What does a negative SAO2 reading during the modified Allen test indicate?

A negative SAO2 reading during the modified Allen test is indicative of inadequate blood flow to the hand, suggesting potential issues with collateral circulation in the radial and ulnar arteries. This test typically measures the oxygen saturation (SAO2) levels in the blood of the hand before and after occluding both the radial and ulnar arteries.

When the blood flow is compromised, a negative SAO2 registered means that, upon release of the occlusion, the oxygen saturation does not return to baseline levels as expected; it either does not show improvement or is lower than the initial value. This finding signals that the hand is not receiving sufficient arterial blood flow, which could indicate underlying vascular complications such as arterial occlusion or severe arterial insufficiency.

In contrast, the other options provided do not directly relate to the implications of a negative SAO2 reading during this specific test. The modified Allen test aims to assess blood flow, and the presence of pain, normal sinus rhythm in EKG, or unrestricted blood flow are not relevant indicators when evaluating the results of this particular examination.