Overview

Epidemiology

• Population statistics:
  • Sports diving: 3 cases per 10,000 dives
  • Commercial diving: 1.5–10 cases per 10,000 dives
  • 2.5 times more likely in men than women 
• Risk factors:
  • Dive details:
    • Depth
    • Duration
    • Number of dives
    • Interval surface time between dives
    • Water conditions
  • Diver: 
    • Weight ( obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity is predisposing)
    • History of lung or cardiac disease
    • Right-to-left cardiac shunts (e.g., patent foramen ovale Patent Foramen Ovale A patent foramen ovale (PFO) is an abnormal communication between the atria that persists after birth. The condition results from incomplete closure of the foramen ovale. Small, isolated, and asymptomatic PFOs are a common incidental finding on echocardiography and require no treatment. Patent Foramen Ovale)
    • Inexperienced divers are more commonly affected.
    • Rate of ascent
    • Length of time between low altitude (scuba dive) and high altitude (air travel or ground ascent)

Etiology

Decompression sickness (DCS) comprises varied symptoms caused by gas bubbles that come out of solution in the body after ascending from a deep dive.

• Most likely to occur when: 
  • Scuba diving is followed closely by travel to high altitudes 
  • Divers do not adhere to dive protocols 
• Panic can make divers ascend too quickly.

Classification

Based on severity of symptoms and location of gas bubbles:

• Type I: mild bubbles form in:
  • Lymphatic system 
  • Skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin
  • Muscles and joints
• Type II: severe/lethal bubbles form in:
  • Heart
  • Lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs
  • Central nervous system Nervous system The nervous system is a small and complex system that consists of an intricate network of neural cells (or neurons) and even more glial cells (for support and insulation). It is divided according to its anatomical components as well as its functional characteristics. The brain and spinal cord are referred to as the central nervous system, and the branches of nerves from these structures are referred to as the peripheral nervous system. General Structure of the Nervous System

Pathophysiology

• Descent: gas in body under higher atmospheric pressure → dissolves into tissues and blood
• Rapid ascent: partial pressure of gas > ambient pressure → gas comes out of solution → formation of bubbles
• Bubbles affect:
  • Organ tissue
    • Mechanical disruption/damage to tissue 
    • Alteration of the functionality of important structures
  • Venous circulation → picks gas up from tissues
    • In ↓ quantities → bubbles are asymptomatic and filtered in pulmonary capillaries Capillaries Capillaries are the primary structures in the circulatory system that allow the exchange of gas, nutrients, and other materials between the blood and the extracellular fluid (ECF). Capillaries are the smallest of the blood vessels. Because a capillary diameter is so small, only 1 RBC may pass through at a time. Capillaries
    • In ↑ quantities, bubbles can cause:
      • Inflammatory response
      • Activation of coagulation cascades
      • Damage to endothelium
      • Activation of platelet aggregation
      • Occlusion of blood flow
      • Capillary leakage

Clinical Presentation

• Nonspecific, depending on:
  • Location of gas bubbles
  • Compressibility of gases in body
• Quicker onset of symptoms = ↑ severity
  • Severe cases start < 30 minutes after surfacing.
  • Mild symptoms can take 6 hours to appear.
  • 75% of cases show symptoms in < 1 hour.
• Most cases are mild.
• Pulmonary/cardiovascular manifestations can be lethal.

Diagnosis

Diagnosis is based on: 

• History: relationship of symptoms to a diving event
  • DCS should be considered in any diver manifesting symptoms that cannot be explained by other mechanisms.
• Imaging:
  • Computed tomography (CT) scan can be used to detect vacuum phenomenon of trapped gas.
  • Magnetic resonance imaging (MRI): most accurate for detection of brain and spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord lesions

Management and Prognosis

The main goal of therapy is to dissolve bubbles and recompress gas in body fluids.

First aid

• Trendelenburg positioning → puts right ventricular outflow tract below right ventricular cavity → air migrates up and out of way of flow of blood
• Intravenous (IV) fluids
• Supplementary oxygen → accelerates inert gas washout

Definitive therapy

• Recompression therapy in hyperbaric treatment facility
  • Hyperbaric oxygen
  • Should never be withheld, even if initiation is delayed 
• IV fluids IV fluids Intravenous fluids are one of the most common interventions administered in medicine to approximate physiologic bodily fluids. Intravenous fluids are divided into 2 categories: crystalloid and colloid solutions. Intravenous fluids have a wide variety of indications, including intravascular volume expansion, electrolyte manipulation, and maintenance fluids. Intravenous Fluids
• A consult with diving medicine/hyperbaric oxygen specialist is required, even if symptoms resolve.

Prevention

• Diver education
• Pre-dive medical screening and dive planning
• Strict adherence to dive course, timing, and depths
• Slow and controlled ascent (decompression stops: Experienced divers control their ascent using algorithms that indicate when ascent has to stop at different depths to allow for gas washout.)
• Recommendation to avoid high altitudes for 24 hours after a dive

Contraindications to deep-sea diving

• Active asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma
• Reduced pulmonary function
• Lung cysts
• Recent thoracic trauma or pneumothorax Pneumothorax A pneumothorax is a life-threatening condition in which air collects in the pleural space, causing partial or full collapse of the lung. A pneumothorax can be traumatic or spontaneous. Patients present with a sudden onset of sharp chest pain, dyspnea, and diminished breath sounds on exam. Pneumothorax
• Cardiovascular disease
• History of bowel obstruction
• Recent brain or eye surgery
• Seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures
• Diabetes mellitus Diabetes mellitus Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus and hypoglycemic episodes
• History of syncope Syncope Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope

Prognosis

• 75% of cases completely resolve.
• 16% of cases may have residual symptoms for up to 3 months.
• Spinal cord involvement often causes permanent damage.

Clinical Relevance

The following conditions greatly increase the likelihood of developing decompression sickness:

• Asthma: a chronic inflammatory condition of the airways characterized by bronchial hyperreactivity, which presents as wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing, cough, and dyspnea. People with asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma have increased risk for pulmonary barotrauma and decompression sickness, which can lead to a pneumothorax Pneumothorax A pneumothorax is a life-threatening condition in which air collects in the pleural space, causing partial or full collapse of the lung. A pneumothorax can be traumatic or spontaneous. Patients present with a sudden onset of sharp chest pain, dyspnea, and diminished breath sounds on exam. Pneumothorax and breathing difficulties. Treatment often requires intubation. 
• Pneumothorax: a collection of air in the pleural space that can occur due to dysbarism, causing shortness of breath and hypoxia. Treatment is with thoracostomy (chest tube) placement and oxygen.
• Bowel obstruction: the interruption of the normal transit of intestinal contents either due to a functional decrease in peristalsis or mechanical obstruction. Over-pressurization of the bowels can result in gastric rupture, bowel perforation, or pneumoperitoneum. Treatment often requires surgery.