Diving Disorders

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• The Physics of Dysbarism: Diving emergencies are broadly categorized by the phase of the dive in which they occur: disorders of descent, disorders of depth, and disorders of ascent.
• Decompression Illness (DCI): This is an umbrella term that encompasses both Decompression Sickness (DCS) and Arterial Gas Embolism (AGE).
• Nitrogen Pathophysiology: The core biochemical derangement in DCS involves the accumulation of inert nitrogen gas in the body's tissues under pressure. When a diver ascends (especially if rapid or after prolonged depth), this gas comes out of solution to form bubbles in tissues and the venous circulation, leading to localized mechanical tissue distortion and systemic inflammatory responses. Washing this inert nitrogen out of the lungs is the primary physiologic target of emergent therapy.

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• Immediate Stabilization & Positioning: Assess and stabilize the patient's airway, ventilation, and circulation. It is critical to maintain the patient in a strictly supine or left lateral decubitus (horizontal) position.
• First-Line Antidote (Oxygen): Administer 100% normobaric oxygen as the initial therapy for all diving emergencies. The exact dosage is 15 L/min via a non-rebreather facemask. This creates a diffusion gradient to wash inert nitrogen out of the lungs and reduces DCI morbidity and mortality.
• Fluid Resuscitation: Administer isotonic intravenous fluids, specifically 0.9% sodium chloride or Ringer’s lactate, to counteract dehydration and optimize perfusion. Oral hydration may be utilized depending on the severity of the illness.
• Temperature Management: Keep the patient warm and aggressively correct hypothermia, but explicitly avoid causing hyperthermia.
• Definitive Disposition: Ensure rapid transfer of care to a facility equipped with a hyperbaric oxygen chamber.

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

• Critical "Can't-Miss" Mimics:
• Cerebrovascular Accident (Stroke): AGE or severe DCS frequently mimics an acute stroke due to focal neurologic deficits.
• Traumatic Brain or Spinal Cord Injury: Must be ruled out if the patient struck their head or neck while diving.
• Marine Envenomation: Systemic toxicity from jellyfish, coral, or stingrays.
• Ciguatera Poisoning: Neurotoxic symptoms secondary to the consumption of reef fish.
• Diagnostic Workup Strategy:
• The Clinical Exam: The majority of dive injuries are diagnosed strictly on the basis of a focused dive history (depth, time, ascent) and physical examination.
• Baseline Labs: A Venous Blood Gas (VBG) analysis is sufficient; an arterial blood gas is not usually needed.
• Advanced Imaging: Consider a brain CT (with or without angiography) to rule out CNS pathology, and a chest CT (with or without angiography) to evaluate for suspected pulmonary embolism or severe barotrauma.

4. THE VISUAL BOARD (ECG / POCUS / Imaging)

• Chest X-Ray (CXR): Obtain a standard CXR to visualize pulmonary barotrauma. The resident must actively look for signs of a pneumothorax or pneumomediastinum.
• Physical Visual/Auditory Cues: Inspect and palpate the neck for subcutaneous emphysema. Auscultate the chest for a "crunching sound over the heart" (Hamman's crunch), which is a classic indicator of mediastinal air.
• ECG: Perform a standard 12-lead ECG to evaluate for dysrhythmias, ischemia, or right heart strain that may complicate the presentation.

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

• Expert Guidelines: While traditional scoring tools (like HEART or PERC) are not used to clear diving disorders, emergency providers must strictly adhere to the guidelines set by the U.S. Navy Diving Manual and the Divers Alert Network (DAN).
• Risk Factors: The risk of decompression sickness is directly correlated with depth and time; increased depth and increased dive time significantly elevate the risk, while decreasing depth and dive time reduces the risk.
• Mandatory Consultation: DAN provides a 24-hour medical emergency database and hotline (1-800-446-2671 or 1-919-684-9111) to guide clinical decision-making and dictate the specific protocols for hyperbaric transfer.

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• Pitfall (In-Water Recompression): Attempting to treat the patient by placing them back into the water for a recompression dive with a slow ascent. This is exceptionally dangerous and is almost never feasible, especially in children, without perfectly stable patients and highly experienced oversight.
• Pitfall (Withholding Oxygen): Delaying the application of 100% oxygen while waiting for imaging or diagnosis.
• CRITICAL ACTION: You must position the patient horizontally (supine or left lateral decubitus) immediately upon presentation to prevent the cerebral propagation of gas emboli.
• CRITICAL ACTION: You must notify the Divers Alert Network (DAN) immediately upon recognizing a diving emergency to coordinate definitive hyperbaric care.

7. MCQ MASTERCLASS (Written Exam Tips)

• Buzzword: "Subcutaneous emphysema, crepitus, and a crunching sound over the heart" + "recent scuba diver" -> Think Barotrauma resulting in pneumomediastinum.
• Common Distractor: A question stem may present a patient with focal neurologic deficits 30 minutes after surfacing from a dive and offer "Tissue Plasminogen Activator (tPA)" as an option. This is a lethal distractor. The symptoms are caused by an Arterial Gas Embolism (DCI), and the correct answer is "100% normobaric oxygen and hyperbaric chamber transfer".
• Pathophysiology Pearl: A question may ask what specific intervention reduces the risk of DCS. The correct answer is "decreased depth and decreased dive time".

8. THE BOARDROOM SCRIPT (OSCE & Oral Board Tips)

• Mandatory Physical Exam Maneuver: "I am immediately placing the patient on a cardiac monitor. I will perform a detailed cardiopulmonary exam, specifically palpating the neck for crepitus and auscultating the chest for a crunching sound indicating pneumomediastinum. I will follow this with a comprehensive neurologic exam to rule out focal deficits suggestive of an arterial gas embolism.".
• Communication Pearl: "Nurse, please place the patient strictly in a supine or left lateral decubitus position. I need 100% oxygen applied immediately at 15 Liters per minute via a non-rebreather mask to facilitate inert nitrogen washout.".
• High-Stress Articulation: "Given the patient's history of a recent dive and their current neurologic symptoms, my primary differential includes Decompression Sickness and Arterial Gas Embolism. I am administering isotonic intravenous fluids, ensuring the patient remains normothermic, and initiating a VBG, CXR, and ECG. I will have the unit clerk contact the Divers Alert Network (DAN) at 1-800-446-2671 immediately to guide our management and arrange for emergent transfer to a hyperbaric oxygen facility.".