Pneumonia and Respiratory Infections Tutorial Flashcards
Why is pneumonia common?
Many different ways to acquire it: community, hospital or ventilator acquired
What is the difference between bronchitis, bronchiolitis and pneumonia?
Bronchitis = infection of the bronchi Bronchiolitis = infection of the bronchioles Pneumonia = infection of the alveoli
Why, physiologically, does pneumonia present a more challenging disease than bronchitis and bronchiolitis?
Affects gas exchange more significantly
Aveoli nearer to blood supply - directly disrupts gas exchange via cellular infiltration or fluid leakage into the airspace over substantial area of the respiratory tract preventing uptake of O2 and removal of CO2
What is the first immune cell recruited to the site during acute bacterial pneumonia?
Neutrophils
Rapid release of neutrophil chemokines e.g. IL-8
Alveoli have specialised resident immune cells = alveolar macrophages
How might this change during prolonged pneumonia?
Prolonged inflammation = accumulation of lymphocytes (primary cells), macrophages and monocytes at the site of inflammation
If the innate immune system is not sufficient to rapidly clear an infection from the alveoli then adaptive immune responses will develop to clear the infection
Case Study: Mr AH
77M - lives with son, daughter-in-law and their 2 young children. Past history of diabetes and is on metformin
5 day history of productive cough, right sided pleuritic chest pains and fevers
On examination he was lethargic, fatigued and memory impairment
O2 sats = 86 % on air, Temp = 38.0C, HR 110, BP = 92/59 mm Hg, RR = 26/minute and crepitations could be heard at the right mid zone
What risk factors does he have for the development of pneumonia?
Think about demographic and lifestyle factors, social factors, medical history and medications; and what signs and symptoms indicate potential pneumonia?
Risk factors: Diabetes Age Male In contact with young children
Signs and symptoms: Confusion - lack of lucidity Low BP Fever Cough Chest pain Rapid breathing Low pO2 Crepitations
The CRB-65 (in primary care) and CURB-65 (in secondary care) scores are commonly used to assess the severity of pneumonia.
What is the CRB-65 score for Mr AH and what course of action would you take for each?
2-3 points > suitable for hospital referral / admission
Mr AH is admitted to hospital and a chest radiograph is carried out. Comparing with a healthy chest radiograph image what does Mr AH’s chest radiograph show, and what does this indicate may have happened to the lungs from a physiological and cellular perspective?
Opacity in the right upper lobe - indicates fluid and cellular infiltration into the alveolar space of the right upper lung
Blurring towards the edges of the lungs - indicates fluid in the pleura
Tracheal deviation - associated with a thyroid enlargement
Mr AH tested positive for Streptococcus pneumoniae and was treated with a 7 day course of amoxicillin and clarithromycin.
Explain and discuss the treatment choice and length.
Gram-positive bacteria = susceptible to beta-lactams that bind proteins in the bacterial cell wall to prevent transpeptidation and bacterial replication
Case Study 2: Mrs BK
64F - lives on her own. Current smoker, history of COPD and is on Seretide and Salbutamol.
Experiencing 10 days of symptoms progressing from a cold to chest pain and fevers.
O2 sats 92% on air, Temperature = 380C, HR = 80, BP = 110/80 mm Hg and RR = 17/minute
What risk factors does she have for the development of pneumonia?
Think about demographic and lifestyle factors, social factors, medical history and medications; and what signs and symptoms indicate potential pneumonia?
Risk Factors:
COPD
Smoker
Seretide (inhaled corticosteroid)
Signs and symptoms:
Cough
Fever
Low pO2
The CRB-65 (in primary care) and CURB-65 (in secondary care) scores are commonly used to assess the severity of pneumonia.
What is the CRB-65 score for Mrs BK, and what course of action would you take for each?
0 points > suitable for home treatment with antibiotics
Mrs BK tested positive for Chlamydia pneumoniae and was treated with a 7-14 day course of clarithromycin.
Explain and discuss the treatment choice and length.
Penicillin resistant due to difference in cell wall structure
Gram neg = longer treatment time as they replicate slower
Clarithromycin = inhibits the 50S ribosomal subunit limiting protein synthesis
Case Study: Mr GS
61M - lives with wife and has 2 adult children.
Presented at hospital after 6 days of cough, aches, shortness of breath and fever. He was lucid and aware.
O2 sats = 85%, Temp = 38.60C and RR = 32/minute.
Given oxygen, penicillin and clarithromycin but no improvement. Chest radiography 8 days post symptom onset and 11 days post symptom onset showed the following:
Describe Mr GS’s chest radiography compared to a normal image and between days 8 and 11.
Shows bilateral fluffy opacities at both day 8 and 11 (like white cotton balls taking up the lungs in the x-ray)
Increase in density, profusion and confluence on day 11 image, and most marked in the lower lungs
Also found changes consistent with accumulation of fluid in the pleural cavity at day 11
What would the next stage of supportive treatment be?
Mr GS has been intubated and ventilated by day 11
Requires invasive mechanical ventilation
ALTERNATIVELY: continuous positive airway pressure (CPAP) or if available, veno-aterial-venous extracorporeal membrane Oxygenation (VAV-ECMO).
Despite being placed on mechanical ventilation Mr GS died 20 days after symptom onset
Posthumous diagnosis shows SARS-CoV-2. Study on COVID shows:
Dexamethasone improves mortality when given with invasive mechanical stimulation and oxygen, but not when no oxygen is received.
Based on this data, at what stage would you have chosen to administer dexamethasone to Mr GS?
Discuss why it may be effective at this time but not so if administered at other stages?
And what is the mechanism of action?
Administer when Mr GS required oxygen, or when he was put on ventilation
Dexamethasone (steroid) works by supressing the immune inflammation and thus further damage to the lungs
If administered too early, it may stop immune response from clearing out the virus
