Patients in acute respiratory failure are not uncommon in the emergency department, and a decisional branch point often lies between intubation and noninvasive support. Noninvasive support typically takes the form of supplemental oxygen via nonrebreather. However, as more literature emerges, noninvasive positive pressure ventilation (NIPPV) has surfaced as an important instrument in the emergency physician’s toolbox.
NIPPV refers to mechanical ventilation that is not delivered via endotracheal or tracheostomy tube (often through a facemask). The benefits of NIPPV include and are not limited to:
- Decreased technical difficulty.
- Avoiding sedation.
- Avoiding complications of intubation, for example, nosocomial infections such as ventilator-associated pneumonia.
- Decreased morbidity/mortality.
- Decreased cost
Despite these benefits, there are data showing NIPPV is still underutilized by clinicians.1
NIPPV provides positive end-expiratory pressure and ventilatory support to recruit collapsed alveoli, increase tidal volume and functional residual capacity, and improve lung compliance. The physiological sum manifests as decreased respiratory effort and improved oxygenation. Recruitment of alveolar units maintains gas exchange during the entire respiratory cycle, as well as increasing intra-alveolar forces against pulmonary edema.
In addition to these respiratory benefits, NIPPV can increase cardiac output by decreasing LV preload in heart failure or decreasing LV afterload by reducing systolic wall stress.2,3,4
The fundamental success of NIPPV lies in the emergency physician’s selection of the appropriate patient. NIPPV is ultimately used to improve or prevent worsening acute respiratory failure. In objective measures, this can be described as5:
- SaO2 less than 90%.
- Use of accessory muscles.
- Inability to speak in full sentences.
- Respiratory rate greater than 24.
- Altered mental status.
Not all disease processes are equally amendable to NIPPV. Table 1 summarizes the disease processes for which NIPPV is most useful; these are addressed later in more detail.
As important as knowing indications for the NIPPV, knowledge of the contraindications is equally vital (Table 2).5
Monitoring pH and CO2 is helpful to trend patient status, but these should not be used as exclusion criteria. In 2005, Diaz and colleagues used NIPPV successfully in patients with hyerpcapnic comas.6