Acute respiratory failure in children

Introduction to acute respiratory failure in children Acute respiratory failure means that the patient's original respiratory function is normal. Due to some sudden causes, such as airway obstruction, drowning, drug poisoning, and central nervous system disorders, the body often has no time to compensate. If it is not diagnosed in time and effective control is taken as soon as possible. Measures can often be life-threatening. However, the original respiratory function of patients with this type of respiratory failure is often good. If timely and effective rescue, the prognosis is often better than chronic respiratory failure. However, patients with poor original respiratory function can also be common in the clinic. Due to some sudden causes, common airway infections cause airway obstruction, which can cause a sharp rise in PaCO2 and a sharp drop in PaO2. It is clinically accustomed to classify this type of respiratory failure to chronic breathing. Acute exhaustion is exacerbated. Urgent, chronic respiratory failure, in addition to the cause, the cause of the rapid, the length of the disease has a large difference, in the pathogenesis, pathophysiology, clinical features, diagnosis and treatment principles are similar. Acute respiratory distress syndrome (ARDS) is a special type of acute respiratory failure, which is a critical emergency involving clinical subjects. Pediatric respiratory failure is the first cause of death in neonates and infants. Due to the deep understanding of pediatric respiratory physiology and advances in medical technology, the therapeutic effect of respiratory failure in children has been significantly improved. basic knowledge The proportion of illness: 0.006% (related to pneumonia infection in children) Susceptible people: children Mode of infection: non-infectious Complications: atelectasis respiratory infection lung injury pulmonary edema

Causes of acute respiratory failure in children

(1) Causes of the disease

The causes of respiratory failure can be divided into three categories, namely, airway obstruction, lung parenchymal disease and abnormal breathing pump.

Airway obstruction

Upper airway obstruction is more common in infants and young children. The throat is the narrow part of the upper respiratory tract. It is the main part of obstruction. It can be caused by infection, neurohumoral factors (throat), foreign body, congenital factors (throat cartilage softening), lower respiratory tract obstruction. Including obstruction caused by asthma, bronchiolitis, secretions from severe pulmonary infection, and necrosis of viral pneumonia can block the bronchioles and cause lower airway obstruction.

2. Pulmonary parenchymal disease

(1) General pulmonary parenchymal diseases: including various pulmonary infections such as pneumonia, bronchiolitis, interstitial lung disease, pulmonary edema, etc.

(2) Neonatal respiratory distress syndrome (RDS): mainly due to immature lung development in premature infants, pulmonary surfactant deficiency caused by extensive atelectasis.

(3) Acute Respiratory Distress Syndrome (ARDS): often occurs in severe infections, trauma, major surgery or other serious illnesses. It is characterized by severe lung injury. Infiltration and edema of the interstitial and alveolar diffuse of the two lungs is a pathological feature. .

3. Abnormal breathing pump

Abnormal breathing pump includes lesions from the respiratory center, spinal cord to respiratory muscles and thoracic regions. The common feature is that it causes hypoventilation. Brain edema and intracranial hypertension caused by various causes can affect the respiratory center. The lesions of the nervous system can be soft. Paralysis, such as acute infectious polyradiculitis, can also be a tonic sputum, such as tetanus, abnormal breathing pump can also lead to sputum weakness, resulting in airway obstruction, atelectasis and infection, the original respiratory failure Aggravation, respiratory failure caused by chest surgery is also often of this type.

(two) pathogenesis

1. Pathophysiology of respiratory failure

Due to abnormal respiratory function, the lungs can not complete the gas exchange required for metabolism of the body, leading to arterial blood oxygenation and CO2 retention, which is respiratory failure. The occurrence of respiratory failure is caused by insufficient ventilation and ventilation disorder. All kinds of causes can cause hypoventilation. The main result is elevated PCO2, accompanied by different degrees of hypoxemia. Ventilation disorders are caused by various lung diseases, mainly causing a decrease in PO2. PCO2 can be reduced depending on the severity of the disease, normal or increased. It should be pointed out that there are often many factors in the clinical coexistence or mutual influence, such as children with central respiratory failure, dysphagia, dysfunction, and pneumonia; severe pneumonia may have central respiratory failure.

