Noninvasive ventilation for acute respiratory failure in patients with hematologic malignancies: what an Italian 5-year multicenter survey tells us

New puzzles for the use of non-invasive ventilation for immunosuppressed patients

On October 27, 2015, Lemile and colleagues published an article in JAMA entitled "Effect of Noninvasive Ventilation vs. Oxygen Therapy on Mortality among Immunocompromised Patients with Acute Respiratory Failure: A Randomized Clinical Trial", which investigated the effects of non-invasive ventilation (NIV) in 28-day mortality of 374 critically ill immunosuppressed patients. The authors found that among immunosuppressed patients admitted to the intensive care unit (ICU) with hypoxemic acute respiratory failure, early NIV compared with oxygen therapy alone did not reduce 28-day mortality. Furthermore, different from the previous publications, there were no significant differences in ICU-acquired infections, duration of mechanical ventilation, or lengths of ICU or hospital stays. The study power was limited, median oxygen flow used was higher than used before or 9 L/min, NIV settings provided tidal volumes higher than what is considered protective nowadays or from 7 to 10 mL/kg of ideal body weight and the hypoxemic respiratory failure was moderate to severe (median PaO2/FIO2 was around 140), a group prone to failure in noninvasive ventilatory support. Doubts arose regarding the early use of NIV in immunosuppressed critically ill patients with non-hypercapnic hypoxemic respiratory failure that need to be solved in the near future.

Performance of noninvasive ventilation in acute respiratory failure in critically ill patients: a prospective, observational, cohort study

BACKGROUND

Noninvasive ventilation (NIV) is used in critically ill patients with acute respiratory failure (ARF) to avoid endotracheal intubation. However, the impact of NIV use on ARF patient's outcomes is still unclear. Our objectives were to evaluate the rate of NIV failure in hypoxemic patients with an arterial carbon dioxide partial pressure (PaCO2) < 45 mmHg or ≥ 45 mmHg at ICU admission, the predictors of NIV failure, ICU and hospital length of stay and 28-day mortality.

METHODS

Prospective single center cohort study. All consecutive patients admitted to a mixed ICU during a three-month period who received NIV, except for palliative care purposes, were included in this study. Demographic data, APACHE II score, cause of ARF, number of patients that received NIV, incidence of NIV failure, length of ICU, hospital stay and mortality rate were compared between NIV failure and success groups.

RESULTS

Eighty-five from 462 patients (18.4 %) received NIV and 26/85 (30.6 %) required invasive mechanical ventilation. NIV failure patients were comparatively younger (67 ± 21 vs. 77 ± 14 years; p = 0.031), had lower arterial bicarbonate (p = 0.005), lower PaCO2 levels (p = 0.032), higher arterial lactate levels (p = 0.046) and APACHE II score (p = 0.034) compared to NIV success patients. NIV failure occurred in 25.0 % of patients with PaCO2 ≥ 45 mmHg and in 33.3 % of patients with PaCO2 < 45 mmHg (p = 0.435). NIV failure was associated with an increased risk of in-hospital death (OR 4.64, 95 % CI 1.52 to 14.18; p = 0.007) and length [median (IQR)] of ICU [12 days (8-31) vs. 2 days (1-4); p < 0.001] and hospital [30 (19-42) vs. 15 (9-33) days; p = 0.010] stay. Predictors of NIV failure included age (OR 0.96, 95 % CI 0.93 to 0.99; p = 0.007) and APACHE II score (OR 1.13, 95 % CI 1.02 to 1.25; p = 0.018).

CONCLUSION

NIV failure was associated with an increased risk of in-hospital death, ICU and hospital stay and was not affected by baseline PaCO2 levels. Patients that failed were comparatively younger and had higher APACHE II score, suggesting the need for a careful selection of patients that might benefit from NIV. A well-designed study on the impact of a short monitored NIV trial on outcomes is needed.

Noninvasive ventilation in acute respiratory failure

After the institution of positive-pressure ventilation, the use of noninvasive ventilation (NIV) through an interface substantially increased. The first technique was continuous positive airway pressure; but, after the introduction of pressure support ventilation at the end of the 20th century, this became the main modality. Both techniques, and some others that have been recently introduced and which integrate some technological innovations, have extensively demonstrated a faster improvement of acute respiratory failure in different patient populations, avoiding endotracheal intubation and facilitating the release of conventional invasive mechanical ventilation. In acute settings, NIV is currently the first-line treatment for moderate-to-severe chronic obstructive pulmonary disease exacerbation as well as for acute cardiogenic pulmonary edema and should be considered in immunocompromised patients with acute respiratory insufficiency, in difficult weaning, and in the prevention of postextubation failure. Alternatively, it can also be used in the postoperative period and in cases of pneumonia and asthma or as a palliative treatment. NIV is currently used in a wide range of acute settings, such as critical care and emergency departments, hospital wards, palliative or pediatric units, and in pre-hospital care. It is also used as a home care therapy in patients with chronic pulmonary or sleep disorders. The appropriate selection of patients and the adaptation to the technique are the keys to success. This review essentially analyzes the evidence of benefits of NIV in different populations with acute respiratory failure and describes the main modalities, new devices, and some practical aspects of the use of this technique.