BIOMED - Pathophysiology

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Overview - (Tension) Pneumothorax
A pneumothorax is the collapse of the lung/s. A person presenting with a variation of pneumothorax where there has been a compromise from the normal conditions will appear to have a puffed chest, as the ribs stick out. This is caused by the lungs being incapable of keeping down, where the pressure that usually holds them in being affected, and thus the ribs 'float' up.

The lung collapses from the alveoli' s own surface tension being compromised. substances foreign to the area (such as air, blood, etc) enters the pleural space due to internal / perforation factors. The pressure within the lung rises as the the lung is no longer to hold it's shape and begins to shrink due to the elastic pull (recoil), thus decreasing lung volume.

Pneumothorax is common in classically young, tall and thin men in their teens and 20's and can occur due to physical activity/stretching, however generally occurs at rest.

Types of pneumothorax
Primary spontaneous pneumothorax
The Primary spontaneous pneumothorax can occur without underlying co-morbidities/diseases. As previously mentioned, it is common in young and thin man and can result from activities such as strenuous activity, rest, smoking, genetic predisposition, etc. The primary spontaneous pneumothorax may also occur while deep diving/high altitude aviation flights.

Secondary spontaneous pneumothorax
The Secondary spontaneous pneumothorax occurs in patients with underlying pulmonary disease, especially in patients with COPD, HIV pneumocystis infection, Cystic Fibrosis (CF), and other pulmonary diseases. This type of pneumothorax is more serious that primary as it decreases pulmonary reserve and with underlying diseases, this can severely impact O2 on loading and CO2 offloading.

Haemothorax
Haeme- represents that instead of air 'pneu,' there is blood that has entered the pulmonary environment.

Catamenial pneumothorax
The Catamenial pneumothorax is a type is pneumothorax associated with mensuration and post-menopause associated estrógen supplementation.

Traumatic pneumothorax
Traumatic pneumothorax occurs when there has been a blunt force injury wherein a penetrating/blunt chest force has injured the pulmonary environment. Alterations in pressure cause mediastinum to shift away from affected side, inhibiting venous return. 

Iatrogenic pneumothorax
Iatrogenic pneumothorax occurs as a result of medical intervention such as needle aspiration, Central venous catheter placement, mechanical ventilations and cardiopulmonary resuscitation.

Pathophysiology of Pneumothorax
Anatomy - normally, the intrapleural pressure is negative (as in, less than atmospheric pressure). This is due to the lung recoil and natural predisposition of the chest wall wanting to outwardly recoil.

Pathophysiology - In the instance of a pneumothorax, air (or haemothorax - blood) enters the pleural space from outside the environment, such as outside the chest such as a penetrating injury, or from within the body where air and/or fluid enters the space between the chest wall and lung. This causes the lungs to naturally recoil (collapse), becoming smaller and therefore increasing the intrapleural pressure, meaning that air will leave that lung and rush out into the lower pressure of the atmosphere. This decreases lung volume and therefore has an impact on respiration and O2/CO2 exchange.

This process shifts the mediastinum and thus affects the placement in the chest and impedes upon venous return to the heart. Air/fluid that enters the pleural space is not able to exit, and therefore chest tubes are required to drain this pleural space.

Pneumothorax that impedes upon venous return thus leads to Hypotension and respiratory/cardiac arrest within a very short period of time (Minutes).

Symptoms and Signs of Pneumothorax/Haemothorax
The person presenting with a pneumothorax will display a 'puffed up' chest from the ribs lifting due to their natural recoil. They will experience dyspnea & chest pain, and may express chest pain which is likely due to cardiac ishemia. They are likely to be slightly hypotensive and thus must be investigated.

Diagnosis of Pneumothorax
Usually via Chest x-ray

Treatment
Chest drain - This is a chest tube that enters the pleural space via the intercostal space (2nd space) at the mid clavicular line.

The drain is connected to a drain in which can be monitored and will display a 'bubble' that shows it is draining. The aim is for the lung to expand once again. Thsi is usually for secondary & traumatic pneumothoraces.

Note 
In a pneumothorax, with air in the pleural space, we have a high tube. Whereas in a Haemothorax, we have a lower tube. Pneumohaemothorax - blood and air, we will see mostly low tubes, with sometimes both high and low (2 tubes). These ICCs (Intercostal Catheters) will have 1hr observations, but more regularly in beginning according to facility protocol. 

Kinked ICCs can cause tension pneumothorax or pleural effusion

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2/June/21