A noninvasive tissue reflectance oximeter

A newly developed noninvasive tissue reflectance oximeter utilizes 5 light emitting diodes operating at the wavelengths of 0.635, 0.665, 0.795, 0.910, and 0.955 μ, and photodiodes to sample the tissue reflectance spectra. Since the tissue reflectance is affected by changes in both hemoglobin content (Hb _T) and hemoglobin oxygen saturation (OS _T),Hb _T is first determined using the reflectance at 0.795 μ. The hemoglobinOS _T is then estimated using the reflectances at the 5 wavelengths in conjunction with the diffuse reflectance equation which has previously been verified applicable to tissue reflectance oximetry. A quantitative estimation of bothHb _T andOS _T in intestinal mucosa of dogs obtained using this instrument showed thatHb _T values agreed fairly well with those of others and that the standard errors ofOS _T were around 5.0% inOS as compared with theOS values of blood samples for minimized arterial-venousOS differences. The continuous on-line measurement ofHb _T andOS _T should be possible using the reflectance technique and should be valuable for clinical evaluation of the patients.     

Sleepiness and nocturnal hypoxemia in Peruvian men with obstructive sleep apnea

Purpose

To evaluate the intensity of nocturnal hypoxemia associated with sleepiness in Peruvian men with a diagnosis of obstructive sleep apnea (OSA).

Methods

We carried out a secondary data analysis based on a study which includes patients with OSA who were seen in a private hospital in Lima, Peru from 2006 to 2012. We included male adults who had polysomnographic recordings and who answered the Epworth sleepiness scale (ESE). The intensity of nocturnal hypoxemia (oxygen saturation ≤90 %) was classified in four new categories: 0, <1, 1 to 10 and >10 % total sleep time with nocturnal hypoxemia (NH). When the ESE score was higher than 10, we used the definitions presence or absence of sleepiness. We used Poisson regression models with robust variance to estimate crude and adjusted prevalence ratios (PR) for association between sleepiness and NH.

Results

518 male patients with OSA were evaluated. Four hundred and fifty-two (87 %) patients had NH and 262 (51 %) had sleepiness. Of the 142 (27.4 %) patients who had >10 % total sleep time with NH, 98 (69.0 %) showed sleepiness and had a greater probability of sleepiness prevalence, with a crude PR of 1.82 (95 % CI 1.31–2.53). This association persisted in the multivariate models.

Conclusions

We found an association between NH and sleepiness. Only patients with the major intensity of NH (over 10 % of the total sleep time) had a greater probability of sleepiness. This suggests that sleepiness probably occurs after a chronic process and after overwhelming compensatory mechanisms.