Delayed resolution pneumonia

　　(I) Etiology

　　According to the definition, delayed resolution pneumonia conforms to the natural course of pneumonia. The discussion of etiology should mainly refer to non-resolving pneumonia and progressive pneumonia. However, there is often overlap between the three, or it is difficult to strictly distinguish, so they are discussed together here.

　　1. Delayed resolution pneumonia is usually defined as immunocompetent pneumonia patients who have fever subsided and symptoms improved after antibiotic treatment, but the resolution of chest X-ray abnormalities is insufficient by 50% by the fourth week. Although the resolution is slow on X-ray, the prognosis of the patients is good.

　　According to the degree of inflammation resolution and fibrosis, some patients may have residual lesions, which can be further divided into resolving pneumonia with organization, organizing pneumonia, and post-inflammatory pseudotumor.

　　2. Non-resolving pneumonia or chronic pneumonia refers to the persistence of clinical symptoms and X-ray abnormalities for ≥1 month in immunocompetent pneumonia patients who have received what is considered effective antibacterial treatment.

　　3. Progressive pneumonia refers to the abnormal extension of X-ray within the expected time and the deterioration of clinical symptoms, mainly caused by bacterial resistance or special pathogen infection.

　　4. Pathogen Factors

　　(1) Special pathogen infection: especially tuberculosis or atypical mycobacterial lung disease, viral pneumonia, fungal pneumonia, and lung parasitic (protozoan) disease. Certain regional infectious diseases or infectious diseases, including zoonotic diseases, can cause lung lesions, and the epidemiological history should be paid special attention to. The current problem in China is that the diagnostic technology for viral and fungal pneumonia is lagging, and the vigilance for pulmonary tuberculosis, lung fluke disease, and other diseases is not high, which often leads to misdiagnosis and missed diagnosis.

　　(2) Bacterial resistance: Its confirmation depends on precise bacteriological diagnosis and resistance testing. Clinical reference factors that may lead to resistance include a history of antibiotic treatment within 6 months, a history of pneumonia within 1 year, a history of hospitalization within 3 months, hospital-acquired pneumonia, etc.

　　5. Host factors Underlying diseases (COPD, diabetes, alcoholism, etc.) and various primary or secondary immune impairments may cause pneumonia to resolve slowly, not resolve, or progress.

　　6. Inappropriate treatment, inappropriate drug selection, and insufficient dosage are one of the most important factors affecting the efficacy and absorption speed of pneumonia treatment. Penicillin treatment for Streptococcus pneumoniae pneumonia and sulfamethoxazole (SMZco) treatment for Pneumocystis carinii pneumonia cannot be given at conventional doses; otherwise, it may cause underdosing. Aminoglycoside antibiotics have poor penetration ability into lung tissue, and may still need to be administered according to the traditional dosage regimen in the treatment of Pseudomonas aeruginosa pneumonia, with a single daily dose, and there is still a lack of research on the use of a single daily dose in pneumonia patients. In addition, drugs are not easily reached at the local lesion, especially in lung abscess and empyema, ensuring effective drainage is very important. Active treatment should be given. If pneumonia absorption is slow due to inappropriate treatment, drugs and reasonable administration schedules should be selected rationally based on the pathogen and the spectrum, antibacterial activity, pharmacokinetics/pharmacodynamics characteristics of antibacterial drugs. If antibacterial chemotherapy is sufficient and there is a reasonable basis to predict that most of the bacteria have been killed, the use of physical therapy such as infrared therapy may help reduce residual lesions.

　　(II) Pathogenesis

　　Inappropriate drug selection and insufficient dosage are one of the most important factors affecting the efficacy and absorption speed of pneumonia treatment.

　　Pneumonia most commonly occurs in individuals with comorbidities or underlying diseases. Community-acquired pneumonia (CAP) in healthy individuals without comorbidities is usually absorbed on X-ray within 4 weeks, while only 20% to 30% of patients with comorbidities have complete absorption and clear inflammation on X-ray within 4 weeks. Comorbidities increase with age, such as in CAP, the incidence of COPD in individuals under 50 years of age is 30% in CAP over 50 years of age.

　　Risk factors that affect the absorption of X-ray include sepsis, fever or leukocytosis exceeding 6 days, age over 50, and complications such as COPD or alcoholism (Table 1).

　　Haemophilus influenzae is a relatively common pathogen in elderly and smoker's pneumonia. Non-capsulated strain infections have a low mortality rate, but the course of the disease is prone to become protracted, and it can be complicated with chronic feverish tracheobronchitis. The natural course of Haemophilus influenzae infection is rarely known. Risk factors that affect absorption include COPD, malignant tumors, diabetes, alcoholism, and immunosuppression. Legionella is an important pathogen in severe CAP, and its absorption rate is significantly slower than that of other pathogens. Factors include smoking, alcoholism, age over 65, hormone-induced immunosuppression, diabetes, bone marrow transplantation, etc. The radiological lesions of Mycoplasma pneumoniae pneumonia generally last for 2 to 4 weeks, depending on antibiotic treatment. 40% of patients are completely absorbed by the fourth week, while 90% of patients have completely resolved on X-ray by the eighth week. The radiological absorption of Chlamydophila pneumoniae is between that of mycoplasma and legionella. Factors causing delayed resolution of pneumonia include complications.

