Respiratory Flashcards
A patient's arterial blood gas analysis gives the following results: pO2 10 kPa/75mmHg (11.3-12.6 kPa) pCO2 7 kPa/52 mmHg (4.7-6.0 kPa) pH 7.47 (7.36-7.44) Bicarbonate 37 mmol/L (20-28) Which of the following is the most likely cause? (Please select 1 option) Acute exacerbation of chronic obstructive pulmonary disease Chronic hyperventilation syndrome Diabetic coma Pulmonary embolism Pyloric obstruction
These results demonstrate a metabolic alkalosis and there is respiratory compensation with an elevation of pCO2.
Consequently, pO2 is slightly low.
The most probable cause out of those given is pyloric stenosis.
A Metabolic acidosis - acute, normal oxygenation
B Metabolic acidosis - acute with hypoxaemia
C Metabolic acidosis - compensated, normal oxygenation
D Metabolic alkalosis - acute, normal oxygenation
E Metabolic alkalosis - acute with hypoxaemia
F Metabolic alkalosis - compensated, normal oxygenation
G Normal blood gases
H Normal ventilation with hypoxaemia
I Respiratory failure - acute
J Respiratory failure - compensated, normal oxygenation
K Respiratory failure - compensated with hypoxaemia
For each of the following blood gas results select the most appropriate designation from the list of options.
The line labelled ‘oxygen concentration’ represents the concentration of oxygen that each individual is inhaling.
Normal values
PaO2 12.0-14.7 kPa
PaO2 90-110 mmHg
PaCO2 4.5-6.0 kPa
PaCO2 34-45 mmHg
pH 7.36-7.44
H+ molarity 35-45 nmol/l
Bicarbonate 24-30 mmol/l
pO2 12.9 kPa (97 mmHg) pCO2 5.8 kPa (44 mmHg) pH 7.24 H+ molarity 57 nmol/l Bicarbonate 18 mmol/l Base excess -7 mmol/l Oxygen concentration 40%
pO2 6.7 kPa (50 mmHg) pCO2 10.1 kPa (76 mmHg) pH 7.38 H+ molarity 42 nmol/l Bicarbonate 42.4 mmol/l Base excess +14 mmol/l Oxygen concentration 21%
pO2 14.3 kPa (108 mmHg) pCO2 6.3 kPa (48 mmHg) pH 7.52 H+ molarity 30 nmol/l Bicarbonate 39 mmol/l Base excess +14 mmol/l Oxygen concentration 30%
pO2 4.7 kPa (35 mmHg) pCO2 12.7 kPa (95 mmHg) pH 7.12 H+ molarity 76 nmol/l Bicarbonate 29.5 mmol/l Base excess -4 mmol/l Oxygen concentration 21%
pO2 16.3 kPa (122 mmHg) pCO2 7.5 kPa (56 mmHg) pH 7.26 H+ molarity 55 nmol/l Bicarbonate 24.1 mmol/l Base excess -2 mmol/l Oxygen concentration 75%
Metabolic acidosis - acute with hypoxaemia
The low pH with low bicarbonate indicates a metabolic acidosis, and the low normal O2 on inspired [O2] indicates hyperaemia.
Respiratory failure - compensated with hypoxaemia
This is the typical feature of a corrected respiratory failure with hypoxaemia. The PaO2 is low, the PaCO2 is high, with raised bicarbonate indicating renal correction and a high base excess.
Metabolic alkalosis - acute, normal oxygenation
Metabolic alkalosis, for example in a patient with severe vomiting, is characterised by a high pH, high bicarbonate and a raised base excess. In an effort to compensate, the respiratory drive decreases and hence the PCO2 begins to rise.
Respiratory failure - acute
Hypoxia, hypercapnia and acidosis with a normal bicarbonate, indicate an acute respiratory failure, for example in massive pulmonary embolism.
Respiratory failure - acute
Here is an acidosis with a normal bicarbonate, and hypercapnia, on high flow O2. This is the picture of acute respiratory failure often found in patients with chronic obstructive airway disease who have lost their hypoxic drive and have been given high concentrations of O2.
Chest signs A Asthma B Bronchial carcinoma C Bronchiectasis D Chronic bronchitis E Emphysema F Pleural effusion G Pneumonia H Pneumothorax I Pulmonary fibrosis J Pulmonary oedema
Select the most appropriate diagnosis for a 55-year-old male who presents with dyspnoea and the following signs:
Temperature 36.7C, clubbing of fingers, respiratory rate 15/min, JVP not visible, trachea central, percussion note resonant with bronchial breath sounds overlying the left midzone.
