Comparison of COVID-19 and Decompression Illness: Causes and Risk Mitigation

COVID-19 and dive injuries are very different things, but the two have many similarities that are worthy of consideration. The causes are obviously distinct; COVID-19 is caused by a virus while dive injuries (decompression illness, specifically) are caused by exposure to pressure. In both, cases range from mild to severe, and while there are fatalities, the overall fatality rates are low. As with dive injuries, there are some individuals who are at higher risk of contracting COVID-19. There are also some commonalities in the underlying pathophysiological mechanisms and individual factors that increase the probability of severe affliction and bad outcomes. Ultimately, what we learn about how to prevent one may be useful in considering how we prevent the other.

It is important to understand that divers can significantly increase their ability to cope with and prevent either condition by adopting a healthy lifestyle and effectively managing pre-existing conditions.

Aspect COVID-19 DCS AGE Scuba Fatality
Cause Infection with virus Insufficient decompression Rapid ascent without exhalation Multiple causes
Vector Infected person Environmental pressure Intra-alveolar pressure Multiple factors
Exposure Close contact with infected person, crowded closed spaces Compressed gas diving, flying at high altitude Compressed gas diving, medical interventions Immersion, submersion, compressed gas, exertion
Agents Virus Tissue dissolved inert gas Alveolar gas, Ambiental gas in iatrogenic embolism Intrinsic, extrinsic, behavioral
Infectivity/ Injury incidence/ Threshold Unprotected contact – 95% 2/10,000 in rec diving, greater in deco diving, 6x higher with PFO Threshold: 3-foot ascent with a full breath in lungs  
Fatality rates of ill/injured 1% <1% 30% 16/100,000 participants; 10-fold increase among 60 and older; 10-fold increase among CCR divers
Mechanisms Cell entry, multiplication, and cell death, cytokine storm Mechanical and biological effects of bubbles in tissues and blood Lung overexpansion, arterial embolism Multiple mechanisms
Pathophysiology Endothelial damage, inflammation, organ damage, hypoxemia, coagulation Endothelial damage, vascular and tissue damage, local ischemia, coagulation Alveolar damage, air embolism, local ischemia Heart arrest, unconsciousness, drowning, asphyxia
Dose-dependent injury Larger the virus burden, more severe illness. Not completely predictable. Larger the inert gas load, and faster the decompression, DCS more likely. Not completely predictable. The faster the ascent, more likely the AGE. Does effect of embolism exist. Exertion, breathing gas density,
Individual risk factors Obesity, old age, diabetes, hypertension, smoking Patent foramen ovale (PFO), diabetes, obesity, old age, sedentary Smoking, lung disease, old age, lack of skills Old age, atherosclerotic disease, diabetes, obesity
Highest risk group Older divers with multiple pre-existing conditions Older divers with multiple pre-existing conditions Older divers with multiple pre-existing conditions Older divers with multiple pre-existing conditions
Table 1

While divers are already familiar with the causes of COVID-19 and DCI, it’s important to note the dose-dependent nature of both conditions and the role of individual risk factors.

In both COVID-19 and DCS, the greater the dose of the causative agent, the greater the likelihood of severe illness. In cases of COVID-19, close contact with an infected person while unprotected will most likely result in infection, and the greater the viral load, the more severe the illness. In diving, if you go deep, stay long and ascend fast you are likely to get a severe case of DCS.  

The only way to be completely safe is to self-isolate or not dive. But fortunately we have means of protecting ourselves that help us control the risk when we do participate. Learning and adopting protective measures is the focus of scuba training. Protective measures against transmissible diseases like COVID-19 have been always there, too, and we should all be skilled in these measures by now.

Individual Risk Factors

Certain individual risk factors can increase the severity of COVID-19 and DCS.

Among pre-existing health conditions that increase a risk of severe COVID-19, the three leading conditions are:

  • Obesity
  • Diabetes (with complications such as organ damage)
  • High blood pressure (with complications such as heart damage or kidney disease)

Common to all three conditions is inflammation that affects the endothelium, the thin layer of cells that walls the inner surface of blood vessels. Both diving and COVID-19 affect the endothelium. The pre-existing conditions that damage endothelium on their own also increase the risk of severe COVID-19 and of bad outcomes in both COVID-19 and diving injuries. Chronic inflammation weakens the immune response and increases the risk of clotting.

