Remove Continuous Positive Airway Pressure and Bilevel Positive Airway Pressure
Remove Continuous Positive Airway Pressure and Bilevel Positive Airway Pressure Masks Periodically
Bradford D. Winters MD, PhD
Continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BiPAP) are two noninvasive ventilatory modes that are commonly used in the intensive care unit (ICU) as well as other settings. CPAP is commonly used on an outpatient basis to alleviate sleep apnea. Although less common, BiPAP may also be used for this purpose. While both of these modes may also be used for patients in the ICU who have this diagnosis, these modes are also commonly used to assist ICU patients who are having respiratory difficulty unrelated to sleep apnea. These situations include avoiding the need for invasive mechanical ventilation (e.g., endotracheal intubation) or to help bridge patients from invasive ventilation to supplemental oxygen only. This may be done in a variety of disease settings, including cardiogenic pulmonary edema; chronic obstructive pulmonary disease exacerbations postoperatively; adult respiratory distress syndrome; and others. Variable effectiveness has been described depending on the disease state.
Regardless of the disease state being treated or whether one is attempting to avoid intubation or bridging from invasive ventilation, close attention needs to be maintained so that the clinician is able to recognize when the patient is failing this noninvasive mode. While several studies point to these modesâ€™ effectiveness in prevention of or weaning from invasive ventilation, it is clear that early recognition of the patient's failing the noninvasive strategies is crucial to preventing morbidity. In general, a patient who is getting worse after an hour or so of noninvasive ventilation, as determined by his or her blood gas values and clinically assessed work of breathing, should be considered for intubation. If the patient is not improving but is not deteriorating, the CPAP or BiPAP may be continued, perhaps with adjustments to the pressure settings.
What to Do
CPAP uses a consistent pressure setting throughout the respiratory cycle while BiPAP uses a bilevel setting with the inspiratory phase being set higher than the expiratory phase. Values for the pressures set generally range from 5 to 15 cm H2O. Delivery of these airway pressures requires tight-fitting masks. These are usually full-face masks that cover the nose
and mouth, though there are nasal masks that fit only over the nose. For these nasal masks to function well the patient must be cooperative enough to keep his or her mouth closed, or all of the pressure will escape through the mouth and ventilation might be ineffective.
The tight-fitting nature of CPAP and BiPAP masks poses the risk of pressure necrosis of the underlying tissues, particularly over the bridge of the nose where the skin is thin and bone and cartilage lie just near the surface. This is because the tightness required to overcome the flow pressures and prevent leakage of gas often will exceed tissue-perfusion pressure. It is for this reason that every few hours (4 hours is a commonly used interval) the mask should be removed to allow the tissue to receive adequate blood flow. This time period is generally less than a half hour and then the mask is reapplied unless the patient demonstrates the ability to remain off support during that time. If the patient does not tolerate being off the mask for even a short time periodically, the clinician should consider moving to intubation.
Masip J, Roque M, Sanchez B, et al. Noninvasive ventilation in acute cardiogenic pulmonary edema: systematic review and meta-analysis. JAMA 2005;294:3124â€“3130.
Peter JV, Moran JL, Phillips-Hughes J, et al. Effect of non-invasive positive pressure ventilation (NIPPV) on mortality in patient with acute cardiogenic pulmonary oedema: a meta-analysis. Lancet 2006;367:1155â€“1163.