(See also Overview of Mechanical Ventilation.)
NPPV can be given as
With CPAP, constant pressure is maintained throughout the respiratory cycle with no additional inspiratory support. When using BPAP, the physician sets both the expiratory positive airway pressure (EPAP, which is the physiologic equivalent of CPAP and positive end-expiratory pressure [PEEP]) and, additionally, the inspiratory positive airway pressure (IPAP).
Indications
NPPV is primarily used to delay and possibly prevent the need for endotracheal intubation and to facilitate extubation in spontaneously breathing patients. Indications include
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Acute exacerbations of COPD (chronic obstructive pulmonary disease), eg, with PaCO2 > 45 mm Hg or pH < 7.30
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Cardiogenic pulmonary edema with impending respiratory failure
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Immunocompromised patients with impending respiratory failure, in whom intubation poses a higher risk of infection
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Patients with do-not-intubate advance directives who would otherwise require intubation
The optimal patient is alert and cooperative and has minimal airway secretions.
In the outpatient setting,
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CPAP is often used for patients with obstructive sleep apnea.
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BPAP can be used for patients with concomitant obesity-hypoventilation syndrome or for chronic ventilation in patients with neuromuscular or chest wall diseases.
Contraindications
Absolute contraindications
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Cardiac or respiratory arrest, or impending arrest
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Hemodynamic or dysrhythmic instability
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Severe upper gastrointestinal bleeding
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Facial deformity or trauma
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Upper airway obstruction
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Copious secretions or inability to clear secretions
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Vomiting (which may result in life-threatening aspiration) or impaired gastric emptying (as occurs with ileus, bowel obstruction, or pregnancy), which increases risk of vomiting
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Imminent indication for surgery or need to be in a setting inaccessible for close monitoring for prolonged procedures
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Obtundation or inability to cooperate with instructions
Complications
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Possible aspiration into the unprotected airway
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Barotrauma, including simple pneumothorax and tension pneumothorax
Equipment
Additional Considerations
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IPAP must be set below esophageal opening pressure (20 cm water) to avoid gastric insufflation.
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Indications for conversion to endotracheal intubation and conventional mechanical ventilation include the development of decreased alertness and transport to a surgical suite where control of the airway and full ventilatory support are desired.
Positioning
Step-by-Step Description of Procedure
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Determine the appropriate face mask size by fitting the fitting wheel over the bridge of the patient’s nose, and rotating the wheel to select the size that covers the entire mouth.
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Secure the forehead part of the head strap about the patient’s head. Do not fasten the strap too tightly; allow one or two finger widths under the strap and then tighten it.
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Fasten the lower straps to the mask on each side.
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Attach the top portion of the mask to the forehead strap. This top portion of the mask may have fine adjustments: in or out, up or down, to optimize patient comfort.
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Connect the BPAP tubing to the patient, with the carbon dioxide release valve pointing away from the patient.
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Typical initial BPAP pressure settings are: IPAP = 10 to 12 cm water and EPAP = 5 to 7 cm water.
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Adjust the position of the mask as needed to maintain a good seal against the face. A small air leak, such as 5 L/minute, is negligible.
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Sequentially observe the patient, beginning 30 minutes after initiating BPAP, to assess ventilation and patient comfort, and increase IPAP to 15 to 20 cm water as needed.