Temperature 39C, respiratory rate 30/min, JVP not visible, trachea central, percussion note dull over the left midzone and accompanying wheeze and bronchial breath sounds.
Temperature 36.5C, respiratory rate 28/min using accessory muscles of respiration, JVP raised 5 cm, trachea central, percussion note resonant and widespread inspiratory basal crackles.
Clubbing would be associated with bronchial carcinoma, pulmonary fibrosis and bronchiectasis from the choices offered.
In the case scenario, the signs of consolidation in the left midzone suggest an underlying bronchial carcinoma as the most likely explanation.
High temperature, increased respiratory rate and signs of consolidation in the left midzone suggest a pneumonic consolidation. Typically a lobar pneumonia would be caused by Pneumococcus.
Normal temperature, increased respiratory rate, raised JVP, cyanosis and basal crackles would suggest cardiac failure and pulmonary oedema as the likely diagnosis. Other features that may be expected on auscultation of the heart include a third heart sound signifying rapid ventricular diastolic filling.
The diffusion capacity of the lung as assessed by carbon monoxide transfer is raised in all but which of the following states? (Please select 1 option) Altitude Asthma Exercise Polycythaemia Post pneumonectomy
Following lung resection (and in the presence of interstitial lung disease) the diffusion capacity is reduced and there is a reduced alveolar volume.
In emphysema, pulmonary vascular disease and anaemia, the diffusion capacity is reduced but the alveolar volume is increased.
In the other conditions listed above the diffusion capacity is elevated.
By which of the following is peripheral oxygen consumption decreased ? (Please select 1 option) Catecholamines Exercise Hypothermia Infection Thyroxine
Hypothermia
Hypothermia together with rest and paralysis decrease oxygen consumption whereas the other factors listed increase peripheral oxygen consumption.
This phenomenon is taken advantage of in open heart and neurological surgery and in organ preservation.
A 60-year-old man undergoes a lobectomy for bronchial carcinoma.
During the follow-up he undergoes respiratory function testing.
Which of the following factors would not be expected to fall post-operatively?
Dead space Expiratory reserve volume Forced vital capacity Inspiratory reserve volume Tidal volume
Tidal volume
The tidal volume increases as a compensatory mechanism for the reduced surface area for oxygen exchange as does the respiratory rate.
The remaining lung volumes all decrease following pneumonectomy.
A 56-year-old lady undergoes a lobectomy for adenocarcinoma of the lung.
On the second postoperative day she is noted to be tachypnoeic and has oxygen saturations of 92% on 28% oxygen.
Which of the following factors is not contributing to her respiratory dysfunction?
(Please select 1 option)
Abdominal ileus
Anaesthetic agents IncorrectIncorrect answer selected
Poor pain control
Preoperative smoker
Prone position
All patients should be nursed prone if at all possible as this aids gaseous exchange whereas a supine position increases intra-abdominal pressure and further exacerbates the respiratory dysfunction.
The other factors listed are detrimental.
The effects of different anaesthetic agents are numerous and include
Reduced central response to hypercapnia
Reduced mucociliary clearance
Increased production of more viscous secretions.
A 24-year-old man is seen in pre-clerking prior to panproctocolectomy for familial adenomatous polyposis.
His past medical history also includes asthma for which he takes regular inhalers. Preoperative respiratory function tests are requested.
Which of the following changes is likely to be observed?
(Please select 1 option)
Decreased functional residual volume
Increased FEV1/FVC ratio
Reduced FEV1/FVC ratio CorrectCorrect
Reduced forced vital capacity
Reduced total lung capacity
This is characteristic of an obstructive disease such as asthma.
In asthma the forced vital capacity (FVC) is usually normal (but may be slightly reduced in severe cases) and it is the fall in forced expiratory volume in one second (FEV1) that is most important.
Furthermore, there is usually a positive bronchodilator response (greater than 12% improvement) in the FEV1/FVC ratio in obstructive disease.
The forced respiratory volume (FRV) is usually increased in asthma due to air trapping.
A 70-year-old retired coal miner attends for a TURP.
The anaesthetist examines his chest, is concerned about his findings, and requests lung function tests.
Which of the results below is out of character with the condition?
Pneumoconiosis is associated with fibrosis and is, as such, an example of a restrictive pulmonary disease.
In restrictive disease lung volumes are reduced and the forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) ratio is consequently usually increased.
