High altitude and diving Flashcards
how does Pbar change with elevation
decr as elev incr
hypobaric hypoxia at altitude
what is the problem with incr altitude on oxygen availability
moderate
1) incr alittude
2) decr PIO2
3) decr PaO2
4) less for tissues
incr altitude effect on O2 availability
severe
not only decr PIO2
also decr diffusion gradient for O2 from alveoli to blood so less O2 to blood
which people should avoid high altitude if no supplemental O2
COPD, ILD (gas exchange problem)
anemia (low baseline PaO2 already)
difference between adaptation vs. acclimatization
adaptation = genetic events increasing fitness at high altitudes (chronic compensatory)
acclimatization = subacute to chronic for more efficient function at altitude in individual
what are acute compensatory mechaisms at high altitude
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
small changes in PaO2 from incr minute ventilation lead to ___
significant changes in Hb saturation
(between 30-60 pO2 from oxy deoxy curve
what is best way to incr Hb saturation at altitude?
HYPERVENTILATE
chronic compensatory mechanisms at high altitude
1) heritable adaptation
2) incr Hb saturation
3) incr minute ventilation due to higher PaO2 compared to acute
4) skeletal muscle adaptation
describe chronic ways to incr Hb saturation
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
what causes incr minute ventilation as chronic adaptive measure at altitude
1) change in genes for regulator of resp system (carotid, aortic body, brainstem
difference between people who chronically adpated vs accutely acclimated to altitude in terms of ventilation
chronic adapted =incr ventilation when PO2 below 63 while acclimatize incr ventilation when PaO2 below 55
what are chronic ways our skeletal muscle adpats?
1) incr myoglobin amount and affinity for O2
2) angiogenesis
why should people with COPd or asthma be cautious when diving?
diving = incr in density of gas in lung, incr in resistance to flow (exacerbated with obstructive disease)
what problem does asthma cause with diving?
incr barotrauma
because alveoli never drain during exhalation
partially filled –> incr expansion of lung volume during ascent –> barotrauma
Acute mountain sickness (AMS)
1) when do symptom start and peak
2) symptoms
3) treatment for AMS
4) treatment to prevent AMS
KNOW!!!!!
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
High altitude cerebral edema (HACE)
1) symptoms
2) does it recur?
3) treatment
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
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
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
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
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
pulmonary barotraumas
1) caused by
2) when does it occur
3) life threatening effects
4) more common with …
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
decompression sickness (bends)
1) caused by ___
2) symptoms
3) prevented by
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
nitrogen narcosis
1) result of ___
2) symptoms
3) prevented by
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)
shallow water blackout
1) occur when?
2) what do these people not do?
3) effect
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
what is the effect of diving on lungs?
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
what is the effect of incr pressure in lung during diving
2) compresses filled lung and incr density of gas in lung
3) incr resistance to flow
4) incr work to breath
what is the effect of incr venous return with diving
5) incr venous return –> incr filling presure, decr compliance of lung
6) decr Vital capacity
Acute Human response to moderate hypoxia at altitude
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)
Chronic Human response to moderate hypoxia at altitude
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
if you are acclimatized to altitude for month
more sensitive to hypoxia
for given normal PaO2, you would be hyperventil
incr minute ventilation
tight box theory for acute mountain sickness
evidence for inflamm?
1) can’t expand skull
2) so if brain swells, then incr pressure, incr cerebral blood flow on all sides –> headache
NO INFLAMM!!
1) Diseases that cause lower PaO2 at rest
2) diseases that limit minute ventilation
3) other problems
1) lung dieases (not asthma), CHF, hypoventilation
2) COPD, pulm fibrosis, morbid obesity
3) existing pulm HTN or left heart failure
