Upper airway obstruction

Introduction to upper airway obstruction Upper airway obstruction (UAO) is a clinical emergency caused by a variety of causes of severe obstruction of upper airway airflow. Its clinical manifestations are not specific, and it is easy to be confused with diseases such as bronchial asthma and obstructive pulmonary disease. In addition, the disease is more common in children, less common in adults, causing upper airway obstruction. Among them, exogenous foreign body is the most common, the other common are those with laryngeal dyskinesia, infection, tumor, trauma and The iatrogenicity, etc., has a very important clinical significance for the timely understanding and treatment of upper airway obstruction, because most patients are healthy in the past and can fully recover after effective treatment. basic knowledge Sickness ratio: 0.05% Susceptible people: no special people Mode of infection: non-infectious Complications: pulmonary edema

Upper airway obstruction

(1) Causes of the disease

Clinically, upper airway obstruction is rare, but can be caused by a variety of diseases. These reasons include:

1 airway scar stenosis: mostly caused by tracheal intubation or incision;

2 airway wall lesions: such as throat soft tissue inflammation, posterior pharyngeal abscess, tonsil enlargement, vocal cord paralysis, laryngeal or tracheal tumor, tracheal softening and recurrent polychondritis;

3 airway cavity lesions: more common in the airway, as well as pedicled intratracheal polyps or tumors and inflammatory granuloma;

4 external pressure of the airway: space-occupying lesions around the airway such as thyroid cancer, abscess, hematoma or gas compression;

5 airway endocrine retention: respiratory tract bleeding or a large amount of sputum failed to cough up, a large amount of stomach contents inhaled, etc., will cause common causes of airway obstruction in different anatomical parts of adults and children, summarized in Table 1, for clinical diagnosis At the time of reference, in rare cases, functional vocal cord abnormalities or psychological factors can also cause upper airway obstruction.

(two) pathogenesis

Upper airway anatomy: the respiratory airway of the respiratory system includes the nose, throat, trachea, main bronchus, leaf bronchus, segmental bronchus, bronchioles, and terminal bronchioles. According to the surrounding small airway and central airway, mechanical mechanics and other breathing The difference in physiological function generally divides the respiratory tract into three parts, namely:

1 small airway, refers to the airway with a diameter less than 2mm;

2 atmosphere, refers to the airway below the protuberance to a diameter of 2mm;

3 upper airway, a section of the respiratory tract from the nose to the tracheal protuberance, including the nose, pharynx, larynx and trachea.

The upper airway is usually divided into two parts: the upper airway of the thoracic cavity and the upper airway of the thoracic cavity, and the upper airway of the thoracic cavity includes the submandibular cavity (including the Ludwig angina). Area), the posterior pharyngeal cavity (including the area where the posterior pharyngeal abscess can be produced) and the throat, the broad throat range up to the base of the tongue, down to the trachea, can be divided into the upper glottis area (the epiglottis, the epiglottis and the false Vocal cord), the glottis (including the structure in the vocal cord plane of the sacral cartilage) and the subglottic region (an airway surrounded by a ring-shaped cartilage of about 1.5 to 2.0 cm).

The total length of the trachea is l0 ~ 13 cm, wherein the length in the thoracic cavity is about 6 ~ 9cm, and the length of the extrathoracic trachea is about 2 ~ 4cm, from the lower edge of the annular cartilage to the entrance of the chest, which is higher than the sternum in the front chest. Traces 1 to 3 cm, normal intratracheal coronary diameter, males are 13 to 25 mm, females are 10 to 21 mm, and the factors causing tracheal diameter reduction are as follows:

1Saber sheath trachea;

2 amyloidosis;

3 recurrent polychondritis;

4Wegener granuloma;

5 tracheobronchial flat osteochondrplasty;

6 nasal induration;

7 complete annular cartilage;

8Down syndrome.

Pathophysiology of upper airway obstruction: Under normal circumstances, when inhaling, the contraction of the respiratory muscles reduces the intrathoracic pressure, the pressure in the airway is lower than the atmospheric pressure, and the gas enters the lungs from the outside; on the contrary, when exhaled, the muscles of the respiratory muscles relax. The internal pressure rises, the gas is excreted from the lungs, and the acute upper airway obstruction can directly affect the ventilation function of the body. The external oxygen can not be inhaled into the lungs, and the carbon dioxide produced by the body metabolism can not be excreted, causing acute respiratory failure. If not treated promptly, the patient will die due to severe hypoxia and carbon dioxide retention.

The chest part of the upper airway is under atmospheric pressure, and the chest part is under the pressure of the pleural cavity. The pressure difference between the inner and outer sides of the trachea is across the wall. When the external pressure of the trachea is greater than the intrapleural pressure, the transmural pressure For positive values, the airway tends to close; when the transmural pressure is negative, that is, the intratracheal pressure is greater than the extratracheal pressure, the trachea is unobstructed, and the upper airway obstruction mainly affects the patient's ventilation function, because the alveolar ventilation is reduced, in the patient Hypoxemia can occur during exercise, but its diffuse function is mostly normal. The location, degree, nature (fixed or variable) of upper airway obstruction, and changes in expiratory or inspiratory pressure cause different patients. The pathophysiological changes, the inspiratory airflow limitation, the expiratory airflow limitation, or both are limited. Clinically, the upper airway obstruction can be divided into the following three types according to the different obstructed respiratory airflow: variable chest Upper airway obstruction, variable upper thoracic upper airway obstruction and fixed upper airway obstruction.