Respiratory failure has adverse effects on the function of brain parenchyma, kidney and circulatory system. The combination of hypoxia, carbon dioxide retention and respiratory acidosis can cause cerebral edema, damage to the respiratory center, and reduce ventilation. The result is increased breathing. Acidosis and hypoxia form a vicious circle. In addition, hypoxia can cause pulmonary arterioles to contract, leading to pulmonary hypertension and increased right heart load. Severe respiratory acidosis affects myocardial contractility, resulting in circulatory failure and blood pressure. Significant decline, due to circulatory dysfunction can lead to tissue hypoxia, renal insufficiency, the formation of metabolic acidosis, which in turn promotes respiratory acidosis is difficult to compensate, the degree of acidosis is aggravated, so hemoglobin and oxygen binding capacity is reduced, blood The oxygen saturation is further reduced, forming another vicious circle.

Pulmonary surfactant plays an important role in the occurrence of respiratory failure. Various severe lung injuries are often accompanied by lung type II cell damage. At the same time, the protein exuded by inflammation inhibits pulmonary surfactant, and hypoxia and acidosis also affect. The synthesis and secretion of lung type II cell surface active substances, we have observed a decrease in pulmonary surfactant in children with severe infant pneumonia, acute respiratory distress syndrome (ARDS) and lung injury after cardiopulmonary bypass, which is caused by or Aggravating an important part of respiratory failure.

In recent years, the important role of respiratory muscle fatigue in the occurrence of respiratory failure has been paid more and more attention. Especially, the small infant has small respiratory reserve capacity and is prone to fatigue. It is difficult to meet the requirement of increased ventilation when respiratory load is increased, and respiratory failure is more likely to occur.

The most serious consequence of critical respiratory failure is the decrease in blood pH, which is a common result of CO2 retention and hypoxemia. The activity of various proteins and enzymes in the body and the maintenance of normal organ function depend on the pH of the body fluid. Stable, severe acidosis caused by critical respiratory failure is an important cause of death.

2. Types of respiratory failure

(1) hypoxemia respiratory failure: also known as type I respiratory failure or ventilation disorder type of respiratory failure, mainly due to lung parenchymal lesions, the main change in blood gas is the decline in arterial oxygen pressure, such children often in the early stages of the disease With hyperventilation, arterial PCO2 is often reduced or normal. If combined with respiratory obstruction factors, or late disease, PCO2 may also increase. Due to lung lesions, lung compliance decreases, and ventilation dysfunction is the main pathophysiological change. Ventilation/blood flow imbalance is the main cause of blood oxygenation, and most of them have different degrees of intrapulmonary shunt.

(2) Ventilation failure: also known as type II respiratory failure, arterial blood gas changes are characterized by increased PCO2, while PO2 declines, can be caused by intrapulmonary causes (respiratory obstruction, physiological ineffective cavity enlargement) or extrapulmonary causes (respiratory center, respiratory muscles) Or chest abnormalities, the basic pathophysiological changes are insufficient alveolar ventilation. If there is no intrapulmonary lesion in such children, the main problem is CO2 retention and respiratory acidosis. Hypoxemia caused by insufficient ventilation alone will not It is very heavy, and the treatment is easy. The increase in PCO2 is enough to kill the arterial oxygen partial pressure before the hypoxia is low.

Prevention of acute respiratory failure in children

1. Do a good job of pregnancy care, prevent premature birth, dystocia, birth injury and so on.

2. Active prevention and treatment of pneumonia and various infectious diseases in children.

3. Actively prevent various accidents.

4. Prevent drug poisoning or other poisoning.

5. Do a good job of various vaccinations.

Complications of acute respiratory failure in children Complications, atelectasis, respiratory infection, lung injury, pulmonary edema

Complications of respiratory failure include the effects of respiratory failure on the normal functioning of the body's systems and the hazards associated with various treatments (mainly ventilator treatment), such as: respiratory infections, atelectasis, ventilator and lung injury, Complications of tracheal intubation and tracheotomy, pulmonary edema and water retention, circulatory complications, kidney and acid-base balance.

