Fig. 1. Agreement between cardiac output measurements obtained by carbon dioxide rebreathing (CO^NI) and those obtained by thermodilution technique (CO^TD) during controlled mechanical ventilation. (A ) Large tidal volume (V^T, 12 ml/kg) with respiratory rate (RR) of 10 breaths/min. (B ) Small tidal volume (6 ml/kg) with respiratory rate of 20 breaths/min. (C ) Small tidal volume (6 ml/kg) with respiratory rate of 10 breaths/min. Equations and result curves for linear regression analysis are also shown.