Methods: This paper summarizes the related articles and related guidelines based on PubMed selective retrieval.
Results: Dyspnea refers to various subjective feelings, some of which will be affected by the emotional state of patients. There is a difference between acute dyspnea and chronic dyspnea: by definition, the latter has existed for more than four weeks. Medical history, physical examination and observation of patients' breathing patterns usually lead to correct diagnosis, but in 30% to 50% cases, more diagnostic research is needed, including biomarker measurement and other auxiliary examinations. It is difficult to confirm the diagnosis when there are many potential diseases at the same time. Causes of dyspnea include heart and lung diseases (congestive heart failure, acute coronary syndrome, pneumonia, chronic obstructive pulmonary disease) and many other diseases (anemia, mental disorders).
Conclusion: Many causes lead to dyspnea, which makes its diagnosis challenging. Its rapid assessment and diagnosis is very important for reducing mortality and reducing disease burden.
Dyspnea (shortness of breath) is a common symptom, which affects as many as 25% patients in a mobile environment. It may be caused by many different potential diseases, some of which may be acute and life-threatening (for example, pulmonary embolism, acute myocardial infarction). Therefore, rapid assessment and targeted diagnostic research are very important. Overlapping clinical manifestations and complications, such as congestive heart failure and chronic obstructive pulmonary disease (COPD), will make the diagnosis and evaluation of dyspnea a clinical challenge, so the term "dyspnea" covers a variety of subjective experiences. The existence of this symptom can be used to predict high mortality.
This review is based on the relevant articles selectively retrieved in PubMed, the latest guidelines of the European Society of Cardiology (ESC), the German Society of Cardiology (DGK) and the German Society of Pulmonary Diseases and Respiratory Medicine, and the information contained in general internal medicine textbooks. Search terms include the following: "dyspnea"; "dyspnea, epidemiology"; "Dyspnea, Primary Health Care, Prevalence"; "dyspnea, prevalence rate"; Dyspnea, A Guide; "Dyspnea, pathophysiology"; "dyspnea, cause"; "dyspnea, general practitioner"; "dyspnea, primary health care"; "dyspnea, acute coronary syndrome"; Plato's test; "dyspnea, side effects"; "EMS, dyspnea"; "Ed, it's hard to breathe."
In the * * * cognitive paper (1), the American Thoracic Association defines dyspnea as "the subjective experience of respiratory discomfort, including feelings of different intensities ... it comes from the interaction of various physiological, psychological, social and environmental factors, and may induce secondary physiological and behavioral reactions."
Dyspnea is the general term of subjective experience, including the feeling of death or suffocation and the desire for air when trying to breathe. The subjectivity of dyspnea is one of the main difficulties faced by clinicians, and its task is to determine the diagnosis and judgment of potential diseases and their severity. The pathogenesis of dyspnea is still not completely clear, and it is currently under study. At present, the explanation hypothesis is based on the concept of regulatory ring, which consists of afferent information transmitted by the center (chemoreceptors from pH, CO2 and O2 and mechanical receptors of muscles and lungs [essentially C fibers, J fibers of bronchial and pulmonary vessels]) and corresponding ventilation reactions (2).
From simple intensity description (visual analogue scale, Borg scale) to multidimensional questionnaire (for example, multidimensional description of dyspnea), various tools can be used to evaluate dyspnea. These tools have been verified and can be used for communication. There are other disease-specific classifications, including new york Heart Association (NYHA) classification of chronic congestive heart failure (2,3).
Dyspnea is a common symptom of general practitioners and hospital emergency rooms. It is reported that 7.4% of patients in emergency room have difficulty breathing (4); In general clinical diagnosis and treatment, 65,438+00% people complained of dyspnea while walking on the flat ground, and 25% people complained of dyspnea during strenuous exercise (such as climbing stairs) (5). For 1-4% patients, dyspnea is the main reason for their seeking medical treatment (6, 7). In professional practice, patients with chronic dyspnea account for 15% to 50% of the number of cardiologists, but less than 60% of the number of lung surgeons [2]. Among the patients seen by the emergency medical rescue team, 12% had difficulty breathing, and half of them needed hospitalization. The mortality rate of inpatients is about 65438 00% (8). As shown in table 1, the distribution of basic diagnosis varies from case to case.
More accurate classification of patients' symptoms is helpful for differential diagnosis. There are several standards to consider (3):
1.？ course of a disease
* Acute attack and chronic attack (lasting more than four weeks) and acute deterioration of existing symptoms.
*? Intermittent and permanent
* Once (suddenly)
2. Formed by the environment
* at rest
*? Tired
*? Accompanying emotional stress
* Position-related.
*? Special exposure.
