ESA3 - Respiratory - SBA Formative

Question 1

A patient with longstanding COPD presents with worsening breathlessness. His arterial blood gas results are as follows:

pO2 = 8.0 kPa (9.3 – 13.3)
pCO2 = 8.8 kPa (4.7 – 6.0)
pH 7.28 (7.35 – 7.45)
Bicarbonate 32 mmol/L (22 – 26)

What is this patient’s acid base status?

A. Partially compensated Metabolic acidosis
B. Mixed metabolic and respiratory acidosis
C. Uncompensated Respiratory acidosis
D. Partially compensated Respiratory acidosis
E. Uncompensated metabolic acidosis

Answer 1

D. Partially compensated Respiratory acidosis

Answer= D
(the pH of 7.2 indicates an acidosis; the raised pCO2 indicates it is a respiratory acidosis; The increased Bicarbonate indicates that the kidney has started to compensate for the respiratory acidosis; However the pH is still acidic despite the raised bicarbonate indicating that the compensation is partial (if the pH had returned to normal then it would be fully compensated))

Question 2

Consider the control of respiration by the respiratory centre.

What is the most important stimulus controlling the level of ventilation at rest?

A. The effect of Low PO2 on peripheral chemoreceptors
B. The effect of High PCO2 on peripheral chemoreceptors
C. The effect of Low pH on peripheral chemoreceptors
D. The effect of Low pO2 on central chemoreceptors
E. The effect of Low CSF pH on central chemoreceptors

Answer 2

E. The effect of Low CSF pH on central chemoreceptors

E: If arterial pCO2 rises, then after a short delay, CSF pCO2 will follow. This leads to a drop in CSF pH, which is sensed by central chemoreceptors and normally produces changes in breathing which tend to restore CSF pH (i.e. ventilation increases, to lower pCO2 again). This is the principal means by which ventilation is controlled.

Question 3

CO2 is transported from the tissues to the lungs by blood.

In what form is the majority of CO2 transported?

A. As dissolved CO2 in plasma
B. As bicarbonate (HCO3-) ions
C. As carbonic acid
D. As carbamino compounds
E. As dissolved CO2 in RBC

Answer 3

A. As dissolved CO2 in plasma

Question 4

CO2 is transported from the tissues to the lungs by blood.

In what form is the majority of CO2 transported?

A. As dissolved CO2 in plasma
B. As bicarbonate (HCO3-) ions
C. As carbonic acid
D. As carbamino compounds
E. As dissolved CO2 in RBC

Answer 4

B. As bicarbonate (HCO3-) ions

80% of transported CO2 travels as Bicarbonate (HCO3-), 8% as dissolved CO2 and 12% as carbamino compounds

Question 5

A 26 year old athlete has just finished a 200 metre sprint. His respiratory rate is 34 per minute. He is sweating and is experiencing muscle aches due to lactic acid accumulated in his muscles during the race.

What factor has the greatest effect in increasing oxygen delivery to muscles?

A. The large increase in pCO2 in the tissues
B. The large drop in pO2 in the tissues
C. An increase in red cell 2,3 DPG concentration
D. The drop in the blood pH
E. The increase in body temperature

Answer 5

B. The large drop in pO2 in the tissues

Answer = B (while the pH, BPG and Temperature will shift the dissociation curve, the most important factor determining O2 dissociates from Hb is the pO2)

Question 6

A 25-year-old man visiting Peru travels by bus from a coastal city to a town at an altitude of 3000 metres above sea level. The following day he hikes to a town at an altitude of 3500 metres, arriving there within 5 hours. He complains of a headache, feeling dizzy and breathless.

A local doctor checks his oxygen saturation using a pulse oximeter and finds it to be 84%. His respiratory rate is 30/minute. The doctor suspects an acid base disturbance may be also be present.

What is the most likely acid base disturbance in this patient?

A. Metabolic alkalosis
B. Metabolic acidosis
C. Mixed respiratory and metabolic acidosis
D. Respiratory acidosis
E. Respiratory alkalosis

Answer 6

E. Respiratory alkalosis

The low PO2 of inspired atmospheric air results in hypoxia which stimulates the peripheral chemoreceptors. The resulting hyperventilation causes a reduction in pCO2, which results in a respiratory alkalosis.

