3. Pneumothorax

Question 1

Intro

Answer 1

Pneumothorax is an important complication in anaesthesia, trauma and medicine.

This oral will concentrate both on the precise mechanisms
by which pneumothoraces occur and on details of recognition and treatment.

A pneumothorax can develop rapidly into a life-threatening emergency,
and so you must ensure that your management is competent.

Question 2

What is it

Answer 2

By definition, a pneumothorax exists when there is air in the pleural space.

This is a potential space in the area between the
parietal and the visceral layers of the pleura
which are usually in close apposition and separated
only by a small amount of serous fluid.

Question 3

Pathology

Answer 3

At the end of expiration there is no pressure differential between intra-alveolar and
atmospheric pressure.

However, the intrapleural, or transpulmonary, pressure is subatmospheric,
and the slight negative pressure of around 4–6 cm H2O
(caused by the opposing elastic recoil of the lung and the chest wall) keeps the lungs
expanded.

This pressure differential also opposes the tendency of the thoracic wall to move outwards.

When air gains access to the intrapleural space, the negative transpulmonary
pressure is lost and the stretched lung collapses while the chest wall moves outwards

Question 4

Pathology

Answer 4

At the end of expiration there is no pressure differential between intra-alveolar and
atmospheric pressure.

However, the intrapleural, or transpulmonary, pressure is subatmospheric,
and the slight negative pressure of around 4–6 cm H2O
(caused by the opposing elastic recoil of the lung and the chest wall) keeps the lungs
expanded.

This pressure differential also opposes the tendency of the thoracic wall to move outwards.

When air gains access to the intrapleural space, the negative transpulmonary
pressure is lost and the stretched lung collapses while the chest wall moves outwards

Question 5

How does air gain access

Answer 5

Air can enter the intrapleural space via a breach

in the parietal or
visceral pleura (or both), or
via the mediastinal pleura as a consequence of intrapulmonary
alveolar rupture.

Gas insufflated into the abdomen under pressure may also enter
the interpleural space via the mediastinal pleura.

Question 6

Size affected by

Answer 6

The size of a pneumothorax will increase if the patient is ventilated with positive
pressure, or if nitrous oxide is given. (Paramedics routinely carry Entonox to provide analgesia for accident victims.)

It will also increase if there is a significant reduction
in atmospheric pressure, which has obvious implications for the air evacuation of
trauma patients.

Question 7

Causes of Pleural Breach (Parietal and Visceral)

Answer 7

Traumatic:
pneumothorax can follow penetrating injury,
rib fracture or blast injury.

Iatrogenic (surgical):
it may occur during procedures such as nephrectomy,
in spinal surgery,
during tracheostomy (especially in children),
laparoscopy or as a
consequence of oesophageal or mediastinal perforation.

Iatrogenic (anaesthetic):
pneumothorax may result from attempted central venous
puncture and various nerve blocks.

These include supraclavicular, interscalene,
intercostal and paravertebral blocks.

It may be caused by barotrauma due to mechanical
ventilation and from gas injector systems.

Miscellaneous:
it may occur if the alveolar septa are weakened,
as described in the following,

and is associated with many pulmonary diseases,
including asthma.

There are some bizarre and unusual causes;
recurring catamenial pneumothorax, for
example, is a spontaneous pneumothorax, usually right-sided,
which occurs in phase
with the menstrual cycle.

Question 8

Intrapulmonary Alveolar Rupture

Answer 8

Gas escapes from the alveolus,
dissects towards the hilum and ruptures the mediastinal pleura.

Causes include barotrauma from mechanical ventilation
(caused by excessive pressures in the context of reduced lung compliance)

or high-pressure gas delivery systems (injectors).

Patients with chronic obstructive pulmonary disease
(COPD) with bullous emphysema are also at risk.

It is also caused by blast injury and may occur in asthmatics
and in patients in whom the alveolar septa are weakened or
distorted by infection, collagen vascular disease or connective tissue disorders,
such as Ehlers–Danlos and Marfan’s syndromes.

Severe hypovolaemia has been implicated
as a risk factor for the same reason.

Question 9

Diagnosis of Pneumothorax in the Awake Patient

Answer 9

Typical features (which are not invariable and which will depend on the size of the
pneumothorax and whether it is expanding)

include chest pain,
referred shoulder tip pain,
cough,
dyspnoea,
tachypnoea and tachycardia.

There may be reduced movement of the affected hemithorax,
hyperresonance on percussion,
diminished breath sounds and decreased vocal fremitus.

