In thoracic surgery, an open pneumothorax occurs with incision into the thoracic cage on a patient in the lateral decubitus position [1]. The negative pleural pressure that normally keeps the lung inflated is lost, resulting in the lung on the surgical side to collapse by means of its intrinsic elastic recoil [1]. This may be induced purposely to collapse the surgical lung in non-intubated thoracic surgery [1]. When a patient is spontaneously ventilating with an open pneumothorax in the lateral decubitus position, two significant events can occur: Mediastinal Shift and Paradoxical Respiration [1].

Mediastinal Shift

When a patient in this situation inhales, the pleural pressure does not become more negative on the open side, but does become negative on the dependent side. This pressure gradient causes the mediastinum to be pulled down toward the dependent lung during inspiration, decreasing volume delivered to the lung [1]. Keep in mind, the non-dependent lung is collapsed, so this decrease in contribution of the dependent lung to Tidal Volume may cause hypoxemia and hypercapnia [1].

TL;DR: Hole in chest –> Open-side lung collapses –> mediastinum pushes down on closed-side lung -> less Tidal Volume from only working lung -> Hypoxemia/Hypercapnia and possibly circulatory shock

Paradoxical Respirations

In a surgically created pneumothorax, the increase in negative pressure in the thorax relative to the atmospheric pressure causes gas to move from the non-dependent (open-side) lung, into the dependent lung [1]. During expiration, the opposite occurs, with the gas moving from the dependent lung to the non-dependent lung [1]. This process can potentially lead to wasted ventilation and lead to sub-optimal gas exchange [1].

TL;DR: Open thorax + inhale -> high negative pressure in thorax -> gas from open side lung shifts to closed side lung -> opposite on expiration -> wasted gas exchange

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Created on March 05, 2023 By admin

Open Pneumothorax

1 / 3

Two consequences of surgical creation of an open pneumothorax in the spontaneously ventilating patient in the lateral decubitus position are (SELECT 2):

Mediastinal Shift

Hypocapnia

Hypertension

Paradoxical Respirations

The consequences of this patient scenario is mediastinal shift and paradoxical respirations. These are likely to cause HYPERcapnia and Hypoxia.

2 / 3

During inspiration in a spontaneously ventilating patient in the lateral decubitus position with open pneumothorax for thoracic surgery, which is true about air movement

Air escapes the chest leaving high positive pressure in the thorax

Negative pressure in the intact hemithorax is higher than atmospheric pressure

Air moves from the open-side lung to the close side lung

Atmospheric pressure and Intrathoracic pressure are equal and no air movement occurs

during inspiration in open pneumothorax air shifts from the non-dependent lung into the dependent due to high negative pressure in the intact hemithorax relative to the atmospheric pressure

3 / 3

During expiration in a spontaneously ventilating patient with an open pneumothorax for thoracic surgery, the mediastinum will move vertically down toward the dependent lung

True

False

the mediastinum will shift toward the dependent lung during INSPIRATION

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References

[1]Butterworth IV J.F., & Mackey D.C., & Wasnick J.D.(Eds.), (2022). Morgan & Mikhail’s Clinical Anesthesiology, 7e. McGraw Hill. https://accessmedicine.mhmedical.com/content.aspx?bookid=3194&sectionid=266516824