Technique

Nasal-mask or facial-mask ventilation employs a tight-fitting mask that allows for a CPAP or BiPAP support system. The patient with impending respiratory failure receives either continuous pressure or inspiratory/expiratory (bilevel) support, thus allowing a decrease in inspiratory effort, rest for respiratory and accessory muscles, improvement of gas exchange, avoidance of intubation, and improved comfort.914 A nasal-mask protocol with BiPAP appears to be the most advanced protocol and appears to allow more sensitive changes during the course of treatment ( Fig 14-7). The nasal mask allows the patient to eat, drink, and converse with the emergency staff. However, the nasal positive-pressure ventilation (NPPV) does allow for air leaks through the mouth.

FIG. 14-7. A patient with severe COPD on nasal BiPAP. (Used with permission.)

The ventilatory support system frequently preferred is the BiPAP ventilator (Respironics, Murraysville, PA). It is small, relatively inexpensive, very mobile, and tolerates leaks better than other systems. It is possible to set the inspiratory positive airway pressure (IPAP) and the expiratory positive airway pressure (EPAP/PEEP) independently. Three modes of ventilatory triggering are available: spontaneous, combined spontaneous/timed, and timed. The proper-size mask should be chosen (allowing no mouth coverage) and tight enough to allow a good, comfortable seal. Settings should include spontaneous mode, IPAP set at 10, EPAP set at 3 cmH 2O

initially and increasing IPAP by 3-cm increments and EPAP slowly. Continuing hypercarbic failure is treated by increasing IPAP alone by 3-cm increments. 15 Complications

Some of the complications described include difficulty with mask seal requiring multiple readjustments, gastric distention, aspiration (rare), intolerance of the positive pressure, and facial skin breakdown (with long-term use). These complications appear to occur infrequently, but the most common intolerance was excessive respiratory secretions, which, in fact, may be a relative contraindication to NPPV. Other contraindications to NPPV are severe maxillofacial trauma and potential basilar skull fracture where pneumocephalus may occur. Another problem with mask ventilation is that using a conventional ventilator can be difficult or even counterproductive because of the inadvertent triggering of alarms in systems that are not designed for this use. The BiPAP ventilatory system, which has been used with success, may not be readily available in the Ed, and respiratory services may have to be contacted for this setup.

Application of NPPV provides ventilatory support for impending respiratory failure and has been shown to decrease the workload of the respiratory muscles. Oxygen saturation, Paco2, and pH remain stable or improve as compared with unassisted ventilation. Therefore this technique may prove useful in respiratory failure when intubation is questionable. Facial/nasal-mask-assisted ventilation is a simple, noninvasive method that has few complications, and is shown to be well tolerated over long periods of time. It also decreases negative intrathoracic pressure but needs to be studied more fully for situations where suppression of inspiratory effort is desired, as in flail chest.

This modality may decrease long-term hospital admissions, prevent unwanted intubations in the elderly or severely ill, and circumvent borderline respiratory failure intubations. Each patient must be closely monitored for tolerance of upper airway positive pressure. Multiple mask/ventilator adjustments may be required. Finally, any instability in ventilation or oxygenation requires close monitoring in case a more invasive intervention is required.

Patients who receive NIPPV need to be cooperative and should not have life-threatening cardiac ischemia, dysrhythmias, or hypotension. NIPPV is inappropriate in patients who have absent respiratory effort, who are agonal, or who produce excessive airway secretions. Airway management and apparatus associated with NIPPV can be distracting. However, medical treatment, such as in-line nebulized updrafts, anticholinergics, steroids, and respiratory hygiene must proceed as appropriate simultaneous with NIPPV.

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