High altitude and diving

Question 1

how does Pbar change with elevation

Answer 1

decr as elev incr

hypobaric hypoxia at altitude

Question 2

what is the problem with incr altitude on oxygen availability
moderate

Answer 2

1) incr alittude
2) decr PIO2
3) decr PaO2
4) less for tissues

Question 3

incr altitude effect on O2 availability

severe

Answer 3

not only decr PIO2

also decr diffusion gradient for O2 from alveoli to blood so less O2 to blood

Question 4

which people should avoid high altitude if no supplemental O2

Answer 4

COPD, ILD (gas exchange problem)

anemia (low baseline PaO2 already)

Question 5

difference between adaptation vs. acclimatization

Answer 5

adaptation = genetic events increasing fitness at high altitudes (chronic compensatory)

acclimatization = subacute to chronic for more efficient function at altitude in individual

Question 6

what are acute compensatory mechaisms at high altitude

Answer 6

1) incr HR, incr SV (decr afterload from vasodilation), incr CO –> return to normal in few days

2) incr RR, incr VT, incr VE, incr Hb-O2
carotid body hypoxic stim –> stim brainstem resp centers PaO2 days to weeks, decr PACO2 and PaCO2

Question 7

small changes in PaO2 from incr minute ventilation lead to ___

Answer 7

significant changes in Hb saturation

(between 30-60 pO2 from oxy deoxy curve

Question 8

what is best way to incr Hb saturation at altitude?

Answer 8

HYPERVENTILATE

Question 9

chronic compensatory mechanisms at high altitude

Answer 9

1) heritable adaptation
2) incr Hb saturation
3) incr minute ventilation due to higher PaO2 compared to acute
4) skeletal muscle adaptation

Question 10

describe chronic ways to incr Hb saturation

Answer 10

1) incr EPO from kidney, incr Hb and RBC mass
2) incr Hb affinity for O2 and respiratory alkalosis causing hyperventilation (left shift)
3) incr minute ventilation at lower PaCO2 compared to sea level

Question 11

what causes incr minute ventilation as chronic adaptive measure at altitude

Answer 11

1) change in genes for regulator of resp system (carotid, aortic body, brainstem

Question 12

difference between people who chronically adpated vs accutely acclimated to altitude in terms of ventilation

Answer 12

chronic adapted =incr ventilation when PO2 below 63 while acclimatize incr ventilation when PaO2 below 55

Question 13

what are chronic ways our skeletal muscle adpats?

Answer 13

1) incr myoglobin amount and affinity for O2

2) angiogenesis

Question 14

why should people with COPd or asthma be cautious when diving?

Answer 14

diving = incr in density of gas in lung, incr in resistance to flow (exacerbated with obstructive disease)

Question 15

what problem does asthma cause with diving?

Answer 15

incr barotrauma
because alveoli never drain during exhalation
partially filled –> incr expansion of lung volume during ascent –> barotrauma

Question 16

Acute mountain sickness (AMS)
1) when do symptom start and peak

2) symptoms
3) treatment for AMS

4) treatment to prevent AMS
KNOW!!!!!

Answer 16

1) 6 hrs at altitude, peak at 1-3 days
2) mildest form of acute altitude = headache + 2 other sx: fatigue, nausea, malaise, insomnia, anorexia

3) usu resolves but relieve with analgesis
4) GRADUAL ASCENT; acclimatization

dexamethaosne (alters gene expression, decr mediators that cause edema)
acetazolamide (diuretic wasting HCO3- –> METABOLIC ACIDOSIS –> hyperventilation to restore pH–> incr PaO2)
ibuprofen for HA

Question 17

High altitude cerebral edema (HACE)

1) symptoms
2) does it recur?
3) treatment

Answer 17

extreme AMS = emergency
1) cerebral edema –> AMS with ataxia, confusion, coma

2) yes in affected
3) O2, immediate descent, IV dexamethasone (EVERYONE), hyperbaric bag if descent unsafe

Question 18

High altitude pulmonary edema

1) result of?
2) symptoms
3) when do symptoms begin?
4) physical exam, incr likely of having
5) co occur with __ and recur in affected

6) treatment if happen
treatment to prevent

Answer 18

1) acute pulm HTN (hypoxic pulm vasoconstriction) –> capillary breakdown in lung (protein leak)–> noncardiogenic edema, hypoxic, rapid and lethal
2) productive cough, SOB, fatigue
3) within 2nd night
4) rales and bilateral infiltrates, patent foramen ovale
5) AMS

