Chest Drain & The Thoracic Cavity

Question 1

Identify anatomical structures relevant to the placement of a thoracic catheter

Question 2

Describe the anatomy of the thoracic wall

Answer 2

Cone-shaped, with thoracic inlet at apex

Walls formed by ribs (true false and last) and intercostal muscles laterally and diaphragm caudally

Question 3

Outline the structure of ribs

Answer 3

Ribs articulate with the sternebrae via cartilaginous extensions from the costochondral junctions. The sternebrae are connected to one another by fibrocartilage.

The ribs have two articular facets which contact the vertebrae

True ribs: articulating directly with the sternum

False ribs: articulating indirectly through connection of the cartilage with that in front (costal arch)

Last rib may not have contact with neighbor

Question 4

Describe the anatomy of the intercostal muscles

Answer 4

External and internal (deep to external) intercostal muscles between the ribs

Intercostal vein/artery/nerve caudal to the rib

Question 5

Describe the innervation of the thoracic wall

Answer 5

External and internal muscles occupy the intercostal spaces.

Innervated by the corresponding thoracic spinal nerves

Question 6

Describe the anatomy and innervation of the diaphragm

Answer 6

Major muscle of inspiration

Striated musculature

Motor and sensory innervation by the phrenic nerve

Question 7

What is the origin of the phrenic nerve?

Answer 7

Ventral branches of the fifth (C5), sixth (C6) and seventh (C7) cervical spinal nerves

Insertion at inner aspect of thorax, ribs & sternum and via two crura to lumbar vertebrae

Question 8

Outline the openings in the diaphragm

Answer 8

Caudal vena cava: Caval foramen
Oesophagus: Esophageal foramen
Aorta and thoracic duct: Aortic Hiatii

Question 9

What is the crura?

Answer 9

Diaphragm, consists of two muscular crura that arise by tendons from fourth lumbar vertebra and have muscular attachments to the lumbar vertebrae, ribs, and sternum.

The diaphragmatic crurae are joined by a central tendinous portion.

Question 10

Outline the general layout left side of the thoracic cavity

Answer 10

Heart in pericardium
Lungs (largely removed)
Arteries & veins, including aorta
Oesophagus
Nerves & ganglia
Diaphragm
Phrenic nerve
Vagus nerve
Thymus
Can you see the thoracic duct?

Question 11

Outline the general layout right side of the thoracic cavity

Answer 11

Heart
Lungs
Trachea
Arteries
Veins
sympathetic trunk
Diaphragm
Phrenic nerve
Brachial plexus

Question 12

Describe the anatomy of pleura

Answer 12

The surface of the inner wall of the body cavities is lined by a serous membrane

Single layered flat epithelium with thin underlying connective tissue

The membrane is named pleura in the thoracic cavity

Two pleural membranes are arranged as closed pleural sacs

The contact region between the right and left pleural sac is the mediastinum

Question 13

Describe the function of the pleural cavity

Answer 13

The narrow space between the parietal and viscera pleura is the pleural cavity

It contains a small amount of serous fluid spread over the surface of the pleura

Establishes adhesion with thoracic wall (think two glass slides with fluid between them)

Facilitates smooth movement

Lung follows movements of diaphragm and thoracic wall

Sub-atmospheric pressure

Question 14

Describe the mediastinum Structure & Contents

Answer 14

Mediastiunum is the space between the left and right pleural sacs

More or less in the midline of the thorax

Extends from the thoracic inlet to the diaphragm

Contains: heart, thymus, portions of the oesophagus and trachea, blood vessels and nerves

Question 15

Outline the clinical condition Pneumothorax

Answer 15

Pneumothorax = an accumulation of air in the pleural space and is a frequent cause of dyspnoea in dogs and cats

Causes an increase in intrathoracic pressure and collapse of the lungs

Causes of pneumothorax:

Traumatic pneumothorax from injury to the chest is the most common cause of pneumothorax in dogs and cats
-bite wounds, car accidents, gunshot wounds, fights, shearing injuries, falls, kicks or blunt trauma

Question 16

Outline the clinical condition pleural infusion

Answer 16

Pleural effusion is defined as the abnormal collection of fluid in the thoracic cavity

Disease processes that can cause effusion in thorax:

Congestive heart failure, cancer, pneumonia, and pulmonary embolism.

Clinical Signs
tachypnea, shallow respiration, increased respiratory effort, open-mouth breathing, and coughing. In chronic situations lethargy, weight loss, inappetence, and depression may be present
Physical abnormalities may include cyanosis, pale mucous membranes, dyspnea, abdominal pain, abdominal distension from concurrent peritoneal effusion, evidence of trauma, lateral recumbency, poor body condition, hypothermia, lymphadenopathy, and/or fever.

Question 17

Describe what a chest drain is used for

Answer 17

Thoracentesis is also known as thoracocentesis or pleural tap

Thoracostomy tubes are also referred to as chest tubes or thoracic drains, and are used to withdraw air or fluid from the pleural space

Question 18

What preparation will be required before placing a chest drain?

Answer 18

Based on radiographic findings, the TT can be placed unilaterally or bilaterally.

The hemithorax should be clipped, prepared and draped, including the 13th rib.

Ideally, clipping and surgical preparation should be performed while the patient is conscious in sternal recumbency.

General anaesthesia is then induced and the drain inserted with the patient in lateral recumbency.

Question 19

Where is the incision in the skin made for a chest drain?

Answer 19

10th or 11th rib interspace

Question 20

Where does the tube enter the thoracic cavity during a chest drain?

Answer 20

Through the intercostal muscles (caudal to cranial) into the 7th interspace

Question 21

What is the purpose of the subcutaneous tunnel before entering the thoracic cavity during a chest drain?

Answer 21

This provides a “flap valve” effect, limiting air entering the chest along the tube’s surface

Question 22

After the skin, what layers must the trochar pass through before entering the pleural space during a chest drain?

Answer 22

Intercostal muscles, parietal pleura, pleural cavity and visceral pleura

Question 23

Where, in relation to the rib must the drain be placed to avoid the intercostal vessels and nerves during a chest drain?

Answer 23

On the caudal aspect of each rib, introduce the needle close to the cranial rib border. To avoid pulmonary trauma, insert the needle at a 45° angle. the intercostal artery, vein and nerve