Peripheral perfusion index (PPI) is variable measured by Radical-7 (Masimo) device and reflects the ratio between pulsatile and non-pulsatile portions of peripheral circulation. PPI is characterized by being non-invasive, real time, and simple variable. Impairment of various perfusion indices (such as central venous oxygen saturation and serum lactate) during spontaneous breathing trial (SBT) were previously reported; however, these indices are characterized by being relatively invasive. We hypothesized that impairment of PPI during SBT might be predictive of weaning failure. The aim of this work was to evaluate the possible association between PPI and success of SBT

This prospective observational study will be carried out in surgical intensive care unit (SICU) unit of trauma and emergency hospital at Cairo University teaching hospital. Informed consent will be obtained from patients' next-of-kin prior to the enrolment in the study. All mechanically ventilated patients for more than 48 hours presented will be consecutively included.

The excluded patients are: patients < 18 years, patients with peripheral vascular disease, patients on vasopressors, and those with hand injuries hindering which would preclude the application of the device probe will be excluded.

Assessment of readiness to wean from mechanical ventilation will be done by ICU physician according to the ICU protocol Spontaneous breathing trial (SBT) will be applied through pressure support (PS) mode with PS 5 cmH2O and positive end expiratory pressure (PEEP) 5 cmH2O for 30 minutes; then, weaning parameters will be assessed again. The decision of extubation will be taken by the intensivist in charge who is blinded to peripheral perfusion index (PPI) measurements. Weaning failure will be defined according to the guidelines of international conference on weaning from mechanical ventilation PPI will be continuously monitored using Radical-7 device pulse co-oximeter (Masimo corporation, Irvine, CA) via a pulse oximeter probe applied to the third or fourth digit of left hand. The probe will be covered with an opaque shield to avoid any error by external light sources. A baseline reading for PPI will be obtained followed by a reading each 5 minutes till the end of the SBT. We calculated a PPI ratio to evaluate the change in PPI during SBT. PPI ratio is defined as PPI by the end of SBT / baseline PPI).

Inclusion Criteria:

• mechanically ventilated patients for more than 48 hours

Exclusion Criteria:

• patients < 18 years
• patients with peripheral vascular disease
• patients on vasopressors
• patients with hand injuries hindering which would preclude the application of the device probe

mechanically ventilated patients for more than 48 hours