Part 2 Cases 1–25

Case 1

History

A 25-year-old man, with no significant past medical history, presents to the emergency department with a 2-day history of fever, productive cough and worsening breathlessness.

Examination

He is hot and flushed with a temperature of 39.3°C. He does not appear distressed but is using accessory muscles of respiration. There is diminished chest expansion on the left with dullness to percussion, bronchial breathing and coarse crackles in the left lower zone posteriorly.

Pulse	104 beats/min
Respiratory rate	28 breaths/min
Blood pressure	118/70 mmHg
SaO2 (room air)	89%

Arterial blood gas		On room air
23/7/2006
Unit no.: 00654545
ID: John Simpson		Normal
H+	31.8 nmol/L	(35–45)
pH	7.50	(7.35–7.45)
PCO2d	3.74 kPa (4.7–6.0)
	28.1 mmHg	(35–45)
PO2	7.68 kPa	(> 10.6)
	57.8 mmHg	(> 80)
Bicarb	23.9 mmol/L	(22–28)
BE	−0.5 mmol/L	(–2–+2)
SPO2	88.7%	(> 98%)
Lactate	1.2	(0.4–1.5)
K	3.7 mmol/L	(3.5–5)
Na	138 mmol/L	(135–145)
Cl	99 mmol/L	(95–105)
iCa+	1.2 mmol/L	(1–1.25)
Hb	15 g/dL	(13–18)
Glucose	5.4 mmol/L	(3.5–5.5)

Questions

1. a) Describe his gas exchange.

b) Describe his acid–base status.

2. Should the patient receive supplemental O₂?

3. Is pulse oximetry a suitable alternative to repeated ABG monitoring in this case?

Case 2

History

A 34-year-old morbidly obese female with a body mass index of 49 has an ABG sample taken as part of her preoperative assessment for weight reduction surgery.

Apart from morbid obesity and type 2 diabetes, she is otherwise well and has no respiratory symptoms.

Arterial blood gas		On air
14/01/2005
Unit no.: 55392088
ID: Marcella Plantagenet
		Normal
H+	45 nmol/L	(35–45)
pH	7.35	(7.35–7.45)
PCO2	7.3 kPa	(4.7–6.0)
	54.8 mmHg	(35–45)
PO2	9.6 kPa	(> 10.6)
	72.2 mmHg	(> 80)
Bicarb	29 mmol/L	(22–28)
BE	+3.8	(−2−+2)
SPO2	96%	(> 98%)
Lactate	1	(0.4 – 1.5)
K	4.7 mmol/L	(3.5–5)
Na	134 mmol/L	(135–145)
Cl	102 mmol/L	(95–105)
iCa+	1.2 mmol/L	(1–1.25)
Hb	13 g/dL	(13–18)
Glucose	9 mmol/L	(3.5–5.5)

Questions

1. a) Describe her gas exchange.

b) Describe her acid–base status.

2. What is the most likely diagnosis?

Case 3

History

A 24-year-old female nursing student attends hospital complaining of sudden-onset breathlessness. She flew to the UK from Australia the previous day and is very concerned she may have a pulmonary embolism. She has no pleuritic pain, haemoptysis or leg swelling, no past history of lung disease or deep-vein thrombosis and is a non-smoker.

Examination

She appears anxious and distressed. Her respiratory rate is elevated but chest examination is unremarkable and there are no clinical signs of deep-vein thrombosis. A chest X-ray reveals no abnormalities.

Pulse	88 beats/min
Respiratory rate	22 breaths/min
Blood pressure	124/76 mmHg
SaO2 (room air)	95%

23/7/2006
Unit no.: 00654545
ID: Jill Royds
		Normal
H+	31.2 nmol/L	(35–45)
pH	7.51	(7.35–7.45)
PCO2	3.90 kPa	(4.7–6.0)
	29.3 mmHg	(35–45)
PO2	10.3 kPa	(> 10.6)
	77.0 mmHg	(> 80)
Bicarb	25.0 mmol/L	(22–28)
BE	+0.7 mmol/L	(−2−+2)
SpO2	93.7%	(> 98%)
Lactate	1.0	(0.4 – 1.5)
K	4.3 mmol/L	(3.5–5)
Na	141 mmol/L	(135–145)
Cl	101 mmol/L	(95–105)
iCa+	1.2 mmol/L	(1–1.25)
Hb	13 g/dL	(13–18)
Glucose	4.6 mmol/L	(3.5–5.5)

Questions

1. a) Describe her gas exchange.

b) Describe her acid–base status.

