© Springer International Publishing Switzerland 2016
Antonio M. Esquinas (ed.)Noninvasive Mechanical Ventilation10.1007/978-3-319-21653-9_5050. Noninvasive Ventilation in Acute Respiratory Distress Syndrome
(1)
Department of Anesthesiology and Reanimation, Cerrahpasa Medical School, Istanbul University, Istanbul, Turkey
Keywords
ARDSAcute lung injuryMechanical ventilationNoninvasiveAbbreviations
ARDS
Acute respiratory distress syndrome
ARF
Acute respiratory failure
CPAP
Continuous positive airway pressure
EACC
European-American Consensus Conference
NPPV
Noninvasive positive pressure ventilation
PaO2/FiO2
Ratio of arterial oxygen tension to fractional inspired oxygen concentration
PEEP
Positive end-expiratory pressure
PSV
Pressure support ventilation
50.1 Introduction
Acute respiratory distress syndrome (ARDS) is a syndrome of diffuse lung injury that is characterized by acute dyspnea and tachypnea, severe hypoxemia, bilateral opacities on the chest X-ray, and decreased respiratory compliance. The European-American Consensus Conference (EACC) suggested four clinical criteria for a uniform definition of ARDS. These are acute onset of hypoxemic respiratory failure (hypoxemia was defined as the ratio of arterial oxygen tension to fractional inspired oxygen concentration (PaO2/FiO2) below 300 for acute lung injury and below 200 for ARDS), bilateral infiltrations in chest X-ray, pulmonary capillary wedge pressure below 18 mmHg, and the absence of clinical symptoms of left atrial hypertension [1]. In 2011, an expert panel convened to update the EACC definitions of ARDS and the new Berlin definitions were proposed. These definitions make a classification of ARDS in three stages of severity, from mild to severe [2].
Whatever the definition is, the mainstay of treatment of ARDS is mechanical ventilation to improve gas exchange and decrease work of breathing. Moreover, the only evidence-based treatment in ARDS is mechanical ventilation using a lung-protective strategy with high positive end-expiratory pressure (PEEP) and low tidal volumes, which almost always necessitates endotracheal intubation [3]. However, recent efforts have been focused on the use of noninvasive positive pressure ventilation (NPPV) in acute respiratory failure (ARF) to avoid complications associated with intubation. The guidelines suggest use of NPPV in acute exacerbations of chronic obstructive pulmonary disease, cardiogenic pulmonary edema, postoperative patients, and immunosuppressed patients with strong evidence [4]. Use of NPPV in these settings improves outcomes, decreases length of stay in the intensive care unit and hospital, and lowers costs of hospitalization.
50.2 Discussion
The use of NPPV in hypoxemic ARF, especially in ARDS, is somewhat controversial. Early studies, which compared application of NPPV with standard therapy, yielded different success rates in different etiologies. For example, in the work of Antonelli et al. [5], the overall failure rate of NPPV was found to be 30 % in 354 patients, where the highest intubation rate was in ARDS and community-acquired pneumonia (50 and 51 %, respectively). Generally, in these studies, ARDS patients comprised only a small portion of the study patients; in the Antonelli et al. study, only 86 of 354 patients had ARDS. In another randomized controlled study from Ferrer et al. [6], 105 hypoxemic respiratory failure patients were randomized to receive either NIPPV or high-concentration oxygen therapy. In this study, most of the patients had pneumonia or cardiogenic lung edema. Only 7 patients in the NPPV group and 8 patients in high-concentration oxygen group had ARDS when they were recruited. Overall, NPPV decreased the need for endotracheal intubation and rate of septic shock occurrence and decreased mortality in hypoxemic respiratory failure, but the efficacy of NPPV in ARDS subgroup was poor, and ARDS was associated with increased need for endotracheal intubation. In their randomized study, Delclaux et al. [7] observed that use of continuous positive airway pressure (CPAP) was not effective in preventing endotracheal intubation when compared with standard oxygen therapy, although it resulted in a physiological improvement at the early stages.
Actually, there is a strong rationale for the use of NPPV in ARDS. Inflammation and edema in lung tissue collapse alveoli, decrease inflatable lung volume, and cause intrapulmonary shunting. Loss of surfactant function and functional residual capacity cause cyclic opening and closing of alveoli, leading to further lung injury, and increased elastance of the lungs increases work of breathing. Applying positive pressure to the airways increases lung volumes, improves alveolar stability, and decreases work of breathing [8, 9]. All of these may help to stop deterioration in respiratory function and avoid intubation.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
