Diving Flashcards
Describe the process of breath holding
Main stimulus to control of breathing is central hypercapnia
PaCO2
During apnoea continues to utilise O2 and produce CO2
Minimise oxygen consumption, stay still
Hyperventilate before
When CO2 reaches threshold for breathing body trues to take over to breathe
If O2 drops below certain level - you blackout
What is the diving reflex?
Cold water exposed to face
Sensory nerves stimulate:
Peripheral sympathetic vasoconstriction = ⬆️ BP and centralisation of blood volume in middle of body
Vagal bradycardia = reduced CO, decreased HR and SV
Splenic contraction = increase haemoglobin
Important for water to be cold
What is the cold shock response?
All over body If water is very cold, breathe hold is abolished Inspiratory gasp, hyperventilation Peripheral vasoconstriction ⬆️ TPR Sympathetic tachycardia
What happens when you have diving reflex and cold shock response both activated
Vagal bradychardia + sympathetic tachycardia = arrhythmia
What kind of diving is there
Free diving
Snorkelling
SCUBA
How does snorkelling work
Adding dead space
Snorkel cant be too long, as dead space cannot be increased that much
Therefore snorkel cannot be too long
As you dive down you have get compression of lung volume, and increase in negative pressure = fluid leakage in lungs
How does SCUBA work?
Involves an open circuit with compressed air
Air is delivered on demand
Diaphragm pulls down in inspiration creating negative pressure in airway
Opens up valve allowing gas to come in
Lung volume doesn’t change as you descend
If you ascend and forget to breathe out alveoli increase in volume and could burst
What is a rebreather circuit
A closed circuit version of SCUBA
Expired air still contains lots of oxygen so can recylce
Physiology of diving descent
Diver descends Pressure increases Alveolar pressure increases Regulator valve feeds air Increase in alveolar oxygen and nitrogen Increase in arterial o2 and n2 Increase oxygen in tissue Excess o2 and n2 can occur but is eventually metabolised or left in tissues
Physiology of diving ascent
Pressure decreases
If slowly: n2 cleared steadily by diffusion
If rapidly: rapid decompression
Bubbles form in tissue
Depending on tissue can compress nerves
Bubbles can get caught in pulmonary vasculature and diffuse in lungs
Can get arterial gas embolism if patient has a hole between 2 atria (PFO)
How does decompression sickness occur and how is it treated?
Main risk factor is rate of ascent
Rate of ascent should be slow
Use of hyperbaric chamber to repressure body and steadily reduce the pressure to allow gas to move out of solution slowly
Effects of water immersion on human body
There are compressible and non compressible compartments
Air can compress so body cavities with air will compress
There is centralisation of blood volume
Increased load on heart
Fluid seepage from pulmonary capillaries
