Investigation findings

Question 1

What do these stand for? FEV1 FVC PEFR

Answer 1

FEV1 = Forced Expiratory Volume in one second

FVC = Forced Vital Capacity

PEFR = Peak Expiratory Flow Rate

Question 2

Define what these each mean:

FEV1

FVC

PEFR

Answer 2

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.

Question 3

List THREE factors which affect the peak expiratory flow readings (apart from obstructive airways disease)

Answer 3

Age

Sex

Height

Others = Race, smoking history, respiratory muscle strength and effort, time of day, effort made by patient in performing the test

Question 4

Give TWO indications for performing a PEFR on a patient.

Answer 4

Screening for airflow obstruction

Monitoring of asthma and response to treatment

Aid assessment of acute asthma attack

Question 5

Name TWO limitations of using PEFR monitoring

Answer 5

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

Question 6

State the current British Thoracic Society PEFR percentages which aids the classification of patients with moderate, severe and life threatening acute asthma attacks

Answer 6

% of best or predicted best PEFR score:

Moderate attack = >50 - 75%

Severe attack = 33-55%

Life threatening = <33%

Question 7

At what age do lung function tests become unreliable

Answer 7

Under 5

Question 8

Name TWO obstructive disorders of lung function

Answer 8

Obstructive:

• Asthma
• COPD
• Brochiectasis
• CF
• Lung Ca
• Post TB

Question 9

Name TWO restrictive conditions of lunch function

Answer 9

Pulmonary:

• fibrosis
• Abestosis
• pul oedema
• Parenchymal tumours
• Lobectomy

Extrapulmonary:

• Kyphosis/chest wall deformities
• Obesity
• Pregnancy
• Neuromuscular disorders
• RA

Question 10

What FEV1, FVC and FEV1/FVC results would you expect in obstructive lung conditions?

Answer 10

FEV1 - reduced

FVC - Reduced or normal

FEV1/FVC - Reduced

Question 11

What FEV1, FVC and FEV1/FVC results would you expect in Restrictive lung conditions?

Answer 11

FEV1 - Reduced or normal

FVC - Reduced

FEV1/FVC - normal or increased

Question 12

What is used to grade the severity of COPD?

Answer 12

FEV1 % of predicted eg. mild is >80% predicted Severe is 30-49% predicted

Question 13

List THREE clinical features which help us to differentiate COPD and asthma.

Answer 13

Question 14

What conditions may cause an acidosis due to too much acid in the blood/too little buffer?

Answer 14

DKA, respiratory acidosis, lactic acidosis and renal impairment

Question 15

What conditions can cause an alkalotic blood gas?

Answer 15

Too little acid: hyperventilation, persistent vomiting

Overdose on antacids (too much buffer)

Question 16

Acidosis with a raised PaCO2 is a…

Answer 16

Respiratory Acidosis

Question 17

Acidosis with a normal or low PaCO2 is a…

Answer 17

Metabolic Acidosis

Question 18

Alkalosis with a raised or normal PaCO2 is a…

Answer 18

Metabolic alkalosis

Question 19

Alkalosis with a low PaCO2 is a…

Answer 19

Respiratory alkalosis

Question 20

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)

Answer 20

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

Question 21

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)

Answer 21

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

Question 22

What are some relative contraindications to ABG?

Answer 22

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

Question 23

Why may there be a raised bilirubin?

Answer 23

Increased production - haemolysis

Impaired coagulation - hepatitis, cirrhosis, drugs

Congenital

Obstruction - gallstones, pancreati CA, cholangitis, drugs

Question 24

What doe AST and ALT elevations indicate?

Answer 24

Damaged hepatocytes - highly raised suggests hepatitis

Question 25

What does a highly raised ALP indicate?

Answer 25

Cholestasis

Question 26

What 3 coagulation studies will be elevated in severe liver failure?

Answer 26

PT, APTT and TT

Question 27

What does a greater rise in bilirubin than of AST/ALT and ALP elevation indicate?

Answer 27

Cholestatic predominant liver injury

Question 28

What does a greater rise in AST/ALT/ALP than in bilirubin indicate?

Answer 28

Hepatocellular dominant liver injury