2. What is the likeliest diagnosis?

Case 4

History

A 78-year-old male on a surgical ward is found unresponsive, having returned, a few hours previously, from a complicated open cholecystectomy.

Review of his charts reveals he has received three 10 mg injections of morphine since returning to the ward, in addition to the morphine delivered by his patient-controlled analgesia device.

Examination

The patient is unresponsive with shallow respirations and bilateral pinpoint pupils.

Pulse rate	90 beats/min
Respiratory rate	5 breaths/min
Blood pressure	98/64 mmHg
SaO2	99%
BM	5.6 mmol/l

Arterial blood gas		On 28% O2
18/09/2006
Unit no.: 6799986
ID: Henry Spasek
		Normal
H+	65.4 nmol/L	(35–45)
pH	7.18	(7.35–7.45)
PCO2	8.2 kPa	(4.7–6.0)
	62 mmHg	(35–45)
PO2	11.76 kPa	(> 10.6)
	87 mmHg	(> 80)
Bicarb	22.4 mmol/L	(22–28)
BE	−1.5 mmol/L	(−2−+2)
SPO2	99.8%	(> 98%)
Lactate	1	(0.4–1.5)
K	4.4 mmol/L	(3.5–5)
Na	137 mmol/L	(135–145)
Cl	103 mmol/L	(95–105)
iCa+	1.16 mmol/L	(1–1.25)
Hb	11 g/dL	(13–18)
Glucose	3.9 mmol/L	(3.5–5.5)

Questions

1. a) Describe his gas exchange.

Describe his acid–base status.

2. What is the most likely diagnosis?

3. What treatment does this patient require?

Case 5

History

A 75-year-old man is brought into the emergency department by his family. He is extremely short of breath and struggling to speak.

Following a conversation with his family it emerges that he has a long history of chronic obstructive pulmonary disease.

Over the last 3 days his breathing has worsened considerably and he has expectorated increased volumes of sputum.

Examination

The patient is struggling for breath and appears extremely distressed. He exhibits signs of chest hyperinflation and is breathing through pursed lips. Breath sounds are generally diminished but there are no added sounds.

Pulse	120 beats/min
Respiratory rate	26 breaths/min
Blood pressure	150/80 mmHg
Temperature	36°C
SaO2%	81%

Arterial blood gas		On air
10/07/2005
Unit no.: 77655349
ID: Joseph Spielman
		Normal
H+	39.5 nmol/L	(35–45)
pH	7.40	(7.35–7.45)
PCO2	4.9 kPa	(4.7–6.0)
	36 mmHg	(35–45)
PO2	5.8 kPa	(> 10.6)
	44 mmHg	(> 80)
Bicarb	23 mmol/L	(22–28)
BE	−1.2 mmol/L	(−2−+2)
SPO2	80%	(> 98%)
Lactate	1.0	(0.4–1.5)
K	4.1 mmol/L	(3.5–5)
Na	137 mmol/L	(135–145)
Cl	99 mmol/L	(95–105)
iCa+	1.1 mmol/L	(1–1.25)
Hb	16.5 g/dL	(13–18)
Glucose	3.8 mmol/L	(3.5–5.5)

Questions

1. a) Describe his gas exchange.

b) Describe his acid–base status.

2. Should you provide him with oxygen?

Case 6

History

The patient from the previous case is treated in the emergency department with nebulised bronchodilators, oral prednisolone and antibiotics. He is then transferred to a respiratory ward where he is administered 28% oxygen by a fixed concentration mask. Despite this, his SaO₂ (as measured by pulse oximetry) increases only marginally and there is no improvement in his symptoms.

Examination

Examination findings in the chest are unchanged but he now appears exhausted and slightly confused.

Pulse	120 beats/min
Respiratory rate	16 breaths/min
Blood pressure	120/80 mmHg
SaO2	83% (on 28% O2)
Temperature	36°C

A repeat ABG is performed (6 hours after the first ABG).

Arterial blood gas		On 28% O2
11/07/2005
Unit no.: 77655349
ID: Joseph Spielman
		Normal
H+	51.4 nmol/L	(35–45)
pH	7.29	(7.35–7.45)
PCO2	6.9 kPa	(4.7–6.0)
	52 mmHg	(35–45)
PO2	6.4 kPa	(> 10.6)
	48 mmHg	(> 80)
Bicarb	24 mmol/L	(22–28)
BE	−0.9 mmol/L	(−2−+2)
SPO2	84%	(> 98%)
Lactate	1.0	(0.4–1.5)
K	4.0 mmol/L	(3.5–5)
Na	137 mmol/L	(135–145)
Cl	99 mmol/L	(95–105)
iCa+	1.1 mmol/L	(1–1.25)
Hb	16.5 g/dL	(13–18)
Glucose	4.2 mmol/L	(3.5–5.5)

Questions

1. a) Describe his gas exchange.

b) Describe his acid–base status.

