Chest Drain & The Thoracic Cavity Flashcards
Identify anatomical structures relevant to the placement of a thoracic catheter
Describe the anatomy of the thoracic wall
Cone-shaped, with thoracic inlet at apex
Walls formed by ribs (true false and last) and intercostal muscles laterally and diaphragm caudally
Outline the structure of ribs
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
Describe the anatomy of the intercostal muscles
External and internal (deep to external) intercostal muscles between the ribs
Intercostal vein/artery/nerve caudal to the rib
Describe the innervation of the thoracic wall
External and internal muscles occupy the intercostal spaces.
Innervated by the corresponding thoracic spinal nerves
Describe the anatomy and innervation of the diaphragm
Major muscle of inspiration
Striated musculature
Motor and sensory innervation by the phrenic nerve
What is the origin of the phrenic nerve?
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
Outline the openings in the diaphragm
Caudal vena cava: Caval foramen
Oesophagus: Esophageal foramen
Aorta and thoracic duct: Aortic Hiatii
What is the crura?
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.
Outline the general layout left side of the thoracic cavity
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?
Outline the general layout right side of the thoracic cavity
Heart
Lungs
Trachea
Arteries
Veins
sympathetic trunk
Diaphragm
Phrenic nerve
Brachial plexus
Describe the anatomy of pleura
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
Describe the function of the pleural cavity
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
Describe the mediastinum Structure & Contents
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
Outline the clinical condition Pneumothorax
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
Outline the clinical condition pleural infusion
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.
Describe what a chest drain is used for
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
What preparation will be required before placing a chest drain?
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.
Where is the incision in the skin made for a chest drain?
10th or 11th rib interspace
Where does the tube enter the thoracic cavity during a chest drain?
Through the intercostal muscles (caudal to cranial) into the 7th interspace
What is the purpose of the subcutaneous tunnel before entering the thoracic cavity during a chest drain?
This provides a “flap valve” effect, limiting air entering the chest along the tube’s surface
After the skin, what layers must the trochar pass through before entering the pleural space during a chest drain?
Intercostal muscles, parietal pleura, pleural cavity and visceral pleura
Where, in relation to the rib must the drain be placed to avoid the intercostal vessels and nerves during a chest drain?
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
