Part IX Flashcards
What happens when one experiences oxygen toxicity?
seizures followed by coma within 30-60minutes
When the oxygen partial pressures are above 2 atmospheres, what happens?
free radical damage can form, which can damage cell membranes and cellular enzymes and the nervous tissue is highly susceptible, which results in brain dysfunction
How is oxygen toxicity preventable?
if one never exceeds the established max depth of a given breathing gas
and for divers, use “hypoxic blends” containing a lower O2% than ATM air
What is narcosis?
state of stupor, drowsiness or unconsciousness
How does one develop narcosis?
being submerged for over an hour
What happens at 120ft?
jovial, carefree
What happens at 150-200ft?
drowsiness
What happens from 200-250ft?
weakness
What happens above 250ft?
unable to function
What is the mechanism behind gas anesthetics?
dissolves in neuronal membranes altering ionic conductance
When is high PCO2 a problem?
almost never because depth doesn’t increase alveolar PCO2
When could PCO2 be increased?
in certain types of diving gear
What problems occur when CO2 toxicity does occur?
depression of respiratory centers, respiratory acidosis, lethargy, narcosis, anesthesia
What happens when a person breaths air under high pressure for an extended period of time?
the amount of N2 in the body fluids increases as higher N2 levels equilibrate with levels in tissues
Is nitrogen metabolized in the body?
no
When does the dissolved nitrogen come out of the tissues of the body?
when N2 pressure in the lungs decreases as the person ascend back to sea level
How much time is required to bring someone back up from under the sea? Why?
hours, the blood doesn’t flow rapidly enoguh and nitrogen doesn’t diffuse rapidly enough to cause instantaneous equilibration
When is nitrogen dissolved in the blood a problem?
when someone has been under water for hours
What is the Bends?
when nitrogen bubbles out of fluids after sudden decompression
What can happen if nitrogen bubbles out of the blood?
can block blood vessels, large or small
What are the symptoms of the bends?
pain in joints, muscles of arms and legs (85-90%), nervous system symptoms (5-10%), pulmonary capillaries blocked “the chokes” (2%)
How do you prevent decompression sickness?
a diver who has been breathing air and has been on the sea bottom at a depth of 190 feet for an hour needs to stay underwater at various depths for about 3 hours
Where does the lung rank as far as metabolism goes?
second to liver
What is an advantage the lung has over the liver?
all blood passes through the lungs with every complete cycle
What are some examples of metabolism that occurs in the lungs?
angiotensin I converted to angiotensin II
prostaglandins inactivated in one pass through pulmonary circulation
How much air does the average adult breath in a day?
10,000 L of air/day
What is in the air we breath?
inert dust, particulate matter (plants and animals), gases (fossil fuel combusion), infectious agents (viruses and bacteria
What is a major source of contact with the environment?
respiratory membrane
How many microns are between the air and blood?
.5 microns
What do our defense mechanisms do?
protect tracheobronchial tree and alveoli from injury, prevent accumulation of secreions, repair
What depresses defense mechanisms?
chronic alcohol use, cigarette smoke, air pollutants, occupational irritants
Chronic alcohol use is associated with an increase incidence of what?
bacterial infections
Cigarette smoke and air pollutants are associated with an increase incidence of what?
chronic bronchitis and emphysema
Occupational irritants are associated with increase incidence of what?
hyperactive airways or intersitial pulmonary fibrosis
What do nasal passages protect?
airwys and alveolar structures from inhaled foreign material
What things help the nasal passage protect the respiratory system?
long hairs in nose filters our large particles, mucous coating nasal mucous membranes, nasal turbinates
What are nasal turbinates?
highly vascularized structures that act as radiators to warm air
What cranial nerve is associated with coughing?
CN X
What is the process of coughing?
2.5L of air are rapidly inspired, epiglottis closes and vocal cords close tightly
muscles of expiration contract forcefully which causes pressure in lungs to rise to 100 mmHg
epiglottis and vocal cord open widely, which results in explosive outpouring of air to clear larger airways
What is a cough ineffective at doing?
clearing smaller airways due to the total cross sectional area, it just can’t generate enough velocity