3. Etiology
*? Problems related to respiratory system (breathing, airway, gas exchange)
:: Cardiovascular diseases
*? Other reasons, such as anemia, thyroid disease, poor physical condition (muscle weakness)
* Mental factors
At the same time, the existence of various basic diseases sometimes makes the diagnosis and treatment of dyspnea more difficult, especially for elderly patients with various diseases.
Acute dyspnea may be the manifestation of life-threatening diseases. Warning signs include confusion, obvious cyanosis (as a new discovery), dyspnea when speaking, and dyspnea or respiratory failure. Potential threats to life should be assessed immediately. Vital signs (heart rate, blood pressure, oxygen saturation) must be measured in order to make the next decision in time, especially whether the patient needs emergency treatment or invasive treatment and auxiliary ventilation in the intensive care unit. Respiratory frequency is another important criterion of disease sensitivity and severity. The increased respiratory rate at admission indicates poor prognosis (higher possibility of treatment in intensive care unit and higher mortality) (10, 1 1), which is an independent parameter in many scoring systems of emergency medicine and intensive care (such as emergency severity index and APACHE II).
The initial misdiagnosis will lead to prolonged hospitalization and higher mortality (12). Most people who suddenly have difficulty breathing feel that they are in serious danger. Usually, emotional factors such as panic, anxiety and depression will also aggravate patients' subjective pain.
More clues of potential diseases can come from the patient's past medical history (including diagnosis, intervention and operation) and symptoms and signs pointing to specific diagnosis except dyspnea (Table 2, Table E 1). Table 2 lists the possible causes of acute dyspnea.
Electrocardiogram can find acute myocardial infarction or arrhythmia. Chest X-ray plain film can show pulmonary congestion, pneumothorax or pneumonia. Specific blood tests called biomarkers also play an important role in the differential diagnosis of acute dyspnea.
Natriuretic peptide, brain natriuretic peptide (BNP) and N-terminal pro-brain natriuretic peptide (NT-proBNP) can be used to exclude clinically related congestive heart failure (13- 16). In the guidelines of the European Society of Cardiology (ESC), the threshold of BNP is suggested.
If clinical evidence shows that acute coronary syndrome is the cause of dyspnea, it will be helpful to continuously measure cardiac troponin (troponin I or troponin T). This can be used to rule out acute myocardial ischemia with high certainty (18). The threshold (or rising threshold) of a positive test result depends on the specific test used. The positive predictive value of repeated detection of troponin for acute myocardial ischemia was 75% to 80% (18).
D- dimer is the degradation product of fibrin produced by fibrin hydrolysis; Their concentration is higher after the discovery of thrombotic events. They have high negative predictive value in the diagnosis and evaluation of pulmonary embolism, but they cannot be used as screening tests because the increase of D- dimer concentration is not specific. In routine practice, before measuring D- dimer, the possibility of acute pulmonary embolism should be evaluated by other means, for example, using risk score (such as Geneva score) or more commonly used Wells score (e Table 3). If the probability of pulmonary embolism is low (or some cases are moderate), then the probability of excluding pulmonary embolism with normal D- dimer concentration is high. On the other hand, if the Wells score is high, which indicates that pulmonary embolism is likely to occur, the next step of diagnostic evaluation is imaging research. In addition, in the current guidelines for the diagnosis and treatment of pulmonary embolism, the age-adjusted threshold is emphasized (for patients over 50 years old, the suggested threshold is age × 10? G/L) can improve the specificity of D- dimer test and keep its sensitivity above 97% (19,20).
Cardiac troponin and natriuretic peptide in patients with acute pulmonary embolism may also increase, leading to clinically relevant right heart strain [19]. Troponin may be elevated in almost any acute lung disease. If there is any clinical evidence of right heart strain, the patient should be evaluated by chest echocardiography in time.
Chronic dyspnea is usually caused by one of the following reasons: bronchial asthma, chronic obstructive pulmonary disease, congestive heart failure, interstitial lung disease, pneumonia and mental diseases (such as anxiety, panic and somatic diseases) (3, 12). Table 2 gives further reasons. However, in elderly patients with multiple diseases, it is often difficult to attribute dyspnea to a single cause.
Similarly, the clinical history here (including risk factors, exposure and past diseases [Table 2, Table 1]) usually points to the correct diagnosis or at least narrows the scope of differential diagnosis. However, only half to two-thirds of the cases can be correctly diagnosed based on the medical history (2 1-23). Accompanied by auscultation (for example, showing evidence of pulmonary congestion or absence or enhancement of breath sounds), observing patients' breathing patterns usually provides more clues for possible underlying diseases. Rapid and shallow breathing reflects the decrease of lung compliance in interstitial lung disease, while deep and slow breathing is a typical feature of COPD (24).
Select further diagnostic tests according to individual conditions; The proposed general diagnosis algorithm has been clinically tested (22). Some authors suggest that the diagnostic test should be carried out in multiple steps, and the specificity of each step should be improved so that the results of each test can be correctly selected for the next time.
