Abstract
Background and objectives: The role of pulse oximetry in early detection of hypoxemia has been emphasized in different studies. The clinicians are always worried about critical nature of respiratory problems and hypoxemia, but in clinic it is not clear that which level of hypoxemia is tolerable. In the other hand significant hypoxia can result in serious complication in a few minutes. In practice there are different sites for pulse oximetria but in our survey we could not find any study about validity of pulse oximetry that has been done in ear, toe and finger simultaneously. This study was conducted to answer the question of, the most suitable site for pulse oximetry in newborns and children more than one month of age.
Materials and Methods: in a comparative-cross sectional study from December 2004 to Janury2005, one hundred newborns and one hundred children at age of one month or older have been included. The method of sampling was convenience. Blood samples for blood gas analysis were obtained only from patients who needed this test. We used NOVAMETRIX pulse oximeter and GEM3000 blood gase analyzer. In this study the hypoxemia was defined as SpO2 < 92% and Sao2 <90%. The results were analyzed with validity formula (sensitivity, specificity, positive and negative predictive values). We used kappa test for clinical agreement.
Results: in children mean SaO2 on ear, finger and toe were 95.5±3.1, 93.7±3.32, 92.6±5.4 and bias were 0.02 ± 3.71, - 0.82 ± 3.43, -1.94 ± 3.18 respectively. At the same time newborns showed the mean SpO2on ear, finger and toe 96.8 ± 2.2, 95.4 ± 3.2, 94.8 ± 2.4,and bias were 1.53± 3.42, 0.22 ±3.48, - 0.45± 3.9 respectively. Negative predictive values of Spo2 on ear, finger and toe, in children more than one month of age showed 97%, 98%, 93% and in newborn group were 93.5%, 93.6%, 90% respectively. The highest level of clinical agreement was in ear (69.7% and 54%) and the lowest level in toe (56.5% and 28%).
Conclusion: pulse oximetry plays the main role in the early detection of Hypoxemia while significant hypoxia results in serious complications in a few minutes. This study indicated that pulse oximetry of toe either in children or newborns have a higher rate of clinical agreement. At the same time, ear and finger have better negative predictive value that means 93.5% - 98% of patients with SpO2≥ 92% have SaO2≥90% and no hypoxemia.