Exploration of the Nociception Level (NOL™) Index for Pain Assessment during Endotracheal Suctioning in Mechanically Ventilated Patients in the Intensive Care Unit: An Observational and Feasibility Study.

Background: Many patients in the intensive care unit (ICU) suffer from pain and are non-communicative. Therefore, alternative pain measures are necessary. Although behavioral pain measures are available, physiological measures are lacking. The Nociception Level index (NOL™) provides a value from combination of multiple physiological parameters to measure pain and its use in the ICU is new.

Aim: To explore the use of a multiple physiological parameter measure for pain assessment, the NOL™ index, in mechanically ventilated patients able to self-report pain in the ICU.

Methods: A prospective cohort study was performed. Data were collected before, during, and 15 minutes after a non-nociceptive procedure (noninvasive blood pressure using cuff inflation) and a nociceptive procedure (endotracheal suctioning). NOL index, 0 to 10 pain intensity, and Critical-Care Pain Observation Tool (CPOT) scores were also obtained. Data were analyzed using Friedman and Mann-Whitney tests. Feasibility of study procedures was described.

Results: Out of 28 patients who consented, 17 remained eligible and data were analyzed for 15. Technical issues prevented obtaining a NOL signal in 2 patients. NOL values were higher during endotracheal suctioning (median = 41.6) compared with before (median = 11.2) and after the procedure (median = 11.8) and compared with cuff inflation (median = 15.1; Friedman test, p < .001). NOL values were associated with pain intensity and CPOT scores (Mann-Whitney tests, p < .05).

Conclusions: The study procedures with the NOL were found feasible; NOL values could discriminate between nociceptive and non-nociceptive procedures, and values were associated with reference pain measures. Further NOL testing is required in other ICU patient groups and procedures.