Dive Response Lab Report

Effect of Breathing on the Dive Response

INTRODUCTION

Humans and other air-breathing animals have developed a physiological mechanism to conserve oxygen when under water, this mechanism is called a dive response. This reflex is believed to be evolutionary developed to give more protection and increase survival when air-breathing animals go into water whether intentionally or otherwise. Humans may not need this mechanism as much as other animals because of inventions such as scuba gear, oxygen tanks, snorkels, etc. nonetheless, we still have it because of our primitive beginnings.

The characteristics of a human dive response are bradycardia, selective peripheral vasoconstriction, and increased blood flow to the body’s most vital organs (Duprez

2000). This response has been not only observed in full body submersion, but also with facial submersion alone. However, if the body is submerged while the face is let out of water there will be little to no dive response (Campbell et al. 1968). This shows that submersion of the face with apnea is responsible for contributing the most to eliciting the dive response. It has been shown that submersion of the face with apnea will elicit a dive response close to the same magnitude as a full body submersion; this reflex is believed to be caused by cold water stimulating the vagus nerve running along the jawline (Foster and Sheel 2004). These nerves are part of the parasympathetic and the sympathetic nervous system. The parasympathetic response is responsible for causing bradycardia while the sympathetic response can induce selective peripheral vasoconstriction.
This experiment will give an insight into how important apnea is in eliciting a dive response. The face will be submersed into cold water, but there will be a snorkel to eliminate the breath hold factor. This will provide data that shows only the effects of cold water on the face. Similar experiments have been done before such as Ansay et al (NO DATE). In Ansay’s experiment he and his team examined the eliciting conditions of the human dive response. In one of the trials he had his subjects use a snorkel to show how much of an effect the cold water had on eliciting a dive response. His data showed that there was a 14% decrease in the heart rate when diving with a snorkel. It is hypothesized that we will see a similar result in this experiment. We believe that there will be a decrease in heart rate while using the snorkel, but to get a full dive response there must be both face submersion as well as apnea.
METHODS
Subjects included 3 males and 3 females all of which were healthy at the time of experimentation.

Participants were also informed about the tasks they would be asked to complete. Subjects would participate in two trials* one trial would be the classis dive response test with facial submersion and apnea the other trial being face submersion with breathing.

Using a bucket that held about 3 gallons of water, the bucket was filled up with 6-7inches of water. This allowed enough room for the subject to fully submerse the face to ensure stimulation of the vagus nerve. The water was then chilled to 15 degrees Celsius. iWork’s Labscribe 3 software was used to record the subject’s data using a pulse plethysmography and a respiration monitor. This was plugged in and activated to ensure functioning before patient arrived.

Once subject was briefed, the pulse plethysmography was attached to the first or middle finger of their left hand to measure heart rate. The subject was asked to keep this hand at their side, hanging freely, with minimal movement to get the best reading. The respiration monitor was then placed at the bottom of the sternum approximately 1inch above the diaphragm to measure breath rate. The first set of measurements was taken after the subject was seated, calm, and breathing normally. This set of data established the

baseline.
The subject was then prompted to bend over the bucket while in the seat and hold their breath for 20 seconds. They should get as close to the water as possible without contact. This gave us the “breath hold” data, which measured the effect of apnea only on the participant’s heart rate.
After completion of the breath-hold, data was collected for approximately 20 seconds before the dive. The subject was then instructed to hold their breath and submerge their face into the water for 20 seconds. After completion of the dive the participant was instructed to sit still for approximately 20 seconds to allow us to get post-dive data. This gave us the “dive” data, which measured the effect of apnea paired with the cold water on the participant’s heart rate.
Our second trial was the same as the first except that the subject had a plastic tube, which acted like a snorkel in their mouth during the data collections (baseline, breath hold, and dive). During the dive portion of this trial the subject was told to breathe normally through the snorkel while under the water. This gave us the “dive with snorkel” data, which measured only the effect of the cold water on the participant’s heart rate.