Noninvasive positive pressure ventilation (NPPV) is ventilatory assistance without an invasive artificial airway. It is delivered to a spontaneously breathing patient via a tight-fitting mask that covers the nose or both the nose and mouth. Because the airway is unprotected, aspiration is possible, so patients must have adequate alertness and airway-protective reflexes.
(See also Overview of Mechanical Ventilation.)
NPPV can be given as:
Continuous positive airway pressure (CPAP)
Bilevel positive airway pressure (BPAP), which is triggered by the patient’s respirations
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 the inspiratory positive airway pressure (IPAP).
Indications for Noninvasive Positive Pressure Ventilation
NPPV is primarily used to delay and possibly prevent the need for endotracheal intubation and to facilitate extubation in spontaneously breathing patients. Indications include:
Acute exacerbations of chronic obstructive pulmonary disease (COPD) with PaCO2 > 45 mm Hg or pH < 7.30
Cardiogenic pulmonary edema with impending respiratory failure
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,
CPAP is often used for patients with obstructive sleep apnea.
BPAP can be used for patients with concomitant obesity-hypoventilation syndrome or for chronic ventilation in patients with neuromuscular disorders (eg, muscular dystrophies) or chest wall deformities (eg, severe scoliosis or kyphosis).
Contraindications to Noninvasive Positive Pressure Ventilation
Absolute contraindications:
Cardiac or respiratory arrest, or impending arrest
Severe upper gastrointestinal bleeding
Facial deformity or trauma
Upper airway obstruction
Copious secretions or inability to clear secretions
Vomiting (which may result in aspiration) or impaired gastric emptying (as occurs with ileus, bowel obstruction, or pregnancy), which increases risk of vomiting
Imminent indication for surgery or need to be in a setting inaccessible for close monitoring for prolonged procedures
Obtundation or inability to cooperate with instructions
Complications of Noninvasive Positive Pressure Ventilation
Possible aspiration into the unprotected airway
Barotrauma, including simple pneumothorax and tension pneumothorax
Equipment for Noninvasive Positive Pressure Ventilation
BPAP machine (or ventilator capable of providing BPAP)
Face mask or nasal mask
Head strap, to secure the mask against the patient’s face
Additional Considerations for Noninvasive Positive Pressure Ventilation
IPAP must be set below esophageal opening pressure (20 cm water) to avoid gastric insufflation.
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 for Noninvasive Positive Pressure Ventilation
The patient may be seated upright or be semirecumbent.
Step-by-Step Description of Noninvasive Positive Pressure Ventilation
Determine the appropriate face mask size.
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.
Fasten the lower straps to the mask on each side.
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.
Connect the BPAP tubing to the patient, with the carbon dioxide release valve pointing away from the patient.
Typical initial BPAP pressure settings are: IPAP = 10 to 12 cm water and EPAP = 5 to 7 cm water.
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.
Sequentially observe the patient, beginning 30 minutes after initiating BPAP, to assess ventilation and patient comfort, and increase IPAP as needed (to a maximum of 20 cm water).
Aftercare for Noninvasive Positive Pressure Ventilation
It is important to monitor patients closely after beginning NPPV to identify those whose condition does not improve (usually within 1 to 2 hours) and who therefore may need endotracheal intubation. Serial blood gas measurements may help guide management.
Tips and Tricks for Noninvasive Positive Pressure Ventilation
To facilitate patient comfort and acceptance of the mask, have patients hold the mask against their own face before securing the straps.
