Investigation findings Flashcards
What do these stand for? FEV1 FVC PEFR
FEV1 = Forced Expiratory Volume in one second
FVC = Forced Vital Capacity
PEFR = Peak Expiratory Flow Rate
Define what these each mean:
FEV1
FVC
PEFR
FEV1 - Forced Expiratory Volume in 1 second: VOLUME of gas forcibly exhaled from full inspiration in 1 second
FVC - Forced Vital Capacity: Total VOLUME of gas forcibly exhaled from full inspiration
PEFR The maximum flow RATE generated during a forced expiration from full inspiration.
List THREE factors which affect the peak expiratory flow readings (apart from obstructive airways disease)
Age
Sex
Height
Others = Race, smoking history, respiratory muscle strength and effort, time of day, effort made by patient in performing the test
Give TWO indications for performing a PEFR on a patient.
Screening for airflow obstruction
Monitoring of asthma and response to treatment
Aid assessment of acute asthma attack
Name TWO limitations of using PEFR monitoring
Technical - Effort-dependent, Does not reflect small-airway obstruction, Potential for unrecognised device malfunction
Clinically useful? - Cannot substitute for spirometry in initial diagnosis, Inaccurate measurement may prompt overmedication, Overreliance may delay seeking medical advice
State the current British Thoracic Society PEFR percentages which aids the classification of patients with moderate, severe and life threatening acute asthma attacks
% of best or predicted best PEFR score:
Moderate attack = >50 - 75%
Severe attack = 33-55%
Life threatening = <33%
At what age do lung function tests become unreliable
Under 5
Name TWO obstructive disorders of lung function
Obstructive:
- Asthma
- COPD
- Brochiectasis
- CF
- Lung Ca
- Post TB
Name TWO restrictive conditions of lunch function
Pulmonary:
- fibrosis
- Abestosis
- pul oedema
- Parenchymal tumours
- Lobectomy
Extrapulmonary:
- Kyphosis/chest wall deformities
- Obesity
- Pregnancy
- Neuromuscular disorders
- RA
What FEV1, FVC and FEV1/FVC results would you expect in obstructive lung conditions?
FEV1 - reduced
FVC - Reduced or normal
FEV1/FVC - Reduced
What FEV1, FVC and FEV1/FVC results would you expect in Restrictive lung conditions?
FEV1 - Reduced or normal
FVC - Reduced
FEV1/FVC - normal or increased
What is used to grade the severity of COPD?
FEV1 % of predicted eg. mild is >80% predicted Severe is 30-49% predicted
List THREE clinical features which help us to differentiate COPD and asthma.
What conditions may cause an acidosis due to too much acid in the blood/too little buffer?
DKA, respiratory acidosis, lactic acidosis and renal impairment
What conditions can cause an alkalotic blood gas?
Too little acid: hyperventilation, persistent vomiting
Overdose on antacids (too much buffer)
Acidosis with a raised PaCO2 is a…
Respiratory Acidosis
Acidosis with a normal or low PaCO2 is a…
Metabolic Acidosis
Alkalosis with a raised or normal PaCO2 is a…
Metabolic alkalosis
Alkalosis with a low PaCO2 is a…
Respiratory alkalosis
A 24 year old man presents with 3 day history of vomiting and diarrhoea. He has a high respiratory rate, fast heart rate and low blood pressure. He is put on 40% oxygen. His blood gas is as follows:
PaO2 33 kPa (normal range >10 kPa)
pH 7.32 (normal range 7.35 to 7.45)
PaCO2 2.8 kPa (normal range 4.7 to 6 kPa)
HCO3- 18 mmoll-1 (normal range 22 to 26 mmoll-1)
The patient is unwell
He is given 40% oxygen so you would expect his PaO2 to be 10kPa less than that so ~ 30kPA. His is 33kPa indicating no problem with his lungs
He is acidotic
His PaCO2 is low, in an acidosis you would expect it be high indicating that this is unlikely to be metabolic
His bicarb is low which can cause acidosis indicating that this is a metabolic acidosis
A 60 year old man is admitted with pneumonia. He is put on 50% oxygen. His blood gas is as follows:
PaO2 15 kPa (normal range >10 kPa)
pH 7.30 (normal range 7.35 to 7.45)
PaCO2 8.8 kPa (normal range 4.7 to 6 kPa)
HCO3- 22 mmoll-1 (normal range 22 to 26 mmoll-1)
The patient is unwell
The pO2 on 50% of oxygen would be expected to be about 40kPa. It is less than this indicating there is a problem with oxygen delivery to the blood
He has an acidosis
PaCO2 is raised which will cause an acidosis
Bicarb is normal
= Respiratory acidosis
What are some relative contraindications to ABG?
No absolutes but choose sites away from dialysis shunt or mastectomy and be awre of patients on anti-coagulant therapy and avoid any areas of skin infection
Why may there be a raised bilirubin?
Increased production - haemolysis
Impaired coagulation - hepatitis, cirrhosis, drugs
Congenital
Obstruction - gallstones, pancreati CA, cholangitis, drugs
What doe AST and ALT elevations indicate?
Damaged hepatocytes - highly raised suggests hepatitis
What does a highly raised ALP indicate?
Cholestasis
What 3 coagulation studies will be elevated in severe liver failure?
PT, APTT and TT
What does a greater rise in bilirubin than of AST/ALT and ALP elevation indicate?
Cholestatic predominant liver injury
What does a greater rise in AST/ALT/ALP than in bilirubin indicate?
Hepatocellular dominant liver injury