Question 7

A 25-year-old man visiting Peru travels by bus from a coastal city to a town at an altitude of 3000 metres above sea level. At this altitude the atmospheric pressure is 71 kPa. He is breathing atmospheric air which is made up of 21% oxygen, 78% nitrogen and 1% other gases. The saturation vapour pressure of water is 6 kPa.

What is the partial pressure of oxygen of moist inspired air in his trachea? (Disregard any mixing with air already present in the trachea)

A. 12.5 kPa
B. 13.5 kPa
C. 14.5 kPa
D. 15.5 kPa
E. 16.5 kPa

Answer 7

B. 13.5 kPa

Worked out as follows: (71 - 6) x 21% = 13.65 (13.5 is the closest answer)

Question 8

A 28 year old man is seen in the emergency department with sudden onset right sided pleuritic chest pain and breathlessness. A spontaneous right sided pneumothorax is diagnosed.

There are NO clinical or radiological features of a tension pneumothorax.

Where on the chest wall should the chest drain be inserted to drain the pneumothorax?

A. 2nd right intercostal space in the mid clavicular line, just below the 2nd rib
B. 2nd right intercostal space in the mid clavicular line, just above the 3rd rib
C. 4th right intercostal space in the mid clavicular line, just above the 5th rib
D. 4th right intercostal space in the mix axillary line, just below the 4th rib
E. 4th right intercostal space in the mix axillary line, just above the 5th rib

Answer 8

E. 4th right intercostal space in the mix axillary line, just above the 5th rib

Answer= E (COPD)
In a pneumothorax (which is not a tension pneumothorax) the site of placement of a chest drain is the 4th intercostal space in the mid axillary line, and the tube is placed just above the 5th rib, to avoid damaging the intercostal vessels which run in the costal groove along the lower border of each rib.

(The 2nd intercostal space in the mid clavicular line is only used for emergency needle decompression in a tension pneumothorax.)

Question 9

A 67 year old man with diagnosed COPD is admitted with worsening breathlessness following an acute chest infection. His oxygen saturation is 86% on air.

The arterial blood gas results are as follows:
pO2 = 7.1 kPa (9.3 – 13.3)
pCO2 = 7.8 kPa (4.6 – 6.0)

Which statement about the use of oxygen therapy in this patient is FALSE?

A. O2 therapy can result in worsening of pCO2
B. O2 therapy should be avoided due to risk of worsening pCO2
C. Controlled O2 therapy should be used aiming for Sa O2 of 88-92%
D. ABG should be repeated after starting controlled O2 therapy
E. If the use of controlled O2 therapy causes a rise in pCO2, ventilation should be commenced

Answer 9

B. O2 therapy should be avoided due to risk of worsening pCO2

Answer: B

Rationale: Oxygen MUST always be given as the hypoxia can kill.

All the other responses are correct. Since O2 therapy can result in worsening of pCO2, controlled oxygen therapy is used aiming for a oxygen saturation of 88-92%, with the ABGs being repeated to monitor the pCO2 level; if the pCO2 rises, ventilation should be started

Question 10

A 65 year old man with a 60 pack year smoking history is diagnosed with COPD. What is the most important step in the management of this patient?

A. Inhaled long acting bronchodilators
B. Inhaled muscarinic antagonists (anticholinergics e.g. Ipratropium)
C. Smoking cessation
D. Use of inhaled steroids
E. Antibiotic therapy for infective exacerbations of COPD

Answer 10

C. Smoking cessation

Smoking cessation is the most important step in the management as it prevents progression of the disease. All the other responses are medications used in the symptomatic treatment of COPD.

Question 11

Which of the following conditions is the most common cause of Chronic Type 2
respiratory failure?

A. Asthma
B. COPD
C. Diffuse lung fibrosis
D. Lobar pneumonia
E. Pulmonary embolism

Answer 11

B. COPD

Asthma, pulmonary embolism and lobar pneumonia, are all acute conditions and cause type 1 rather than type 2 respiratory failure.

In COPD and diffuse lung fibrosis, chronic type 2 respiratory failure develops very gradually over a long period of time (hence compensatory mechanisms have time to develop which allows the hypoxia & hypercapnia to be tolerated better). Out of these 2 conditions COPD is very much more commonly seen.

Question 12

A 24 year old woman has life-threatening asthma. Which arterial blood gas result is
most likely in this patient?

