What Is Acute Respiratory Distress Syndrome?

Acute respiratory distress syndrome (ARDS) is caused by intrapulmonary and / or extrapulmonary causes. Clinical syndromes characterized by refractory hypoxemia have attracted much attention due to high mortality. There are many causes of acute respiratory distress syndrome, and the pathogenesis of acute respiratory distress syndrome caused by different causes is also different. Clinical manifestations are mostly acute onset, respiratory distress, and hypoxemia that is difficult to correct with conventional oxygen therapy. At present, the "Berlin definition" is often used internationally to diagnose and stratify ARDS. Differential diagnosis of the disease. Clinical examinations include: diagnosis and differential diagnosis, treatment monitoring and guidance treatment, criticality and prognosis evaluation, etc. The treatment of acute respiratory distress syndrome includes mechanical ventilation and non-mechanical ventilation. The effective treatment methods are still being explored. .

Basic Information

Visiting department

Respiratory Medicine

Common causes

Caused by pneumonia, aspiration, lung contusion, severe systemic infection, severe multiple injuries, etc.

Common symptoms

Shortness of breath, lips and fingers (toes), respiratory distress, etc.

Causes of Acute Respiratory Distress Syndrome

The etiology of acute respiratory distress syndrome includes two categories: intrapulmonary and extrapulmonary causes. Intrapulmonary causes include: pneumonia, aspiration, lung contusion, drowning, and inhalation of toxic substances; extrapulmonary factors include: severe systemic infections, severe multiple injuries (multiple fractures, flail chest, severe brain trauma, and burns), shock, high-risk surgery (Heart surgery, aortic surgery, etc.), massive blood transfusions, drug poisoning, pancreatitis, and cardiopulmonary bypass surgery. In addition, according to different pathogens, the causes of ARDS can also be divided into two categories: biological pathogens and abiotic pathogens: biological pathogens mainly include a variety of pathogens, such as bacteria, viruses, fungi, atypical pathogens and Partial damage-associated molecular patterns (DAMPs), malignant tumors, etc .; abiotic pathogens mainly include acidic substances, drugs, inhalation of toxic gases, and mechanical ventilation-related injuries.

Clinical manifestations of acute respiratory distress syndrome

The onset of acute respiratory distress syndrome is more rapid, which can occur within 24 to 48 hours or as long as 5 to 7 days. The main clinical manifestations include: shortness of breath, cyanosis of the lips and fingers (toes), and respiratory distress (a manifestation of extreme hypoxia) that cannot be alleviated by conventional oxygen therapy, which may be accompanied by chest tightness, cough, blood sputum and other symptoms. The critically ill may suffer from conscious disturbance or even death. Physical examination: shortness of breath, nasal flaps, and tricuspid sign; auscultation of both lungs without snoring, occasional wheezing, and wheezing; late snorting and fine wet snoring, and obvious back when lying. Percussion can be dull; percussion with atelectasis can be accompanied by solid sound; subcutaneous emphysema and percussion drum sound can be seen with pneumothorax.

Acute Respiratory Distress Syndrome

The purpose of examination for patients with acute respiratory distress syndrome includes: diagnosis and differential diagnosis, treatment monitoring and guidance treatment, criticality and prognosis evaluation;

Tests related to diagnosis and differential diagnosis include: pathogen detection, arterial blood gas analysis, imaging (chest X-ray, chest CT), pulse index continuous cardiac output (PICOO) monitoring technology, pulmonary artery catheter monitoring technology, ultrasound technology Wait;

Examinations related to treatment monitoring and guided treatment include: mechanical ventilation-respiratory monitoring (respiratory drive monitoring, airway resistance and lung compliance monitoring, airway pressure monitoring, respiratory function monitoring), pulse index continuous cardiac output (PICOO) Monitoring, monitoring of central venous pressure and pulmonary artery pressure, monitoring of oxygen metabolism dynamics, fiberoptic bronchoscopy and treatment, monitoring of end-expiratory carbon dioxide, alveolar lavage fluid and lung tissue pathological examination;

Tests related to criticality and prognosis include APACHEII score, LIS score, SOFA score, and lung injury-specific markers.

