Reliability of Transcutaneous Oxygen Monitoring of Critically III Children in a General Pediatric Unit

Abstract

While transcutaneous continuous monitoring of partial pressure of oxygen (TcPO₂) is a proven valuable diagnostic tool in intensive care of sick neonates, its use in older children is less well defined. The purpose of this study is to establish the accuracy and reliability of TcPo₂ as a reflection of arterial partial pressure of oxygen (Pao₂) in critically ill pediatric patients. Twenty-six children, age ranging from 4 days to 13 years, were studied. The main diagnostic categories were cardiac 54 per cent, respiratory 27 per cent, gastrointestinal 15 per cent, and neurologic 4 per cent. Forty three estimations of Pa _o2 (by radial arterial sampling) and TcPO₂ (by cutaneous monitor) were obtained simultaneously. Their correlation coefficient, regression equation, and confidence limits were calculated by standard statistical methods with the aid of a microcomputer. Our data show that the high degree of correlation between TcPO₂ and Pa_o2 is highly significant (r = 0.90, p < 0.001) for the full range of Pa _o2 between 0 to 200 mm Hg. At the lower range of Pa_o2 (0-79 mm Hg), the degree of correlation (r = 0.91, p < 0.001) is better than that (r = 0.77, p < 0.001) at the higher range (80-200 mm Hg), although the difference between the two correlation coefficients is not significant (p > 0.05). It is important to note that TcPo ₂ consistently underestimates the Pa_o2 and the 95% confidence limits are rather wide. We conclude that TcPO₂ is a reasonably accurate reflection of Pa_o2 in critically ill pediatric patients. Its main advantage is in predicting and showing trends in tissue oxygenation by noninvasive means. However, when critical assessment of the degree of hypoxemia is required, TcPO₂ is no substitute for Pa_o2.