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, additionally, 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 COPD (chronic obstructive pulmonary disease), eg, with PaCO2 > 45 mm Hg or pH < 7.30
Cardiogenic pulmonary edema with impending respiratory failure
Immunocompromised patients with impending respiratory failure in whom intubation poses a higher risk of infection
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 or chest wall diseases.
Contraindications to Noninvasive Positive Pressure Ventilation
Absolute contraindications
Cardiac or respiratory arrest, or impending arrest
Hemodynamic or dysrhythmic instability
Severe upper gastrointestinal bleeding
Facial deformity or trauma
Upper airway obstruction
Copious secretions or inability to clear secretions
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
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 a full-featured ventilator)
Face mask or nasal mask
Head strap, to secure the mask against the patient’s face
Fitting wheel, used to determine the optimal mask size for the patient
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 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.
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 to 15 to 20 cm water as needed.
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 tracheal 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.
