The nurse has just received arterial blood gas (ABG) results on four patients. Which result is most important to report rapidly to the health care provider?

pH 7.46, PaO2 90 mm Hg, PaCO2 32 mm Hg, and O2 sat 98

pH 7.31, PaO2 91 mm Hg, PaCO2 50 mm Hg, and O2 sat 96

pH 7.34, PaO2 82 mm Hg, PaCO2 40 mm Hg, and O2 sat 97

pH 7.35, PaO2 85 mm Hg, PaCO2 4.5 mm Hg, and O2 sat 95 .