Critical Care Medicine

Acute respiratory distress syndrome (ARDS) may be associated with severe hypoxemia and high mortality. Prone positioning has demonstrated some efficacy as a rescue maneuver for severe hypoxemia and is recommended in patients with ARDS. This prospective, multicenter, unblinded, randomized controlled trial (the Prone-Supine II Study) of patients (N = 342) with ARDS receiving mechanical ventilation assessed the possible outcome benefits of prone positioning in patients with moderate and severe hypoxemia. Patients were randomized to undergo supine (n = 174) or prone (20 h/day; n = 168) positioning during ventilation, and the 28-day all-cause mortality was recorded.

Overall, similar mortality rates were observed in the prone and supine groups (28 days: 31.0 vs.  32.8%; P = 0.72 and 6 months: 47.0 vs.  52.3%; P = 0.33). In the subsets of patients with moderate or severe hypoxemia, similar mortality rates were observed (28 days: P = 0.62 and 0.31; 6 months: P = 0.85 and 0.19). Furthermore, a significantly greater proportion of patients in the prone group experienced at least one complication (e.g. , need for increased sedation, muscle paralysis, hemodynamic instability, and device displacement).

This well-designed study clearly indicates that routine prone position in mechanically ventilated patients with moderate to severe ARDS offers no benefits in terms of mortality and complication rates. This does not mean that prone position should necessarily be abandoned in all intensive care unit (ICU) patients with ARDS. However, when deciding to place ICU patients in the prone position to transiently improve oxygenation, the risk–benefit balance should be carefully weighed.

Although the American College of Radiology recommends daily chest radiographs for mechanically ventilated patients in the ICU, there is a lack of consensus among physicians on whether or not this is necessary. In comparison with an on-demand strategy, in which chest radiographs are performed only if warranted by the patient's clinical status, routine daily radiographs increase a patient's radiation exposure and hospital costs.

To compare the benefit:risk of routine versus  on-demand chest radiographs, a cluster randomized, open-label crossover study was conducted in 21 ICUs at 18 hospitals. Each center enrolled 20 consecutive patients per ICU, and patients were monitored until discharge from the unit or for up to 30 days of mechanical ventilation, whichever was first. The primary outcome measure was the mean number of chest radiographs per patient-day of mechanical ventilation.

Patients who received radiographs with the on-demand strategy (n = 425; 3,148 radiographs) received 32% less (3,148 vs.  4,607) radiographs compared with the routine group (n = 424; P < 0.0001). The number of chest radiographs that led or contributed to diagnostic procedures or therapeutic interventions was not significantly different between the two groups. Days of mechanical ventilation, length of stay in the ICU, and mortality were similar between the two groups.

This study clearly supports that the use of an on-demand versus  routine strategy for chest radiograph in mechanically ventilated ICU patients is safe and cost effective. It should therefore be encouraged, provided that standardized, careful review of radiographs is performed.

The 2009 novel swine-origin influenza A (H1N1) is associated with a large number of ICU admissions, especially during the southern hemisphere winter. A high proportion of ICU patients developed ARDS, and a small part of them were refractory to conventional treatment requiring extracorporeal membrane oxygenation (ECMO).

This prospective observational study of patients (N = 201) with ARDS associated with influenza A (H1N1) was conducted in 15 ICUs in Australia and New Zealand. Patients were treated either conventionally (n = 133) or by ECMO (n = 68). Compared with patients who underwent conventional treatment, patients who received ECMO were younger (36 vs.  44 yr, P = 0.02), had fewer comorbidities (P = 0.02), and required more vasopressors (57 vs.  34%, P = 0.02). Before commencement of ECMO, ARDS was severe: Pao²/Fio²ratio at 55 with protective ventilation protocols, 67% of the patients had recruitment maneuvers, 20% were prone positioned, 5% had high-frequency oscillation ventilation, 32% received nitric oxide, and 22% received prostacyclin. The initial mode of ECMO was venovenous in 93% of the patients. The median duration of ECMO support was 10 days, and the median circuit blood flow at 24 h was 4.9 l/min. Hemorrhagic and infectious complications occurred in 54 and 62% of the patients, respectively, during ECMO therapy. Compared with patients who underwent conventional treatment, patients who received ECMO had a longer duration of mechanical ventilation (18 vs.  8 days, P = 0.001), a longer ICU length of stay (22 vs.  12 days, P = 0.001), and a higher mortality rate (23 vs.  9%, P = 0.01). Hemorrhagic complications were associated with 74% of deaths in the ECMO group.

Despite the limitations of this study (e.g. , randomization, ECMO use timing, and transfer organization), overall mortality was low in the conventional group and the ECMO group. It may be hypothesized that a fast use of ECMO in ARDS before the onset of other organ failures is associated with a better outcome. However, this remains to be validated.

Suggested by: Hervé Dupont, M.D., Ph.D.