Figure 32-52 Systolic pressure variation. When compared with systolic blood pressure recorded at end-expiration (1), a small increase occurs during positive-pressure inspiration (2, Δ Up), followed by a decrease (3, Δ Down). Normally, the total variation in systolic pressure does not exceed 10 mm Hg. In this instance, the large Δ Down indicates hypovolemia even though systolic arterial pressure and the heart rate are relatively normal. (Redrawn from Mark JB: Atlas of Cardiovascular Monitoring. New York, Churchill Livingstone, 1998, Fig. 16-16.)