OVERVIEW
Carbon dioxide (CO₂) discharge obstacles or inhalation of excessive pH caused by a drop in dyspnea, agitation, chest tightness, cyanosis and other symptoms, severe confusion, lethargy, etc. Mainly due to a variety of reasons for the reduction of CO₂ discharge caused by the CO₂ inhalation of excessive CO₂ is relatively rare mainly for the treatment of the primary disease
Definition
Respiratory acidosis is caused by decreased alveolar ventilation and gas exchange, CO₂ retention, and increased partial pressure of blood carbon dioxide (PaCO₂), resulting in hypercapnia.
Staging and Classification
Respiratory acidosis can be divided into 2 categories according to the course of the disease.
Acute respiratory acidosis
It is seen in acute airway obstruction, respiratory arrest caused by central or respiratory muscle paralysis, and acute respiratory distress syndrome.
Acute respiratory acidosis mostly has obvious clinical manifestations, such as: shortness of breath, dyspnea, headache, irritability, and even tremor, blurred consciousness and coma.
Chronic respiratory acidosis
Refers to CO₂ retention that lasts for more than 24h.
The symptoms of chronic respiratory acidosis are often masked by the primary disease and are not obvious.
Chronic respiratory acidosis is seen in chronic obstructive pulmonary disorders caused by chronic inflammation of the airways or lungs, extensive fibrosis of the lungs, pulmonary atelectasis, chronic bronchial lesions, thoracic deformities, and myasthenia gravis.
Causes
Causes
Acute respiratory acidosis
Respiratory center inhibition
Intracranial space-occupying lesions, traumatic brain injury, cerebral or meningeal inflammation, cerebrovascular accident, anesthetic or sedative drug overdose, cardiac and respiratory arrest, etc. leading to impaired pulmonary ventilation and reduced alveolar gas exchange.
Respiratory muscle paralysis
Such as severe hypokalemia, acute poliomyelitis, myasthenia gravis crisis and Guillain-Barré syndrome.
Acute airway obstruction or parenchymal lung lesions
e.g. hemoptysis, tracheal foreign body, diphtheria, drowning, or acute extensive lung lesions (e.g. pneumonia, lung abscess, acute pulmonary edema, acute respiratory distress syndrome).
Acute pleural or thoracic lesions
e.g. massive pleural effusion, severe pneumothorax, thoracic trauma, etc.
Improper application of ventilator
Commonly occurs when there is a sudden increase in CO2 production or a decrease in alveolar ventilation without timely adjustment of ventilator parameters.
Chronic respiratory acidosis
Respiratory center inhibition
Mainly seen in long-term application of sedatives, chronic alcoholism, brain tumors, sleep breathing disorders, etc.
Chronic diffuse lung lesions
Such as chronic obstructive pulmonary emphysema, extensive fibrous tuberculosis, severe pulmonary atelectasis, severe silicosis (silicosis), interstitial fibrosis, etc.
Chronic airway lesions
Such as chronic bronchitis, extensive bronchiectasis, bronchial asthma, etc.
Thoracic lesions
Such as thoracic deformity, pleural thickening with pulmonary atelectasis, etc.
Pathogenesis
Obstruction of CO₂ excretion due to respiratory dysfunction is the main pathogenesis of respiratory acidosis.
Inadequate pulmonary ventilation, dysfunctional ventilation or imbalance of alveolar ventilation/blood flow ratios caused by various etiologic factors can lead to CO₂ retention in the body and cause respiratory acidosis.
Symptoms
Main Symptoms
Acute respiratory acidosis
There may be manifestations of central nervous system, cardiovascular system and respiratory system, which are mainly characterized by shortness of breath, dyspnea, agitation, fluttering tremor, delirium and even coma.
Mild and moderate acute respiratory acidosis can be manifested as normal or elevated blood pressure, often with skin congestion and flushing.
Severe acute respiratory acidosis blood pressure decrease, arrhythmia is common, especially in patients with pulmonary heart disease application of digitalis drugs.
Chronic respiratory acidosis
The main manifestations are dyspnea, fatigue, headache, insomnia, irritability, tremor and other symptoms, but the symptoms of chronic respiratory acidosis are often masked by the primary disease.
In severe cases, drowsiness, fluttering tremor, or even convulsions, convulsions, coma and other symptoms may occur.
Consultation
Department of Medicine
Respiratory medicine
If the patient has a history of chronic lung disease, or suddenly develops symptoms such as obvious shortness of breath, agitation, cyanosis, etc., it is recommended to consult the Department of Respiratory Medicine.
