Tracheal etCO2 Level and Gastric pH Level Measurements During the Correct Naso-gastric Tube Placement in Unconscious Patients. A Physiological, Prospective, Observational Study

Numerous methodologies have been evaluated to recognize the correct positioning of NGT at the gastric level, including different clinical techniques (such as gastric auscultation, aspiration of the NGT), ultrasound techniques, etc. Actually, the diagnostic gold standard is the thoraco-abdominal anterior-posterior radiography, which is considered the only non-invasive method capable to confirm the correct pose of the NGT at intra-diaphragmatic level. This method, however, even if it is non-invasive, requires the use of ionizing radiation (4 micro-Sievert (uSv) for radiography) which could be repeated multiple time for the same patient; NGT may need to be repositioned several times during the same hospital stay, increasing patient exposure to ionizing radiation and, potentially, also the health workers exposure.

The aim is to identify into the group A the threshold value between tracheal and esophageal etCO2 and into the group B the theshold value between gastric and esophageal pH.

Phase A: etCO2 measurement will be collected 1. after intubation, when the tube is inserted into the endotracheal tube, before proceeding with the aspiration of secretions and 2. once the NGT has been inserted, by a probe located at the end of the tube.

Phase B: pH measurement will be collected at the end of the procedure, once the NGT is inserted, at 1.a distance of 25 cm from the mouth (oesophageal site) and at 2. a distance of 40 cm (gastric site), aspirating the gastric contents and measuring on specific litmus paper.