(Normal range pO2 = 9.3-13.3, pCO2 = 4.7– 6.0 kPa)

A. pO2 = 12.6 pCO2 = 4.1 
B. pO2 = 11.3 pCO2 = 5.0
C. pO2 = 8.8 pCO2 = 4.1
D. pO2 = 8.1 pCO2 = 4.0
E. pO2 = 7.6 pCO2 = 6.2

Answer 12

E. pO2 = 7.6 pCO2 = 6.2

The rise in pCO2 indicates exhaustion causing hypoventilation and Type 2 respiratory failure. This is a feature of life-threatening asthma - the patient requires ITU care and ventilation.

Responses A and B are normal ABG results. C & D are consistent with severe asthma - the low pCO2 is due to hyperventilation (induced by hypoxia).

Question 13

A 70 year old woman develops sudden onset pleuritic chest pain and acute breathlessness on the fifth post-operative day, following a right hip joint replacement.

The chest examination is normal. The oxygen saturation is 92%. The chest x-ray and ECG
are normal. The ABG results are as follows:

pO2 = 8.0 kPa (9.3-13.3), pCO2 = 4.1 kPa (4.7 – 6.0).

What is the most likely diagnosis?

A. Acute asthma
B. Acute pulmonary oedema
C. Anxiety related hyperventilation
D. Pulmonary embolism
E. Pneumothorax

Answer 13

D. Pulmonary embolism

This is the typical clinical history (predisposing factors, symptoms) of pulmonary embolism, and ABG result further supports the diagnosis. The other options can be ruled out as follows:
Acute asthma – not associated with pleuritic chest pain.
Acute pulmonary oedema: pleuritic chest pain is not a feature; fine crackles in lung bases would usually be present and CXR would be abnormal
Anxiety related hyperventilation – excluded by low pO2 which should be normal, not low
Pneumothorax – excluded by the normal chest x-ray

Question 14

A 65 year old woman has breathlessness on exertion and a productive cough of 6 months duration. She is a heavy smoker. On chest examination there is reduced cardiac and liver dullness and expiratory wheezes are heard over both lung fields.

Her spirometry results are as follows
(Pre-bronchodilator) = FEV1/FVC ratio 53%
(Post-bronchodilator) = FEV1/FVC ratio 54%

What is the most likely diagnosis?

A. Lung fibrosis
B. Pleural effusion
C. COPD
D. Asthma
E. Normal lung function

Answer 14

C. COPD

A FEV1/FVC ratio of > 70% indicates an obstructive disease. The minimal improvement with bronchodilators indicates COPD rather than asthma and the clinical features also suggest COPD

Question 15

A 60 year old woman has a dry cough and progressive breathlessness of 6 months duration. On examination chest expansion is symmetrically reduced bilaterally. The Spirometry results (pre-bronchodilator) are as follows:

• FVC = 1.5 Litres (predicted 2.8 L)
• FEV1= 1.2 Litres (predicted 2.4)
• FEV1/FVC ratio = 80%
• There is no difference in the post-bronchodilator results.

What is the most likely diagnosis?

a. Normal lung function
b. Asthma
c. COPD
d. Diffuse Lung fibrosis
e. Bronchial carcinoma

Answer 15

D. Diffuse Lung fibrosis

The chest expansion is reduced and spirometry shows a restrictive pattern (both FVC and FEV1 are reduced with a FEV1/FVC ratio > 70%). Hence Diffuse lung fibrosis is the most likely diagnosis.

A FEV1/FVC ratio of > 70% rules out obstructive disease. Lung function is not normal since FVC and FEV1 are reduced.

Question 16

A 18 year old man who has been diagnosed with asthma undergoes spirometry.

Which flow volume loop is most likely to be seen in this patient?
[2018 Respiration End of Semester formative SBA and SAQ questions(2) - question 7]

A. A
B. B
C. C
D. D
E. E

Answer 16

B. B

Asthma causes a typical scalloping of the expiratory limb of the flow volume loop

Question 17

A 36 -year-old man with Myasthenia Gravis has difficulty in breathing due to weakness of respiratory muscles.