Emergency Department
For sudden onset of respiratory arrest, cardiac arrest, convulsions, blurred consciousness, convulsions or even coma, call 120 and consult the nearest emergency department.
Preparation
Information on how to get to the emergency room: registration, preparation of documents, and common problems.
Tips for seeking medical treatment
Keep the airway open, if the patient is unconscious, make him/her lie on his/her back, tilt the head back, lift up the lower jaw, and keep the patient’s mouth open.
List of medical preparation
Symptom list
Particular attention should be paid to the time of symptom onset, special manifestations, etc.
Are there symptoms such as shortness of breath, dyspnea, cyanosis, etc.? How long have they lasted?
Are there symptoms such as restlessness, talkativeness or drowsiness, confusion?
Are there symptoms such as weakness, headache, insomnia or drowsiness?
Are there any symptoms such as drowsiness, fluttering tremor, or convulsions?
List of medical history
Is there any history of brain tumor, encephalitis, chronic alcoholism, etc.?
Are certain medications, such as tranquilizers, applied for a long period of time?
Is there any past history of chronic bronchitis, chronic obstructive pulmonary disease, pulmonary atelectasis, lung abscess, bronchial asthma, etc.?
Any past history of severe hypokalemia, myasthenia gravis, etc.?
Checklist
Test results from the last six months, which can be brought to the doctor’s office
Laboratory tests: arterial blood gas analysis, electrolyte analysis, lung function.
Imaging tests: chest CT.
Medication list
Medication in the last 3 months, if there is a medicine box or package, you can bring it to the doctor
Antibiotics: penicillin, etc.
Bronchodilators: Salbutamol, etc.
Alkaline drugs: sodium bicarbonate, etc.
Diagnosis
Diagnosis is based on
The diagnosis can be confirmed on the basis of blood gas analysis, but a careful history and other relevant investigations can help to clarify the cause of the disease.
1. Medical history
History of intracranial space-occupying lesions, encephalitis, and sleeping pill poisoning.
History of chronic bronchitis, bronchial asthma, chronic obstructive pulmonary disease, and pulmonary atelectasis.
History of pneumonia, lung abscess, severe hypokalemia, or tracheal foreign body.
Past history of chest trauma, thoracic deformity, etc.
History of myasthenia gravis or progressive myasthenia gravis.
2、Clinical manifestations
Symptoms
Acute severe respiratory acidosis is often manifested as shortness of breath, dyspnea and obvious neurological symptoms, at first there may be headache, blurred vision, irritability, further development may appear tremor, confusion or even delirium, coma and so on.
Most of the patients with chronic respiratory acidosis are caused by chronic obstructive pulmonary diseases, so the clinical manifestations are often dominated by these diseases, including cough, shortness of breath, dyspnea, cyanosis and other hypoxic symptoms.
3、Laboratory examination
Arterial blood gas analysis
Arterial blood gas analysis is the only way to confirm the diagnosis of respiratory acidosis, and is of great significance in determining the severity of the disease and guiding the treatment.
The diagnosis of respiratory acidosis can be made with a pH <7.35 and PaCO₂ >45 mmHg.
A decrease in blood pH, normal or slightly increased standard bicarbonate (SB), buffered base (BB), and base remaining (BE), and serum bicarbonate ion (HCO₃¯) may be normal or mildly elevated, suggesting acute respiratory acidosis.
An insignificant decrease in blood pH, with increases in SB, BB, and BE, and an increase in HCO₃¯, suggests chronic respiratory acidosis.
Electrolyte analysis
To assist in the diagnosis of respiratory acidosis, and at the same time to clarify the electrolyte changes, if necessary, timely treatment.
Blood potassium, blood calcium, blood magnesium, blood phosphorus may be elevated, and blood chloride may be lowered.
Lung function
Helps to determine the cause of respiratory acidosis.
Although pulmonary function tests are limited in some critically ill patients, they can be used to determine the nature of the ventilation dysfunction (obstructive, restrictive, or mixed) and whether it is combined with ventilatory dysfunction, as well as to make judgments about the severity of ventilation and ventilatory dysfunction.
Respiratory muscle function tests can indicate the cause and severity of respiratory muscle weakness.
Imaging
Chest CT
Assists in examining the cause of respiratory acidosis.
Chest CT can detect lung and chest disorders and help in the diagnosis of the primary cause.
