HIV-Associated Respiratory Infections

Introduction to HIV-related respiratory infections Human immunodeficiency virus (HIV) is also known as HIV. HIV mainly destroys CD4T cells, causing damage to cellular immune function. Eventually, it is accompanied by serious opportunistic infections and tumors. The disease spreads rapidly, the incidence is slow, and the mortality rate is extremely high. basic knowledge The proportion of illness: 0.001% Susceptible people: no specific population Mode of transmission: sexual transmission, blood transmission, mother-to-child transmission complication:

Causes of HIV-related respiratory infections

(1) Causes of the disease

In 1984, Murray analyzed a multicenter study conducted by the American Heart, Lung, and Blood Institute. HIV is a single-stranded positive-strand RNA virus, and its RNA genome, reverse transcriptase, and viral-encoded proteins form the core.

(two) pathogenesis

HIV is a single-stranded positive-strand RNA virus. The RNA genome, reverse transcriptase and virus-encoded proteins form the core. When HIV enters the body, its membrane glycoprotein pg120 is highly compatible with the helper T lymphocyte (CD4) surface receptor. And enter the cell to replicate, propagate and destroy the helper T cells (T4H); HIV-infected CD4 cells can fuse uninfected CD4 receptors, form megakaryocytes, reduce the number of TH cells, and after being infected by HIV, the body can pass Antibody or non-antibody-mediated cytotoxic T lymphocyte killing causes CD4 cells to die, resulting in decreased CD4 cells and impaired function, such as decreased response to specific antigens and non-specific antigens, and helper B lymphocytes to produce antibodies. Reduced ability, HIV also inhibits non-specific defense mechanisms such as phagocytic phagocytosis and NK cells. In short, the immune function of HIV/AIDS patients, especially cellular immune mechanisms, is impaired, which is the main cause of infection in the body. the reason.

The incidence of pulmonary infection in HIV/AIDS patients is high. The reason for this is not fully understood. Recently, it has been found that alveolar macrophages are also one of the target cells for HIV attack, and the number of cells is not reduced but function (antigen presentation, etc.). Decreased; the proportion of T4H/TS in bronchoalveolar lavage fluid decreased, Ts increased, and HIV viral load was linearly correlated with CD4 cell depletion, while CD4 cells in blood predicted the possibility of immunodeficiency and opportunistic infection of the lung, infection An important indicator of the type and its pathogen spectrum.

The number of CD4 cells in HIV/AIDS patients is closely related to the pathogen type of lung infection. For example, avian-intracellular mycobacteria are mainly found in CD4 counts <50/l, CD4 counts and major lung infections. The type relationship is shown in Table 3.

HIV-related respiratory infection prevention

Chemoprevention of opportunistic infections in HIV/ADIS patients has accumulated some experience in recent years, but there are still different perspectives.

1. The current status of HIV/AIDS is estimated to be about 6 million people living with HIV worldwide, and 14 million AIDS deaths have been reported so far. In 1998, there were approximately 5.8 million new HIV-infected people, an increase of about 10% over 1997. In some parts of southern Africa, the proportion of HIV-infected adults is as high as 20%. Since the discovery of the first case of AIDS in China in 1985, the rate of HIV infection has been low. The rate of HIV transmission has increased significantly in the past five years. In 1997, there were 9333 cases of HIV infection in the country, including 281 cases of AIDS. About 50% of HIV-infected people develop AIDS within 10 years without treatment or intervention after HIV infection. The adverse effects on social and economic development brought about by HIV/AIDS are extremely serious. The prevalence of global HIV and its infections in 1998 is shown in Table 1.

2. HIV transmission pathways The main routes of transmission of HIV infection are: 1 sexual transmission: homosexual and heterosexual sexual intercourse can spread HIV; 2 blood transmission: use of dirty syringes, blood transfusions or blood products; 3 mother-to-child transmission: pregnant women with HIV infection HIV is transmitted vertically to the baby through the placenta or postpartum feeding; 4 other: if the medical staff cares for HIV/AIDS patients; the experimental operator or medical staff is accidentally stabbed by sharp blood vessels such as blood of HIV/AIDS patients, etc. .

