Current guidelines recommend Routine daily chest radiographs (CXRs) for mechanically ventilated patients in intensive care units (ICUs). However, some ICUs have shifted to an On-demand strategy, in which this CXR is only prescribed if warranted by the patient's status at the morning physical examination. Here the investigators compared Routine and On-demand strategies in 21 French ICUs. The working hypothesis was that CXR prescriptions would fall by at least 20% with the On-demand strategy, with no reduction in quality of care.