Diagnostic Criteria
Arterial blood gas analysis reveals an arterial partial pressure of carbon dioxide >45 mmHg and pH <7.35, which confirms the diagnosis of respiratory acidosis.
Differential diagnosis
Metabolic acidosis
Similarities: shortness of breath and dizziness are present, and the pH drops.
Differences: In respiratory acidosis, PaCO₂ is markedly elevated, actual bicarbonate (AB) > SB, and AB, SB, and BB are all elevated. In metabolic acidosis, on the other hand, PaCO₂ is decreased, AB < SB, and AB, SB, and BB are all decreased.
Treatment
Aim of treatment: timely correction of respiratory acidosis, to avoid serious complications, sequelae and the possibility of recurrence.
Treatment principle: acute and chronic respiratory acidosis treatment principles are different, on the basis of keeping the airway open, acute respiratory acidosis is mainly to treat the primary disease and respiratory support, and chronic respiratory acidosis is mainly to improve lung function.
Keeping the airway open
Keeping the airway open is the most basic and important treatment measure.
If the patient is unconscious, make him/her in supine position, tilt his/her head back, lift up his/her jaw and open his/her mouth.
Remove secretions and foreign bodies from the airway.
If the above methods do not work, an artificial airway should be established if necessary, including simple artificial airway, tracheal intubation and tracheotomy.
If the patient has bronchospasm, bronchodilator drugs should be actively used, such as β2-adrenoceptor agonists, anticholinergics, glucocorticoids or theophyllines.
Treatment of primary disease
There are various primary diseases that cause respiratory acidosis, under the premise of solving the harm caused by acidosis itself, it is necessary to clarify and take appropriate treatment measures for different causes, especially for acute respiratory acidosis, which is the fundamental part of its treatment.
The causes of chronic respiratory acidosis are often more difficult to eradicate, but it does not mean that they do not need to be treated. It is still necessary to actively control and slow down the progress of the disease, and take targeted measures to control infection, dilate the small bronchial tubes, and promote the expectoration of sputum, in order to improve the function of gas exchange and reduce the degree of acidosis.
Respiratory support
Mainly used in the treatment of acute respiratory acidosis.
Tracheal intubation or tracheotomy and the use of a ventilator can effectively improve the ventilation and gas exchange function of the body. Attention should be paid to adjusting the tidal volume and respiratory rate of the ventilator to ensure sufficient effective ventilation, which can both rapidly expel the trapped CO2 and correct the hypoxia.
However, for patients with combined metabolic risk factors, it is important not to use the artificial ventilator too rapidly to bring PaCO2 down to normal, which may complicate the condition. It is even more important to avoid excessive artificial ventilation that reduces PaCO2 to a more dangerous situation of severe respiratory alkalosis.
Do not err on the side of using CO2-producing alkaline medications such as NaHCO3 before ventilation improves, as this tends to cause metabolic alkalosis and can increase CO2 retention.
Prognosis
The prognosis depends on the original cause of the disease, which is removed, and the prognosis is good.
Cure
The prognosis is usually good with prompt treatment of the primary disease, restoration of alveolar ventilation and gas exchange function, and correction of respiratory acidosis.
Acute respiratory acidosis can lead to serious complications, such as cardiac arrest, if not treated promptly and effectively.
Chronic respiratory acidosis may progress to pulmonary encephalopathy if the cause of the disease is not removed and treated rationally and effectively, and the cause of the disease is not removed, and it is difficult to recover completely after treatment.
Harmfulness
If respiratory acidosis is not corrected in time, it can lead to serious complications, such as ventricular fibrillation, which can lead to coma and death.
Daily
Daily management
Cessation of smoking.
Food rich in high quality protein and vitamins, such as lean meat and cucumber, should be consumed.
Pay attention to rest and maintain good work and rest habits.
Keep the room well ventilated, pay attention to the changes of weather heat and cold, and keep warm.
Do aerobic exercise in moderation to improve lung function.
Receive health education to understand the knowledge about the disease and correct the wrong perception of the disease in order to relieve anxiety and maintain a good state of mind. Seek help from friends, relatives and healthcare professionals if you are emotionally unstable.
Follow-up and review
During and after treatment, the patient should take medication as prescribed by the doctor to prevent complications and sequelae, and actively treat the primary disease to prevent recurrence.
Prevention
Actively treat diseases that affect pulmonary ventilation, such as chronic obstructive pulmonary disease.
Pay attention to preventing cold and keeping warm to avoid lung diseases caused by cold.