The respiratory rate is increased to try and compensate for the reduced volumes.
You are carrying out a pleural aspiration for a patient with a persisting post-operative effusion. Which of the following structures do you want the needle to avoid? (Please select 1 option) External intercostal muscle Internal intercostal muscle Parietal pleura Transversus thoracis muscle Visceral pleura
The visceral layer of pleura is adherent to the lung and should not be pierced during pleural aspiration. This will cause damage to the lung.
However, all of the other structures will be pierced by the needle as you perform a pleural aspiration.
A 34-year old lady with asthma attends the Emergency department with laboured breathing. You note that she is using accessory muscles of respiration. Which of the following is an accessory muscle of respiration? (Please select 1 option) External intercostal Internal oblique Serratus anterior Subscapularis Trapezius
The accessory muscles of respiration are used in deep inspiration and include:
Sternocleidomastoid Scalenus anterior, medius and posterior Serratus anterior, and Pectoralis major and minor. Trapezius is not attached to the ribs so cannot be an accessory muscle of respiration.
There appears to be no clear agreement on the number of muscles that can be considered ‘accessory’. Any muscle that can affect chest expansion is included in some lists.
In an anatomy practical class you are asked to distinguish between right and left lungs on the basis of their anatomical features.
Which of the following statements is correct regarding the right lung?
(Please select 1 option)
Has a lingular segment
Has a longer bronchus than the left lung
Has a single pulmonary vein within the hilum
Has no middle lobe
Has oblique and horizontal fissures
The right lung is divided into upper, middle and lower lobes by oblique and horizontal fissures.
The lingular segment is the left lung’s equivalent of the middle lobe.
The right bronchus is shorter and wider than the left bronchus and two pulmonary veins return blood from each lung.
You are arranging pre-operative investigations for a patient who needs a hemiarthroplasty after sustaining a fractured neck of femur. The patient smokes and is known to have chronic obstructive airway disease.
Arterial blood gases show raised CO2 levels, reduced O2 levels, a reduced pH, and a raised bicarbonate.
What is the explanation?
(Please select 1 option)
Metabolic acidosis
Metabolic alkalosis
Partially compensated respiratory acidosis
Uncompensated respiratory acidosis
Uncompensated respiratory alkalosis
The reduced pH and elevated CO2 levels indicate a respiratory acidosis.
The plasma bicarbonate concentration increases to compensate for the increased hydrogen ion concentration. The pH is not returned to normal so there is only partial compensation.
Respiratory acidosis is typically caused by a reduction in ventilation or ventilation/perfusion mismatch. This can occur with chronic obstructive pulmonary disease (COPD), asthma and chest wall injuries.
ou are called to see a patient on the ward who is short of breath and complaining of chest pain.
She has recently had a total knee replacement. You suspect she might have had a pulmonary embolism.
An ECG has been performed.
Which of the following are typical ECG findings in pulmonary embolism?
(Please select 1 option)
Bradycardia
Left bundle branch block
S1Q1T3
S3Q3T3
Tachycardia
ECG changes usually occur only with large pulmonary emboli.
The characteristic changes include:
Tachycardia
A right ventricular strain pattern with inverted T waves in V1-V4
Right bundle branch block
S1Q3T3 pattern and
Transient arrhythmias, such as atrial fibrillation.
A 45-year-old woman presents to the Emergency Department with a 48 hour history of right upper quadrant abdominal pain, dyspnoea, non-productive cough and high temperature. She says that the pain is radiating to her right shoulder tip.
She had undergone repair of a perforated duodenal ulcer three weeks ago. On examination, her temperature is 39.3°C and she is acutely tender over the right hypochondric region. Chest x ray reveals a right sided pleural effusion.
Subphrenic abscesses usually arise as a result of direct contamination after surgery especially of the biliary tract, duodenum or stomach, or a perforated viscus. The other causes include infections or trauma to the liver and gall bladder.
The subphrenic space is in direct contact with the para-colic gutter, thereby allowing peritoneal contamination such as bile, blood or bowel contents to spread. Clinical features include
pyrexia (sometimes swinging) anorexia loss of appetite loss of weight. Chills and rigors may be seen in some patients.
Diaphragmatic irritation may affect the right lung, which may result in chest pain, dyspnoea and non-productive cough. Basal atelectasis, pneumonia and pleural effusion are also recognised complications which cause percussion dullness and decreased breath sounds on the affected side.