The coin test (bruit d’airain – ‘noise of bronze’)
may be positive, as may
Hamman’s sign (auscultation reveals a ‘crunching’ sound of
air in the mediastinum which occurs in time with the heartbeat).

In the coin test, the tapping of one coin against another placed flat on the chest wall can be heard on auscultation as a ringing sound.

These signs are less definitive than chest X-ray which
will confirm the clinical diagnosis.

If a patient is relatively symptom-free and is managed conservatively,
the rate of reabsorption of air from a pneumothorax cavity
is slow at up to 2% of the volume of the hemithorax in 24 hours.

Question 10

Diagnosis of Pneumothorax in the Awake Patient

Answer 10

Typical features (which are not invariable and which will depend on the size of the
pneumothorax and whether it is expanding)

include chest pain,
referred shoulder tip pain,
cough,
dyspnoea,
tachypnoea and tachycardia.

There may be reduced movement of the affected hemithorax,
hyperresonance on percussion,
diminished breath sounds and decreased vocal fremitus.

Question 11

Tests

Answer 11

The coin test (bruit d’airain – ‘noise of bronze’)
may be positive, as may
Hamman’s sign (auscultation reveals a ‘crunching’ sound of
air in the mediastinum which occurs in time with the heartbeat).

In the coin test, the tapping of one coin against another placed flat on the chest wall can be heard on auscultation as a ringing sound.

These signs are less definitive than chest X-ray which
will confirm the clinical diagnosis.

If a patient is relatively symptom-free and is managed conservatively,
the rate of reabsorption of air from a pneumothorax cavity
is slow at up to 2% of the volume of the hemithorax in 24 hours.

Question 12

Tension

Answer 12

If the pneumothorax is expanding under tension,

the clinical features are more dramatic
because mediastinal compression by the expanding mass
decreases venous return,
impairs ventricular function and reduces cardiac output.

Patients will complain of dyspnoea;
signs include tachypnoea and eventual cyanosis.

Cardiovascular compromise will manifest as tachycardia,
hypotension and, ultimately, cardiac arrest.

There may be tracheal deviation (which is not always easy to identify) and subcutaneous
emphysema. Tension pneumothorax can be bilateral. The diagnosis of a
tension pneumothorax should never await chest X-ray confirmation.

Question 13

Diagnosis of Pneumothorax in the Anaesthetized Patient

Answer 13

Initial signs may be non-specific,
with hypotension and tachycardia; others include
diminished
unilateral chest movement,
wheeze, hyperresonance,
decreased breath sounds and increased airway pressure.

There may be tracheal deviation and elevated central venous pressure
(if it is being monitored).

Cyanosis, arrhythmias and circulatory collapse may supervene.

If the diagnosis is suspected,
treatment must not be delayed pending chest X-ray.

Ultrasound provides effective diagnosis in experienced hands.

The critical care patient with acute respiratory distress syndrome (ARDS)
may have a pneumothorax but with little evidence of pulmonary collapse.

This is because the non-compliant lung loses the elasticity which would otherwise allow it to
collapse away from the chest wall. Pneumothoraces in patients with chronic lung disease may be loculated.

Question 14

Management of Pneumothorax

Answer 14

Management:

discontinue nitrous oxide (in the anaesthetized patient)
and give 100% oxygen.

Immediate management is decompression via needle thoracocentesis
followed rapidly by insertion of a definitive chest drain
(intravenous cannulae are too small to provide continued effective decompression).

The traditional recommended site is the fourth intercostal space
in the mid-axillary line.

The British Thoracic Society (BTS) suggests that the drain should be inserted in the so-called
safe triangle, which is the area bordered by the lateral border of the pectoralis major
muscle, by the anterior border of the latissimus dorsi and by a line superior to the
horizontal level of the nipple.

Its apex is just below the axilla.

Question 15

Drain sizes

Answer 15

The BTS recommend small-size drains for simple pneumothorax (8–14 F),
there being no evidence of benefit from larger diameter tubes;

however, larger sizes (24–28 F) are recommended for drainage of blood or fluid.

Question 16

Underwater seal drain:

Answer 16

Underwater seal drain:

air from the pneumothorax drains under water via a
submerged tube in a sealed bottle and is then vented to the atmosphere.

The depth of water is important: if it is too shallow,
air may be entrained back into the drainage
tube; if it is too deep,

the pressure may be too great to blow off the pneumothorax gas.

The typical depth is 3–5 cm.

Clamping a chest drain risks converting a simple
pneumothorax to one that is under tension.

Question 17

Pneumothorax

Answer 17

Is the commonest leak from an air-filled space that is seen in anaesthetic practice.

