A Comprehensive Review of Prone Position in ARDS

Abstract

Prone position (PP) has been used since the 1970s to treat severe hypoxemia in patients with ARDS because of its effectiveness at improving gas exchange. Compared with the supine position (SP), placing patients in PP effects a more even tidal volume distribution, in part, by reversing the vertical pleural pressure gradient, which becomes more negative in the dorsal regions. PP also improves resting lung volume in the dorsocaudal regions by reducing the superimposed pressure of both the heart and the abdomen. In contrast, pulmonary perfusion remains preferentially distributed to the dorsal lung regions, thus improving overall alveolar ventilation/perfusion relationships. 1660RESPIRATORY CARE • NOVEMBER 2015 VOL 60 NO 11Moreover, the larger tissue mass suspended from a wider dorsal chest wall effects a more homogeneous distribution of pleural pressures throughout the lung that reduces abnormal strain and stress development. This is believed to ameliorate the severity or development of ventilator-induced lung injury and may partly explain why PP reduces mortality in severe ARDS. Over 40 years of clinical trials have consistently reported improved oxygenation in approximately 70% of subjects with ARDS. Early initiation of PP is more likely to improve oxygenation than initiation during the subacute phase. Maximal oxygenation improvement occurs over a wide time frame ranging from several hours to several days. Meta-analyses of randomized controlled trials suggest that PP provides a survival advantage only in patients with relatively severe ARDS (P aO 2 /F IO 2 <150 mm Hg). Moreover, survival is enhanced when patients are managed with a smaller tidal volume (<8 mL/kg), higher PEEP (10 -13 cm H 2 O), and longer duration of PP sessions (>10 -12 h/session). Combining adjunctive therapies (high PEEP, recruitment maneuvers, and inhaled vasodilators) with PP has an additive effect in improving oxygenation and may be particularly helpful in stabilizing gas exchange in very severe ARDS.

Efficacy and safety of early prone positioning combined with HFNC or NIV in moderate to severe ARDS: a multi-center prospective cohort study

“…Acute respiratory distress syndrome (ARDS) has a high mortality of 25~40%, even with improvement in supportive therapies. Previous studies suggest that prone positioning (PP) can increase the average ratio of arterial oxygen tension to the fraction of inspired oxygen (PaO 2 / FiO 2 ) by + 35 mmHg and reduce mortality in moderate to severe ARDS, especially when combined with neuromuscular blocker (NMB) and low tidal volume ventilation, which decrease the risk of ventilator-induced lung injury (VILI) [1][2][3][4][5]. However, PP was only recommended in severe ARDS with PaO 2 /FiO 2 < 100 mmHg, and the actual use of PP is less than 33% of severe ARDS patients [6].…”

Prone Positioning for Acute Respiratory Distress Syndrome in Adults

“…Additionally, it is postulated that less strain is applied to lung parenchyma as recruitment of alveoli allows for a more homogenous distribution of tidal volume during respiration 6 . Furthermore, some believe that this positioning allows for improvement of postural drainage of the lungs and limits pooling of oropharyngeal secretions above the endotracheal tube cuff, possibly decreasing incidence of ventilator‐associated pneumonia (VAP) 7 …”

Prone positioning in severe acute hypoxemic respiratory failure in the emergency ward

“…Prone position also improves resting lung volumes in dorso-caudal regions by reducing the superimposed pressures of both heart and abdominal organs. [1][2][3] The final result of prone positioning in most subjects with acute hypoxemic respiratory failure due to severe pulmonary consolidation is to exhibit mild to dramatic improvements in oxygenation.…”