Symptoms of acute respiratory failure in children Common symptoms Difficulty breathing, heart rate, increased irritability, restless sleepiness, gas diffusion disorder, consciousness disorder, blood pressure drop, three concave signs, metabolic acidosis

1. Performance of breathing

Respiratory failure due to lung disease, often have varying degrees of difficulty breathing, three concave, nasal fan, etc., the number of breaths increased faster, can be slowed in the late stage, central respiratory failure is mainly the change of respiratory rhythm, severe cases may have Apnea should be specifically noted that the respiratory performance of children with respiratory failure may not be obvious, and the performance of dyspnea may be caused by non-respiratory causes, such as severe metabolic acidosis, which is difficult to accurately predict respiratory failure. diagnosis.

2. Effects of hypoxia and carbon dioxide retention

An important manifestation of early hypoxia is an increase in heart rate. At the beginning of hypoxia, blood pressure can be increased, followed by a decrease. In addition, there may be a pale or pale complexion. The acute severe hypoxia begins with irritability, and further development may lead to a conscious coma. , convulsions, when PaO2 is below 5.3 kPa (40 mmHg), the brain, heart, kidney and other vital organs are insufficiently oxygenated, which is a serious threat to life.

Common symptoms of carbon dioxide retention are sweating, irritability, disturbance of consciousness, etc., due to body surface telangiectasia, there may be skin flushing, dark red lips, conjunctival congestion, early or mild heart rate, high blood pressure, severe blood pressure Falling, older children may be accompanied by muscle tremors, etc., but small babies are rare. The exact diagnosis of carbon dioxide retention depends on blood gas examination. The above clinical manifestations are for reference only and are not always visible. It is generally believed that PaCO2 is raised to 10.6. kPa (80mmHg) or so, clinical may have lethargy or paralysis, severe coma, the degree of influence is related to the speed of PaCO2 increase, if PaCO2 gradually increases within a few days, the body has a certain compensation and adaptation, blood The pH value can be only slightly lower or in the normal range, and the effect on the sick child is small. If the ventilation volume is sharply decreased and the PaCO2 is suddenly increased, the blood pH value can be significantly decreased. When it falls below 7.20, the cyclic function and cell metabolism are seriously affected. The risk is extremely high. The serious consequences of carbon dioxide retention are related to the decline of arterial pH. Hypoxia and carbon dioxide retention often exist at the same time. Clinical findings are often Influencers comprehensive.

3. Changes in other systems during respiratory failure

(1) nervous system: irritability is an early manifestation of hypoxia. Older children may have headaches, arterial pH drops, CO2 retention and hypoxemia may affect consciousness, even coma, convulsions, symptoms and breathing The rate of failure is related to respiratory failure caused by lung disease can lead to cerebral edema and central respiratory failure.

(2) Circulatory system: early hypoxic heart rate is accelerated, blood pressure can also be increased, severe blood pressure is lowered, and arrhythmia may also be present. North Medical University reports that infants with pneumonia have increased pulmonary arterial pressure, which may be associated with hypoxia-induced plasma endothelium. Increased in hormones, the obvious cyanosis of the lips and nail bed is a sign of hypoxemia, but it is not obvious when anemia occurs.

(3) Digestive system: Intestinal paralysis may occur in severe respiratory failure. In some cases, there may be digestive ulcers, hemorrhage, and even an increase in alanine aminotransferase due to impaired liver function.

(4) Water and electrolyte balance: blood potassium is high in respiratory failure, blood sodium is not changed, some cases may have hyponatremia, some cases have water retention tendency in respiratory failure, sometimes edema, respiratory failure lasts For those who compensate for respiratory acidosis, plasma chlorine is reduced. Long-term severe hypoxia can affect renal function, severe oliguria or anuria, and even acute renal failure.

4. Infant respiratory failure

Pneumonia is an important common disease in infants and young children, and it is also the most important cause of death in hospitalized children. It mainly dies from respiratory failure and its complications caused by uncontrollable infection, and deeply understands the pathophysiology of pneumonia respiratory failure in infants and young children. The rational treatment of the foundation is an important task in the daily emergency of pediatrics. This section focuses on the changes of respiratory function and respiratory therapy in severe pneumonia.

