Resp Session 7 Flashcards
What causes TB?
7 closely linked but genetically distinct species of which M.tuberculosis, M.bovis and M.africanum are the most relevant
What is the definition of a clinical case of TB?
Infectious individual who is producing infectious droplets
Is M.tuberculosis fast or slow growing?
Slow-generation time is 15-20 hrs
How is M.tuberculosis spread?
Infected droplets
How easily is M.tuberculosis transmitted?
Infectious dose is 1-10 bacilli but needs prolonged exposure
What virulence factors do M.tuberculosis possess?
Complex waxes and glycolipids in cell wall
Long-chain mycolic acid in wall
Structural rigidity
Able to survive in lower airway macrophages
Acid and alcohol fast
Doesn’t dry in environment
How does an individual exposed to TB not become infected?
Not prolonged enough exposure
Insufficient infecting dose
Mucosal barriers
How does an individual exposed to TB clear the infection?
95% of infections will self cure due to effective immune response
How does an individual exposed to TB contain the infection?
Mounts T-lymphocyte response to intracellular infection in local lymph nodes to form Gohn’s focus and draining lymph nodes
Describe the epidemiology of TB.
1/3 of the world’s population infected with the majority in Africa, Asia and Latin America. In UK leaks of case reports in non-UK born young adults and elderly
How does an individual exposed to TB develop latent infection?
Mycobacteria remain in lung focus and multiply but do not cause damage due to immune control by cell-mediated immune response
How does an individual exposed to TB develop active/primary TB?
Immune destruction of the lungs by response to causative agent –> S/S and visible X-ray changes
How does primary TB usually present?
Usually pulmonary but can be extra-pulmonary in miliary or disseminated TB seen in the larynx, brain, kidney, bone
How does latent TB develop into post primary TB?
Exogenous reinfection/reactivation leads to immune destruction of lungs
Why must all suspected and confirmed cases of TB have an HIV test?
Risk of post primary TB increases with immunocompromise
How is active TB identified?
Blood test usually +ve
CXR abnormal
Smears and cultures +ve
Cough, fever, weight loss
Are pts with primary TB infectious?
Yes
How do the tubercle bacilli differ in active and latent TB?
Active and multiplying in active
Inactive and contained in latent
How does latent TB present?
IFN-alpha results +ve due to immune response
CXR normal
Smears and sputum -ve
No S/S
Are pts with latent TB infectious?
No
Where are caseating granulomas found in TB?
Anywhere there is infection e.g. Lung parenchyma, mediastinal lymph nodes, hilar lymph nodes, liver
When do cavities form in the pathogenesis of caseating granulomas?
When responding cells successfully remove the caseous dead cell material
What are the responding cells present in a caseating granuloma?
Lymphocytes
Epithelioid cells
Langhans cells
How is TB controlled in the community?
Treat index cases –> notify PHE –> contact tracing –> identify primary and secondary cases
Vaccinate and prevent transmission
Which pts fit into the index of suspicion for TB?
Non-UK born HIV Immunocompromise Homeless IV drug users Close, prolonged contacts
What Hx leads to a suspicion of TB?
Ethnicity Recent arrival/travel Contact with TB BCG vaccination Specific clinical features: fever, weightloss, malaise
What S/S are seen in pts with TB?
General chronic inflammation symptoms + Cough Haemoptysis SoB \+/- CXR abnormalities and pleural involvement
What does SoB in a pt with TB indicate?
Pleural effusion
What investigations can be performed in assessment of suspected TB?
CXR Microscopy Culture Speciation Tuberculin skin test Interferon-gamma-releasing assays
How does the CXR of a pt with TB appear?
Ill defined, patchy consolidation with cavitation
Healing –> fibrosis
How many samples are taken for microscopy in TB investigation?
3xearly morning
How long does culture of TB take?
6 weeks
How does speciation investigate TB?
Confirms pathogen identity by examining DNA
Looks at drug sensitivity
How does the tuberculin skin test investigate TB?
Measures cell-mediated immunity to TB antigen (non-specific as shared between strains)
What is a +ve tuberculin skin test?
Visible reaction 2/3 days later
How does interferon-gamma-releasing assay investigate TB?
Measures release of interferon-gamma from interaction between mycobacterium and T-lymph but doesn’t distinguish between latent and active infection
What is the first line treatment for TB?
Rifampicin (R) Isoniazid (H) Pyrazinamide (Z) Ethambutamol (E) 3/4 for 2/12 and then R&H for 4/12 Vitamin D and surgery as needed
When is first line TB treatment extended to 8/12?
In CNS TB
What are the S/E associated with each of the drugs used in first line TB Tx?
R= orange secretions H= peripheral neuropathy and hepatotoxicity Z= hepatotoxicity E= visual disturbance
When are second line treatments used for TB?
Drug resistant strains
What are second line treatments for TB?
Quinolones
How can extra-pulmonary TB present?