Others include subcutaneous emphysema which is formed by
air that tracks along tissue planes.

It can be seen on X-ray but simple palpation will
elicit the characteristic crepitus.

The condition can be dramatic, extending up into the tissues of the neck or, in males, down into the scrotum but usually presents no undue threat to the patient.

This is also true of pneumomediastinum itself, but not of
its underlying causes,
which include pharyngeal, oesophageal and gastrointestinal tract perforation.

Pneumopericardium in contrast may be associated with cardiac
tamponade and the need for immediate pericardiocentesis.

Question 18

What are the likely causes of this presentation?

Answer 18

Respiratory causes include
Asthma
Pneumothorax
Infection
Pleural effusion
Systemic allergic reaction.

Cardiovascular causes include
Pulmonary embolism
Pulmonary hypertension
Pulmonary oedema.

Physiological responses to underlying metabolic disorders should be
considered, e.g. acute abdomen, DKA, etc.

Question 19

Flail chest

Answer 19

Occurs when there are two or more fractures in a rib or one fracture and
costo-chondral dislocation.

Clinically, the flail segment shows paradoxical movement, i.e. on inspiration
it is drawn inwards and on expiration it is pushed outwards.

There is pain and respiratory distress.

Question 20

Pneumothorax

Answer 20

Symptoms include pleuritic pain and shortness of breath.
Signs include
Reduced movement or expansion on the affected side
Hyper-resonant percussion note
Reduced breath sounds
Tracheal deviation away from the affected side with a large pneumothorax.

NB Pneumothorax and flail segment may both be present at the same time

Question 21

How do you treat a patient with a pneumothorax?

Answer 21

Pneumothoraces are designated ‘small’ or ‘large’, depending on the visible
rim of air between lung and chest wall seen on a PA CXR.
The cut off is 2 cm.
50% of lung volume may be lost in the presence of a 2 cm rim.

Question 22

Management of pneumothorax

Answer 22

Small pneumothorax, patient not breathless – observe.
Small pneumothorax and patient breathless – reassess, but if
symptoms remain then aspirate.
Large, primary pneumothorax – aspirate.
Large secondary pneumothorax – unlikely to treat definitively with
aspiration:
especially if age > 50 years but may be attempted.
Likely to need intercostal drain.
Aspiration should improve symptoms and drain at least 2.5 litres of air.
Otherwise, consider repeat aspiration or intercostal tube drainage.

Question 23

Describe how a chest drain is inserted.

Answer 23

The patient should be adequately prepared and consented.
Establish i.v. access.
Infiltrate the area with local anaesthetic (10–20 ml of 1% lignocaine).
Insertion should be in the ‘safe triangle’ bordered by the anterior border of
the latissimus dorsi, the lateral border of the pectoralis major muscle, a line
superior to the horizontal level of the nipple, and an apex below the axilla.
Traditional blunt dissection.
A small incision (parallel to and just superior to the rib).
Dissection as close to the top of the rib as possible to avoid the
neuro-vascular bundle.

Puncture the pleura with blunt forceps.
Finger sweep into the pleural cavity to ensure that the lung is not adherent
to the insertion site.
Clamp the proximal end of the tube and insert without the trocar.
Direct the tube towards the apex (towards the base for fluids – not
essential).
Connect the tube to an underwater drainage system.
Suture in place and apply dressing.
Obtain a chest X-ray.

Question 24

Seldinger technique

Answer 24

A guide-wire is passed through a needle into the pleural cavity
Followed by dilators and then the drain.
Seldinger drains are smaller, generally cause less of a scar and the technique
is familiar to most anaesthetists.
The complication rates for both techniques are similar

Question 25

Ventilated Patients

Answer 25

If the patient is on a ventilator, then the BTS advice is to disconnect the
ventilator prior to entering the pleural cavity and inserting the drain.
This will help avoid lung lacerations.

Question 26

What can you connect the drain to?

Answer 26

All chest tubes should be connected to a single flow closed drainage system.
An underwater seal (UWS) bottle or
A flutter (Heimlich) valve

Question 27

Spontaneous breathing no seal

Answer 27

On inspiration, a negative intrapleural pressure is created (around –8 cm of
water in tidal breathing). The fluid level in the tube will therefore rise. If the
underwater seal was not present, air would be sucked into the pleural cavity.

On expiration, intrapleural pressure will become positive if chest wall pressure
exceeds alveolar pressure. If this occurs, then air will be expelled via the drain.

Question 28

IPPV

Answer 28

On inspiration, a positive intrapleural pressure is created, which results in the
drainage of air.