Usually, a specific diagnosis can be suspected only by medical history and physical examination, but if it is impossible, a small number of basic examinations can be carried out as a quick and simple method to narrow the scope of differential diagnosis and maintain the diagnosis. Minimize the need for further testing (Figure 1). Pulmonary plethysmography can help to determine the main cause by distinguishing between heart and lung diseases.
According to these preliminary findings, the next step can be to choose appropriate types of auxiliary diagnostic tests, such as echocardiography, computed tomography or invasive right or left cardiac catheterization for hemodynamic evaluation (Figure 1). The selection of the initial test should depend on the possible diagnosis. Compared with more comprehensive testing, the advantage of this selective testing is that it can avoid too many tests. Obviously, its disadvantages are potential diagnosis delay and patients with various dyspnea factors may not be able to make a diagnosis.
In some cases, the cause of dyspnea can only be found through a variety of tests. In a study of 1969 dyspnea patients without known heart or lung diseases, we tried to determine which parameters were most helpful to determine the appropriate type of further diagnostic tests (25). The following parameters were studied:
The only independent predictors of dyspnea were FEV 1, NT-proBNP concentration and the percentage of emphysema change on CT.
Bronchial asthma-the cause is airway obstruction caused by chronic airway inflammation. Patients complain of frequent shortness of breath, usually at night. There may be many allergic factors. Inducing factors may include respiratory tract irritation, allergen exposure, exercise, weather change and infection. Auscultation found expiratory wheezing caused by obstruction. The determination of vital capacity showed that the expiratory volume (FEV 1) and the maximum expiratory flow (PEF) in one second decreased (26), which may be normal during the interval of asymptomatic attacks. After inhaling bronchodilators (β2- agonists or anticholinergic drugs), the obstruction and symptoms were obviously improved. Acute dyspnea in patients with asthma is called acute exacerbation. Typical clinical manifestations are shortness of breath, prolonged breathing and expiratory time (27).
Chronic obstructive pulmonary disease (COPD)-According to the definition of the World Health Organization, chronic bronchitis is defined as coughing for at least three months for two consecutive years. In COPD, chronic inflammation leads to the destruction of lung parenchyma, which leads to excessive expansion of lung and decreased elastic recovery ability. COPD is usually characterized by fixed obstruction of the lower respiratory tract. The affected patients are usually over 40 years old, and almost all of them are smokers or former smokers (28-30 years old). Pulmonary function examination and plethysmography can provide further diagnostic help. Tiffeneau index (FEV 1/IVC, where IVC is inspiratory vital capacity) is usually lower than 0.7, and the residual volume may be increased due to excessive lung expansion. Abnormal low diffusion of carbon monoxide suggests emphysema. Chest X-ray plain film shows that the diaphragm is flattened and the pulmonary vessels are often sparse. The aggravation of illness requiring hospitalization is related to poor prognosis. Chronic obstructive pulmonary disease has the same risk factors as left heart failure, and is often found together with left heart failure (28, 29).
Many current or past smokers suffer from symptoms similar to COPD, but they do not reach the classic definition. A recently published study shows that these patients have the same anatomical evidence of deterioration, reduction of daily activities and airway changes (airway wall thickening) as COPD patients. They often receive anti-airway obstruction drugs, although there is no evidence of this practice (3 1).
Pneumonia-dyspnea is the main symptom of pneumonia, which mainly occurs in patients over 65 years old (about 80%) (29). Chest pain, fever and cough are typical accompanying symptoms. The examination showed shortness of breath, breath sounds and sometimes bronchial breathing. Laboratory examination (inflammatory parameters; In severe cases, arterial blood gas analysis is hypoxemia), and chest X-ray examination and chest CT examination are helpful for diagnosis in some cases.
CRB-65 score is used to evaluate the severity of pneumonia. Each item will get an integral: C stands for the disturbance of consciousness of new diseases, R stands for the respiratory rate ≥30 beats/min, and B stands for systolic blood pressure.
Interstitial lung disease-Patients report chronic shortness of breath and dry cough, and they often smoke (34). Examination revealed rales at the bottom of the lungs and sometimes clubbed fingers.
Lung function examination showed that vital capacity (VC) and total vital capacity (TLC) were low, Tiffeneau index was normally high, and CO diffusion was reduced. The differential diagnosis of interstitial lung disease is complicated, and the prognosis and treatment of different types of interstitial lung disease are different. It is best to consult a lung doctor (29, 35).
Pulmonary embolism-The clinical manifestations of acute pulmonary embolism are usually characterized by acute dyspnea. Patients often report pleural pain and sometimes hemoptysis. Examination revealed shallow breathing and tachycardia. There is usually evidence that deep venous thrombosis of lower limbs is the source of pulmonary embolism (19).