Lymphadenitis - scrofula, cervical CNS, abscesses
GI
Peritoneal - ascetic or adhesive
GU - renal disease
Bone and joint disease - spine/Pott’s disease
Meningitis
How can TB spread to the GI system?
Swallowing of tubercles
What is the pathogenesis of miliary TB?
Bacilli –> bloodstream –> widespread infection
When does miliary TB occur?
During primary infection or reactivation
Describe the organ involvement in miliary TB.
Lungs always involved but few resp S/S
Often multiple organ involvement –> meningeal, pericardial, ascites, retinal S/S
Why must compliance be carefully monitored in Tb treatment?
To decrease risk of MDR strains
Describe the epidemiology of lung cancer.
Causes most cancer related deaths worldwide
After pancreatic cancer has worst 5yr survival rate
1 yr survival rate is also poor
Most pts 60-80 y.o.
What are the risk factors for developing lung cancer?
Smoking Asbestos Radon Occupational carcinogens Genetics
What does TNM staging examine?
T: tumour size, number and local invasion
N: nodes involved
M: metastasis in or out of chest
How do the treatment options for lung cancer vary with staging?
Staging ranges from IA to IV
As staging increases treatment moves from surgical with curative intent –> chemo/radiotherapy with curative intent –> palliative care which may include radiotherapy to Tx symptoms
What imagine is used to assess lung cancer?
CXR for all pts
CT scan for metastases
PET scan examines whole body
MRI, ultrasound, bone scan, echocardiogram as necessary
When is a CT scan not carried out in lung cancer?
It curative Tx would not be offered
What methods of tissue sampling are used in lung cancer?
Bronchoscopy
US guided
Surgical
In cases of metastasis in lung cancer would you biopsy the primary tumour or metastasis and why?
Metastasis to prove cancer and assess staging with one invasive procedure
What are the S/S of lung cancer?
Often asymptomatic
Primary tumour: cough, dyspnoea, chest/shoulder pain, weight loss, malaise
Regional metastases: bloated face, LRN obstruction, dyspnoea, dysphagia, chest pain
Distant metastases: CNS symptoms
Hypercalcaemia, hyponatraemia, anaemia, finger clubbing
What type of tumour accounts for ~80% of lung cancers?
Non-small cell: squamous cell carcinoma, adenocarcinoma, large cell carcinoma
What types of tumour form ~20% of lung cancers?
Small cell and rare tumours e.g. carcinoid
What can be used to give a more personalised Tx in lung cancer?
Gene mutations can be detected and utilised to personalise Tx
What are the 6 stages of performance status used when assessing a pt with lung cancer?
0: fully active with no restriction
1: restricted in physically strenuous work
2: ambulatory and self caring. Mobile >50% of waking hours
3: limited self care. Mobile
At what performance stage is no radical Tx considered and therefore no need for biopsy?
3-5
When is surgery used to treat lung cancer?
Mostly non-small cell which gives best chance of cure
What is the difference between neoadjuvant and adjuvant chemotherapy?
Neoadjuvant = before surgery to shrink tumour Adjuvant = after surgery
What treatment options are available for lung cancer?
Surgery Radiotherapy Combination chemotherapy Combination therapy Targeted biological therapies Palliative care
What is the single biggest cause of preventable and avoidable mortality?
Smoking
What cancers are associated with tobacco smoking?
Head or neck Lung Leukaemia Kidney Stomach Pancreas Colon Bladder Cervix
What chronic diseases are associated with tobacco smoking?
Stroke Blindness Gum infection Aortic rupture Heart disease Pneumonia/chronic lung disease/asthma Decreased fertility Hip Fx
What causes addiction in tobacco smoking?
Nicotine
What are markers of addiction?
Use despite know,edge of harmful consequences
Cravings during abstinence
Failure of attempts to stop
Withdrawal symptoms during abstinence
Why does cigarette smoking cause instant satiety of nicotine addiction?
Faster delivery than sprays, gums etc
Describe the +ve reflex loop which occurs in nicotine addiction.
Nicotine on ACh receptors –> dopamine release –> satiety –> chronic exposure to nicotine causes ACh receptors to be upregulated –> increased affinity and functional sensitivity –> decrease in nicotine causes withdrawal –> nicotine on receptors etc
What acts in addition to the +ve reflex loop to provide satiety in cigarette smoking?
Sensation of smoke hitting back of throat
Ask: record smoking status
Advise: health benefits
Act: build confidence, refer for help, prescribe NRT
How should HCPs approach smoking cessation?
What is recommended if smoking cessation cannot be completed by pt?
Harm reduction by smoking less in the long term/abstinence for an agreed period of time/e-cigarettes
Why are e-cigarettes considered to be an effective harm reduction approach to tobacco smoking?
They have variable nicotine content and no tobacco
How long does it take for ACh receptors to desensitise from nicotine binding?
6-12 was
