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Concept: Prone position


Background Previous trials involving patients with the acute respiratory distress syndrome (ARDS) have failed to show a beneficial effect of prone positioning during mechanical ventilatory support on outcomes. We evaluated the effect of early application of prone positioning on outcomes in patients with severe ARDS. Methods In this multicenter, prospective, randomized, controlled trial, we randomly assigned 466 patients with severe ARDS to undergo prone-positioning sessions of at least 16 hours or to be left in the supine position. Severe ARDS was defined as a ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen (FiO2) of less than 150 mm Hg, with an FiO2 of at least 0.6, a positive end-expiratory pressure of at least 5 cm of water, and a tidal volume close to 6 ml per kilogram of predicted body weight. The primary outcome was the proportion of patients who died from any cause within 28 days after inclusion. Results A total of 237 patients were assigned to the prone group, and 229 patients were assigned to the supine group. The 28-day mortality was 16.0% in the prone group and 32.8% in the supine group (P<0.001). The hazard ratio for death with prone positioning was 0.39 (95% confidence interval [CI], 0.25 to 0.63). Unadjusted 90-day mortality was 23.6% in the prone group versus 41.0% in the supine group (P<0.001), with a hazard ratio of 0.44 (95% CI, 0.29 to 0.67). The incidence of complications did not differ significantly between the groups, except for the incidence of cardiac arrests, which was higher in the supine group. Conclusions In patients with severe ARDS, early application of prolonged prone-positioning sessions significantly decreased 28-day and 90-day mortality. (Funded by the Programme Hospitalier de Recherche Clinique National 2006 and 2010 of the French Ministry of Health; PROSEVA number, NCT00527813 .).

Concepts: Oxygen, Pulmonology, Medical statistics, Intensive care medicine, Acute respiratory distress syndrome, Mechanical ventilation, Supine position, Prone position


We aimed at evaluating the efficacy of extracorporeal shockwave lithotripsy (SWL) for treating distal ureteral calculi performed in supine vs. prone position.

Concepts: Systematic review, Meta-analysis, Supine position, Extracorporeal shock wave lithotripsy, Prone position


The glymphatic pathway expedites clearance of waste, including soluble amyloid β (Aβ) from the brain. Transport through this pathway is controlled by the brain’s arousal level because, during sleep or anesthesia, the brain’s interstitial space volume expands (compared with wakefulness), resulting in faster waste removal. Humans, as well as animals, exhibit different body postures during sleep, which may also affect waste removal. Therefore, not only the level of consciousness, but also body posture, might affect CSF-interstitial fluid (ISF) exchange efficiency. We used dynamic-contrast-enhanced MRI and kinetic modeling to quantify CSF-ISF exchange rates in anesthetized rodents' brains in supine, prone, or lateral positions. To validate the MRI data and to assess specifically the influence of body posture on clearance of Aβ, we used fluorescence microscopy and radioactive tracers, respectively. The analysis showed that glymphatic transport was most efficient in the lateral position compared with the supine or prone positions. In the prone position, in which the rat’s head was in the most upright position (mimicking posture during the awake state), transport was characterized by “retention” of the tracer, slower clearance, and more CSF efflux along larger caliber cervical vessels. The optical imaging and radiotracer studies confirmed that glymphatic transport and Aβ clearance were superior in the lateral and supine positions. We propose that the most popular sleep posture (lateral) has evolved to optimize waste removal during sleep and that posture must be considered in diagnostic imaging procedures developed in the future to assess CSF-ISF transport in humans.

Concepts: Brain, Neuroimaging, Brain tumor, Human brain, Magnetic resonance imaging, Cerebrospinal fluid, Supine position, Prone position


Prone positioning has been used for many years in patients with acute respiratory distress syndrome (ARDS). The initial reason for prone positioning in ARDS patients was improvement in oxygenation. It was later shown that mechanical ventilation in the prone position can be less injurious to the lung and hence the primary reason to use prone positioning is prevention of ventilator-induced lung injury (VILI).