(1) Ventilation dysfunction: The characteristics of respiratory changes in children with pneumonia are firstly small tidal volume, rapid breathing, and superficial (related to decreased lung compliance). When the disease progresses heavier, the tidal volume is further reduced due to the increase in force. Breathing, although the ventilation per minute is higher than normal, due to the increase of physiological ineffective cavity, the actual alveolar ventilation has not increased, only maintained at normal level or slightly lower; arterial oxygen saturation decreased, carbon dioxide partial pressure increased slightly, the condition When critically ill, the sick child is extremely exhausted, unable to breathe, the number of breaths is reduced, the tidal volume is less than 1/2 of normal, the physiological void is more enlarged, the ventilation effect is lower, and the alveolar ventilation is greatly reduced (only normal) 1/4), resulting in severe hypoxia, carbon dioxide emissions are also severely blocked, arterial blood carbon dioxide partial pressure is significantly increased, non-compensatory respiratory acidosis, pH value to life-threatening levels, on average below 7.20, lack Oxygen and respiratory acidosis are the main causes of severe pneumonia. In the rescue of critical pneumonia, the key is to improve ventilation and correct hypoxia and respiratory acidosis.

(2) arterial blood gas examination: the degree of arterial oxygenation in infants with acute pneumonia varies according to the type of pneumonia, with the lightest bronchiolitis, the most severe pneumonia with extensive consolidation, and the compensatory capacity of pneumonia in children under 4 months. Weak, airway stenosis and other factors, PaO2 decline is more obvious, ventilation dysfunction is the most important cause of PaO2 decline, hypoxia caused by intrapulmonary shunt is the most serious, combined with congenital heart disease, lower PaO2, children with pneumonia The change of arterial PaCO2 is not consistent with PaO2. The increase of PaCO2 may have both lung and central causes.

(3) Compliance and pulmonary surfactant: Pulmonary compliance is mostly decreased to varying degrees. The more severe the disease, the more obvious the decline. The reasons are various, inflammation, edema, edema, tissue destruction can make elastic resistance On the other hand, inflammation destroys lung type II cells, reduces pulmonary surfactant and inactivates its function in inflammatory exudates, which can increase the surface tension of the alveolar gas-liquid interface and reduce lung compliance. We observed that the severity of lung lesions was consistent with the compliance and changes in tracheal aspirate phospholipids. The heavier the lung lesions, the lower the saturated lecithin (the main component of the pulmonary surfactant), the worse the compliance, and the lower the compliance. Arrhythmia, caused by ventilation disorders and blood oxygenation, and difficulty in lung expansion, a basic cause of insufficient ventilation, children with pneumonia with markedly decreased lung compliance suggest severe lung disease and poor prognosis. Parental treatment with pulmonary surfactant provides the basis.

(4) Two different types of respiratory failure:

1 respiratory obstruction-based: this type of child lung lesions are not necessarily serious, due to secretion blockage and inflammation edema caused by extensive bronchiole obstruction, respiratory fatigue caused by respiratory muscle fatigue, ventilation can not meet the needs of the body, lack of oxygen at the same time Combined with heavier respiratory acidosis, causing cerebral edema, early onset of central respiratory failure, mainly manifested as changes or pauses in respiratory rhythm, this type is more common in small babies.

2 extensive lung lesions: although such children may also have severe airway obstruction, but hypoxia is more prominent than carbon dioxide retention, because the lesions in these patients have extensive and serious lung disease, once the ventilator is applied, it is often necessary Maintain for a long time.

The above is a more typical case. It is common in clinical practice to be a mixed type. It is difficult to distinguish exactly, but regardless of the type, if it is not treated in time, maintaining adequate ventilation will be the common basic cause of death.

Examination of acute respiratory failure in children

pH

pH is a pH indicator, normal is 7.35 ~ 7.45, the average is 7.40, venous blood pH is about 0.03 lower than arterial blood, pH>7.45 indicates alkaliemia, pH <7.35 indicates acidemia, pH normal indicates normal acid Alkali balance, compensatory acid (alkali) poisoning or complex acid-base balance imbalance, it is generally considered that it is difficult to survive when pH < 6.8 or > 7.8, human acid resistance is strong, [H ] rises to normal 3 times Survival; and the tolerance to alkali is poor, [H] is life-threatening when it drops to half of normal, but if metabolic acidosis and respiratory alkalosis exist at the same time, pH can sometimes be normal, so one by one The pH can only indicate whether there is acid or alkaliemia. It must also be combined with other acid-base indicators (such as PaCO2, HCO3-, BE, etc.), biochemical indicators (such as potassium, chlorine, calcium) and medical history to correctly determine whether acid ( Alkali) poisoning, or complex acid-base poisoning.

