Does significant arterial hypoxemia alter vital signs?

Abstract

Study Objective: To determine the cardiovascular and respiratory effects of arterial hypoxemia in adult volunteers. Design: Prospective, subject-controlled. Setting: University-affiliated hospital. Subjects: 16 awake, unsedated, unanesthetized adult volunteers. Interventions: Inspired oxygen concentration (FIO 2) was decreased in decrements to reduce pulse oximeter values to a range of 95% to 90%, 89% to 85%, 84% to 80%, and 79% to 70%. Measurements and Main Results: Heart rate, (HR), blood pressure (BP), respiratory rate (RR), arterial blood pH, gas tensions, and oxyhemoglobin saturation were determined during normoxia and each level of oxyhemoglobin desaturation. FI0 2 was reduced from 21% to 10%. Arterial blood oxyhemoglobin saturation and oxygen tension ranged from 100% to 71% and 103 to 35 mmHg, respectively. There were no significant changes in RR, BP, or HR during the study. Conclusions: HR, BP, and RR are not reliable indicators of arterial hypoxemia in awake volunteers. If this finding is also true for sedated or anesthetized patients, then continuous monitoring with pulse oximetry should be used whenever patients are at risk for arterial hypoxemia. Stable HR, BP, and RR may not eliminate the possibility of significant arterial hypoxemia and impending catastrophic events.