The Relationship of SpO2 93%–95% to Arterial Blood Gases and Pulmonary Function Parameters
The primary task of the respiratory system is oxygenation of the blood and maintenance of an adequate ventilation. These vital aspects cannot be definitely assessed on the basis of clinical findings. Comprehensive surveillance through blood gas analyses is indispensable with critically endangered patients. Assessment of oxygenation and ventilation are just as necessary in the context of pulmonary function testing in order to evaluate respiratory sufficiency in patients with pulmonary disorders. Arterial blood oxygen saturation (SaO2), as measured by pulse oximetry (SpO2), determines, in a sufficiently precise and reliable way, the functional saturation even in the presence of dyshemo-globinemia up to 15% [2, 6–8]. As a simple noninvasive screening method, in preoperative pulmonological diagnostics and on the ward, it therefore offers the possibility of easily recognizing disorders in oxygenation. Since the first disorders in oxygen exchange occur at a SaO2 of 94% (PaO2 70 mm Hg), this saturation point suggests itself-with certain limitations — as the boundary indicating an arterial blood gas analysis, provided that the theoretically possible CO2 retention, according to the alveolar air equation, can be excluded in clinical practice. Besides describing the relationships of SpO2 to PaO2 and PaCO2, the goal of this study was to clarify whether changes in pulmonary function occur in the range of SpO2 93%–95%.
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