Table 2.

Summary of ICU studies

Author (year)	Study population	Purposes and measured outcomes	Related findings
Trivedi et al ., 2015 [ 27 ]	A total of 140 patients who underwent intubation	To compare short-term outcomes between patients with a pre-intubation SI value ≥0.9 and those with a pre-intubation SI value < 0.9	A pre-intubation SI value ≥ 0.90 was significantly associated with PIH and ICU mortality
Smischney et al ., 2016 [ 24 ]	A total of 147 patients who underwent intubation	To determine the incidence and risk factors of PIH	- PIH occurred in 20% of intubations and was associated with higher mortality and longer hospital stays-The pre-intubation SI value was not associated with PIH because the SI value was 0.92 for stable patients and 0.99 for patients who developed PIH (P = 0.36)
Wardi et al ., 2017 [ 28 ]	Twenty-nine patients who underwent cardiac arrest within 20 min after intubation were compared with116 patients who were intubated without cardiac arrest	The authors examined patient characteristics, interventions, that may predict post-intubation cardiac arrest	- A pre-intubation SI value ≥ 1 was an independent predictor of post-intubation cardiac arrest
Smischney et al ., (2017) [ 29 ]	A total of 269 immunocompromised patients who underwent intubation	To identify the incidence and risk factors of PIH in immunocompromised critically ill patients	A pre-intubation SI value of 1 was found in the PIH group and a pre-intubation SI value of 0.84 was found in the non-PIH group (P < .01)
Smischney et al ., 2018 [ 30 ]	A total of 420 patients who underwent intubation	To identify the predictors of hemodynamic derangement	- The mean pre-intubation SI value was 0.96 in the hemodynamic derangement group and 0.81 in the patients without complications (P = 0.001)