2. Standard bicarbonate (SB) and actual bicarbonate (AB)

SB refers to the concentration of bicarbonate ion [HCO3-] measured by whole blood specimens isolated from air under standard conditions (temperature 38 ° C, PaCO 2 5.33 kPa, hemoglobin complete oxygenation, ie oxygen saturation 100%). PaCO2 and SaO2 affecting [HCO3-] have been restored to normal conditions, so the effect of [HCO3-] caused by respiratory acid-base imbalance has been eliminated, so the increase and decrease of SB reflects the reserve of [HCO3-] in the body. It reflects the quantitative index of metabolic acid-base balance in the body, and the normal value is 22~27mmol/L.

AB is directly measured from plasma [HCO3-], which is a whole blood sample isolated from air. The value of bicarbonate ion measured without any treatment is affected by both metabolic and respiratory factors. Under AB=SB, the difference between AB and SB reflects the degree of influence of respiratory factors on acid-base balance. When AB>SB, it indicates that CO2 retention in the body is more common in respiratory acidosis or metabolic alkalosis caused by insufficient ventilation function; AB

3. Alkali surplus (BE) or base loss (-BE)

Alkali residual or base loss refers to the amount of acid or base required to titrate 1 L of blood to pH 7.4 under standard conditions (38 ° C, PaCO2 5.33 kPa, hemoglobin 150 g/L, blood oxygen saturation 100%). If the pH is > 7.40, it needs to be titrated with acid, which is called alkali residue (BE); if the pH is <7.4, it needs to be titrated with alkali, it is called alkali deletion (BD or -BE), and its normal range: neonatal is -10~ -2mmol/L, infants are -7~-1mmol/L, children are -4~+2mmol/L, and adults are ±3mmol/L. Because they are not affected by respiratory factors, they usually only reflect metabolic changes, and their significance is SB. similar.

BE is divided into two types: actual alkali surplus (ABE) and standard alkali surplus (SBE). ABE is the measured BE, which reflects the alkali residue of whole blood. SBE reflects the alkali residue of interstitial fluid because interstitial fluid is the body cell. The exact external environment is in place, so SBE is more ideal than ABE to reflect the alkali residue of the body.

4. Carbon dioxide binding capacity (CO2CP)

CO2CP refers to the plasma CO2 content obtained by equilibrating venous plasma specimens with normal human alveolar gas (PaCO2 is 5.33 kPa), that is, the amount of carbon dioxide contained in plasma HCO3-, mainly refers to the amount of CO2 in the combined state. Approximate value of HCO3-, normal value is 2331mmol/L (5570Vo1%) for adults, and 2029mmol/L (4565Vo1%) for children, CO2CP is affected by metabolic and respiratory factors, CO2CP Decreased, suggesting metabolic acidosis (HCO3-reduced) or respiratory alkalosis (excessive CO2 excretion), and vice versa, but there is no decisive significance in mixed acid-base disorders, such as in respiratory acidosis The pH decreases and CO2CP rises. Conversely, CO2CP decreases when respiratory alkalosis occurs. Therefore, CO2CP does not reflect the true acid-base balance in the body during respiratory acid-base balance.

5. Total amount of carbon dioxide (T-CO2)

Refers to the sum of carbon dioxide in various forms in plasma, including the ionized part of HCO3-, the sum of HCO3-, CO3- and RNH2COO, and the non-ionized HCO3- and physically dissolved CO2, the normal value for adults is 24 ~32mmol / L, children 23 ~ 27mmol / L.

