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Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • Presence of air within the pleural space, resulting in lung collapse and inadequate ventilation
  • Most common with penetrating thoracic wounds or birth trauma and affecting one or both hemithoraces
  • Open/closed PTX—air freely enters and leaves the pleural cavity through a chest wound (open) or a breach in the visceral pleura or mediastinum (closed)
  • Tension PTX—air accumulates in the pleural space with each breath and cannot escape

Signs!!navigator!!

  • Tachypnea, nasal flaring, and superficial breathing
  • Dyspnea can occur in severe and bilateral cases, and can progress to distress and cyanosis
  • Mild cases can be asymptomatic at rest
  • Absence of lung sounds dorsally, and increased resonance on percussion
  • Inspection and palpation may reveal a penetrating thoracic or axillary wound. Thoracic pain, subcutaneous emphysema, and instability of the thoracic wall are compatible with fractured ribs

Causes and Risk Factors!!navigator!!

  • Trauma
  • Bronchopleural fistulas from pleuropneumonia
  • Distal tracheal or esophageal lacerations
  • Transtracheal wash, bone marrow aspiration, lung biopsy

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Pain can cause rapid, shallow breathing
  • Diaphragmatic hernia
  • Pleural effusion

CBC/Biochemistry/Urinalysis!!navigator!!

  • Stress leukogram
  • Leukocytosis with secondary bacterial infection

Other Laboratory Tests!!navigator!!

Arterial blood gas analysis may reveal hypercapnia and hypoxemia.

Imaging!!navigator!!

Thoracic Ultrasonography

  • Air accumulates dorsally in standing horses or laterally in recumbent foals
  • In 2D mode, the pleural line appears as a hyperechoic line that twinkles with normal lung movement (“gliding lung sign”). Absence of the “gliding sign” is strong, but not absolute, evidence for the presence of PTX
  • Determination of the “lung point” (the point where the gliding sign meets free gas) is useful to assess the severity and monitor change over time

Thoracic Radiography

Retraction of lung margins from the thoracic wall (dorsoventral projection in recumbent foals) or from the ventral aspect of the thoracic vertebrae (lateral projection in standing horses)

Other Diagnostic Procedures!!navigator!!

N/A

Treatment ⬆ ⬇

TREATMENT

  • These animals may suffer from polytrauma. If IV fluids are indicated, keep in mind that contused lung is more susceptible to fluid overload
  • Open PTX—temporarily close the wound using sterile gauze. Suture it whenever possible to achieve an airtight seal. For wounds that are not amenable to primary closure, apply a thin film dressing to provide an airtight seal
  • Thoracocentesis—indicated when respiratory distress is present. The site is the dorsal thoracic cavity between the 12th and 15th ribs. Avoid intercostal vessels along the caudal border of the ribs. A teat cannula, a 14 G over-the-needle catheter, or a large-gauge needle attached to a three-way stopcock, extension set, and 60 mL syringe
  • With severe or active PTX, a thoracostomy tube can be placed dorsally in the pleural cavity and attached to a Heimlich valve or, in the case of rapid reaccumulation of air, a continuous suction apparatus. When PTX has persisted for some time, it should be aspirated slowly to avoid reexpansion pulmonary edema
  • Uncontrolled PTX or recurrence is an indication for thoracoscopy. It is also useful to evaluate concurrent pulmonary and diaphragmatic trauma, or identify foreign bodies
  • Administer oxygen to dyspneic and hypoxemic patients
  • In mild cases, PTX can resorb with confinement alone, over a few weeks. In people, 1.5% of the volume can be reabsorbed each day

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Broad-spectrum antibiotics, NSAIDs, and tetanus prophylaxis.

Contraindications/Possible Interactions!!navigator!!

Avoid drugs such as xylazine or opioids, because they may reduce PaO2.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Monitor hourly (including respiratory rate and pattern) for the first 24–48 h
  • Serial blood gas analyses and ultrasonography or radiography to monitor progress and document reexpansion of the lungs
  • Thoracostomy tubes may be removed if ≤50 mL of air is aspirated over 12 h

Possible Complications!!navigator!!

  • Recurrence
  • Pyothorax with open PTX

Expected Course and Prognosis!!navigator!!

  • Tension PTX is a serious life-threatening condition if left untreated
  • Full recovery is expected if the injury is not severe and does not involve other thoracic structures

Miscellaneous ⬆ ⬇

Outline

Miscellaneous

Associated Conditions!!navigator!!

  • Thoracic trauma
  • Fractured ribs
  • Diaphragmatic hernia
  • Ruptured trachea

Abbreviations!!navigator!!

  • NSAID = nonsteroidal anti-inflammatory drug
  • PaO2 = partial pressure of oxygen in arterial blood
  • PTX = pneumothorax

Suggested Reading ⬆ ⬇

Hassel MH. Thoracic trauma in horses. Vet Clin North Am Equine Pract 2007;23(1):67–80.

Jean D, Laverty S, Halley J, et al. Thoracic trauma in newborn foals. Equine Vet J 1999;31(2):149–152.

Laverty S, Lavoie JP, Pascoe JR, Ducharme N. Penetrating wounds of the thorax in 15 horses. Equine Vet J 1996;28(3):220–224.

Partlow J, David F, Hunt LM, et al. Comparison of thoracic ultrasonography and radiography for the detection of induced small volume pneumothorax in the horse. Vet Radiol Ultrasound 2017;58(3):354–360.

Author(s) ⬆

Authors: Florent David and Sheila Laverty

Consulting Editors: Mathilde Leclère and Daniel Jean