Evaluation of accuracy of pharyngeal pulse oximetry in critically ill patients with low perfusion state

ABSTRACT

The reliability of pulse oximeter, when applied to fingers or toes, may be compromised in critically ill patients with low perfusion state. So modification of oximeter probes to be applied to an area more central and highly perfused is required for more accurate monitoring. This prospective controlled study was designed to compare pharyngeal pulse oximetry to the finger pulse oximetry in critically ill patients with low perfusion state. Sixty patients were divided into two equal groups according to their perfusion status [30 patients for each] into, a normal perfusion group [control group] and a low perfusion group. The low perfusion group was specified by a mean arterial blood pressure less than 60 mmHg and cardiac output less than 4 l/min. All the selected patients were intubated with a cuffed endotracheal tube and a cuffed oropharyngeal airway [COPA] device was used for application of the pharyngeal pulse oximeter For each patient, the hemodynamic monitoring data including, mean arterial pressure, heart rate, cardiac output stroke volume and systemic vascular resistance, and reading of the pharyngeal pulse oximetry, the finger pulse oximetry and arterial saturation obtained from blood gas analysis [which was taken as an indicator of accuracy] were recorded every 30 min for 3 hours. Compared to the control group, the mean arterial pressure [MAP], cardiac output [CO] and stroke volume [SV] were significantly lower while systemic vascular resistance [SVR] was significantly higher in low perfusion group at all time intervals [P<0.05] Results showed a statistical significant difference with under reading of finger oximetry in low perfusion group [P<0.05]. Also there was statistical significant difference in relative accuracy between the pharyngeal and finger oximetry in the low perfusion group [P<0.05]. The pharyngeal pulse oximetry [using COPA device as a method of application] provides a simple, non-invasive and feasible method for tracing oxygen saturation and is more accurate than finger pulse oximetry in critically ill patients with low perfusion state