An ultrasound scan is the investigation of choice to diagnose subphrenic abscess, and, if an abscess is identified, ultrasound guided percutaneous drainage catheter may be placed at the same time.
However, if the abscess is diagnosed early (but no air fluid level) it may then be treated with broad spectrum antibiotics for a short duration.
You are asked to see a patient who attends the emergency department with shortness of breath.
The chest x ray shows right lower lobe consolidation.
Which of the following features should prompt you to consider admission to hospital?
Audible bronchial breathing A PaO2 of 9.8 kPa (11-13) A respiratory rate of 32/min A SaO2 of 95% A white cell count of 16.8x109/l (4-10)
The British Thoracic Society guidelines for community acquired pneumonia in adults recommend use of the CURB-65.
This is a 5-point score, one point for each of
Confusion
Urea more than 7 mmol/l
Respiratory rate 30/min or more
Systolic Blood pressure below 90 mmHg (or diastolic below 60 mmHg)
Age 65 years or older.
If the CURB score is 1-2 then risk of death is increased and hospital admission should be considered.
A CURB score of 3 or more puts the patient at high risk of death and hospital admission is warranted.
A 19-year-old male attends the Emergency department complaining of a sudden left-sided chest pain followed by dyspnoea. These symptoms developed whilst playing football.
Which of the following investigations is most likely to provide a definitive diagnosis?
Blood gases Chest x ray Echocardiogram Electrocardiogram (ECG) Pulmonary function tests
CXR
The history is suggestive of a pneumothorax, and of the available investigations a chest x ray is the only test which will provide a definitive diagnosis.
ECG would be unlikely to reveal any abnormality and blood gases would be most likely to reveal a highish O2 with lowish CO2 in the absence of any appreciable respiratory compromise.
A 22-year-old golf course groundsman develops sudden onset of breathlessness and right-sided chest pain whilst maintaining the 18th hole. He is rushed to hospital, but his condition worsens when being examined by a junior doctor.
She reported finding a trachea that was deviated to the left, and hearing very distant breath sounds over his right lung. Following the intervention of a senior doctor, his condition improves rapidly.
What is the most probable diagnosis?
Myocardial infarction Pericarditis Pneumonia Pulmonary embolism Tension pneumothorax
Tension pneumothorax
Sudden onset of chest pain and respiratory distress in a previously fit young man should alert one to the diagnosis of pneumothorax.
Tales of patients who developed a clinically obvious tension pneumothorax in hospital are told frequently, so it is best to be able to recognise one if it occurs while you are actually examining the patient!
A 45-year-old, overweight shop assistant is admitted to hospital with sudden onset of breathlessness and right posterior lower chest pain three weeks after undergoing right total hip replacement surgery.
She has a past medical history of bronchiectasis and asthma, but denies any recent change in sputum colour or quantity.
Oxygen saturation is 89% on air, but rises to 95% on (35%) oxygen. She is apyrexial. Chest examination reveals coarse leathery crackles at both lung bases.
Peak flow rate is 350 L/min and chest radiograph shows bronchiectatic changes, also at both lung bases. Full blood count is normal.
What is the most appropriate investigation to conduct next?
Blood cultures CT-pulmonary angiography Echocardiogram Full blood count Ventilation/perfusion scan
CTPA
Computerised tomography (CT) pulmonary angiography is the investigation of choice in this patient who almost certainly has a pulmonary embolism.
Ventilation perfusion scan is not ideal in a patient with chronic lung disease, because the scan can be difficult to interpret.
A 12-year-old girl presents with left ear pain and fever, worsening over the past three days. Today her mother has noted a whitish creamy discharge from the ear canal.
She was born at 38/40 gestation weighing 3.8 kg and there were no neonatal problems. She is fully immunised. She trains regularly in a swimming team.
On examination she has a temperature of 38.2°C and has a red left tragus. This is exquisitely tender, and examination of the drum is impossible because of the pain and creamy thin discharge. She has shotty tender posterior cervical glands.
What is the most likely diagnosis?
Group A streptococcal pharyngitis Mastoiditis Otitis externa Otitis media, acute Otitis media, recurrent
The history suggests an acute otitis externa. The tight adherence of skin to the underlying perichondrium and periosteum make the pain worse than the degree of inflammation would suggest.
An ear swab culture should be sent and neomycin and colistin/polymyxin ear drops commenced. This covers the common Gram positive and Gram negative bacteria usually responsible.