6) Avoid altitude
descent + O2 + hyperbaric
vasodilator (nifedipine (Ca2+ blocker))

vasodilator (nifedipine, sildenafil, tadalafil) to decr pulm pressure
bronchodilator (inhaled salmeterol), incr Na+/K+ atpase to remove fluid
dexamethasone

NO DIURETICS

Question 19

chronic mountain sickness for people living at altitude

1) caused by …
2) which patients
3) assoc with what in pregnancy
4) lab finding

5) treatment

Answer 19

1) pulm HTN –> incr risk for right heart failure and storke
2) live at ow birth weight and higher infant mortality
3) pre-eclampsia
4) polycythemia, (incr HCT), pulm HTN/RV failure

5) lower altitude
supplemental O2
periodic phelbotomy

Question 20

pulmonary barotraumas

1) caused by
2) when does it occur
3) life threatening effects

4) more common with …

Answer 20

1) incr pressure of air in lung –> extravasation of air in bronchial tree
2) when breath holding diver resurface too fast, gas expand
difference between trachea and pleura –> interstitium –> pleural space or blood

3) pneumothroax or pneumomediastinum (if air in pleural space/mediastinum)
stroke or MI (if air in blood)

4) poor asthma, lung blebs/cysts, single breath dives

Question 21

decompression sickness (bends)

1) caused by ___
2) symptoms
3) prevented by

Answer 21

1)deeper/longer dives, incr Pp of inert N2 in tissue and blood
supersaturated in tissues –> bubbles, quick decr in pressure
air bubble incr in size and damage organs

2) confusion, MSK pain, dyspnea, coma, seizure, death

3) gradual resurfacing
avoiding high altitude after dive

Question 22

nitrogen narcosis

1) result of ___
2) symptoms
3) prevented by

Answer 22

1) breathing compressed air (79% N2) at depths > 100 ft,
incr Pp N2 in tissues

2) incr N2 in brain –> clumsiness and bizarre (like EtOH tox)
3) use helium instead of nitrogen > 100 ft (> 30 m)

Question 23

shallow water blackout

1) occur when?
2) what do these people not do?
3) effect

Answer 23

1) breath holding, forced hyperventilation (decr PaCO2 input to brainstem)
if PaCO2 low enough –> anoxic –> unconscious –> drown

2) do not surface hyperventilate before submerging to incr PaO2
so PaO2 decr while submerged and PaCO2 only rise slightly for each minute of apnea so may not feel apneic until PaCO2 too low

3) pass out

Question 24

what is the effect of diving on lungs?

Answer 24

1) Patm incr by 1 every 10 m depth
2) compresses filled lung and incr density of gas in lung
3) incr resistance to flow
4) incr work to breath
5) incr venous return –> incr filling presure, decr compliance of lung
6) decr Vital capacity
7) N2 comes out of solution

Question 25

what is the effect of incr pressure in lung during diving

Answer 25

2) compresses filled lung and incr density of gas in lung
3) incr resistance to flow
4) incr work to breath

Question 26

what is the effect of incr venous return with diving

Answer 26

5) incr venous return –> incr filling presure, decr compliance of lung
6) decr Vital capacity

Question 27

Acute Human response to moderate hypoxia at altitude

Answer 27

1) incr HR to incr CO
hypoxia = periph vasodilator and pulm vasoconstrictio

2) incr VE (carotid body sends more signals to resp center, rapid deep breathing) (decr CO2, incr PaO2)

Question 28

Chronic Human response to moderate hypoxia at altitude

Answer 28

1) decr HR, decr CO
continue increased VE

2) hypoxia incr EPO –> incr Hb
3) more sensitive to CO2, so hyperventilate more (gene expression changes)
4) incr capillary density anad myoglobin

Question 29

if you are acclimatized to altitude for month

Answer 29

more sensitive to hypoxia

for given normal PaO2, you would be hyperventil
incr minute ventilation

Question 30

tight box theory for acute mountain sickness

evidence for inflamm?

Answer 30

1) can’t expand skull
2) so if brain swells, then incr pressure, incr cerebral blood flow on all sides –> headache

NO INFLAMM!!

Question 31

1) Diseases that cause lower PaO2 at rest
2) diseases that limit minute ventilation
3) other problems

Answer 31

1) lung dieases (not asthma), CHF, hypoventilation
2) COPD, pulm fibrosis, morbid obesity
3) existing pulm HTN or left heart failure