Syndrome of insufficient ventilation in children with obesity

　　1. Etiology

　　Long-term energy intake exceeding consumption leads to excessive accumulation of body fat, resulting in a significant weight gain beyond the normal standards for children of the same age and height. Obese individuals, due to increased weight, require more oxygen, but their lungs not only fail to increase in function, but also have significantly lower lung capacity compared to normal children. The main reasons for the syndrome of incomplete cardiorespiratory function are the increased fat tissue in the chest, abdominal cavity, and throughout the body of patients, leading to a decrease in chest volume, restricted diaphragmatic movement, limited pulmonary ventilation and gas exchange function, and a series of changes such as impaired cardiac function and nervous system damage.

　　Two, Pathogenesis

　　1, Abdominal fat accumulation, increased intra-abdominal pressure, elevation of the diaphragm, increased thoracic pressure, and excessive accumulation of fat in the mediastinum, thickening of the chest wall, restriction of chest expansion and diaphragmatic movement, and restriction of lung respiratory function. The decrease in total chest compliance leads to poor lung ventilation, reduced tidal volume, reduced pulmonary ventilation, and weakened lung function. The patient's vital capacity, reserve vital capacity, functional residual capacity, and total volume all decrease. Moreover, with the continuous increase in weight, the degree of uneven ventilation also increases, causing increased partial pressure of carbon dioxide in arterial blood at rest and decreased partial pressure of oxygen.

　　2, Severe obesity patients may also have excessive accumulation of fat around the neck, macroglossia, and posterior laryngeal collapse, which can lead to varying degrees of upper airway obstruction; coupled with further reduced ventilation volume, exchange is restricted, resulting in carbon dioxide retention and hypoxemia. The symptoms include difficulty breathing, inability to lie flat, intermittent breathing during sleep, cyanosis, and in severe cases, excessive accumulation of carbon dioxide in the blood can lead to respiratory acidosis, causing confusion and drowsiness. During sleep, periodic airway obstruction can occur, leading to insomnia or sleep deprivation syndrome, and the syndrome of sleep apnea (airway obstruction or central) occurs, with the interval between each breath extending when sleeping. Long-term elevated partial pressure of carbon dioxide in arterial blood makes the central nervous system less sensitive to hypercapnia, leading to reduced respiratory center excitation induced by increased carbon dioxide in the blood, resulting in a state of exhaustion. The respiratory response to hypoxia is also insensitive, resulting in periodic respiration, disturbing the patient's rest, causing daytime sleepiness, lack of vitality, and other symptoms.

　　3, Due to prolonged hypoxia, patients are prone to secondary polycythemia, increased blood viscosity, increased circulatory resistance, and the early use of heart reserve during activity, leading to insufficient heart function. Severe obesity patients often have increased total blood volume caused by increased left ventricular load and venous return obstruction, increased venous pressure, pulmonary hypertension, and increased right ventricular load, resulting in edema, distension of the jugular veins, and even cardiac insufficiency. Decreased ventilation function, reduced oxygen capacity, and other factors lead to shortness of breath, difficulty breathing, hypoxia, cyanosis, and at the end stage, obesity-related cardiopulmonary insufficiency syndrome is prone to occur, which is easy to lead to right ventricular hypertrophy, cardiac enlargement, or congestive heart failure.

　　1, Cardiovascular system failure due to long-term overload of the heart can lead to heart failure, although right heart failure is more common, left heart failure should also be paid attention to (it can sometimes be the main manifestation). Arrhythmias are also common.

　　2, Gastrointestinal bleeding may occur when the digestive system has concurrent gastritis or ulcers. The causes include stress response, gastric dilation, excessive gastric acid, and the use of hormones. Close attention should be paid to the hemoglobin concentration, changes in hemoglobin, and the presence of occult blood in stool. 50% of patients may have varying degrees of fatty liver, cholelithiasis, and other conditions.

