Clinical evidence supports the use of NIV to avoid intubation in patients with ARF due to chronic obstructive pulmonary disease (COPD) exacerbations and acute cardiogenic pulmonary edema [2–4]. Although supporting evidence is less abundant, NIV may also be considered for patients with acute respiratory distress syndrome (ARDS) [2–4]. In patients with hypoxemic ARF, a trial of NIV is justified if patients are carefully selected by highly experienced teams in accordance with the available guidelines, while considering the known risk factors and predictors for NIV failure [2, 3].

Regarding ventilatory strategy, both CPAP and PEEP prevent alveolar collapse, reduce atelectasis by recruiting and stabilizing previously collapsed lung units, and reduce ventilation/perfusion mismatch and shunt fraction, thereby resulting in improved gas exchange. They decrease the work of breathing, counterbalancing the inspiratory threshold load imposed by intrinsic PEEP in some patients (e.g., those with COPD). Furthermore, PEEP and CPAP reduce left ventricular afterload and increase cardiac output. PSV is more effective than CPAP at achieving improved muscle unloading and relief from dyspnea during NIV. PSV plus PEEP improves alveolar ventilation compared with that achieved using CPAP alone [2, 3].

Randomized controlled trials (RCTs) describing whether NIV is beneficial in pneumonia are scarce. Most have considered very heterogeneous populations of patients with varying causes of ARF including, even if a small percentage, pneumonia [3]. Ferrer et al. [4], in a study involving 105 ARF patients, showed that BiPAP (BiPAP Vision, Respironics Inc., Murrysville, PA, USA) produced a faster improvement in oxygenation and dyspnea in patients receiving NIV and reduced the need for intubation from 52 % with conventional oxygen therapy to 25 % with NIV (p = 0.01). Furthermore, NIV was linked to a decreased incidence of septic shock (p = 0.028). These benefits were also evident for patients with pneumonia, in whom ICU mortality was reduced from 53 % with conventional therapy to 15 % with NIV (p = 0.03).

The role of NIV in patients with CAP has been reported in the literature, each with a different response to NIV. To better understand the benefit, the patients should be considered as part of different subgroups [5–9]. They include a “de novo” group, defined as patients with CAP without previous cardiac or pulmonary disease; a “comorbidities” group, defined as CAP in patients with cardiac or pulmonary diseases (i.e., COPD); and an “immunodepressed” group, defined as CAP in patients with an impaired immune system due to a hematologic malignancy or being a transplant recipient [5–9].

Whereas older studies consistently reported that NIV in “de novo” CAP patients was associated with a high likelihood of failure and consequently high intubation rates, some more recent studies have suggested otherwise. Brambilla et al. [5] reported promising results in a RCT conducted in 4 Italian ICUs evaluating 81 patients with no history of COPD or heart failure, who developed severe hypoxemia (PaO₂/FiO₂ <250 mmHg) due to pneumonia. Patients were randomized to receive either CPAP (VitalSigns Inc., Totowa, NJ, USA) by helmet or oxygen therapy by Venturi mask [5]. Compared with those receiving supplemental oxygen therapy, patients in the CPAP group exhibited a faster improvement in PaO₂/FiO₂ ratio, respiratory rate, and dyspnea, and a lower percentage met intubation criteria (15 % vs 63 %, p <0.001) [5]. In a multicenter RCT comparing CPAP (high-flow generator, VitalSigns Inc., Totowa, NJ, USA) via a helmet to conventional oxygen therapy in 47 CAP patients with moderate-severe hypoxemia, Cosentini et al. [6] found that NIV was associated with a faster improvement in oxygenation (median 1.5 h vs 48 h, p <0.001), but as soon as the CPAP was stopped, oxygenation returned to lower levels in most patients. The latter finding suggests that longer use of CPAP may be needed to recruit the flooded alveoli characteristic of the initial phase of pneumonia [6].

For patients with previous cardiac or pulmonary diseases, the available RCTs report more encouraging results. In a study of 56 patients with CAP randomized to receive either conventional oxygen therapy via Venturi mask or noninvasive PSV (Cesar [Thaema, Antony Cedex, France]; Puritain Bennett 7200 [Puritain Bennett Co., Overland Park, KS, USA]; Vential [Saime, Savigny-le-Temple, France]; Servo 900 C [Siemens Elema, Uppsala, Sweden]) via face mask, Confalonieri et al. [7] reported a decrease in intubation rate from 50 % with Venturi mask to 21 % with PSV (p = 0.03) but no reduction in mortality or length of hospital stay. Subgroup analysis found that COPD patients with hypercapnic respiratory failure benefited from NIV and had a reduced mortality rate at 2 months (11 % vs 63 %, p = 0.05). More recently, Carrillo et al. [8] prospectively followed 250 CAP patients treated with BiPAP (BiPAP ST-D and VISION Ventilator, Respironics, Inc., Murrysville, PA, USA) by means of nasal or face mask in a highly experienced center. They found that NIV success was more frequent in patients with a history of cardiac and pulmonary disease compared with those with “de novo” ARF (74 % vs 54 %, p = 0.007) [8].

Immunodepressed patients in whom ARF develops often require mechanical ventilatory support. In these patients, NIV has the potential to avoid endotracheal intubation and its complications [2, 3]. In a RCT by Squadrone et al. [9], 40 neutropenic patients with ARF, tachypnea, and pulmonary infiltrates were randomized to early CPAP (WhisperFlow, Caradyne, Ireland) with helmet or conventional oxygen therapy. Among patients admitted to the ICU, oxygenation was better and the intubation rate was lower in the CPAP than in the control group (p = 0.0001). NIV showed a reduction in the relative risk for intubation to 0.46 (95 % confidence interval [CI], 0.27–0.78) [9]. A systematic review by Zhang et al. [1], which included one RCT involving immunodepressed patients with fever and pulmonary infiltrates, reported that, compared with standard treatment, PSV (Evita, Dräger, Lübeck, Germany) by means of a full face mask decreased the need for endotracheal intubation (odds ratio [OR], 0.26; 95 % CI, 0.08–0.85), shortened the ICU length of stay (mean difference −2; 95 % CI, −3.92 to −0.08), reduced the incidence of complications (OR, 0.24; 95 % CI, 0.07–0.82), and reduced in-hospital mortality (OR 0.24; 95 % CI, 0.07–0.82). However, NIV did not affect the duration of mechanical ventilation [1].