Diagnosis of acute respiratory distress syndrome

After Ashbaugh first proposed the definition of ARDS in 1967, the "AECC Definition" of the 1994 US-European Joint Conference, the "Guidelines for the Diagnosis and Treatment of Acute Lung Injury / Acute Respiratory Distress Syndrome (2006)" in China, and the "Berlin Definition" in 2012 Etc., are the embodiment of the progressive development of ARDS diagnosis.

At present, the definition and severity stratification of ARDS is mostly adopted by the Berlin Definition internationally. Berlin definition of ARDS ^[1] :

Onset time

Within 1 week after the known clinical cause or the onset of new / existing respiratory symptoms;

2. Chest image

That is a chest radiograph or CT scan, showing bilateral shadows that cannot be completely explained by pleural effusion, lobar / pulmonary collapse, nodules;

3. Pulmonary edema

The cause of respiratory failure cannot be explained by heart failure or increased water load. If there are no risk factors, objective assessment is required to rule out hydrostatic edema;

4. Degree of hypoxia

Mild: 200mmHg <PaO ₂ / FiO ₂ 300mmHg, PEEP or CPAP5cmH ₂ O, noninvasive ventilation may be used in mild ARDS group; Moderate: 100mmHg <PaO ₂ / FiO ₂ 200mmHg, PEEP5cmH ₂ O; Severity: PaO ₂ / FiO ₂ 100mmHg, PEEP 5cmH ₂ O, Note: If the latitude of the area is higher than 1000 meters, a correction factor calculation should be introduced: [PaO2 / FiO2 (air pressure / 760)].

Note: FiO ₂ : Inhaled oxygen concentration; PaO ₂ : Arterial oxygen partial pressure; PEEP: Positive end-expiratory pressure; CPAP: Continuous positive airway pressure.

In addition, during the diagnosis and treatment of patients with acute respiratory distress syndrome, ventilator-associated pneumonia, ventilator-associated lung injury, deep vein thrombosis, offline mechanical ventilation, and interstitial fibrosis often occur.

Differential diagnosis of acute respiratory distress syndrome

Acute respiratory distress syndrome has many causes and complicated pathogenesis, so its differential diagnosis is also difficult. The diseases that usually need to be identified include: severe pneumonia, cardiac insufficiency, pulmonary embolism, excessive fluid replacement, acute exacerbation of idiopathic pulmonary fibrosis, etc .; because these diseases have symptoms such as respiratory distress and hypoxemia, they are identified Diagnosis depends on medical history, physical examination, laboratory tests, and imaging studies.

Acute respiratory distress syndrome treatment

The treatment of acute respiratory distress syndrome includes mechanical ventilation and non-mechanical ventilation.

Mechanical ventilation is the main treatment for patients with acute respiratory distress syndrome. According to the different methods of mechanical ventilation, it can be divided into non-invasive ventilation and invasive ventilation. Non-invasive ventilation depends on the mask for ventilation. Invasive ventilation depends on tracheal intubation or tracheotomy for ventilation. The choice of the two depends on the specific condition and determine the timing. ; At present, mechanical ventilation strategies for patients with acute respiratory distress syndrome mainly include the following: lung protection ventilation strategy (small tidal volume ventilation [LTVV], pressure-limited ventilation, permissive hypercapnia [PHC], inverse ventilation, PEEP Application, etc.), lung opening strategies (specific techniques include: lung expansion [RM], optimal PEEP application, and selection of mechanical ventilation modes, etc.), and mechanical ventilation adjuvant therapy (intra-airway medication [nitrogen monoxide, prostaglandin], Prone ventilation, extracorporeal lung oxygenation, etc.).

Although there are many non-mechanical ventilation treatments for acute respiratory distress syndrome, its reliable efficacy has not yet been determined. Non-mechanical ventilation treatments include: pulmonary water clearance and fluid management, alveolar surfactant supplement therapy, beta receptor agonist applications, statin applications, glucocorticoid applications, anticoagulant applications, antioxidants and enzyme inhibitors Application, blood purification treatment, nutrition intervention, etc .; its effective treatment methods are still being explored. ^[1]