Ключевые слова: blue, bluish, breathless, breathlessness, cardiac, central, changes, chronic, color, covid, covid 19, cyan, cyanosis, cyanotic, dark, discoloration, discolored, discolouration, discoloured, disease, finger, fingers, fingertips, hand, hands, heart, hypoxemia, hypoxia, ill, isolated, lung, nails, omicron, pallor, palm, palmar, patient, peripheral, problem, purple, respiratory, skin, smoker, smoking, stain, stained, unhealthy, young,