Non-invasive ventilation (NIV) has become a common treatment for acute and chronic respiratory failure. The main theoretical advantage of NIV is avoiding the side effects and complications related to endotracheal intubation, improving patient comfort and preserving airway defense mechanisms. NIV has been demonstrated to reduce ICU and hospital length of stay and improve outcome in select patient groups.

NIV can be delivered nasally or by face-mask, using either a conventional mechanical ventilator or a machine designed specifically for this purpose. NIV has two major modes of supplying ventilatory support, namely, continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BiPAP). CPAP provides continuous positive pressure throughout the respiratory cycle. CPAP recruits underventilated alveoli by increasing lung volume at the end of expiration, resulting in improved gas exchange. CPAP is also effective in decreasing work of breathing compared with unsupported ventilation [1].

NIV is usually delivered either by portable positive pressure BiPAP ventilators or critical care ventilators designed to deliver invasive mechanical ventilation. No study has shown better NIV success rates for one type of ventilator than the other, but the ventilator mode used and specific settings are important for patient comfort and decreased work of breathing. Generally, pressure support ventilation is rated as more tolerable by patients than assist-control modes when using a conventional ventilator [2].

BiPAP ventilators provide high-flow positive airway pressure that cycles between high-positive pressure and low-positive pressure. In the spontaneous mode, BiPAP responds to the patient’s own flow rate and cycles between high-pressure inspiration and low-pressure exhalation. BiPAP reliably senses the patient’s breathing efforts and even air leaks that occur within the unit. When inspiration is detected the inspiratory pressure is known as inspiratory positive airway pressure (IPAP). During this cycle, higher pressures are delivered for a fixed time or until the gas flow rate falls below a threshold level, usually 25 % of the expiratory volume. At this point in time, the expiratory positive airway pressure (EPAP) cycle begins delivering a lower positive pressure that splint and maintains a fixed alveolar pressure. BiPAP is similar to pressure support ventilation. The terminology differs, however; for BiPAP, the expiratory pressure is equivalent to the sum of the positive end-expiratory pressure and the inspiratory pressure. Thus, a BiPAP setting of 12 cm of inspiratory pressure and 5 cm of for expiratory pressures is equivalent to a standard ventilator setting of 7 cm for pressure support and 5 cm for positive end-expiratory pressure (PEEP).

The advantages of NIV include improved patient comfort, reduced need for sedation, and avoidance of the complications of endotracheal intubation, including upper airway trauma, sinusitis, and nosocomial pneumonia. Furthermore, airway defense mechanisms and speech and swallowing are left intact, and the patient remains alert and communicative. NIV has been used successfully to treat acute respiratory failure in postoperative patients and in those with pulmonary edema, chronic obstructive pulmonary disease, and obstructive sleep apnea. NIV has also been used to facilitate weaning. However, NIV appears to be particularly effective in patients with an exacerbation of COPD who are alert and cooperative.

The most common complication with the use of NIV is facial trauma related to the use of tight fitting masks. The problem of skin necrosis, particularly over the bridge of the nose, makes it difficult for patients to be ventilated continuously for more than 1–2 days. Retention of secretions and gastric distension may be problematic in some patients.