2. Should his oxygen now be stopped?

Case 7

History

A 77-year-old woman is admitted to the stroke ward with right-sided weakness, visual disturbance and slurred speech. She is commenced on nasogastric feeding due to swallowing problems but has a large vomit 24 hours later. She initially appears well but over the next few hours develops worsening breathing difficulties.

Examination

She is agitated, distressed and pyrexial. A dull percussion note and coarse crackles are evident at both lung bases. Other than acute confusion, neurological findings are unchanged from admission.

Pulse	92 beats/min
Respiratory rate	28 breaths/min
Blood pressure	112/65 mmHg
SaO2 (60% O2)	92%

Arterial blood gas		On 60% O2
23/7/2006
Unit no.: 00654545
ID: Mary Waters
		Normal
H+	38.8 nmol/L	(35–45)
pH	7.41	(7.35–7.45)
PCO2	4.43 kPa	(4.7–6.0)
	33.2 mmHg	(35-45)
PO2	8.67 kPa	(> 10.6)
	65.0 mmHg	(> 80)
Bicarb	21.2 mmol/L	(22–28)
BE	−2.8 mmol/L	(−2−+2)
SPO2	92.7%	(> 98%)
Lactate	1.6	(0.4–1.5)
K	4.0 mmol/L	(3.5–5)
Na	144 mmol/L	(135–145)
Cl	103 mmol/L	(95–105)
iCa+	1.2 mmol/L	(1–1.25)
Hb	13 g/dL	(13–18)
Glucose	6.6 mmol/L	(3.5–5.5)

Questions

1. a) Describe her gas exchange.

b) Describe her acid–base status.

2. What is the most likely diagnosis?

3. Is her condition mild, moderate or severe?

Case 8

History

A 68-year-old man with chronic obstructive pulmonary disease is referred to hospital by his doctor with a short history of increased breathlessness and reduced effort tolerance. He is normally capable of walking around 500 metres but now has difficulty dressing and is breathless at rest.

Examination

He is lucid, alert and mildly distressed. He is using accessory muscles of respiration and breathing through pursed lips. Chest examination reveals features of hyperinflation, generally diminished breath sounds and scattered rhonchi (wheeze).

Pulse	96 beats/min
Respiratory rate	24 breaths/min
Blood pressure	138/82 mmHg
SaO2 (room air)	78%

Arterial blood gas		On air
23/7/2006
Unit no.: 00654545
ID: Hamish Roy
		Normal
H+	43.2 nmol/L	(35–45)
pH	7.36	(7.35–7.45)
PCO2	7.20 kPa	(4.7–6.0)
	54.1 mmHg	(35–45)
PO2	5.3 kPa	(> 10.6)
	40 mmHg	(> 80)
Bicarb	30.6 mmol/L	(22–28)
BE	+4.9 mmol/L	(−2−+2)
SPO2	75.2%	(> 98%)
Lactate	1.2	(0.4–1.5)
K	3.7 mmol/L	(3.5–5)
Na	144 mmol/L	(135–145)
Cl	102 mmol/L	(95–105)
iCa+	1.2 mmol/L	(1–1.25)
Hb	16 g/dL	(13–18)
Glucose	4.9 mmol/L	(3.5–5.5)

Questions

1. a) Describe his gas exchange.

b) Describe his acid–base status.

2. Which one of the following ABG values is most likely to have changed significantly in the past 24 hours: pH, PCO₂, PO₂ or HCO₃?

3. Which two of the above ABG values indicate the need for caution when providing O₂ therapy?

Case 9

History

The patient from the previous case is treated with nebulised bronchodilators, oral prednisolone and 60% O₂ by face mask. His oxygen saturations improve significantly but when he is reviewed 1 hour later, his condition has deteriorated and he is unable to provide a history.

Examination

He is drowsy and barely rousable. He no longer appears to be in respiratory distress and his respiratory rate has fallen to 14 breaths/min. Chest examination is unchanged from previously.

Pulse	88 beats/min
Respiratory rate	14 breaths/min
Blood pressure	132/80 mmHg
SaO2 (room air)	96%

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1. Common ABG values
2. When and why is an ABG required?
3. Pulmonary gas exchange: the basics
4. Making ABG interpretation easy

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