Gas Exchange/TB Flashcards
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Tuberculosis - Mycobacterium tuberculosis
A disease caused by a bacterium called Mycobacterium tuberculosis. The bacteria usually attack the lungs, but TB bacteria can attack any part of the body such as the kidney, spine, and brain
> If not treated properly, TB disease can be fatal
> Spread can happen to other body parts through the lymphatic system
Epidemiology
- Potentially life-threatening respiratory infection
- Caused by organism M. tuberculosis
- Infects 1/3 of world’s population
- Populations living outside of the US, low socioeconomic groups that have obstacles in accessing healthcare, and racial and ethnic minorities have highest incidence
- TB disproportionately affects blacks, Hispanics, and Asians; is also a persistent problem in the homeless and incarcerated populations
Transmission is Airborne - Pathophysiology
- Transmitted by aerosolized droplets inhaled from the coughing or sneezing of an infected individual; can remain suspended in air for several hours
- Focused studies documenting transmission of active tubercle bacilli have shown that in close-contact situations, those whose sputum is infected with AFB are most likely to transmit the infection
REMEMBER
! TB is spread by AIRBORNE particles and requires AIRBORNE precautions
- Particles are spread by talking, laughing, coughing, sneezing, or singing
! DO NOT CONFUSE this with droplet precautions
For example, patients with the flu may be on droplet precautions; i.e. keep 3 ft away
- This is AIRBORNE. Droplets go airborne and can stay suspended in the air for hours.
> N95 for nurse; use of negative pressure rooms
TB is NOT spread by…
- Shaking someone’s hand
- Sharing food or drink
- Touching bed linens or toilet seats
- Sharing toothbrushes
- Kissing
Interestingly, TB exposure does NOT usually cause infection
The Process
- The bacilli is inhaled
- It multiplies freely in the bronchi or alveoli
- This causes an exudative nonspecific pneumonitis
- Acquired immunity prevents further growth
- Lesions resolve leaving little or no bacilli
- Cell-mediated immunity develops 2-10 weeks after infection
- Only a small percentage of people initially infected actually develop active TB!
- Greatest risk for active TB in HIV negative population is within 2 years after infection
- About 1/3 of the world’s population is infected with tuberculosis (TB) bacteria. Only a small proportion of those infected will become sick with TB
- People with a weakened immune system have a much greater risk of falling ill from TB
- A person living with HIV is about 20-30x more likely to develop active TB
- A third of the total HIV positive population are infected with TB and it’s currently the leading killer of those with HIV infections
Primary infection may be so small that it doesn’t show up on CXR
- The inflammation created by the tubercle in the lung becomes surrounded by collagen, fibroblasts, and lymphocytes
- The necrotic tissue or caseation necrosis, turns into a granular mass in the center of the lesion
- If this shows on CXR it’s called a Ghon tubercle or primary lesion
- These lesions either calcify or liquefy. If they liquefy, they can travel through the lymph and go to other parts of the lung
- If it travels to the blood, it can spread to other parts of the body
At Greatest Risk - Weakened Immune Systems
- HIV infection (virus that causes AIDS)
- Substance abuse
- Silicosis (is a respiratory disease caused by inhaling silica dust)
- DM
- Severe kidney disease
- Low body weight
- Organ transplants
- Head and neck cancer
- Medical treatments such as corticosteroids or organ transplant
- Specialized treatment for RA or Crohn’s disease
Those who have been recently Infected
- Close contacts of a person with infectious TB disease
- People who have immigrated from areas of the world with high rates of TB
- Children less than 5 years of age who have a positive TB test
- Groups with high rates of TB transmission, such as homeless persons, injection drug users, and persons with HIV infection
- Those who work or reside with people who are at high risk for TB in facilities or institutions such as hospitals, homeless shelters, correctional facilities, nursing homes, and residential homes for those with HIV
TB - Exposure
- A brief exposure doesn’t usually cause infection
- Close, repeated exposures, or those who are immune-compromised may develop an infection; this may develop into either active or latent disease
Some people with latent disease may develop active disease later in life
Latent TB infection
- In those individuals with an intact immune system, a granuloma forms and limits further proliferation and spread of the Mycobacterium
- Individuals with a weakened immune system response are unable to control the multiplication of Mycobacterium. Granuloma formation is initiated but is unable to progress to calcification and results in a primary tuberculosis infection (PTBI)
Symptomatic TB infection, referred to as primary progressive TB infection (PPTBI), develops in a very small percentage of individuals who have been exposed to the bacterium. Initial symptoms are relatively nonspecific and consist of fatigue, weight loss, and night sweats
Drug-resistant M. tuberculosis (MDR-TB) can be mono-drug or poly-drug resistant. This means that 1 or more of the first-line medications used for the treatment of TB are not effective
Assessment: Symptoms = What are they? (depends if it’s active or latent)
Person with TB Disease (Infectious)
- Has a large amount of active TB bacteria in his/her body
- May spread TB bacteria to others
- May feel sick and may have symptoms such as a cough, fever, and/or weight loss
- Usually has a TB skin test or TB blood test reaction indicating TB infection
- Radiograph may be abnormal
- Sputum smears and cultures may be positive
- Needs treatment for TB disease
- May require respiratory isolation
- Is considered a TB case
Person with LTBI (Infected)
- Has a small amount of TB bacteria in his/her body that are alive, but inactive
- Cannot spread TB bacteria to others
- Does not feel sick, but may become sick if the bacteria become active in his/her body
- Usually has a TB skin test or TB blood test reaction indicating TB infection
- Radiograph is typically normal
- Sputum smears and cultures are negative
- Should consider treatment for LTBI to prevent TB disease
- Does not require respiratory isolation
- Not a TB case
Goal: Cure the patient and minimize exposure
Management -
- Diagnosis by lab testing, skin test, and CXR
- Mantoux tuberculin skin test
- Treatment goal to cure patient and minimize exposure
Diagnostic Studies
- CXR/CT scans
- Skin testing - Mantoux test and/or serum TB testing
- Bronchoscopy
- Mediastinoscopy
- PFT’s
- Sputum tests for AFB
- ABG’s (perhaps r/t respiratory alkalosis from anxiety, tachypnea, fever, tachycardia)
The goals of treatment for TB infection are 1) to cure the patient and 2) to minimize the transmission of M. tuberculosis to other persons
Purified Protein Derivative (PPD) - Intradermal Injection
- May turn red (erythema), but a positive test must have induration (an area of hardness) greater than 5mm reaction should be measured (palpable, raised, hardened area or swelling >5); reader should not measure erythema (redness)
- Diameter of the indurated area should be measured across the forearm (perpendicular to the long axis)
! There are 3 categories of induration for positive
If you have a patient with HIV, positive for them will be >__mm
For us, nurses in healthcare fields, as employees, we would fall into the >__mm category and those with absolutely no risk factors, no exposure, they would fall into the >__mm category
5
10
15
If the skin test is positive, then the patient gets a CXR
If the CXR shows signs of TB, then a sputum culture is obtained
BCG (Bacille Calmette-Guerin) is not normally administered in the US, but many foreign-born persons have received it; this may effect PPD testing if patient has received this in the past
Assessments / Complications
- Public health outbreak
- Death
- Resistant strains
> Multi-drug resistant (MDR-TB)
> Extensive drug-resistant (XDR-TB)