6. Arterial oxygen partial pressure (PaO2)

Refers to the pressure generated by physically dissolved O2 molecules in plasma. The arterial partial pressure of oxygen can better reflect the function of the lungs. It is mainly used for respiratory hypoxia, PaO2, SaO2 (oxygen saturation), O2CT (oxygen). The content or CO2, which refers to the total amount of oxygen contained in every 100 ml of blood, including the oxygen carried by hemoglobin and dissolved oxygen, can reflect the hypoxia of the body, but the sensitivity is not consistent, SaO2 and O2CT are affected by hemoglobin. For example, children with anemia may have hypoxia even if SaO2 is normal, and PaO2 is not affected by it. Therefore, PaO2 is a good indicator for judging the presence or absence of hypoxia. However, when analyzing the results, it is necessary to know whether or not to take oxygen because of absorption. Oxygen is completely different from non-oxygen, so it is best to measure without oxygen.

The normal value of PaO2 is 10.6413.3.kPa (80100mmHg), the neonatal is 811.0kPa (6080mmHg), and the venous blood oxygen partial pressure is 5.3kPa (40mmHg). It is generally considered that PaO2 is 7.98kPa (60mmHg). The above does not cause hypoxia. At this time, SaO2 is 90%, which is the part where the oxygen dissociation curve begins to turn. Below this, with the decrease of oxygen partial pressure, SaO2 can be reduced to 75%, which is obvious in clinical practice. Bun.

7. Carbon dioxide partial pressure (PaCO2)

It refers to the pressure generated by carbon dioxide dissolved in arterial blood. Because CO2 has a large dispersion capacity, about 25 times that of oxygen, it can be considered that PaCO2 can basically represent the partial pressure of carbon dioxide in the alveoli, and PaCO2 can reflect the volume of alveolar ventilation. Is a good indicator of alveolar ventilatory function, therefore, in the alveolar interstitial edema, congestion, exudation, oxygen exchange has been significantly reduced, but carbon dioxide exchange can still be normal, such as patients with arterial oxygen partial pressure reduction, carbon dioxide partial pressure Normal, that is, suggesting ventilation dysfunction, but if the arterial oxygen partial pressure is reduced and the partial pressure of carbon dioxide is increased, it indicates insufficient ventilation.

The normal value of PaCO2 is 4.665.99kPa (3545mmHg), and the child is low, 4.55.3kPa (3440mmHg), which may be related to the metabolism of children and the rapid respiratory rate. The PCO2 of venous blood is more than that of arterial blood. 0.8 to 0.93 kPa (6 to 7 mmHg).

Diagnosis and diagnosis of acute respiratory failure in children

diagnosis

Although blood gas analysis is the main means of diagnosing respiratory failure, the comprehensive diagnosis and evaluation of the child's condition can not rely solely on blood gas, but also make a comprehensive diagnosis and analysis based on medical history, clinical manifestations and other examination methods.

History

At present, there are many instruments to check, and we should pay attention to the detailed history. The importance of diagnosis of respiratory failure is that it is often replaced by other diagnostic methods, which not only helps us understand the basis of the disease, but also facilitates Targeted treatment, the following is what you need to pay attention to.

(1) Current disease: What kind of disease is currently suffering, whether there is infection or major surgery, which are high risk factors for ARDS; whether there are lung, heart or nervous system diseases, these diseases may lead to respiratory failure; The respiratory manifestations of illness, uremia or diabetic acidosis may resemble respiratory failure, and attention should be paid to identification.

(2) Accidents: Whether there are accidents that suddenly cause difficulty in breathing, such as vomiting or inhalation of foreign bodies, which is especially likely to occur in infants and young children; whether or not the drugs that can inhibit breathing are accidentally taken.

(3) history of trauma: traumatic brain injury, chest trauma can affect breathing, with or without drowning or respiratory burns.

(4) What kind of treatment has been received by the child: whether the drug that inhibits breathing has been used, whether the tracheal intubation or tracheotomy has been performed, and whether or not the pneumothorax is caused.

(5) Past history: history of dyspnea, history of asthma or respiratory allergy.

(6) History of neonatal: pay attention to the perinatal history, such as the mother's medication, whether the delivery is smooth, whether there is premature delivery, whether there is intrauterine asphyxia, or congenital malformation that causes respiratory distress (such as diaphragmatic hernia, esophageal atresia).