A 7-year-old girl presents with right ear pain and fever, worsening over the past few days. Symptoms began seven days ago with severe ear pain and fever, which was treated with paracetamol. The following morning the pain resolved and a purulent discharge mixed with blood was noted on her pillow. Four days later the pain is throbbing and her ear is tender.
She was born at term weighing 3.68 kg and there were no neonatal problems. She is fully immunised, and there is no FH/SH of note.
On examination she has a fever to 39.7°C, and her right ear is displaced downwards and forwards. She is extremely tender behind the right ear, and has a purulent discharge from the ear canal. Her pulse is 100/min and respiratory rate is 15/min.
What is the most likely diagnosis?
Cholesteatoma Mastoiditis CorrectCorrect Otitis media with effusion Otitis media, acute Otitis media, recurrent
Mastoiditis
The history suggests acute otitis media with perforation, followed by acute mastoiditis (acute mastoid osteitis).
This can be confirmed by CT scan of the mastoid.
Pneumococcus and H. influenzae are the commonest cause.
Most resolve with antibiotics, but some require surgical drainage.
Carcinoid tumours of the lung (bronchial adenomas) originate from which of the following cell types?
Ciliated cell Clara cell Kulchitsky (K) cell Mucus (goblet) cell Type 2 alveolar cell
Kulchitsky (K) cell
Carcinoid tumours (so called argentafinomas as they take up silver) are neuroendocrine cells and are derived from the K cells in the lung.
Which one of the following is true regarding acute pulmonary embolism?
A normal ECG excludes the diagnosis
Embolectomy is more effective than thrombolysis in improving survival IncorrectIncorrect answer selected
Heparin is as effective as thrombolytic therapy
The presence of hypoxaemia is an indication for thrombolysis
Thrombolysis administered through a peripheral vein is as effective as through a pulmonary artery catheter
Embolectomies are rarely done nowadays due to the excellent results with thrombolysis.
Thrombolytic therapy is reserved for those with severely compromised circulation (equally effective through peripheral vein or via catheter in pulmonary artery).
Heparin reduces risk of further embolism (anticoagulant) and reduces pulmonary vasoconstriction.
Blood gas analysis
A Metabolic acidosis - acute, normal oxygenation
B Metabolic acidosis - acute with hypoxaemia
C Metabolic acidosis - compensated, normal oxygenation
D Metabolic alkalosis - acute, normal oxygenation
E Metabolic alkalosis - acute with hypoxaemia
F Metabolic alkalosis - compensated, normal oxygenation
G Normal blood gases
H Normal ventilation with hypoxaemia
I Respiratory failure - acute
J Respiratory failure - compensated, normal oxygenation
K Respiratory failure - compensated with hyperaemia
For each of the following blood gas results, select the most appropriate designation from the list of options.
The line labelled oxygen concentration represents the concentration of oxygen that each individual is inhaling.
Normal values are: PaO2 12.0-14.7 kPa (90-110 mmHg) PaCO2 4.5-6.0 kPa (34-45 mmHg) pH 7.36-7.44 H + molarity 35-45 nmol/L Bicarbonate 24-30 mmol/L
pO2 10.0 kPa (80 mmHg) pCO2 5.8k Pa (44 mmHg) pH 7.24 H+ molarity 57 nmol/L Bicarbonate 18 mmol/L Base Excess −7 mmol/L Oxygen concentration 40%
pO2 6.7 kPa (50 mmHg) pCO2 10.1 kPa (76 mmHg) pH 7.38 H+ molarity 42 nmol/L Bicarbonate 42.4 mmol/L Base excess +14 mmol/L Oxygen concentration 21%
pO2 14.3 kPa (108 mmHg) pCO2 6.3 kPa (48 mmHg) pH 7.52 H+ molarity 30 nmol/L Bicarbonate 39 mmol/L Base excess +14 mmol/L Oxygen concentration 30%
pO2 4.7 kPa (35 mmHg) pCO2 12.7 kPa (95 mmHg) pH 7.12 H+ molarity 76 nmol/L Bicarbonate 29.5 mmol/L Base excess −4mmol/L Oxygen concentration 21%
pO2 16.3 kPa (122 mmHg) pCO2 7.5 kPa (56 mmHg) pH 7.26 H+ molarity 55 nmol/L Bicarbonate 24.1 mmol/L Base excess −2 mmol/L Oxygen concentration 75%
The low pH with low bicarbonate indicates a metabolic acidosis, and the low normal O2 on inspired [O2] indicates hypoxaemia. This may occur with poisoning and associated respiratory failure.