Concepts: Pulmonology, Pneumonia, Intensive care medicine, Acute respiratory distress syndrome, Mechanical ventilation, Infant respiratory distress syndrome, Pulmonary contusion, Prone position


Prone position and PEEP can both improve oxygenation and other parameters, but their interaction has not been fully described. Limited data directly compare selection of mechanically “optimal” or “best” PEEP in both supine and prone positions, either with or without changes in chest wall compliance. To compare best PEEP in these varied conditions, we used an experimental ARDS model to compare the mechanical, gas exchange, and hemodynamic response to PEEP titration in supine and prone position with varied abdominal pressure.

Concepts: Respiratory physiology, Abdominal pain, Gas, Supine position, Prone position, Mechanical, Three positions


In this article we review recent advances made in the pathophysiology, diagnosis, and treatment of inhalation injury. Historically, the diagnosis of inhalation injury has relied on nonspecific clinical exam findings and bronchoscopic evidence. The development of a grading system and the use of modalities such as chest computed tomography may allow for a more nuanced evaluation of inhalation injury and enhanced ability to prognosticate. Supportive respiratory care remains essential in managing inhalation injury. Adjuncts still lacking definitive evidence of efficacy include bronchodilators, mucolytic agents, inhaled anticoagulants, nonconventional ventilator modes, prone positioning, and extracorporeal membrane oxygenation. Recent research focusing on molecular mechanisms involved in inhalation injury has increased the number of potential therapies.

Concepts: Mode, Respiratory physiology, Medical imaging, Respiratory system, Inhalation, Extracorporeal, Prone position


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. Moreover, 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 (PaO2 /FIO2 <150 mm Hg). Moreover, survival is enhanced when patients are managed with a smaller tidal volume (≤8 mL/kg), higher PEEP (10-13 cm H2O), 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.

Concepts: Better, Clinical trial, Improve, Respiratory physiology, Effectiveness, Pressure, Supine position, Prone position


To examine the association between prone position and sudden unexpected death in epilepsy (SUDEP).

Concepts: The Association, Prone position


We identified 810 reports that described ECMO in ARDS, and 61 fulfilled our inclusion criteria (Figure). 61 reports were included, and the authors of 26 (43%) responded to email requests for confirmation (or clarification). Based on the aggregate (published and emailed) information, 9 papers were excluded because key data were unclear; unambiguous data were available relating to 17 papers. These 17 papers represented 672 patients with ARDS who were cannulated with VV-ECMO; of these patients, 208 (31%) received a trial of prone positioning before ECMO, and 464 (69%) did not. The proportion of studies that clearly identified whether prone positioning was used prior to ECMO was similar before (30% of 20 papers) and after (34% of 32 papers) the publication in 2013 of a key RCT reporting a survival benefit associated with prone positioning (P>0.05) (3). However, the proportion of all VV-ECMO patients in whom prone positioning was used before ECMO was lower in the more recent studies (84/452, 19%) vs. those published before 2013 (124/220, 56%; P<0.05). These data suggest a systematic bias in the literature reporting outcomes after ECMO. The vast majority of reported patients who receive ECMO did not first receive therapy that (in contrast to ECMO), is simple, cheap and of proven benefit; therefore, inferences about the efficacy of ECMO in ARDS are of limited use.

Concepts: Intensive care medicine, Report, Bias, Extracorporeal, Extracorporeal membrane oxygenation, Positioning, The Colbert Report, Prone position


While prone positioning (PP) has been shown to improve patient survival in moderate to severe acute respiratory distress syndrome (ARDS) patients, the rate of application of PP in clinical practice still appears low.

Concepts: Pulmonology, Intensive care medicine, Acute respiratory distress syndrome, Infant respiratory distress syndrome, Pulmonary contusion, Pulmonary alveolus, Syndromes, Prone position