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.
It is important that we use the ABC method for drowning victims; explain it.
Airway = Make sure airway is open
Breathing = Check for breathing; if victim is not breathing, give 5 rescue breaths (if not already done in water rescue).
Circulation = Check circulation by feeling for pulse; if pulse is absent, initiate chest compressions.
Victims of near drowning who have no neurological symptoms should be evaluated by a Diving Medical Officer for what?
Pulmonary aspiration
Pneumonia is the classic result of near drowning
What are some causes of involuntary hyperventilation?
Fear experienced during stressful situations
The smothering sensation that accompanies an increase in equipment dead space
Increase in static lung loading, or an increase in breathing resistance.
Cold water exposure
What are symptoms of involuntary hyperventilation?
Dizziness
Tingling of the extremities
Spasm of the small muscles of the hands and feet.
Over a long period, produces additional symptoms such as weakness, headaches, numbness, faintness, and blurring of vision.
What can symptoms of involuntary hyperventilation be confused with?
CNS O2 Toxicity
What is a laryngospasm?
When a small amount of water is inhaled, it can cause a spasm of the muscles of the larynx (voice box)
Is carbon monoxide a normal part of the process of metabolism?
Yes
Carbon monoxide poisoning can be fatal at what ata?
0.002 ata
What are the symptoms of severe carbon monoxide poisoning?
Severe headache
Mental status changes
Neurological symptoms
Rapid heart rate
What are the three bones in the ear?
Malleus
Incus
Stapes
What is the most common type of barotrauma?
Middle ear barotrauma
What is the hallmark symptom of middle ear squeeze?
Sharp pain caused by the stretching of the eardrum
How is vertigo caused?
Caused by violent disturbance of the malleus, incus, and stapes
Can you have a squeeze in the inner ear?
No, the inner ear does not contain any gas
What are the two organs of the inner ear?
Cochlea (organ of hearing) Vestibular apparatus (organ of balance)
What can damage to the cochlea cause?
Hearing loss
Ringing in the ear (tinnitus)
Why is it more common for the round window to rupture than the oval window (IEB)?
The oval window is a tougher membrane and is protected by the footplate of the stapes
What are the two types of IEB?
IEB with / with-out perilymph fistula
Vertigo associated with IEB may be accentuated when what is done?
The head is placed in certain positions (between the legs)
Is nystagmus a symptom of IEB?
Yes
Any hearing loss or vertigo occurring within 72 hours after hyperbaric exposure should be evaluated as possibly being what?
Inner Ear Barotrauma
Increased pressure in the middle ear can cause what kind of paralysis?
Facial Baroparesis: paralysis of the facial muscles
Over-pressurization cuts off blood to the nerve causing it to stop transmitting nuero impulses to the facial muscles (10 – 30 min)
Takes 5 -10 minutes for full function to return
Can you have IEB during ascent?
Yes
When overpressure occurs in the maxillary sinus (reverse sinus squeeze), the blood supply to the infraorbital nerve may be reduced, leading to numbness of what?
Lower eyelid, upper lip, side of the nose, and cheek on the affected side.
Gastrointestinal Distention is caused by what?
Abdominal pain during ascent because of gas expansion in the stomach or intestines.
Caused by gas being generated in the intestines during a dive , or by swallowing air(aerophagia)
What is the first step in pulmonary over-inflation?
Interstitial Emphysema: rupture of the alveolus with a collection of air in the lung tissues
What is the most common cause for AGE?
Exhaustion of air supply
The need for an emergency ascent
What are symptoms of mediastinal emphysema?
Mild cases unnoticed by diver
Pain under breast bone: often described as dull ache or feeling of tightness. Pain may radiate to shoulders and may increase upon deep inspiration, coughing or swallowing.
Treatment of mediastinal and subcutaneous emphysema?
100% O2 (mild) / Shallow water recompression on 100% O2 (severe) recommended by a DMO / Usually 5 or 10 fsw (1 hour should be sufficient)
Symptoms of simple/tension pneumothorax?
Simple: sudden sharp chest pain, followed by shortness of breath, labored breathing, rapid heart rate, weak pulse, anxiety.
Tension: same symptoms as simple but more severe
If a pneumothorax, if present in combination with arterial gas embolism or decompression sickness, should immediate recompression therapy be delayed?
No
What is nitrogen narcosis?
State of euphoria and exhilaration that occurs when a diver breathes a gas mixture with nitrogen partial pressure greater than 4 ata
What are the causes of nitrogen narcosis?
