Figure 77-20 Alterations in gas exchange caused by total parenteral nutrition (TPN) are shown (mean ± SD). Glucose was the primary source of nonprotein calories, and two responses are seen. Depleted patients show a respiratory quotient (RQ) above 1.0 with a small increase in V̇O₂ , and hypermetabolic patients have an RQ less than 1.0 with a marked increase in V̇O₂ . Both groups show a large increase in V̇CO₂ . (Adapted from Askanazi J, Carpentier YA, Elwyn DH, et al: Influence of total parenteral nutrition on fuel utilization in injury and sepsis. Ann Surg 191:40, 1980.)