What are three cardiovascular mechanisms seals use to maximize their dive time? Do you possess any of these mechanisms? How do yours differ from those of the seal? The Bajau? Why is this response in mammals more pronounced in cold waters?
Answers
Explanation:
The diving reflex commonly referred to as the mammalian dive reflex, diving bradycardia, and the diving response is a protective, multifaceted physiologic reaction that occurs in mammals including humans in response to water submersion. Aspects of the dive reflex were first described in 1786 by Edmund Goodwyn; however, it would take until an 1870 publication by Paul Bert for the physiologic adaptations to be recognized. The dive reflex is believed to aid in the conservation of oxygen stores in mammals by initiating several specific physiologic changes during aquatic immersion. When a human holds their breath and submerges in water, the face and nose become wet which in turn causes bradycardia, apnea, and increased peripheral vascular resistance; these three main physiologic changes are collectively referred to as the diving reflex. The cause of increased peripheral resistance is thought to redistribute blood to the vital organs while limiting oxygen consumption by non-essential muscle groups. In addition to vascular resistance, bradycardia is initiated to decrease the work of the heart and further limit unnecessary oxygen consumption. Overall, the dive reflex is an innate multi-system physiologic response present in all vertebrates that functions to preserve oxygen stores during times of water immersion.
Issues of Concern
The dive reflex has been shown to be an effective means by which to treat paroxysmal supraventricular tachycardia (PSVT). Current medical literature supports several techniques that can trigger the dive response, the most common being a cold application to the face to increase vagal tone. However, at this present time, there is no data or studies that support a best practice approach in terms of equipment to use, duration of application, or optimal temperature range for therapeutically treating PSVT. Thus, further studies and research must be conducted to provide evidence-based information that reveals the optimal methods of inducing the dive reflex to alleviate PSVT.[1]
In addition to further research needed to determine the most effective maneuver in the clinical setting to elicit the dive response, there are other limitations of study for the dive reflex. Although there have been significant advancements in current research equipment and technology the dive reflex has proven difficult to study in its entirety due to the aquatic conditions a subject must be present in to trigger the response. Specifically, cardiovascular adaptations in mammals during water submersion are only moderately understood due to the technical difficulty of studying mammals while completely submerged in water.[2] To further research the physiologic changes present within the dive reflex, advancements must be made in technology that can withstand the aquatic environment in which the dive reflex is observable.