3. The spectrum of HIV/AIDS-related respiratory infections and their changes In 1984, Murray analyzed the multicenter study conducted by the American Heart, Lung, and Blood Institute. Pulmonary complications occurred in 441 (41%) of 1064 HIV/AIDS cases in 6 hospitals, accounting for 92% of infections, of which Pneumocystis carinii (PCP) was 85%. In 1981, the authors reported an increase in infection with pathogens other than PCP, including purulent bacterial pneumonia. Since the 1990s, SMZco and Pentamone aerosol inhalation have been recommended in the United States to prevent PCP from achieving good results. The spectrum of infection changed, and although PCP was still the first in composition, bacterial infections increased significantly.

HIV-related respiratory infection complications Complication

Concurrent with a variety of serious bacterial, fungal and/or viral infections.

Symptoms of HIV-related respiratory infections Common symptoms HIV infection, dyspnea, extrapulmonary symptoms, hypotension, purulent sputum, dry cough, lung infection, tachycardia, sepsis, cyanosis

Symptom

Respiratory symptoms in patients with HIV/AIDS are common, and the incidence increases with the decrease of CD4 count. Huang et al reported that in 12,000 follow-up patients, cough accounted for 27%, dyspnea accounted for 23%, and fever accounted for 9%. In general, clinical manifestations lack diagnostic specificity, because other complications of HIV-infected patients can cause respiratory symptoms such as cough and dyspnea, but some clinical symptoms are still helpful for suggesting diagnostic clues, such as the nature of cough needs to be differentiated. Is cough and purulent sputum or dry cough, the former usually need to consider bacterial pneumonia, the latter is more common with PCP, Selwyn and other studies found that cough and yellow sputum as an independent factor of the odds ratio (OR) = 2.5, 95 %CI=1.15.4; P=0.03; on the contrary, dry cough supports PCP, its OR=2.1, 95%CI=1.04.9, P=0.008, the duration of symptoms also has certain reference value, Streptococcus pneumoniae or Haemophilus influenzae Pneumonia often begins with acute symptoms. The symptoms persist for 3 to 5 days. PCP usually has subacute onset. Typical symptoms last for 2 to 4 weeks. Kovacs et al reported that the clinical symptoms of HIV and PCP lasted for an average of 28 days. Fever and weight loss suggestive Sexual or disseminated disease Such as mycobacterial or fungal infections, contribute to the diagnosis of pulmonary symptoms, patients with respiratory symptoms and headache such as CD4 <200 / l, should consider Cryptococcus neoformans pneumonia and meningitis.

2. Signs

HIV complicated with pulmonary infection can have fever, tachycardia, cyanosis, hypotension often suggest an acute course (such as bacterial sepsis), blood oxygen saturation decline can be one of the important indicators of serious disease, there are reports of blood oxygen Saturation is a sensitive indicator for detecting PCP, but lacks specificity. 50% of PCP lungs have no abnormalities in lung examination. Some patients can smell inspiratory (phase) bilateral slaps. Bacterial pneumonia can have consolidation or chest cavity. Fluid accumulation, abnormal brain and lung lesions, C. neonatal cryptococcal infection when CD4 <200 / l; central nervous system symptoms combined with abnormal lung signs, suggesting that Toxoplasma infection may be.

HIV-related respiratory infections

1. HIV-infected patients with pulmonary bacterial infections have a higher white blood cell count than the baseline value

(Because of HIV infection, the white blood cell basis is often lower than normal), with the left side of the nucleus, the risk of lung bacteria and fungi (such as Aspergillus) infection is significantly increased when HIV is associated with granulocyte deficiency.

2. Serum LDH

Serum LDH is usually elevated at PCP, but it can be elevated in other lung diseases (such as bacterial pneumonia and tuberculosis) or non-pulmonary diseases, so it lacks specificity, and LDH has high sensitivity in patients with severe PCP. On the contrary, PCP with milder condition has poor sensitivity to LDH, and LDH value is associated with PCP treatment response and prognosis.

3. Arterial blood gas

HIV-infected patients with pulmonary infection usually have arterial blood gas abnormalities, such as hypoxemia, alveolar-arterial oxygen partial pressure difference [PO2 (Aa)] increased, carbon dioxide alkalosis, but lack of diagnostic specificity, for PCP , it is helpful to judge the prognosis and decide whether to accept admission, or whether to use glucocorticoids.

