ABG, arterial blood gases test and related measurements belong to the first group of diagnostic tools especially in treating criticly ill patients, based on the results, immediate clinical decisions are made to assess and monitor the condition of all critically ill among which are also COVID-19 patients. POCT provides an insight into the accurate assessment of gas exchange and oxygenation status of patients, which is extremely important in the treatment of COVID positive patients with more severe forms of the disease. Testing is a fast, accessible and inexpensive. The body has a wide array of mechanisms to maintain homeostasis controlling the concentration of hydrogen ions in body fluids. The main 3 are: buffer system, renal mechanisms and respiratory mechanisms. Analizing the acid-base balance directly indicates what type of disorder may be happening in the body, such as metabolic and respiratory alkalosis, as well as metabolic and respiratory acidosis. Studies show that in patients with COVID-19 disease, all types of metabolic disorders have been reported, with metabolic and respiratory alkalosis being among the most common cases, which was also confirmed by a study conducted in the hospital in Pula at the COVID 1 department. Nurse's role is aimed towards recognizing signs and symptoms of metabolic disorders, preparing the patient before drawing blood, an adequate technique of blood sampling, correct transport of the blood sample and using of a POCT device for blood analysis, asessment of possible complications and side effects of arterial blood sampling. It's also important to acquire basic knowledge on the interpretation of the findings, which can positively affect the speed of decidion making when it comes to medical procedures.