Diagnostic tests] The diagnosis of cyanosis is based on the comprehensive analysis of medical history, physical examination and auxiliary examinations to determine whether cyanosis is present – to distinguish the type of cyanosis – to find the cause – to establish the diagnosis. There are many diseases that cause cyanosis. As long as the causes of cyanosis are more than 50g/L or abnormal hemoglobin derivatives in blood, cyanosis may occur. The following issues should be noted when asking the patient: the presence of cyanosis, the cause of the onset, age, urgency of onset, underlying diseases and concomitant symptoms, etc. 1. To determine the presence or absence of cyanosis, the first step is to determine the presence of cyanosis in the first-time patient. Good natural light is a necessary condition for early detection of cyanosis. Significant skin pigmentation, jaundice or edema can mask the occurrence of cyanosis. Cold environments can cause cyanosis in healthy individuals due to vasoconstriction of the skin, which must be noted during the examination. Some healthy people with dark red or purplish red lips instead of red lips can be seen clinically, but other parts of the skin and mucous membranes do not have such changes, which should be considered normal and not cyanosis. Due to the increase in the number of red blood cells in highland areas, the lips, mouth and face may become dark red, which is a compensatory reaction and should be considered as normal. It is not cyanosis. Pseudocyanosis of abnormal skin pigmentation, such as the blue color produced by silver hyperpigmentation and gold hyperpigmentation, does not subside when the blood is drained by forceful pressure, while cyanosis subside immediately after forceful pressure, and silver hyperpigmentation is usually confined to the skin, but not on the mucous membrane. In addition, Addison’s disease, liver cirrhosis and other diseases have increased skin pigmentation, similar to “cyanosis”, but there are other manifestations of the disease, so pay attention to differentiation. Most of the patients with pulmonary cyanosis have a corresponding trigger before the onset of cyanosis, and most of them have cyanosis aggravated after activity. Patients with tetralogy of Fallot are easily induced by standing and can be relieved by squatting. Patients with Raynaud’s disease have pale – cyanotic – flushed triphasic skin color changes in the terminal limbs triggered by cold and mental stimulation. Cyanosis with the menstrual cycle is characteristic of idiopathic paroxysmal methemoglobinemia. In case of acute onset of cyanosis without cardiopulmonary manifestations, attention should be paid to the presence of eating spoiled vegetables, application or exposure to certain chemical drugs to alert for abnormal hemoglobinemia. 3.The majority of cyanosis appearing since childhood is congenital heart disease. Occasionally, it is seen in congenital pulmonary arteriovenous fistula or congenital methemoglobinemia. Those who appear after middle age are mostly seen in pulmonary cyanosis, such as emphysema, pneumonia, pulmonary edema and large amount of pleural effusion. 4. The acute cyanosis with slow onset is mostly seen in acute respiratory obstruction, acute pulmonary embolism, shock, acute left heart bed, chemical cyanosis, etc. The cyanosis with slow onset is mostly seen in cyanotic congenital heart disease and chronic lung disease. The recurrent cyanosis of extremities is often due to local blood circulation disorder. 5. Basic diseases: Ask about the presence of extensive and serious lung diseases. Such as emphysema, bronchial asthma, pulmonary fibrosis, bronchiectasis, etc. Any history of congenital or acquired heart disease, such as ventricular septal defect, patent ductus arteriosus, heart failure, rheumatic heart disease, etc. Physical examination 1.General observation of body temperature, respiration, blood pressure, pulse and other vital signs, pay attention to the presence of dyspnea, body grams, etc., pay attention to the presence of anemia, jaundice, edema and other signs that affect the judgment of cyanosis. 2, the degree of cyanosis severe systemic cyanosis is mostly seen in chemical cyanosis and early manifestation cyanosis of congenital heart disease, while patients with acute exacerbation of chronic pulmonary heart disease and late manifestation cyanosis of congenital heart disease often have more obvious cyanosis because of secondary erythrocytosis; cyanosis appearing in acute pulmonary disease (except asphyxia) is mostly small with erythrocytosis, so cyanosis is generally lighter; cyanosis with shock or anemia The cyanosis in patients with true erythrocytosis is often purplish or bronze in color. The distribution of cyanosis differs between central cyanosis and peripheral cyanosis depending on the mechanism of occurrence. The cyanosis caused by spastic vascular lesions is generally symmetrically distributed on both sides, especially in the fingers of both hands. Bipedal or toe cyanosis is less severe; vaso-occlusive diseases (such as thrombo-occlusive vasculitis, occlusive arteriosclerosis, etc.) often show asymmetric distribution and mainly involve unilateral lower limbs. In addition, cyanosis caused by some diseases has a special distribution, for example, in rheumatic heart disease mitral stenosis, cyanosis is often obvious in the lips and cheeks, which is called “mitral face”; in congenital ductus arteriosus with pulmonary hypertension, cyanosis is obvious in the lower extremities or under the torso; in complete large-vessel dislocation with ductus arteriosus and pulmonary hypertension, cyanosis in the head and upper body is obvious. In case of pulmonary hypertension, cyanosis in the head and upper limbs is obvious, etc. 4.Consciousness disorder with general cyanosis is mostly seen in chemical cyanosis or shock, but shock also has the manifestation of circulatory failure such as decreased urine volume, wet and cold skin, decreased blood pressure and fine pulse. 