Congestive heart failure-accompanied by dyspnea and other symptoms, including fatigue, decreased exercise endurance and fluid retention (17). The common causes are advanced coronary heart disease, primary cardiomyopathy, hypertension and valvular heart disease. There are important clinical differences between heart failure with reduced ejection fraction (HFrEF) (that is, heart failure with left ventricular ejection fraction (LVEF) less than 40%) and heart failure with high cardiac filling pressure and maintained ejection fraction (HFpEF) (Figure 2). There is also a newly described entity called heart failure (HFmrEF, showing signs of diastolic dysfunction, LVEF is between 40% and 49%), and the ejection fraction is moderate (17). In all types of congestive heart failure, stroke volume and cardiac output will decrease.
Echocardiography is the main diagnostic test. It can evaluate the decline of systolic and/or diastolic function with the help of surrogate parameters (Figure 2)(36).
Coronary heart disease-dyspnea may also be a symptom of coronary artery stenosis, although it is not a "classic" symptom (37). It can coexist with angina pectoris, or it can be the main or only symptom of coronary heart disease, such as in diabetic patients.
Medical history, especially the time and place of dyspnea (oppression, chills, etc. ) It is usually suggested that coronary heart disease is the potential cause. Patients with unexplained dyspnea should be evaluated for coronary heart disease. The evaluation includes routine dynamometer and stress test combined with imaging research, such as stress echocardiography, myocardial perfusion imaging and stress magnetic resonance tomography. It is recommended that cardiac catheterization be performed after positive finding (37).
Dyspnea is more common in acute coronary syndrome or myocardial infarction, and it is a part of the symptom group caused by cardiogenic shock and low cardiac output (18,39).
Valvular heart disease-especially in elderly patients, valvular heart disease is another possible cause of dyspnea. The most common valve diseases are aortic stenosis and mitral insufficiency (40). Typical manifestations of aortic stenosis include decreased body function, syncope and dizziness, and sometimes chest pain similar to angina pectoris. Auscultation usually points to diagnosis (the largest systolic heart murmur is heard near the second intercostal sternum and transmitted to the carotid artery). Patients with mitral regurgitation show signs of heart failure. Because of the left atrial volume overload, ECG often shows atrial fibrillation. Here, auscultation also points to diagnosis (complete systolic murmur at the top of the heart, sometimes projected to the armpit). Echocardiography is an authoritative diagnostic study.
Heart disease and lung disease usually occur in the same patient at the same time. If the cause of dyspnea is found in one of these two organ systems, we must continue to look for other possible causes in the other organ system, because complications are common.
The World Health Organization (WHO) defines anemia as that the hemoglobin (Hb) value of men is lower than 8.06 mmoL/L( 13 g/dL) or that of women is lower than 7.44 mmoL/L( 12g/dL). Dyspnea has no obvious Hb threshold. Anemia requires further diagnosis and evaluation in all cases, especially when the Hb concentration is lower than 1 1g/dL or decreases for unknown reasons.
Otolaryngology diseases that affect the respiratory tract can also cause dyspnea. In upper respiratory tract diseases, the main symptom except dyspnea is wheezing (exhaling when the bronchopulmonary airway is damaged, inhaling when the supraglottic airway is damaged, and biphasic respiratory tract damage at or below the glottis). A rule of thumb points out that when tidal volume is reduced by 30% (e 1), dyspnea will occur. Possible causes include congenital malformation, infection, trauma, tumor formation and neurogenic disorder.
Neuromuscular diseases that may lead to dyspnea include muscular diseases, such as Duchenne muscular dystrophy, myasthenia, motor neuron diseases, such as amyotrophic lateral sclerosis and neuropathy, such as Guillain-Barre syndrome (e 1). In most cases, these diseases have other nervous system manifestations besides dyspnea.
After extensive physical examination, mental diseases such as anxiety, panic disorder, somatization disorder or "functional disease" should be regarded as excluded diagnosis. Improving dyspnea through distraction or physical exercise may be the clue of this intervention.
Finally, it is worth mentioning the causes of iatrogenic (drug-induced) dyspnea. Non-selective beta blockers can cause bronchospasm through their β _ 2 blocking effect, thus causing dyspnea. Non-steroidal anti-inflammatory drugs that inhibit cyclooxygenase 1 increase the conversion of arachidonic acid to leukotrienes by increasing the activity of lipoxygenase; Leukotrienes in turn cause bronchoconstriction. In addition, acetylsalicylic acid (one of these drugs) can also cause dyspnea through central receptors if taken in large doses. Although the initial PLATO study (e2) showed that it appeared in 13.8% of patients, dyspnea caused by platelet aggregation inhibitor tigrello is undoubtedly a rare event in routine practice. This effect may be mediated by adenosine receptor.