Chapter 3 Flashcards
How many liters of blood does the human body contain?
5 Liters
What is the normal respiratory rate for an average adult?
12 to 16 breaths per minute
What is the normal total lung capacity?
Between 5 and 6 liters
What is respiratory minute volume for an individual at rest and severe work?
Rest: 6 to 10 liters per minute
Severe Work: 100 per minute
What is a respiratory quotient and what do the values range from?
The ratio of the amount of carbon dioxide produced to the amount of oxygen consumed during cellular processes per unit time
0.7 to 1.0 depending on diet and physical exertion and is usually assumed to be 0.9 for calculations
What UBA is the respiratory quotient significant for?
Closed circuit breathing apparatus
How long does each cycle of gas exchange take?
20 seconds
Changes in the partial pressure (concentration) of oxygen and carbon dioxide (ppO2 and ppCO2) in the arterial circulation activate what in the body?
Central and peripheral chemoreceptors
What two arteries are the chemoreceptors?
Carotid (Neck): activated by ppCO2 in the blood and signals the respiratory center in the brain stem to increase or decrease respiration?
Aortic (Heart): causes the aortic body reflex; this is a normal chemical reflex initiated by decreased oxygen concentration and increased carbon dioxide concentration in the blood.
Does low oxygen tension alone increase breathing?
Not until dangerous levels are reached
What is oxygen consumption measured in, and is it depth dependant?
LPM
No, it is not depth dependent
Unlike oxygen consumption, what is depth dependent?
The amount of gas a diver inhales
What is the only factor that carbon dioxide production dependent on?
Level of exertion
Carbon dioxide production and RQ are used to compute what?
Ventilation rates for chambers and free-flow diving helmets.
Partial pressure of oxygen below what causes the onset of hypoxia?
0.16
At what ppO2 do individuals become hypoxic to the point of helplessness? Unconsciousness?
- 11 (helplessness)
0. 10 (Unconsciousness)
What tissue is the most susceptible to hypoxia?
Brain Tissue
Unconsciousness and death can occur before the effects of other tissues become apparent
Why does your pulse rate and blood pressure increase when you become hypoxic?
The body tries to offset the hypoxia by circulating more blood
What is not a reliable indication of hypoxia and why?
Cyanosis
Same signs could be caused by prolonged exposure to cold water
What is the treatment of hypoxia?
Basic first aid
100% oxygen
Excessive breathing resistance is an important cause of hypercapnia and arises from what two sources?
Flow resistance
Static lung load
When do symptoms of hypercapnia become apparent?
When divers attempt heavy work at depths deeper than 120 FSW on air
Deeper than 850 FSW on helium/oxygen
At 1,600-2,000 FSW, shortness of breath and other signs of CO2 toxicity may occur even at rest.
What is static lung load and how does it happen?
Result of breathing gas being supplied at different pressure than the hydrostatic pressure surrounding the lung.
If a divers flips on his back, the regulator diaphragm is shallower than his mouth and the regulator supplies gas at a slightly negative pressure. Inhalation is harder but exhalation is easier
What UBA’s is static lung load more apparent in?
Closed and semi-closed circuit underwater breathing apparatus such as the MK 25 and MK16
What is dyspnea?
Shortness of breath
Labored breathing
Excessive breathing resistance may cause shortness of breath and a sensation of labored breathing (dyspnea) without what?
Any increase in blood carbon dioxide levels (static lung load).
Is a convulsion a symptom of hypercapnia?
Yes
If the PPO2 is above what, the shortness of breath usually associated with excess carbon dioxide may not be prominent and may go unnoticed by the diver, especially if he is breathing hard because of exertion?
0.5 ata
A diver who loses consciousness because of excess carbon dioxide in his breathing medium and does not inhale water generally revives rapidly when given fresh air and usually feels normal within how many minutes?
15 minutes
What is thought to explain the headaches often associated with carbon dioxide intoxication?
The excess carbon dioxide dilating the arteries of the brain
Why does hypercapnia speed the onset of CNS O2 toxicity?
Excess carbon dioxide dilates the arteries of the brain
The increased blood flow through the brain is thought to explain why excess carbon dioxide speeds the onset of CNS O2 toxicity.
Excess carbon dioxide during a dive is also believed to increase the likelihood of what?
Decompression sickness
In surface-supplied diving, hypercapnia is prevented by ensuring what things happen?
Gas supplies do not contain excess carbon dioxide.
Maintaining proper manifold pressure during the dive
Ventilating the helmet frequently with fresh gas.
For dives deeper than 150 fsw, what gas mixtures should be used to reduce breathing resistance?
Helium-Oxygen
What is asphyxia?
Condition where breathing stops, and hypoxia and hypercapnia occur simultaneously
What can cause paralysis of the respiratory muscles?
High cervical spinal cord injury due to trauma or decompression sickness
Respiratory center in the brain stem may become non-functional during a prolonged episode of what?
Hypoxia
What is drowning?
Fluid induced asphyxia.
What is a near drowning?
A victim is successfully resuscitated following a drowning episode.
What are the symptoms of Drowning/Near Drowning?
Unconsciousness
Pulmonary edema
Increased respiratory rate
In water rescue of unconscious drowning victims require what?
Ventilation alone
What are the steps to remember when rescuing an unconscious drowning victim?
Open/Maintain an airway.
Check breathing
Provide 5 rescue breaths if victim not breathing.
DO NOT attempt chest compressions in water
Patient should be placed on 100% O2 and AED placed on chest – although a shockable rhythm is unlikely.
Be prepared to turn patient on their side and suction their airway – vomiting is common.
Even if AGE/DCS cannot be ruled out for a drowning victim, immediately transport patient to nearest hospital for continued treatment of what?
Cardiac/respiratory arrest. The mildest cases of drowning will still require post rescue hospitalization and possibly intensive care.