　　Ageing, in addition to increasing complications, can itself be an independent factor affecting the absorption of pneumonia. 90% of pneumonia in young people under 50 years of age resolves within 4 weeks; in contrast, only 30% of CAP in patients over 50 years of age without complications can be absorbed within 4 weeks.

　　To determine whether the resolution of pneumonia is delayed or not, it is first necessary to understand the natural course of pneumonia, but to date, there is little known about it. The judgment of the natural course of pneumonia includes both clinical and X-ray aspects. Although the clinical criteria are preliminary and rough, they are still the most basic and indispensable. The currently used clinical indicators include fever, rales, cough, leukocyte count, PaO2, and C-reactive protein. Among these indicators, C-reactive protein recovers the fastest (1-3 days), the improvement and disappearance of cough are relatively slow (4-9 days), and other indicators are in the middle, such as fever for 2-5 days, lung rales for 3-6 days, and leukocyte count for 3-4 days. Delayed resolution or non-resolution of pneumonia is not based on clinical symptoms, but on the dispersion speed of pulmonary infiltration in imaging (mainly routine X-ray chest film). There are many factors affecting the resolution of pneumonia, including complications, age, severity of the course, and pathogens, etc.

　　As for infectious pneumonia itself, the reasons for the resolution exceeding the expected time are as described above. The key to treatment is to identify the cause, the most important being the etiological diagnosis, thereby selecting sensitive antimicrobial treatment. The main factors affecting the resolution of pneumonia should be distinguished and actively removed.

　　1. Antimicrobial treatment, also known as 'root treatment', which is the most important. Special attention should be paid to the correct and rational use of antibiotics.

　　2. General supportive therapy: including adequate intake of calories, nutrition, and protein, maintaining the balance of water and electrolytes in the body.

　　1. Laboratory examination

　　Leukocyte count increases for 3 to 4 days.

　　2. Other auxiliary examinations

　　The severity of CAP affects the absorption speed of pneumonia. Severe CAP generally requires about 10 weeks for absorption on X-ray, while mild to moderate CAP absorption takes 3 to 4 weeks. The absorption speed of pneumonia caused by different pathogens and clinical improvement can vary greatly. Pneumococcal pneumonia in patients without complications shows a rapid clinical improvement. According to research, fever subsides very quickly, and only about 6% have a duration of more than 20 days; only 8% have abnormal signs after a month, mainly seen in patients with severe illness and multi-lobar lesions. However, the absorption on X-ray is relatively slow, and 20% to 30% of patients do not show absorption after one week of follow-up, and there is often an initial deterioration. In summary, the natural course of pneumonia or the dispersion time of X-ray may present a normal distribution curve and be affected by many factors.

　　1. Walnut

　　Walnuts have the functions of benefiting the lung and asthma, nourishing the stomach and aiding digestion, moistening the intestines and promoting defecation, regulating the liver and blood, and tonifying the kidney and brain.

　　2, Apple

　　Apples are also good for the lungs. Eating 5 or more apples per week can improve the respiratory system and lung function. Moreover, eating an apple every day can make you less likely to get sick. Apples contain a large amount of flavonoids called quercetin, which can protect the lungs from pollution and the harmful effects of smoking. Onions, tea, and red wine also contain quercetin.

　　3, Honey

　　Modern medicine has proven that honey is effective for neurasthenia, hypertension, atherosclerosis of the coronary arteries, lung diseases, and so on. Regularly taking honey in autumn is not only beneficial for the recovery of pneumonia but also can prevent the harm of autumn dryness to the human body, playing a role in moistening and nourishing the lungs.

　　4, Pear

　　Pears have the effects of moistening the lungs and clearing heat, resolving phlegm and reducing fire, clearing the stomach and relieving heat, nourishing the yin and generating fluid, nourishing the kidneys and replenishing deficiency, and moistening the intestines and promoting defecation. It has a unique and obvious effect on cough and expectoration caused by lung diseases. The famous 'pear syrup candy' is a cough medicine made mainly from sweet pears.

　　(I) Treatment

　　Penicillin treatment for Streptococcus pneumoniae pneumonia and sulfamethoxazole/trimethoprim (SMZco) treatment for Pneumocystis carinii pneumonia cannot be given at conventional doses; otherwise, it will cause underdosing. Aminoglycoside antibiotics have poor penetration ability in lung tissue, and may still need to be administered according to traditional dosage regimens in the treatment of Pseudomonas aeruginosa pneumonia. There is still a lack of research on the use of a single daily dose in pneumonia patients. In addition, drugs are not easily reached at the local lesion, especially in lung abscess and empyema, ensuring effective drainage is very important. Active treatment should be given, and if the absorption of pneumonia is slow due to improper treatment, reasonable drugs and dosing regimens should be selected based on the pathogen and the spectrum, antibacterial activity, pharmacokinetics/pharmacodynamics characteristics of antibacterial drugs. If antibacterial chemotherapy is sufficient and there is a considerable reason to predict that most of the bacteria have been killed, physical therapy such as infrared therapy can be tried to possibly reduce the residual lesions.

　　(II) Prognosis

　　There are reports that 71% of Haemophilus influenzae pneumonia occurs in severely immunosuppressed individuals, and 55% of invasive infection cases occur in individuals over 50 years old. This invasive infection is often caused by capsulated strains, prone to complications of sepsis, with a high mortality rate.