　　3. Hormonal metabolism disorder in severely obese women, androgen levels can increase to twice the normal value, and estrogen levels are also significantly increased, which can lead to early menarche in adolescent girls, abnormal ovarian function in adult women, including amenorrheic infertility or oligomenorrhea, and can also stimulate abnormal hyperplasia of the breasts and uterus.

　　4. Infections Pulmonary infections are common complications, caused by secondary immune dysfunction, impaired pulmonary clearance function, catheter placement, respiratory therapy, and other equipment contamination, often leading to respiratory system infections. After respiratory tract infections, acute respiratory failure may occur. It is also prone to dermatitis, skin boils, urinary system, and digestive system infections.

　　5. Other symptoms such as respiratory distress and sleep apnea can lead to sudden death, renal failure, and acid-base imbalance. Long-term bed rest and dehydration can trigger deep vein thrombosis and pulmonary embolism.

　　1. Symptoms and signs of inadequate ventilation include a series of respiratory failure symptoms such as cyanosis and respiratory distress, with hypoxemia and carbon dioxide retention seen in blood gas tests.

　　2. Respiratory symptoms and signs include shallow breathing, frequent episodes of apnea during the night, and peripheral or mixed sleep apnea phenomena, accompanied by upper airway obstruction and snoring during sleep.

　　3. Cardiac symptoms and signs include early symptoms such as cough, shortness of breath, palpitations, and lower limb edema. Prolonged hyperventilation can lead to chronic pulmonary heart disease and heart failure. When right heart failure is severe, symptoms such as dyspnea, cyanosis, oliguria, and a few cases with systemic heart failure may occur.

　　4. Neurological symptoms and signs include hypoxia, fatigue, headache, dizziness, palpitations, sweating, restlessness, delirium, convulsions, carbon dioxide retention, which can lead to hallucinations, mental abnormalities, daytime sleepiness, and in a few cases, intellectual decline or retardation.

　　1. Based on the medical history, signs, and laboratory data, first differentiate between simple and secondary obesity. In cases with hypertension, central obesity, striae, amenorrhea, and those with elevated 17-hydroxycorticosteroids in 24-hour urine, Cushing's syndrome should be considered, and a low-dose (2mg) dexamethasone suppression test should be performed for differentiation. In cases with low metabolic rate, further examination of T3, T4, and TSH for thyroid function tests should be conducted to clarify whether there is hypothyroidism. There is also a need to consider the anterior pituitary function

　　2. Patients with hypothalamic syndrome or those with symptoms of hypothalamic syndrome should undergo pituitary and target gland endocrine tests, check the sella turcica, visual fields, and vision, and necessary cranial CT scans. For those with an enlarged sella turcica, pituitary adenoma should be considered, and empty sella syndrome should be ruled out. In cases of amenorrheic infertility with virilization, polycystic ovary syndrome without obvious endocrine disorder, edema in the afternoon with relief in the morning should be differentiated from water and sodium retention obesity. The water test in the supine and standing positions can be quite helpful. In addition, it is often necessary to pay attention to the presence of diseases such as diabetes, coronary heart disease, atherosclerosis, and gout, as well as other less common types of obesity, which can be analyzed and judged based on their clinical characteristics.

　　1. Blood gas changes PaO2↓, PaCO2↑.

　　2. Metabolic disorders are mainly manifested as abnormal insulin receptors, decreased glucose transport and metabolic capacity, etc., often leading to hyperinsulinemia, insulin antagonism, decreased glucose tolerance, increased blood sugar, and at the same time, increased blood lipids may also occur.

　　3. Blood count peripheral blood erythrocyte增多.

　　4. X-ray examination of chest films shows elevation of both diaphragms, prominence of the pulmonary artery segment, and hypertrophy of the right heart.

　　5. Pulmonary function tests mainly show restrictive ventilation impairment, decreased lung volume, vital capacity, tidal volume, reduced functional residual capacity, and significantly lower vital capacity than normal children.

