Figure 4: Changes in respiratory kinetics. A. Increase in PtcCO2. B. Percentage of patients in whom PtcCO2 increased to greater than 50 mmHg. C. Reductions in SpO2. D. The percentage of patients who’s SpO2 decreased to less than 92%. PtcCO2: transcutaneous arterial carbon dioxide tension. SpO2: transcutaneous arterial oxygen saturation.