5. Pestle-like fingers (toes) are most often seen in cyanotic congenital heart disease, and its degree is also the most obvious. Chronic lung diseases such as bronchiectasis, lung abscess, and pulmonary heart disease are also associated with pestle-like fingers. Acute lung diseases, acquired heart disease, abnormal hemoglobinemia, etc. are usually not accompanied by pestle finger. 6, chest signs (1) thoracic abnormalities: barrel-shaped chest suggests emphysema, one side of the thorax is inflated, seen in large amounts of pleural effusion, pneumothorax, tumors, diaphragmatic hernia, etc.; one side of the thorax is flat or sunken, common in pulmonary atelectasis, extensive pleural adhesions and thickening, etc.; the precordial area is elevated, common in precordial disease, cardiomegaly. Paradoxical breathing of the chest and abdomen may occur in severe pulmonary cyanosis. It is a reliable clinical sign of respiratory muscle fatigue and an indication for mechanical ventilation. (2) Pulmonary cyanosis often has pulmonary signs, such as emphysema, pulmonary atelectasis, pulmonary edema, pleural effusion, and pneumothorax. All have corresponding abnormal changes in the chest, and comprehensive visual, palpation, percussion and auscultation examinations should be performed. (3) Cardiac cyanosis often has cardiac signs, such as jugular vein anger, enlarged heart border, abnormal heart sound, valve murmur, arrhythmia, with dyspnea and swelling of both lower limbs. Auxiliary examination 1. Blood test includes blood routine, blood autoantibodies, liver function and so on. An increase in total white blood cells and neutrophil ratio suggests infectious diseases, such as pneumonia and pus thorax, while an increase in eosinophils is most often seen in bronchial asthma. Significantly higher amounts of red blood cells and hemoglobin suggest true erythrocytosis or secondary erythrocytosis. Autoantibodies are important for identifying peripheral cyanosis caused by connective tissue disease. 2. Arterial oxygen saturation (SaO2) measurement is mainly used to distinguish central cyanosis from peripheral cyanosis. In central cyanosis, there is obvious decrease of SaO2, and SaO2 that can be found cyanosis by naked eye is generally below 85%, and it is generally considered that SaO275%~85% is mild, 6s%~75% is moderate, and below 65% is severe cyanosis; while in peripheral cyanosis, SaO2 is normal or only mildly decreased. Noninvasive pulse oximetry can indirectly determine oxygen saturation, but abnormal hemoglobin (e.g., carboxyhemoglobin, methemoglobin) has an absorption spectrum as well, and the measured oxygen saturation is not accurate. In this case, it is necessary to rely on arterial blood gas analysis. 3. Blood gas analysis is a mandatory test for cyanosis with dyspnea. The decrease in partial pressure of arterial blood oxygen suggests that cyanosis is caused by increased reduced hemoglobin, and the increase in partial pressure of carbon dioxide indicates ventilation dysfunction, especially when combined with respiratory acidosis, which is basically identified as pulmonary cyanosis. In addition, some blood gas analyzers can automatically detect methemoglobin and carboxyhemoglobin, which can help the diagnosis of chemical cyanosis. 4.Electrocardiogram has some diagnostic value for cardiopulmonary diseases, such as chronic pulmonary heart disease, congenital heart disease, coronary heart disease, cardiomyopathy and arrhythmia. 5.Chest X-ray or CT is the main method to diagnose various lung diseases and the cause of cyanosis of heart disease. 6.Ultrasound examination of the heart has an important diagnostic value for cardiac cyanosis, and is indispensable for determining whether there are defects in intracardiac structures, valve changes, right-to-left shunts, pericardial cavity effusion and evaluation of cardiac function. Vascular ultrasound is useful in the diagnosis of localized blood flow disorders. Chest ultrasound can determine the presence of pleural effusion and assist in the localization of thoracic knee puncture. 7. Pulmonary function tests help to distinguish obstructive from restrictive ventilatory dysfunction. Obstructive emphysema is manifested as obstructive ventilation disorder with increased residual air volume. Bronchodilatation test or bronchial excitation test can be used for the diagnosis of bronchial asthma; restrictive ventilation dysfunction is common in diffuse interstitial lung disease, pleural disease, heart failure, etc. 8.Bronchoscopy Bronchoscopy is an indispensable diagnostic method for cyanosis caused by unexplained pulmonary atelectasis, lung tumor and foreign body in the trachea. 9.After 15 minutes of pure oxygen inhalation test, most of the pulmonary cyanosis can be significantly reduced or disappeared, and peripheral cyanosis can be slightly reduced, while the cyanosis caused by cardiac cyanosis and abnormal hemoglobinemia has no change. 10.Other difficult cases of cardiac cyanosis and patients with pulmonary hypertension often require cardiovascular imaging for early confirmation of the diagnosis. For those with deep cyanosis and the cause cannot be explained by cardiopulmonary examination, blood tests (spectroscopy, hemoglobin electrophoresis) should be performed to determine the presence of abnormal hemoglobin.