1. Variable upper thoracic upper airway obstruction: variable obstruction refers to the upper endotracheal obstruction of the tracheal lumen size due to changes in the pressure inside and outside the trachea, variable upper thoracic upper airway obstruction, seen in the tracheal softening and vocal cords In patients with diseases such as paralysis, under normal circumstances, the pressure on the outer circumference of the upper thoracic airway is atmospheric pressure throughout the respiratory cycle, and the pressure in the airway is increased due to the decrease of the internal pressure of the airway during inhalation, and the direction of action is from the outside of the tube to the inside of the tube. As a result, the upper airway of the chest tends to shrink. In patients with variable upper chest airway obstruction, when the force is inhaled, the airway pressure at the distal end is significantly reduced due to Venturi effect and turbulence, and the transmural pressure is obvious. Increase, causing the airway diameter of the obstruction part to further shrink, and the inspiratory airflow is severely blocked; on the contrary, when it exhales vigorously, the pressure inside the trachea increases, and the degree of obstruction can be reduced due to the decrease of the transmural pressure, therefore, In this type of patient performing dynamic flow-volume ring tracing, the inspiratory flow rate is limited to present the inspiratory platform, but the expiratory flow rate is limited to lighter, no platform appears, or even positive. Graphics.

2. Variable intrathoracic upper airway obstruction: variable intrathoracic upper airway obstruction, seen in the tracheal softening of the thoracic airway and tumor patients, because the pressure around the upper airway in the chest is close to the intrapleural pressure, the lumen The external pressure (pleural pressure) is negative pressure compared with the intraluminal pressure. The direction of the transmural pressure is from the lumen to the outside of the lumen, causing the airway in the chest to expand. When the patient exhales vigorously, Venturi The effect and turbulence can reduce the airway pressure at the proximal end of the obstruction, and the airway diameter of the obstruction site is further reduced, but the expiratory flow is severely blocked. When the dynamic flow-volume ring is recorded in this type of patient, the expiratory flow rate is expressed. The expiratory platform is presented in a limited manner, but the inspiratory flow rate is limited.

3. Fixed upper airway obstruction: fixed upper airway obstruction refers to the stiffening of the upper airway obstructive lesion, and the change of transmural pressure during respiration can not cause airway caliber change in obstruction, seen in tracheal stenosis and thyroid tumor. Patients, in this type of patients, the airflow during inhalation and exhalation are significantly limited and similar, and the inspiratory flow rate and expiratory flow rate of the dynamic flow-volume loop are presented as platforms. Most scholars believe that the expiratory flow rate is 50% of the vital capacity. The ratio of the inspiratory flow rate (FEF50%/FIF50%) equal to 1 is a characteristic of the fixed upper airway obstruction, but the normal airway adjacent to the obstructed lesion may have a variable obstruction, which has a certain influence on the FEF50%/FIF50%. Should be noted.

Upper airway obstruction prevention

Active treatment of primary disease has important implications for airway infarction.

Upper airway obstruction complications Complications pulmonary edema

Complicated with pulmonary edema.

Upper airway obstruction symptoms Common symptoms Snoring airway narrowing dry cough, cough, phlegm, asthma, swallowing, difficulty breathing, epiglottis, paralysis

In the early stage of upper airway obstruction, there is usually no manifestation. The symptoms often appear when the obstruction is severe. The acute upper airway obstruction starts rapidly, the condition is serious, and even causes asphyxia and death. There are often obvious symptoms and signs, upper airway obstruction. The clinical manifestations are not specific, and can be expressed as irritating dry cough, asthma and dyspnea; the difficulty in breathing is mainly due to difficulty in inhalation, activity can cause significant difficulty in breathing, and paroxysmal seizures often occur due to changes in body position. A small number of patients have snoring at night, and may be awakened several times due to increased difficulty in breathing. It is characterized by sleep apnea syndrome. Inhalation of foreign body may have a history of cough, often with obvious respiratory distress, abnormal expression of pain, from time to time. Grab the throat, occasionally the chronic upper airway obstruction caused by repeated pulmonary edema and pulmonary edema.

The symptoms and signs of upper airway obstruction are related to the degree and nature of obstruction. Most of the upper airway obstruction seen in the clinic is incomplete obstruction. The main signs are inspiratory wheezing, mostly in the neck, and the lungs. Can also smell but weak, forced inhalation can cause wheezing significantly worse, wheezing prompts obstruction is more serious, at this time the airway diameter is often less than 5mm, inspiratory wheezing more than the chest upper airway obstruction, more Seen in the vocal cords or above the vocal cords; biphasic wheezing suggests obstruction under the glottis or in the trachea; changes in the intensity of wheezing sounds during the curved neck indicate that obstruction occurs at the entrance to the thoracic cavity, and the child has a canine-like cough, especially at night. More prompts for laryngeal bronchitis, and salivation, difficulty swallowing, fever without cough is more common in severe epiglottis, some patients may have changes in sound, the characteristics of which are related to the location and nature of the lesion, such as unilateral vocal cord paralysis The voice is hoarse; the bilateral vocal cords have normal numbness, but there is wheezing; the lesions above the glottis often have low voice, but no hoarseness; the oral abscess has a material-like sound.

