Internal Heart and Lungs

• A pneumothorax is the entry of air into the pleural cavity from a penetrating wound or lung damage that causes the lung to collapse.
• if air enters the pleural cavity, the transpulmonary pressures increase above -5 mm H2O (equalizes with atmospheric pressure) and the elastic recoil of the lungs causes the lungs to collapse.
• Simple pneumothorax: Occurs when an injury does not create continuous communication between the pleural cavity and the atmosphere.
• Communicating pneumothorax: Opening in thoracic wall that allows air to freely move into and out of the pleural cavity; known as a "sucking chest wound."
• Tension pneumothorax: A one-way and progressive accumulation of air in the pleural cavity, where air enters the pleural cavity but does not exit.
• Air accumulation in a tension pneumothorax results in a shifting of the mediastinum to the opposite side, causing a compression of the contralateral lung and great vessels.
• Consequences of tension pneumothorax include: decreased cardiac output, hypoxia, acidosis, and shock
• Primary spontaneous pneumothorax can occur without a known eliciting event in patients without underlying pulmonary disease.
• Secondary spontaneous pneumothorax can occur without a known eliciting event in patients with underlying pulmonary disease.
• Iatrogenic pneumothorax is caused by treatment, while traumatic pneumothorax is caused by an injury
• The layers the needle penetrates through during thoracentesis are the skin, subcutaneous tissue/superficial fascia, deep fascia, external, internal, and innermost intercostal muscles, endothoracic fascia, parietal pleura, pleural cavity.
• A thoracentesis often occurs along the mid-axillary line, between ribs 9 and 10, within the costo-diaphragmatic recess to avoid damaging the lung.
• The needle is inserted just superior to inferior rib along intercostal space to avoid the intercostal nerves and their collateral branches.
• A thoracostomy is the insertion of a chest tube to remove air or other fluids from the pleural cavity.
• For a thoracostomy, a short incision is often made at the level of the fifth or sixth intercostal space along the midaxillary line.
• The tube in a thoracostomy can be moved superiorly to remove air from the pleural cavity, and moved inferiorly to remove fluids from the pleural cavity.
• Blood entering the pleural cavity is called a hemothorax.
• In a right-dominant heart, the left coronary artery supplies the anterior 2/3 of interventricular septum, right ventricle adjacent to it, the left atrium and ventricle, and the AV structures.
• In left-dominant heart, the left coronary artery supplies everything but the right atrium and ventricle, and the SA node.