Diving Physiology (ppt) - Dr. Miyake Flashcards
Ambient pressure at sea level
1 atmosphere
For every 10 meters of sea water
1 ata
O m/ O ft
1 ata/ bar
10 m/ 33 ft
2 ata/bar
20 m/ 66 ft
3 ata/bar
30 m/ 99 ft
4 ata/bar
During descent, the volume of a body of air decreases while density ________.
Increases
Increased external water pressure does not compress body’s fluid and solid components until a depth of _______.
1.5 km
It compresses each of body’s air compartments that depends on the compliance of the compartment.
Increased external water pressure
Examples of COMPRESSIBLE:
Middle ear space
Sinuses
Lungs
Bowel lumen
According to __________, P and V vary inversely with each other
Boyle’s law
Thus, if the chest wall were perfectly compliant, a breath-holding dive to _____ below the surface would double the pressure and compress the air held in the lungs to half its original volume.
10 m
Volume of gas is ___________ to pressure to which it is subjected, temperature remaining __________.
Inversely proportional
Constant
Diver is exposed when breathing air:
- Nitrogen
- Oxygen
- Carbon dioxide
4/5 air
Nitrogen
Almost useless as a result of nitrogen narcosis
> 250 ft
Normal range of alveolar PO2 below __________, almost none of total oxygen in blood is accounted for by dissolved oxygen.
120 mmHg
Has high lipid solubility and dissolves readily in adipocytes and membrane lipids.
Nitrogen
Strength wanes, too clumsy to perform the work required.
200-250 ft
When PO2 in blood rises _______, amount of O2 dissolved in water of blood increases markedly.
> 100 mmHg
Drowsy
150-200 ft
As PN2 _______, N2 equilibrates only slowly with body’s lipid stores because adipose tissue is relatively underperfused.
Rises
At high pressures can cause degrees of narcosis
Nitrogen
Lose many of his/her cares
120 ft
Depth at which 1st symptoms of mild nitrogen narcosis is ________.
120 ft
As O2 pressures rises into thousands of mmHg, large portion of __________ is then dissolved in water of blood.
Total O2
Prolonged elevation has detrimental effects on nonpulmonary tissues including CNS
Acute oxygen poisoning
Breathing O2 at 30-40 mmHg will cause BRAIN SEIZURES followed by coma within _________.
30-60 minutes
Preliminary symptoms of acute oxygen poisoning:
NMDDID
Nausea Muscle twitchings Dizziness Disturbance of vision Irritability Disorientation
Has little capability of oxidizing other chemical compounds.
Molecular O2
Molecular O2 must 1st be converted into ______ form of O2.
Active
Forms of active O2 is called ________.
Oxygen free radicals
When tissue PO2 is normal at the level of _________ small amounts of free radicals are continually being formed from dissolved molecular O2.
40 mmHg
Enzymes rapidly remove free radicals:
Peroxidases
Catalaes
Superoxide dismutases
Above critical alveolar PO2 amounts of ____________ literally swamp enzyme systems and have serious destructive and even lethal effects on cells.
Oxidizing free radicals
After only about 12 hours of 1 atm oxygen exposure develops:
Chronic oxygen poisoning
Lung passageway congestion, pulmonary edema and atelectasis.
Chronic oxygen poisoning
Caused by damage to the linings of bronchi and alveoli begin to develop.
Chronic oxygen poisoning
To prevent, divers must reduce fraction of inspired air that is O2 in compressed gas mixture.
Oxygen toxicity
A replacement gas
Helium
Has only a fraction of narcotizing effect of N2.
Helium
Dissolves in tissues to a lesser extent than N2
Helium
Has lower density than N2 and this lowers effective airway resistance.
Helium
During decompression phase of a dive, _______ diffuses out of tissues more rapidly than does N2 and alleviates most of problems associated with decompression.
Helium
If diving gear is properly designed and functions properly, diver has no problem due to CO2 toxicity because depth alone does not __________ CO2 partial pressure in alveoli.
Increase
In some types of diving gear ________ can build up in dead space air of apparatus and be rebreathed by diver.
CO2
Up to PCO2 of _______ (twice that in normal alveoli) diver usually tolerates this buildup by increasing the minute respiratory volume to compensate for increased CO2
80 mmHg
The total amount of new air moved into the respiratory passages each minute _________ on an average.
6 L/min
A person will die if minute respiratory volume falls as low as ________ or RR falls below _________.
1.5 L/min
2-4 breath/min
Also known pulmonary ventilation
Minute respiratory volume
Beyond ______ PCO2, becomes intolerable and eventually respiratory center begins to be depressed because of negative tissue metabolic effects of high PCO2.
80 mmHg
Develops severe respiratory acidosis, lethargy, narcosis and even anesthesia.
Carbon dioxide toxicity
Following extended dive, diver must decompress slowly to avoid ____________.
Decompression sickness
Serious difficulties also arise if - after a __________ - diver returns to surface too quickly.
Deep saturation dive
At end of saturation dive, _______ is at same high value in alveoi and most tissues.
PN2
As ______ falls during ascent, alveolar PN2 will fall as well, creating a PN2 gradient from mixed venous blood to alveolar air.
PB - Barometric pressure
Washout of N2 from blood creates a PN2 gradient from ______ to _______.
tissues to blood
To allow enough tome for dissolved N2 to move from tissues to blood to alveoli, a diver must rise to surface slowly (no faster than _________).
3 m/hr
