## Understanding the Effects of Pressure on the Heart Rate when Diving

Human Diving responses can be studied and recorded to help understand the aquatic mammals’ response during diving. As mammals dive down the ocean they experience significant pressure. According to Palmer at a thousand meters down, whale experiences one hundred times the pressure that they usually do at the ocean’s surface. The pressure is enough to compress the air held in their lungs.

The best divers are not able to hold breath for five minutes, but some sea mammals can remain underground for more than one hour and thirty minutes without a breath (Arsdale). The experiment was carried out to understand the effects of the heart rate when diving and how the pressure affects the pulse rate. It is hypothesized that the heart rate of the subject decreases during diving. A basin filled with chilled water was used and the subject requested to immerse their entire face (the water was supposed to cover the face, head and ears). The data was recorded for thirty seconds while the participant rested before their dived and thirty seconds when underwater and for thirty seconds after surfacing from the water.

By studying the human diving response, researchers can get an idea of what occurs during diving.
The pressure of water can be determined by measuring the force acting on the gate which is acted upon by the fluid. The pressure of the fluid varies linearly depending on the depth of the water. A rectangular gate is considered in this experiment as it easy to determine the area and use it to calculate the pressure at specific depths. The pressure equation is given in equation 1 below.
Pressure at a particular depth, p=γh (1)
Where p= pressure (N/m^2), γ=specific weight of water( N/m^3), h= the depth of the fluid (m)
The pressure is assumed to be uniform on the entire gate plane. The resultant force causing the moment on the gate can be calculated using the equation 2.
Resultant force; F_R=pA (2)
Where FR= Resultant force (N), A= cross-sectional area (m^2)
When equation 1 is substituted to equation 2, the result is:
F_R=pA=γhA (3)
In the experiment, the resultant force can be measured after the introduction of the moment that acts on the gate. Consequently, equation 3 can be rearranged to determine the pressure acting on the fluid at a specific depth.
p=F_R/A=F_R/γhA (4)
The cross-sectional area of the gate can be calculated as:
A= LW = hW
Where L=h = height of the gate (m), W= width (horizontal length) (m)
From the pressure equation (eqn 4), it is obvious that the pressure is dependent on the depth of the fluid. Notably, the fluid pressure decreases with increase in the depth (depth is in the denominators). Hence, for the case of the experiment setup, the highest pressure will occur at H1 while H5 will have the lowest pressure. The heart rate changes with change in the water depth, hence, it is important to compare the two variables.
Materials
Finger Pulse Transducer
Basin
Power Lab
Thermometer
Timer
Two Participants
Experimental Setup

## Experimental Set up for Determining the Fluid Pressure at a Particular Depth

Figure 1: Experimental set up for determining the fluid pressure at a particular depth
Methods
The power lab was initially connected and turned on. The middle finger was attached to the Finger Pulse Transducer and connected to the power lab to help measure the pulse rate. A basin was filled with cool water between 50 and 600 F. Ice cubes were used to ensure that the temperature was steady.

The subjects were supposed to remain still before the timer was started. The computer Start button was pressed after the subjects were ready. The subject took a deep breath, partially exhaled and then held their breath while entire face submerged in the basin.

The data was recorded for about thirty seconds when the participant had immersed their head on the water. The subject pulled their face from the water after the thirty seconds duration. The subject waited for thirty seconds after surfacing and the Stop button was pressed. The process was repeated for the second participant.

Results

The tables below show the data that will be recorded for the dive of the two subjects, recorded data when the subjects held their breath above the water. The tables show that if the change in the heart rate occurred due to diving or from holding the breath.
Table 1: Participant 1 diving and heart rate while on rest
Condition Rate Beats Per Minute. (BPM)
At Resting Position
15 seconds after diving into the basin
After Emerging from the basin
Thirty seconds after they had recovered.

Table 2: Participant 1 heart rate while holding their breath and heart rate at rest.
Condition Rate (Measured in BPM)
At Resting Position
15 seconds after diving into the basin
After Emerging from the basin
Thirty seconds after they had recovered.

Table 3: Participant 2 diving and heart rate while on rest
Condition Rate (Measured in BPM )
At Resting Position
15 seconds after diving into the basin
After Emerging from the basin
Thirty seconds after they had recovered.

Table 4: Participant 2 heart rate while holding their breath and heart rate at rest.
Condition Rate (BPM)
At Resting Position
15 seconds after diving into the basin
After Emerging from the basin
Thirty seconds after they had recovered.

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