2. Clinical manifestations of suspected respiratory failure

Difficulty breathing and shortness of breath, nose fan, breathing effort and inspiratory sternum, lower and intercostal sag reflect respiratory resistance increase, children are trying to maintain ventilation, but not all indicate that respiratory failure has occurred, and Children with respiratory failure do not necessarily have the above-mentioned performance. Respiratory frequency changes in respiratory failure, and severe cases slow down. However, in the early stage of pneumonia and ARDS, breathing can be increased. Chest undulation has reference value for judging ventilation. Breathing When exhausted, the breathing is shallower, the breathing sound is weakened, and the experienced person can roughly estimate the amount of intake air from the breathing sound.

3. Blood gas analysis

(1) Infant and child: PaO2, PaCO2 and residual alkali (BE) are lower than children. The diagnosis of respiratory failure in children of different ages should be judged according to the normal blood gas level of this age group; ignore the difference between infants and children, application The same standard for diagnosing respiratory failure is not appropriate.

(2) PaO2, PaCO2 meaning: usually PaCO2 reflects ventilation function, PaO2 reflects ventilation function, if PaO2 decreases and PaCO2 does not increase, it means simple ventilation disorder; PaCO2 increase indicates insufficient ventilation, and may be accompanied by a certain degree of PaO2 decline, but Whether or not there is a ventilation disorder, the alveolar arterial oxygen pressure difference should be calculated. The simpler method is to calculate the sum of PaO2 and PaCO2, which is less than 14.6 kPa (110 mmHg) (including oxygen inhalation), suggesting ventilatory dysfunction.

(3) Central or peripheral respiratory failure: for respiratory failure caused by hypoventilation, according to the history and clinical differences for central or peripheral, central ventilatory insufficiency often shows respiratory rhythm changes, or decreased respiratory, peripheral ventilation, Frequent respiratory tract obstruction, uneven gas distribution or limited breathing amplitude, most of them have difficulty breathing.

(4) The nature and extent of ventilation disorder: For respiratory failure caused by ventilation disorder, the nature and degree of ventilation disorder can be judged according to the change of blood oxygen partial pressure after inhaling different concentrations of oxygen, and the low concentration (30%) is inhaled. Oxygen, due to diffuse dysfunction, PaO2 decline can be significantly improved; due to ventilatory / blood flow imbalance caused by a certain degree of improvement; due to pathological intrapulmonary shunt increased, PaO2 increased after oxygen absorption is not obvious, According to the change of PaO2 in the arteries after inhalation of high concentration (60% or more), the amount of intrapulmonary shunt can be found from the relevant map.

4. Evaluation of the condition

A comprehensive evaluation of the condition of children with respiratory failure, in addition to lung function, combined with the circulation and hemoglobin values to evaluate the oxygen transport, whether the child is hypoxic, can not only look at PaO2, but depends on whether the tissue oxygen supply can meet the metabolism Need, tissue accumulation of lactic acid in the absence of oxygen.

It is necessary to make a diagnosis based on dynamic observation during the evolution of the disease. Children with respiratory acidosis should pay attention to the compensation situation. The blood pH of the uncompensated person decreases, which has a great impact on the child, and the compensatory ability is affected by renal function and circulation. And liquid balance in all aspects, acute respiratory failure compensation takes 5 to 7 days, therefore, if the child has been on the disease for several days, pay attention to the child's previous breathing and blood gas changes, in order to make an accurate judgment of the current condition, such as the onset 2 days of uncompensated acute respiratory failure and 8 days of onset of respiratory failure with metabolic acidosis can have the same blood gas changes (PaCO2 increased, BE normal).

Differential diagnosis

Clinically, it is necessary to identify respiratory failure caused by various causes. Firstly, it is necessary to rule out the decrease of PaO2 and the increase of PaCO2 caused by the intracardiac anatomical shunt and the primary cause of decreased cardiac output. Secondly, it is necessary to identify various causes of acute respiratory failure. Can be diagnosed by means of medical history, clinical manifestations and a variety of auxiliary examination methods, pay attention to the identification of two different types of respiratory failure, respiratory obstruction or extensive lung disease caused by respiratory failure.

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