On expiration, the intrapleural pressure will still be positive if
there is PEEP applied to the lungs and therefore air will still drain.

A potential problem may arise when using traditional chest drain bottles to
drain fluid and air simultaneously. As the fluid level in the bottle (and thus the
submerged end of the tube) rises, a higher positive intrapleural pressure will
be required to drain air.

Hence, the lung may not fully re-expand and in the
case of a persistent leak a tension pneumothorax could develop (or may just
drain at a higher pressure).

Modern chest drain bottles are now designed to
maintain the submerged end of the intercostal drain at less than 2–3 cm below
the level of the fluid.

Question 29

How far beneath the water must the tube be placed?

Answer 29

In a closed UWS bottle the tube is placed under water at a depth of
approximately 3 cm with a side vent which allows the escape of air.
The UWS allows you to see:
Air bubble out as the lung re-expands in the case of pneumothorax.
Fluid evacuation rate in empyemas, pleural effusions, or haemothorax.
Continuous bubbling suggests a visceral pleural air leak (bronchopleural
fistula).
The respiratory swing in the fluid in the chest tube is useful for assessing
tube patency and confirms the position of the tube in the pleural cavity

Question 30

What is the significance of the depth of the underwater seal?

Answer 30

The effective drainage of air, blood or fluids from the pleural space requires
an airtight system to maintain subatmospheric intrapleural pressure.
With a collection chamber of approximately 20 cm diameter and a 3 cm
depth of water, this ensures minimum resistance to drainage of air and
maintains the underwater seal even in the face of a large inspiratory effort.
The chamber should be 100 cm below the chest as subatmospheric pressures
up to −80 cmH2O may be produced during obstructed inspiration.
Lifting the drainage system above the patient’s chest will cause siphoning of
the contents back into the pleural cavity.

Question 31

Tell me about suction applied to intercostal drains?

Answer 31

Suction can be used to increase the drainage from the pleural space. Only high
volume, low pressure pumps should be used. A pressure of 10–20 cmH20 is
adequate for a pneumothorax. Low volume, high pressure pumps are dangerous and should not be used.

The low volume displacement may not be
able to cope with large air leaks, resulting in tension. High pressure may result
in damage to the visceral surface of the lung.

Question 32

When would you clamp an intercostal drain?

Answer 32

This is controversial. Some authorities state that there are no indications to
clamp a drain. Some points to note are:

Never clamp a bubbling chest drain.
Drains should not be clamped during transfer.
Drains should be clamped after a pneumonectomy. If they are not, then
catastrophic mediastinal shift can occur. Every hour the drain should be
unclamped briefly to look for significant post-operative bleeding.

Large effusions can drain rapidly resulting in re-expansion pulmonary oedema
(may be unilateral). This can cause chest discomfort and tightness and has
resulted in death. Clamping the drain for a period of time (4 hours has been
suggested.

Question 33

Chest drains – additional information

Answer 33

The underwater seal
UWS first used in 1875, but used in its modern form since 1916 when
Kenyon described a ‘siphon method of draining traumatic haemothorax’.
It has potential hazards apart from insertion in that the UWS system
must be kept upright and the draining tube must always be under the
water. A bubbling chest tube should never be clamped, as this risks
creating a tension pneumothorax if there is persistent air leak.

Question 34

Does size matter?

Answer 34

There is no evidence that large tubes (20–24 F) are any better than small
tubes (10–14 F) in the management of pneumothorax. The initial use of
large (20–24 F) intercostal tubes is not recommended, although it may
become necessary to replace a small chest tube with a larger one if there
is a persistent air leak. Larger tubes are used when one wishes to drain
blood or viscous fluids.

Question 35

Pre-drainage risk assessment

Answer 35

Risk of haemorrhage
Where possible, any coagulopathy or platelet defect should be
corrected prior to chest drain insertion.
Routine measurement of the platelet count and prothrombin time
are only recommended in patients with known risk factors.

Differential diagnosis between a pneumothorax and bullous disease
requires careful radiological assessment.

Similarly, it is important to differentiate between the presence of
collapse and a pleural effusion when the chest radiograph shows a
unilateral ‘whiteout
Lung densely adherent to the chest wall throughout the hemithorax is
an absolute contraindication to chest drain insertion.
Drainage of a post-pneumonectomy space should only be carried out
by or after consultation with a cardiothoracic surgeon.

Question 36

Tension pneumothorax

Answer 36

If tension pneumothorax is present, a cannula of adequate length should
be promptly inserted into the second intercostal space in the mid
clavicular line and left in place until a functioning intercostal tube can be
positioned.