Increase of pp of nitrogen
(4 ata) onset of nitrogen narcosis
(8 ata) very marked impairment
(10 ata) hallucinations, unconsciousness
On air, usually appears at 130fsw and very prominent at 200fsw
Pulmonary O2 Toxicity
Low pressure oxygen poisoning
Can occur whenever ppo2 exceeds 0.5 ata
Treatment Tables 4, 7, 8
When could an individual start to feel the symptoms pulmonary oxygen toxicity?
Whenever the oxygen partial pressure exceeds 0.5 ata.
A 12 hour exposure to a partial pressure of 1 ata will produce mild symptoms and measurable decreases in lung function.
The same effect will occur with a 4 hour exposure at a partial pressure of 2 ata.
What are symptoms of pulmonary oxygen toxicity?
Burning sensation on inspiration
Progresses to pain on ispiration
CNS Oxygen toxicity can occur when ata’s exceed what wet and dry?
- 3 ATA (WET)
2. 4 ATA (DRY)
The random impulses of the clonic phase of a convulsion to various muscles may cause violent thrashing and jerking for how long?
A minute or so
How long does the depression phase (postictal phase) last?
Sometimes lasts as little as 15 minutes, but an hour or more is not uncommon.
At the end of the postictal phase, the patient often becomes suddenly alert and complains of what symptoms?
Fatigue
Muscular soreness, and possibly a headache
How long after a diver experiences and early symptom of CNS O2 toxicity and is removed from high O2 breathing can a supervisor assume that an O2 convulsion will not occur?
Has been off O2 for 2-3 minutes
Why is the risk of hypoxia greatly reduced during the breath holding tonic phase of a O2 convulsion?
Because of the high pressure of ppO2 in the tissues and the brain
If a convulsing diver is prevented from drowning or causing other injury to himself, full recovery with no lasting effects can be expected within how many hours?
24 hours
Does susceptibility to oxygen toxicity increase as a result of a convulsion?
No
At sea level how much nitrogen does an average human body contain?
1 liter
Nitrogen is how much more soluble in fat than water?
5 times
A water temperature of approximately what is required to keep an unprotected, resting man at a stable temperature?
91 degrees
The unprotected diver will be affected by excessive heat loss and become chilled within a short period of time in water temperatures below what?
72 degrees
To treat mild hypothermia, passive and active rewarming measures may be used and should be continued until the victim is what?
Sweating
Symptoms of mild/severe hypothermia?
Mild: uncontrolled shivering, slurred speech, imbalance, poor judgment,
Severe: loss of shivering, impaired mental status, irregular heartbeat, shallow pulse, shallow respiration
What are the two treatment of hypothermia?
Passive re-warming
Active re-warming
Severe cases avoid exercise, keep victim lying down, initiate passive re-warming only, transport to a medical facility.
What is diving reflex?
Sudden exposure of the body to cold water may cause immediate slowing of the heart rate (bradycardia) and intense constriction of the peripheral vessels. Sometimes abnormal heart rhythms accompany the bradycardia.
When should hyperthermia be considered a potential risk?
Air temp exceeds 90 degrees
Water temp is above 82 degrees
At what core temperature is a person considered to have hyperthermia?
When core rises 1.8 degrees above 98.6 degrees (should not exceed 102.2 degrees)
What is the minimum consecutive days to warm water diving is needed to increase tolerance to heat?
5 days
What is the treatment of immersion pulmonary edema?
100% O2
Transported to medical facility
Signs and symptoms will usually resolve spontaneously over 24 hours with just bed rest and 100% O2
What is carotid sinus reflex?
Excess pressure on the carotid artery from tight fitting neck damn, wet suit, or dry suit can activate receptors in the arterial wall, causing a decrease in heart rate with possible loss of consciousness.
Treatment of otitis externa?
External ear prophylaxis (otic domboro)
2 % acetic acid in aluminum acetate solution
Must remain in canal for 5 minutes (timed by watch)
A water temperature of what is required to keep an unprotected, resting man at stable temperatures?
91 degrees fahrenheit
What is High Pressure Nervous Syndrome (HPNS)?
Derangement of central nervous system function that occurs during deep helium-oxygen dives, particularly saturation dives.
The cause is unknown
At what depth is HPNS first noted?
Between 400 and 500 fsw
Severity appears to be both depth and compression rate dependent.
When do symptoms of compression arthralgia occur?
Mild symptoms may occur with rapid compression on air or helium-oxygen dives as shallow as 100 fsw.
In deep helium saturation dives with slower compression rates, symptoms usually begin between 200 and 300 fsw.
Under average conditions, a shock wave of 500 psi or greater will cause injury to what organs?
Lungs and intestinal tract
The maximum shock pressure to which a diver should be exposed is what?
50 psi
If in the water during an explosion, how should a diver position himself?
Float face up, presenting the thicker tissues of the back to the explosion.