4. Chest X-ray examination

Chest X-ray can provide clues for the diagnosis of HIV lung infection and provide a reference for the choice of diagnostic procedures. Bacterial pneumonia is more common with localized lesions (71%), diffuse relatively rare (29%); multi-lobular lesions account for 54% Interstitial and nodular lesions accounted for 17% and 10%, respectively, and some patients may have a cavity (1%), pleural effusion (7%), lymphadenopathy (2%), pulmonary tuberculosis infection Chest X-ray findings are related to peripheral blood CD4 counts. Overall, the proportion of miliary changes is low, only 6% to 9%, if CD4 <200/l, 29% of cavities, 58% of non-cavitary lesions, and chest 11% effusion, 20% lymph node enlargement; CD4 200-390/l, 44% of cavities and non-cavitary lesions, 11% pleural effusion, 14% lymph node enlargement; CD4 >400/l, cavity type 63%, non-cavitating 33%, pleural effusion 3%, no lymphadenopathy, Pneumocystis carinii pneumonia mostly bilateral or diffuse distribution, interstitial or mixed type change 88%, alveolar type 12%, combined cysts 7% and honeycomb-like lesions 4%, 1/3 of patients with cytomegalovirus pneumonia no abnormalities in chest X-ray examination, the distribution is mostly bilateral, accounting for 71%, the lesion is Reticulated granules 33%, alveolar type 22%, nodular type 11%, concurrent cavities 11%, cysts 6%, pleural effusion 33%, lymph node enlargement 11%, neonatal cryptococcal pneumonia mostly diffuse distribution 76% The lesions were 76% of interstitial or mixed type, 19% of alveolar type, 5% of nodular type, 11% complicated with cavities, 11% of lymph nodes, and 5% of pleural effusion.

5. Chest CT examination

For the differential diagnosis of multiple lesions in the lungs, if most of the nodules are less than 1cm in diameter and distributed along the central bronchus, most of them are opportunistic infections of the lung; if accompanied by intrathoracic lymphadenopathy, and nodules More than 1cm is considered new organisms, Kaposi sarcoma often accompanied by widening of the blood vessels around the bronchi in addition to the nodules in the lungs.

6. Gallium 67 lung scan

It is highly sensitive (99%) for patients with HIV/AIDS complicated with PCP diagnosis, but lacks specificity (see PCP section for details).

7. Pulmonary function test

Carbon monoxide diffusion (DICO) is a very sensitive indicator for detecting PCP, but lacks specificity. If DLCO is normal, the probability of PCP is very small. If the chest radiograph is normal or no change, if the DLCO is less than the predicted value of 75%, diagnose PCP. The sensitivity is 90% and the specificity is only 53%.

Diagnosis and identification of HIV-related respiratory infections

Diagnostic criteria

1. Cheats and confirmation of HIV infection: China has entered the rapid rise of HIV infection epidemic, and the clinical experience and knowledge of clinicians in diagnosing HIV/AIDS is relatively insufficient. Therefore, all patients with clinically specific infections should be alert to HIV/ AIDS possibilities, for high-risk individuals (multi-sex couples with homosexuality and heterosexuality, history of intravenous drug addiction, history of imported blood products or blood transfusions without HIV testing, history of other sexually transmitted diseases, residence in high-population countries or regions) In particular, it is necessary to be vigilant. It is necessary to collect serum samples and send them to specialized prevention and treatment institutions for HIV screening and confirmation tests.

2. Laboratory and auxiliary examination of HIV/AIDS complicated with lower respiratory tract infections

(1) White blood cell count: HIV-infected patients complicated with bacterial infection of the lungs, the white blood cell count is higher than the basic value (because of the HIV-infected patients whose white blood cell base value is often lower than the normal value), with the left shift of the nucleus, HIV with granulocytes In the absence of lung disease, the risk of bacterial and fungal (such as Aspergillus) infection is significantly increased.

(2) Serum LDH: PCP is usually elevated in serum LDH, but can also be elevated in other lung diseases (such as bacterial pneumonia and tuberculosis) or non-pulmonary diseases, so lack of specificity, LDH in patients with severe PCP With higher sensitivity, the less severe PCP is less sensitive to LDH, and LDH is associated with PCP response and prognosis.

(3) arterial blood gas: HIV-infected patients with pulmonary infection usually have arterial blood gas abnormalities, such as hypoxemia, alveolar-arterial oxygen partial pressure difference [PO2 (Aa)] increased, low carbon dioxide alkalosis, but Lack of diagnostic specificity, for PCP, it is helpful to judge the prognosis and decide whether to accept admission, or whether to use glucocorticoids.

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