Obesity increases the probability of severe COVID-19 and death to 40 percent. Among other problems, it inhibits normal lung expansion during breathing and makes administering ventilations in an emergency more difficult. For divers, obesity introduces issues with buoyancy control, fat tissue may play a role in bubble formation, and in emergencies, assistance to heavy divers may be more complicated.

In both COVID-19 and dive injuries, the age of the individual is a well-established risk factor. Age is associated with symptomatic and asymptomatic changes in the body that damage endothelium and decrease overall capacity to heal. With aging, the immune system becomes weaker. Older divers are more likely to produce bubbles and suffer DCS.

The worst-case scenario is the presence of multiple pre-existing conditions and risk factors. With COVID-19, multiple pre-existing conditions can result in severe cases of the illness, even in younger people. In diving, multiple pre-existing conditions significantly increase the risk of a scuba fatality.

Adoption of certain lifestyle changes can help alleviate pre-existing conditions and decrease a person’s susceptibility to DCS or COVID-19.

Risk Mitigation

Stopping short of complete lockdown from COVID-19 and abstinence from scuba, there are basic principles in risk mitigation for transmissible diseases and injuries that can help improve outcomes. These include:

  1. Avoid or reduce exposure
  2. Use protective equipment
  3. Decrease individual susceptibility
  4. Increase individual resistance
  5. Maintain awareness
  6. Diagnose and treat early

Due to the different natures of the two conditions, controlling exposure and protection are different. In scuba diving, limit the load of inert gas by diving conservatively and controlling your ascent. To limit the spread of COVID-19, socially distance and wear a facemask.

Decreasing an individual’s susceptibility to either condition can be achieved through the same interventions. With obesity, for example, reduction of body weight by 5 percent can help control diabetes and high blood pressure and make physical exercise less arduous. This translates to decreased risk of both severe COVID-19 and diving injuries.

Although a person’s age cannot be lowered, the aging process can be slowed down by a healthy lifestyle and regular physical activity.

More comparisons of risk mitigation measures are provided in Table 2: Risk Mitigation.

Link COVID-19 DCS AGE Scuba fatality
Avoid exposure or mitigate burden of agent Socially distance, facemask, full hazmat suit for medical personnel Observe no-decompression limit, use nitrox, control ascent, safety stops Prevent emergency, control ascent Pre-participation health screening, conservative diving, avoid exertion
Decrease in susceptibility by removing risk factors Healthy lifestyle, weight reduction, no smoking, regular exercise:
— minimize inflammation
— lower blood pressure
— improve endothelial health
— improve cardio-respiratory capacity
Healthy lifestyle, weight reduction, no smoking, regular exercise:
— minimize inflammation
— lower blood pressure
— improve endothelial health
— improve cardio-respiratory capacity
Healthy lifestyle, weight reduction, no smoking, regular exercise:
— minimize inflammation
— lower blood pressure
— improve endothelial health
— improve cardio-respiratory capacity
Healthy lifestyle, weight reduction, no smoking, regular exercise:
— minimize inflammation
— lower blood pressure
— improve endothelial health
— improve cardio-respiratory capacity
Increase host resistance Vaccination PFO closure Practice skills, pre-dive checks Stay healthy
Early recognition Typical symptoms, testing Post-dive symptoms Severe neurological symptoms upon surfacing Rapid progression to cardio-respirator arrest, in water or upon surfacing
First aid N/A Surface oxygen Surface oxygen AED
Early diagnosis Testing Neurological exam Neurological exam Check vital signs
Evacuation Specialized aircraft with hazmat protection Aircraft with 1 ATA cabin pressure Aircraft with 1 ATA cabin pressure Repatriation of mortal remains
Treatment Low-risk patients: symptomatic
High-risk patients: monoclonal antibodies, anti-inflammatory, O2 and ICU as needed
Recompression ASAP, hyperbaric oxygen Recompression ASAP, hyperbaric oxygen Life support
Residual damage Possible Possible Possible Fatal
Table 2: Risk Mitigation

Divers can do a lot to mitigate their risk of contracting severe COVID-19 or getting injured while diving. Maintaining a healthy lifestyle and managing chronic illnesses are key in both contexts.

The lockdowns associated with the COVID-19 pandemic can negatively affect people’s lifestyles, including their physical activity and mental health. And during this time many have been unable to participate in activities they enjoy, including diving. But be prepared for when lockdowns and restrictions are lifted. To the best of your ability, use time away from diving to reduce your health-related risk factors and thus increase your resistance to COVID-19 and diving injuries.