31

31 CASE 31


A 29-year-old man is transported by the rescue squad to the emergency department in acute respiratory distress after being stabbed in the left lateral chest.


The patient was involved in a domestic dispute. He has a 3-cm puncture wound on the left lateral chest between the third and fourth ribs. He is conscious, is able to speak, complains of chest pains associated with each breath, and has difficulty breathing. The puncture wound has minimal bleeding, and total blood loss is estimated at 100 mL. Air can be heard entering the thorax through the stab wound during inspiration, and bubbles formed at the stab wound during exhalation. This air movement was minimized by placing a compression bandage at the site of injury before transport.



PHYSICAL EXAMINATION



VS: T 36.7°C, P 105/min, R 28/min, BP 130/110 mm Hg

PE: Patient’s breathing is labored and involving abdominal muscles. The thoracic cage is asymmetrical, with the left side protruding more than the right side. The left side shows much less movement than the right during breathing. Breath sounds are decreased on the left side, and the left side shows hyperresonance to percussion.


LABORATORY STUDIES



Pulse oximetry: 85% oxygen saturation

Chest radiograph: Confirms unilateral left-sided pneumothorax

Arterial blood gases: PO2 90 mm Hg, PCO2 44 mm Hg


DIAGNOSIS


Pneumothorax



COURSE


The patient is sedated, and an endotracheal tube is inserted. The wound is exposed and opened, and the patient is placed on positive-pressure ventilation (tidal volume 500 mL, rate 18, positive end-expiratory pressure 5 mL). The injury is surgically repaired, and a negative pressure is applied to the thoracostomy tube to reinflate lung. The patient is admitted to the intensive care unit for observation.



PATHOPHYSIOLOGY OF KEY SYMPTOMS


Breathing requires the creation of a pressure gradient between the alveoli and the atmospheric air. Normally, this pressure gradient is created by altering the volume of the thoracic cavity, which then expands or compresses the lungs. There is no direct passageway between the intrapleural thoracic space and the atmosphere. Consequently, the change in thoracic volume alters the size of the lungs.


Intrapleural pressure in the thorax is negative, created by the inward directed elastic recoil of the lung and the outward directed elastic recoil of the chest wall. During inspiration, contraction of the diaphragm creates a more negative intrapleural pressure and the consequent expansion of the lungs creates a negative alveolar pressure. Air flows into the lungs from outside the body in response to the pressure gradient between the alveoli and the atmospheric air (Fig. 31-1).


image

FIGURE 31–1 Changes in lung volume, alveolar pressure, pleural pressure, and transpulmonary pressure during normal breathing.

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Jul 4, 2016 | Posted by in PHYSIOLOGY | Comments Off on 31

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