What are the relationships between the parietal and visceral pleura, and how does a perforation in the thoracic wall and parietal pleura disrupt pleural linkage in a patient with a penetrating chest injury and signs of respiratory distress, including difficulty breathing and shortness of breath?

From the Guidelines

The parietal pleura lines the inner surface of the thoracic cavity, while the visceral pleura covers the outer surface of the lungs, and the two mechanisms contributing to pleural linkage are surface tension and negative pressure within the pleural space. The relationships of the parietal and visceral pleura to each other, to the lungs, and the thoracic cavity are as follows:

• The parietal pleura lines the inner surface of the thoracic cavity
• The visceral pleura covers the outer surface of the lungs
• The two pleural layers are continuous with each other at the hilum of the lung where blood vessels, bronchi, and nerves enter and exit
• Between these two pleural layers is the pleural cavity, which contains a thin film of pleural fluid The two mechanisms that contribute to 'pleural linkage' are:
• Surface tension: causes the pleural surfaces to adhere to each other like two wet glass slides
• Negative pressure: helps maintain lung expansion, approximately -4 mmHg during normal breathing Pleural linkage contributes to inhalation by:
• Forcing the lungs to expand along with the thoracic cavity during inhalation
• Decreasing intrapulmonary pressure and drawing air into the lungs If there were a perforation in the thoracic wall and parietal pleura, this would disrupt pleural linkage by:
• Allowing air to enter the pleural space (pneumothorax) and equalizing the negative pressure with atmospheric pressure
• Eliminating the pressure differential and causing the elastic lung to recoil and collapse away from the chest wall, resulting in impaired breathing and respiratory distress, as described in the management of complicated diaphragmatic hernia 1 and the use of chest seals in open chest wounds 1. In the context of a penetrating injury to the chest, it is essential to consider the potential for pneumothorax and the importance of maintaining pleural linkage to ensure adequate lung expansion and respiratory function, as highlighted in the emergency ultrasound imaging criteria compendium 1.

From the Research

Part A - Normal PA Chest X-ray

The structures labelled 1-6 on a normal PA chest x-ray can be identified as follows:

• 1. Right clavicle or other bony structure 2
• 1. Trachea or other mediastinal structure
• 1. Right atrium or other cardiac structure
• 1. Right ventricle, as it is a heart chamber
• 1. Costophrenic angle, which is the angle between the ribs and diaphragm
• 1. Diaphragm or other structure in the thoracic cavity

Part B

No information is provided for this section.

Part C - Relationships of Parietal and Visceral Pleura

Relationships of the Parietal and Visceral Pleura

The parietal pleura lines the inner surface of the thoracic cavity, while the visceral pleura adheres to the lungs 3. The two pleurae are in close contact with each other, with a thin layer of fluid between them.

Mechanisms of Pleural Linkage

The two mechanisms that contribute to 'pleural linkage' are:

• The negative pressure in the pleural space, which helps to keep the lungs expanded
• The surface tension of the fluid between the pleurae, which helps to maintain contact between the parietal and visceral pleura

Contribution to Inhalation

Pleural linkage contributes to inhalation by allowing the lungs to expand and contract with the movement of the thoracic cavity. As the diaphragm and intercostal muscles contract, the thoracic cavity increases in volume, which creates a negative pressure in the pleural space. This negative pressure helps to expand the lungs, allowing air to enter the lungs.

Disruption of Pleural Linkage

If there were a perforation in the thoracic wall and parietal pleura, it would disrupt pleural linkage by allowing air to enter the pleural space and equalize the pressure between the pleural space and the atmosphere 3. This would prevent the lungs from expanding and contracting properly, leading to respiratory distress.