Upper airway obstruction

Upper airway obstruction is more common than infection, such as white blood cells can be elevated when infected.

1. Pulmonary function test :

The maximum expiratory flow rate (speed)-volume curve (ring) is the preferred method for diagnosing upper airway obstruction. When the upper airway is blocked, the flow-volume curve shows a significant change, which has diagnostic value, as described above, according to the flow rate. - The change of volume curve shape can determine different upper airway obstruction, 1 variable type upper chest upper airway obstruction, and its flow-volume curve shows that the inspiratory flow rate is obviously limited and presents the inspiratory platform, and the expiratory flow rate is basically normal. Therefore, FEF50%/FIF50%>1; 2 variable intrathoracic upper airway obstruction, the flow-volume curve shows that the expiratory flow rate is obviously limited and presents the exhalation platform, FEF50%/FIF50%<1; 3 fixed type In the upper airway obstruction, the flow-volume curve showed that the inspiratory and expiratory flow rates were significantly reduced, and the degree was equivalent, showing a rectangle with FEF50%/FIF50%=1.

Other lung function indicators, such as FEV0.5, FEV1.0 decreased, PEFR, MVV progressive decline, FIF50%100L/min, FEV1.0/PEFR10ml/(L·min), FEVl.0/FEV0.5 1.5.

Closed volume lung capacity and normal VC and CV suggest that there may be upper airway obstruction, but pulmonary function tests are not possible for patients with acute respiratory distress and are not sensitive to upper airway obstruction.

2. Radiological examination:

(1) Plain film of the neck: for the flat film of the trachea, it has high sensitivity to exudative bronchitis, airway foreign body and upper airway obstruction caused by innominate arterial compression, but sensitive to throat or tracheal softening. Poor sex, inhalation neck flat film has a discriminating value for laryngotracheitis and epiglottis. The typical sign of laryngotracheitis is the "minars" sign. The subglottic stenosis is more common in patients with laryngotracheitis, but it can also be seen in epiglottis. Inflammation, epiglottis can show swelling of the epiglottis and hypopharyngeal dilatation in the lateral position of the neck. The diagnosis of upper airway obstruction by the airway plain film can provide important information, but its accuracy is poor, and should be related to medical history and physical signs. Combine to judge.

(2) Chest CT scan: Airway CT scan can understand the size and shape of the lesion at the obstruction, the degree of airway stenosis and its relationship with the airway wall, and the surrounding tissue of the lesion. Blood supply situation.

(3) Chest MRI examination: It has good resolving power, can predict the degree and length of airway occlusion, and evaluate the mediastinum.

3. Acoustic inspection :

Respiratory audio spectrum analysis found that the peak frequency and frequency spectrum of normal people are mainly below 200 Hz. The peak frequency of breath sounds is significantly increased in patients with upper chest airway obstruction, mostly more than three times the baseline, and the frequency spectrum is widened. Moving to a high frequency region greater than 200 Hz, the above changes are greater in the inspiratory phase than in the expiratory phase, and the signal in the neck is stronger than the chest. When the variable chest is blocked, the spectral change of the breath sound is greater than the inspiratory phase. Phase, chest signal is stronger, therefore, respiratory audio spectrum analysis has a good clinical application value for judging airway obstruction.

4. Endoscopy:

Fiberoptic laryngoscopy or fiberoptic bronchoscopy can directly observe the upper airway, understand the changes of the vocal cords, tracheal rings and the dynamic characteristics of the lesions during the breathing process, and can collect the pathological examination of the living tissue, so it is decisive for the diagnosis, doubt For patients with upper airway obstruction, endoscopy should be considered, but those with severe dyspnea should not be examined, and biopsy is strictly prohibited for vascular diseases.

Diagnosis and diagnosis of upper airway obstruction

diagnosis

To diagnose the upper airway obstruction, the key is to consider the possibility of upper airway obstruction. If there are the following clinical conditions, the relevant examination should be carried out in time: 1 with shortness of breath, dyspnea as the main performance, obviously worse after the activity, sometimes symptoms The increase is related to body position, and is not treated by bronchodilator; 2 there is upper airway inflammation, injury, especially those with tracheal intubation and tracheotomy; 3 pulmonary function test shows maximum expiratory flow rate, maximum ventilation Sex decreased, lung capacity remained unchanged, FEV1 decreased not significantly, and was not proportional to the decrease in maximum ventilation; or FEV1 decreased, but closed volume was normal.

Differential diagnosis

It must be differentiated from cerebrovascular accidents, seizures, overdose, overdose of coronary heart disease, acute throat and laryngeal edema, and other causes of airway obstruction.

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