Accuracy of a pulse oximeter in the measurement of the oxyhaemoglobin saturation

The aim of the present study was to evaluate the accuracy, in comparison with a reference method, of the Nellcor N-20P pulse oximeter in the assessment of oxyhaemoglobin saturation (Sa,O2). Sa,O2 was monitored at rest by the Nellcor N-20P pulse oximeter in 100 subjects (82 males, mean age 68+/-12 yrs) consecutively enroled. At the same time, an arterial blood sample was collected for the measurement of Sa,O2, carboxyhaemoglobin, and methaemoglobin by an IL-282 Co-oximeter. A significant difference was found between Sa,O2 values measured with the two methods (t=11.78, p<0.05), but the two series of measurements were significantly correlated (r=0.97). Both the level and the limits of agreement between the two methods were satisfactory when the more appropriate Bland and Altman method was applied. Nevertheless, a lack of accuracy of the pulse oximeter was found, but only for Sa,O2 values <82% and >94%, as demonstrated by the Youden index. In conclusion, these data show that Nellcor N-20P is sufficiently reliable for the assessment and monitoring of oxyhaemoglobin saturation. The lack of accuracy does not seem clinically relevant since it is appreciable only for values at the extremes of the oxyhaemoglobin saturation range.     

The value of pulse oximetry during the performance of a forced spirometry maneuver

Given that forced spirometry is the main routine exploration in any laboratory of pulmonary functional assessment, we have analyzed the behaviour of O2 arterial saturation (SaO2) during such maneuver in patients with airflow chronic obstruction (AFCO), in order to verify any potential alterations. We have studied three groups of patients: Group A, control, 17 healthy subjects; group B, 18 patients with AFCO and initial saturation higher than 90%; group C, 15 patients with AFCO and saturation equal to or lower than 90%. Total duration of the maneuver was significantly higher in groups B and C compared with the control group (p < 0.001). In groups A and B, we did not observed any significant reductions in SaO2 with respect to the initial value, although we did observed such differences in group C (p < 0.001). None of the patients presented a subjective clinical disorder, although the absence of both complexity and risk suggest the convenience of including the oximetry as an additional parameter when conducting a forced spirometry in patients with AFCO and respiratory failure.     

Mechanism of the occurrence of the alternating pulse

In 59 consecutive vasectomies for the purpose of sterilization, one-half, chosen by random numbers, received an irrigation of the vas deferens with 40 ml of sterile water on each side. Afterwards, the men sent in every fourth ejaculation, until two consecutive samples were without spermatozoa. The postoperative sperm samples were examined microscopically without knowing whether the man belonged to the treated group or the control group. The irrigation procedure did not shorten the time needed to reach azoospermia.     

A review of the principles of pulse oximetry and accuracy of pulse oximeter estimates during exercise

OBJECTIVE: The outcomes of patients with squamous cell carcinoma of the anal canal treated by either sphincter-preserving procedures or radical surgery were evaluated, with the goals of identifying factors predicting treatment failure and quantifying results of salvage therapy in patients with recurrent disease. BASIC PROCEDURES: A population-based study on all patients in all 159 hospitals of the Department of Veterans Affairs (VA) from 1987 to 1991 was carried out. Data were compiled from several national computerized VA data sets. Supplementary information from local tumor registrars also was obtained, including demographic information, discharge summaries, operative reports, pathology reports, and medical oncology and radiation oncology summaries. From these sources, information on tumor histology, tumor stage, tumor grade, presence of regional or distant metastases, surgical procedures, use of chemotherapy and radiation therapy (RT), toxicity of chemotherapy and RT, development of recurrent disease, treatment of recurrence, survival, and cause of death were obtained. MAIN FINDINGS: Four hundred five patients with anal cancer were identified by computer search, and 204 (51%) were evaluable; 164 of 204 (80%) had squamous cell carcinoma, 137 of whom (84%) were treated with sphincter-preserving procedures, and 27 of whom (16%) were treated by by radical surgery. One hundred fourteen of 138 (83%) were treated by multimodality therapy, which we defined as local excision followed by chemotherapy and RT. The mean dose of RT among patients treated by multimodality therapy was 4200 +/- 540 cGy and 82% of those treated with multimodality therapy received 5-FU/mitomycin C. Recurrent disease was diagnosed in 43 of all 149 patients (29%) with potentially curable disease. (stages I-III) Multivariate analysis revealed that stage at diagnosis (p = 0.04) and method of treatment (p = 0.03) were the sole predictors of recurrence. Fifty-three percent of patients who underwent salvage abdominoperineal resection (APR) are alive, whereas only 19% who underwent salvage chemotherapy with or without RT are alive. PRINCIPAL CONCLUSIONS: These data indicate that multimodality therapy currently is being employed in the majority of patients with squamous cell carcinoma of the anal canal in the VA system. Tumor stage and method of treatment appear to affect the likelihood of development of recurrent disease. Salvage APR has curative potential. Results with salvage chemotherapy and RT are disappointing.