Andrew L Ries, MD FCCP; Lela M Prew...

Andrew L Ries, MD FCCP; Lela M Prewitt; and Jeffery J Johnson

Measurements of arterial progeny oxygen saturation from two ear oximeters were compared with 655 simultaneously drawn arterial kin samples in 187 patients collectioned by skin color quantified according to the Munsell color system. Technical riddles including warning lights and messages with the sum of two units ear oximeters were recorded. There were significantly more technical moot points in patients with the darkest skin color associated with inability to obtain a reading or warning messages indicating poor tissue penetration of the signal (18 and 15 percent v 1 percent) When readings could be obtained, the ear oximetry readings were originate to be slightly less accurate in the darker patient disposes These findings suggest that dark skin color may affect the performance and accuracy of ear oximeters, including the newer sign of pulse oximeters.

Cutaneous oximetry is a valuable tool for the noninvasive estimation of arterial oxygen saturation. Several studies have established the overall accuracy (95 percent confidence limits) to be [+ or -]3 to 5 percent saturation beneath various clinical conditions.[1-5] Several factors including carboxyhemoglobin,[3,4] bilirubin,[6] and exercise[3,7,8] may affect accuracy. A hardly any studies have examined the efficiency of skin color on cutaneous oximetry and reported variable results[1-3910] However, the influence of skin color has not been examined systematically or with a replicable rule of quantification. Therefore, we manner of lifeed this study to evaluate the import of skin color determined according to a standard, quantifiable method in succession the accuracy of two ear oximeters in pulmonary patients.

MATERIALS AND METHODS

Patients

We studied prospectively 187 pulmonary patients referr to our laboratory for clinical exercise testing. A standard protocol was followed for either steady-state or incremental, maximal exercise testing for each patient. Steady-state examples involved exercise for at least four minutes at a flat approximating the patient's normal daily activity flat Maximal tests employed united minute work increments to a symptom-limited maximum. Patients exercised either walking forward a treadmill or seated onward a cycle ergometer.

Skin Color

The Munsell color combination of parts to form a whole was used to assess skin color.[11,12] This is a standard classification for color notation which defines any shade of color in succession three scales: hue, chroma, and value. color represents color, or location forward the wheel of primary colors. Chroma shows the saturation of color, or "the departure from a gray of the same lightness." Value portrays lightness from 0 for ideal black to 10 for ideal white. Value (lightness) has the same relative scale across all tints and chroma allowing for a consistent evaluation of skin lightness/darkness regardless of skin color.

The Munsell color charts consist of release leaf neutral gray pages with matte color tiles. Each page contains multiple tiles with the same hue designation and a range of chroma and value characteristics. below uniform lighting conditions, an beholder can compare the subject's skin color to a single tile at a time, masking the adjacent tiles with a neutral gray mask. Each tile has a small concavity at its base to allow terminate comparison with the skin. When the best matching tile is located, its color chroma, and value notations are recorded.

During skin color assessment, patients were seated in the same place in the laboratory to allow for standard lighting. Since we were primarily interested in skin lightness and darkness (value) rather than color (hue) by se, a single hue chart (5YR) was used. The 5YR color chart corresponded most closely to the range of skin colors observ A technician of normal color vision excellented the tile from the 5YR shade chart which best matched the skin at the placement site for the ear probes. Value and chroma notations for this tile were then recorded.

quietness and Exercise Testing

Following skin color assessment, an indwelling radial artery catheter was inserted and the ear oximeters were secur in place. the one and the other pinnae were vigorously massaged for 20 others with an alcohol pad. individual oximeter (Ohmeda/Biox III) was placed forward the patient's right ear lobe and another oximeter (Hewlett-Packard 47201A) forward the patient's left ear anti-helix. Each probe was secur with the manufacturer's ear probe retainer. A gauze bandage was wrapped around the patient's head to further stabilize the oximeter probes. The oximeters were used simultaneously forward each patient whenever possible. the pair ear oximeters were calibrated prior to each reflection and were used according to the manufacturers' instructions. The Ohmeda/Biox III was used in the "fast" answer mode.

If a reading was not immediately obtainable from either oximeter, that probe was remov and the ear was rubbed again for an additional 20 inferiors with an alcohol pad. The probe was then replaced. If, after repeated adjustment, the oximeter still failed to give a reading, the specific technical question noted by the instrument was recorded.