A pilot study of pharyngeal pulse oximetry with the laryngeal mask airway:A comparison with finger oximetry and arterial saturation measurements in healthy anesthetized patients

We compared pharyngeal Spo(2) by using the laryngeal mask airway (LMA) to f inger Spo(2) and oxygen saturation from arterial blood samples (Sao(2)). We studied 20 hemodynamically stable, well oxygenated, anesthetized patients (ASA physical status I-III, aged 18-80 yr). A single-use pediatric pulse ox imeter was attached to the back plate of a size 5 LMA. Pharyngeal and finge r Spo(2) (dominant index finger) and Sao(2) (nondominant radial artery) wer e measured with the cuff volume at 0-40 mL in the neutral position. The int racuff pressure was then set at 60 cm H2O in the neutral position, and read ings were taken with the head-neck flexed, extended, and rotated. Sao(2) wa s the same as pharyngeal Spo(2) at 20 and 30 mL cuff volume, but higher tha n pharyngeal Spo(2) at all other cuff volumes and head-neck positions (P < 0.04). Sao(2) was always higher than finger Spo(2) (P < 0.01). Pharyngeal S po(2) was higher than finger Spo(2) at cuff volumes 10-40 mL and in the fle xed and rotated head-neck positions (all: P < 0.007), but was lower at 0 cu ff volume (P < 0.0001) and similar in the extended head-neck position. Ther e was an increase in pharyngeal Spo(2) between 0 and 10 mL cuff volume (P < 0.0001), but no changes thereafter. Pharyngeal Spo(2) was similar in the f lexed, rotated and extended head-neck positions. Pharyngeal Spo(2) agrees m ore closely with Sao(2) (mean difference < 0.7%) than finger Spo(2) (mean d ifference > 1.1%) at 10-40 mL cuff volume and in head-neck flexion. The sta ndard error of limits was identical (0.09) for both finger Spo(2) and phary ngeal Spo(2) if data at 0 cuff volume are excluded. We conclude that pharyn geal Spo(2) with the LMA is feasible and generally provides more accurate r eadings than finger Spo(2), in hemodynamically stable, well oxygenated, ane sthetized patients. Implications: Pharyngeal oximetry with the laryngeal ma sk airway is feasible and generally provides more accurate readings than fi nger oximetry in hemodynamically stable, well oxygenated, anesthetized pati ents.