His arterial blood gas results are as follows:
• pH = 7.31 (7.35 – 7.45)
• PaO2 = 7.9 kPa (9.3-13.3)
• PaCO2 = 7.1 kPa (4.7-6.0)
• HCO3
- = 23 mmol/L (22-26)

What is this patient’s acid base status?
A. Compensated respiratory acidosis
B. Partially compensated metabolic acidosis
C. Partially compensated respiratory acidosis
D. Uncompensated metabolic acidosis
E. Uncompensated respiratory acidosis

Answer 17

E. Uncompensated respiratory acidosis

the pH of 7.31 indicates an acidosis; the raised pCO2 indicates it is a respiratory acidosis; The bicarbonate level is still in the normal range, indicating that the kidney has not yet started to compensate for the respiratory acidosis;

Question 18

A 60 year old woman has a dry cough and progressive breathlessness of 6 months duration. She is diagnosed with diffuse lung fibrosis

Which of the following is NOT a feature of this condition?

A. Increased deposition of collagen fibres in the interstitium
B. Reduced lung compliance
C. Airways obstruction
D. Increased elastic recoil of the lung
E. Hypoxia due to a diffusion defect

Answer 18

C. Airways obstruction

Diffuse lung fibrosis is characterised by increased deposition of collagen in the interstitium, in response to various forms of lung injury. Collagen is less stretchable than elastin fibres, and the greater amount of collagen fibres makes the lungs stiff, and less compliant, with increased lung recoil. The thickening of the alveolar capillary membrane causes a diffusion defect.

The airways are not affected by this pathological process, so there is no airways obstruction.

Question 19

A baby girl is born at 32 weeks gestation to a mother with type 2 diabetes. The medical team anticipate Respiratory Distress Syndrome of the Newborn due to lack of surfactant. What abnormality is most likely to be present her lungs?

A. Increased surface tension of fluid lining alveoli
B. Reduced lung compliance
C. Collapse of small alveoli into larger alveoli
D. Failure of some alveoli to inflate
E. All of the above

Answer 19

E. All of the above

Surfactant reduces surface tension of alveolar fluid, increasing lung compliance, and facilitating inflation of alveoli, with the first breath. It also prevents small alveoli from collapsing into big alveoli, by keeping the pressure within alveoli of differing sizes the same. Hence, Lack of surfactant causes all of the changes listed in responses a - d

Question 20

A man writing quietly at his desk has normal quiet respiration. What is his pleural pressure most likely to be?

A. Same as atmospheric pressure
B. Same as alveolar pressure
C. Slightly above atmospheric pressure
D. Slightly below atmospheric pressure
E. Slightly more than alveolar pressure

Answer 20

D. Slightly below atmospheric pressure

At rest, the lung is subject to two equal and opposing forces. (the tendency of chest wall to recoil outwards, vs that of the lung to recoil inwards) which balance each other and also creates a negative pressure within the intrapleural space relative to atmospheric pressure. This pressure becomes more negative during the inspiratory phase due to expansion of the thorax and returns to the resting (negative) pressure at the end of quiet expiration.

Question 21

Consider the resting expiratory level. What is the status of respiratory muscles at this stage in the respiratory cycle?

A. The diaphragm is contracted
B. The rectus abdominis muscle is contracted
C. The Sternocleidomastoid muscle is contracted
D. The respiratory muscles are totally relaxed
E. The internal intercostal muscles are relaxed

Answer 21

D. The respiratory muscles are totally relaxed

This is the end of a quiet expiration (before the next inspiration). Quiet expiration is passive and is brought about by relaxation of muscles of inspiration. Hence all respiratory muscles are totally relaxed

Question 22

The chest CT of a man diagnosed with a left sided pneumothorax is shown below.

[2018 Respiration End of Semester formative SBA and SAQ questions(2) - question 1]

What are the structures indicated by the pink, yellow and green dashed lines?

Pink line Yellow line Green line
A. Visceral pleura, Visceral pleura, Parietal pleura
B. Parietal pleura – costalpart, Visceral pleura, Visceral pleura
C. Parietal pleura -
diaphragmatic part, Parietal pleura –
mediastinal part, Parietal pleura - costal
part
D. Parietal pleura – costal part, Parietal pleura - diaphragmatic part, Visceral pleura
E. Parietal pleura - costal part, Parietal pleura – mediastinal part, Visceral pleura

Answer 22

E. Parietal pleura - costal part, Parietal pleura – mediastinal part, Visceral pleura

The parietal pleura is named for the part of the thoracic cavity it is adjacent/ adherent to: part lining rib cage = costal part; part adjacent to the mediastinum (including pericardial sac) = mediastinal part; part adjacent to diaphragm = diaphragmatic part. Part extending to the root of the neck=apical part.

The visceral pleura is adherent to the lung and becomes continuous with the parietal pleura at the hilum.