It provides continuous PAP that allows independent control of inspiratory & expiratory pressures.  It can be administered in a spontaneous setting (requiring the patient to initiate every ventilation), a timed setting (preset ventilation intervals independent of patient effort), or both (allowing the caregiver to determine a minimal respiratory rate).
• Volume-cycled Ventilator
  It delivers a set volume for each breath.  It is often poorly tolerated because of the increased inspiratory pressure; It can be uncomfortable & can cause air leaks around the mask.
• Pressure-cycled Ventilator
  It delivers a set pressure for each breath, is commonly administed with bilevel PAP ventilators or with standard ventilators that use pressure support or pressure control modes.  

Candidates for NPPV

• Ideal candidates are respiratory-insufficiency patients who are cooperative and hemodynamically stable.

Indications for NPPV - hypoxemia & hypercapnia    

• Short-Term Applications
  • Acute Respiratory Failure due to COPD
    It should be initiated before severe symptoms develop.
    It decreases the need for endotracheal intubation & decreases mortality.  It causes fewer complications, & length of stay in ICU & hospital is shorter.
  • Acute Respiratory Failure Not Related to COPD (Acute hypoxic respiratory failure)
  • Asthma Exacerbation & Status Asthmaticus
    - Need more controlled studies for these problems
  • Cardiogenic Pulmonary Edema
    CPAP improves oxygenation & hypercapnia & decreases the need for endotracheal intubation & the length of stay in the ICU.
• Long-Term Applications
  • Chronic Respiratory Insufficiency due to Neuromuscular disease, thoracic deforminities, & idiopathic hypoventilation.
  • Severe Stable COPD

Contraindications for NPPV    

• Respiratory arrest
• Evidence of acute cardiac ischemia or acute myocardial infarction
• Unstable hemodynamic status
• Impaired mental status
• Need for airway protection to prevent aspiration
• Inability to fit or wear the mask properly (facial deformity, claustrophobia, etc.)

Complications of NPPV

• Nasal congestion (may need in-line humidifiers, topical nasal corticosteroids, or anticholinergics)
• Eye irritation
• Nasal bridge ulceration or Facial skin reddening (may need protective synthetic covering as Duoderm)
• Aspiration
• Gastric distention (may need nasogastric tube)

From Mayo Clin Proc, August 1999, Vol 74:817 Jefferey T. Rabatin & Peter C. Gay

REF:
Mayo Clin Proc, August 1999, Vol 74:817 Jefferey T. Rabatin & Peter C. Gay (Review)
Chest 1999;115:863 Loube DI, Gay PC, etc.
NEJM 1998 Aug. 13 ;339:429 Antonellli M, Conti G, Rocco M, etc.
NEJM 1997 Dec. 11:337:1746 Hillberg RE (Review)
Crit Care Med 1997;25:1685 Keenan SP