This is the typical feature of a corrected respiratory failure with hypoxaemia. The PaO2 is low, the PaCO2 is high, with raised bicarbonate indicating renal correction and a high base excess.
Metabolic alkalosis, for example in a patient with severe vomiting, is characterised by a high pH, high bicarbonate and a raised base excess.
There is a type 2 respiratory failure with hypoxia, hypercapnia and acidosis with a normal bicarbonate, indicating an acute respiratory failure, for example in severe asthma or pneumonia.
There is an acidosis with a normal bicarbonate, and hypercapnia, on high flow O2. This is the picture of acute respiratory failure often found in patients with chronic obstructive airways disease who have lost their hypoxic drive and have been given high concentrations of O2.
A 27-year-old female with adult respiratory distress syndrome (ARDS) is ventilated on intensive care.
Her inspired oxygen is 100%, positive end expiratory pressure is 15 cmH2O and peak airway pressure is 40 cmH2O.
Her arterial blood gas shows:
PaO2 6 kPa (11.3-12.6)
PaCO2 6.9 kPa (4.7-6.0)
SpO2 88% (>92%)
What treatment has been shown to decrease mortality in this patient group?
(Please select 1 option)
High frequency oscillatory ventilation (HFOV)
Increasing tidal volume and respiratory rate on the ventilator
Inhaled nitric oxide therapy
Prone position
Extracorporeal membrane oxygenation (ECMO)
This lady is on maximal ventilatory therapy but is still hypoxic. Her high CO2 is a reflection of permissive hypercapnia to prevent overdistension of the lungs with high tidal volumes.
Treatment of these patients used to be extremely difficult, with no significant improvement in prognosis seen will any technique. However, in 2010 the CESAR trial demonstrated a significant increase in survival without significant disability with the use of extracorporeal membrane oxygenation (ECMO).
ECMO involves connecting a patient’s circulation to an external oxygenator and pump, via a catheter placed in the right side of the heart. It requires the continuous infusion of anticoagulant, and as such bleeding is the most commonly associated complication. Infection and haemolysis are also a risk.
A recent study1 published in the NEJM concluded that prone positioning improved outcome in severe ARDS. However, it is only one study in a controversial area. There are a number of studies, including one by the same group, which have not shown a mortality benefit (and others which show a detrimental effect on mortality). Prone positioning is therefore not yet widely accepted in clinical practice, although this may change in the future. For the purpose of the MRCP (where there are single best answers), ECMO remains the correct answer.
A 25-year-old male is involved in a high speed road traffic accident and after extraction from his car is brought to the Emergency department. On initial primary survey, he is triple immobilised. He is making slightly confused conversation.
Initial observations reveal a tachycardia of 120 bpm, and a systolic blood pressure of 90 mmHg. He has a respiratory rate of 30 and his chest is dull to air entry on the right hand side. He is tender over his right upper quadrant on abdominal examination.
How much of his circulating blood volume is he likely to have lost?
(Please select 1 option)
Nil
Up to 15%
15% to 30%
30% to 40%
Greater than 40%
The most common cause of shock in the trauma patient is haemorrhage.
The patient has decreased blood pressure and a tachycardia which means that he is in at least class III shock, signifying a blood loss of 1500 to 2000 ml, or approximately 30 to 40% of circulating blood volume.
An otherwise healthy 32-year-old man was the driver of a car involved in a high speed RTA three days ago.
He has sustained a closed fracture of his femur which has been treated surgically with an intramedullary nail, as well as fractures of his right clavicle and left radius. He was managed according to ATLS protocol when he attended the emergency department.
On examination he is acutely short of breath and has a temperature of 37.5oC. The patient seems confused when you speak to him, and as you examine him, you note petechial haemorrhages.
What do you think is the most likely diagnosis?
Asthma attack Chest infection Fat embolism CorrectCorrect Pulmonary embolism Tension pneumothorax
The two diagnoses which should be considered first in this scenario are pulmonary embolism and fat embolism.
Although the patient is at high risk of pulmonary embolism, and appropriate measures should be undertaken to reduce this, the clinical scenario is more suggestive of fat embolism. Fat embolism is thought to occur as a result of release of lipid globules from damaged bone marrow fat cells. Another mechanism that has been suggested is the increased mobilisation of fatty acids peripherally.
The effects that are seen clinically depend on what part of the microvasculature is affected by the lipid globules.
Pulmonary symptoms are caused by ventilation perfusion mismatch.
Confusion (cerebral effects) may be seen, as well as a petechial rash caused by capillary damage in the skin.
