By April White, MBS 2019, Geisinger Commonwealth School of Medicine

Mentor: David Averill, PhD



Much like many opportunities in life, SCUBA diving became a passion for me accidentally. A few friends whom I worked with were SCUBA instructors, and they offered me a spot in their class. I really didn’t know what I was getting myself into at that moment, but sometimes that’s how the best adventures in life are made. Fast Forward: I’ve been a certified diver for nearly three years, and recently joined my friends in volunteering on the local dive-rescue team, which works to rescue people and recover submerged objects and evidence. My specific role on the team is to take the lead on diver health and safety by tracking pre- and post-dive vital signs to ensure that our divers are healthy to continue the operation until the mission is complete. This position sparked my interest in researching SCUBA’s influence on diver physiology, particularly in terms of respiratory, cardiovascular, and autonomic nervous system impacts. 

Diving is highly dependent upon the manipulation of physics to permit the diver to enter and explore harsh environments while bringing the essential surface environment with them. This feat requires that the diver undergoes stress to adapt his or her physiology in the face of increased breathing air density, increased surrounding water pressure, and water resistance imposed by swimming and navigating through a dense underwater environment. Imagine yourself weighted down with heavy equipment, including a few lead blocks strapped to your waist, breathing through a mouthpiece like a snorkel with somewhat restricted air flow, all in an environment with diminished lighting, potentially cold temperatures, and maybe murky visibility. Likely you can already feel some of that physical and mental stress settling in. 

I would like to focus on the changes in heart and lung functions as a direct result of entering and operating in an underwater environment. Under high pressure, high oxygen concentrations, and cold-water conditions, blood flow is redistributed to the core vital organs from the arms and legs, attempting to conserve heat, oxygen, and blood flow to ensure their survival. This shunting of blood to the core was demonstrated to increase pressures and volumes in the heart, which could then also influence the workings of the lungs and nervous system regulating the heart’s functions. The lungs and respiratory system were observed to change their efficiency at the level of oxygen-fueled energy production, attempting to reserve oxygen for brain function. Breathing on SCUBA under pressure also showed that airway resistances and pressures changed as well. Overall, these findings mean that a diver’s heart and lungs face significant transformation during the act of descending and ascending.

Current research is examining the function of the autonomic nervous system in the diving environment. This division of the nervous system deals with involuntary and unconscious acts, such as controlling heart and breathing rates. Studies have found activity in both the sympathetic and parasympathetic branches under a variety of dive situations and circumstances; however, more predominant effects are with parasympathetic activation. This means that contrary to what we expected, the stresses of diving actually produces a calming, so called “resting” effect on the heart, which opens many doors for further investigation as to why.

These days, I am learning a great deal about physical peocesses that are impacting me as a diver. I am now more aware and educated about the impacts that SCUBA and improper technique and emergency situations can have on a diver, which is certainly something I will keep in the back of my mind now on every dive call and drill. I have also learned techniques to make myself a more efficient and safer diver, with a greater respect and understanding for our unique physiology that occurs in the mighty deep.