First look at the pH: if it is low it is acidosis, high indicates alkalosis. Second use the ROME mnemonic to determine if you have respiratory vs. metabolic. For Metabolic look at HCO3. For Respiratory, look at pCO2. Metabolic Acidosis – pH Low, HCO3 Low. Metabolic Alkalosis – pH High, HCO3 High. Respiratory Acidosis – pH Low, pCO2 High. Respiratory Alkalosis – pH High, pCO2 Low.