　　6. ECG myocardial ischemia and hypoxia damage.

　　Strict control of total calories: dietary calorie control is detailed in obesity treatment. First, slow down the eating speed, limit chocolate, various sweet pastries, candies, fatty meat, sugary drinks, puffed food, beer, etc.; eat less rice, noodles, potatoes, sweet potatoes, apples, watermelons; eat more cabbage, rapeseed, cucumbers, celery, carrots, lean meat, eggs, milk, chickens, fish, mushrooms, oranges, yogurt, etc. It is advisable to ensure a moderate amount of animal protein containing essential amino acids (one-third of the total protein), with a protein intake of not less than 1g per kilogram of body weight per day. The intake of fat should be strictly limited, and at the same time, the intake of sodium should be limited to avoid water and sodium retention when weight loss occurs, and it is also beneficial for lowering blood pressure and reducing appetite.

　　I. Treatment

　　1. The purpose of weight loss is to adjust the dietary structure, reasonably absorb various nutrients, and ensure good physical condition. Adopt a comprehensive treatment plan, weight loss is the fundamental measure to prevent this condition. After weight loss, abnormal respiratory dynamics can be reversed, symptoms can be alleviated, ventilation can be improved, and the incidence of sleep apnea can be reduced. Reducing energy intake and increasing energy expenditure, dietary and exercise therapy are the main measures. The efficacy of drug therapy is not certain, and there are many side effects, so it can only be used as an auxiliary means. Surgical treatment of complications is serious and not suitable for children.
　　2. When dietary and exercise therapy are ineffective, drug-assisted treatment can be adopted. Drugs are mainly divided into six categories: appetite suppressants - central appetite suppressants, peptide hormones, short-chain organic acids; digestive and absorption blocking drugs - carbohydrate absorption blocking drugs, lipid absorption blocking drugs; fat synthesis blocking drugs; insulin secretion inhibitors; metabolic stimulants; fat cell proliferation inhibitors. Common drugs include amphetamines, fenfluramine, and cilazapride (chlorophenylpyrimidine) and others.

　　(1) Thyrocalcitonin (triiodothyronine) and diuretics: The use of thyrocalcitonin (triiodothyronine) and diuretics can cause significant weight loss, but has high risk and can cause arrhythmia.

　　(2) Appetite suppressants: Amphetamines can suppress appetite, but have poor efficacy and significant side effects, and are generally not used.

　　(3) Colestipol (cholestyramine), Neomycin: They can cause steatorrhea and reduce weight, but have significant side effects.

　　(4) Chorionic Gonadotropin (hCG): It can cause rapid weight loss, but has significant side effects.

　　(5) Progesterone: It can increase the central nervous system's responsiveness to carbon dioxide and hypoxia, increase ventilation to improve gas exchange, correct respiratory acidosis, improve heart failure and polycythemia, but sleep apnea still exists.

　　3. Improve ventilation Local iron lung, tracheotomy, etc., can improve hypoxemia, carbon dioxide retention, and pulmonary heart disease.

　　4. Oxygen therapy Low concentration oxygen inhalation can improve hypoxia and heart failure, and avoid high concentration oxygen, otherwise it can cause more serious alveolar ventilation failure.

　　5. Prevention and treatment of respiratory tract infections. Respiratory tract infections are often the direct cause of the progression of this symptom to acute respiratory failure and death.

　　6. Anticoagulant therapy to prevent and treat thrombosis and embolism.

　　7. Active and effective treatment for heart failure and respiratory failure in pulmonary heart disease.

　　8. Surgical treatment such as gastric or small intestine bypass surgery, mandibular bone bed wire fixation surgery, and vagus nerve section for weight loss is effective, but has significant side effects and even risks, making it difficult to accept and promote.

　　II. Prognosis

　　This is a special form of pulmonary heart disease. If not discovered and treated promptly for respiratory and heart failure, it can lead to death, with a mortality rate of up to 25%. Active symptomatic treatment and weight loss can hope to improve the condition. Once weight decreases, most pathological indicators of lung ventilation and gas exchange function, as well as the heart, can be improved, and a few can even return to normal.