Effects of barometric pressure Flashcards
What is 2 adaptations to altitude?
Hyperventilation and polycythaemia
What does hyper
Other adaptations to altitude? 5 main points
- Right shifted O2-Hb dissociation curve (moderate altitudes)
- Better unloading at tissue level (possible loading limitation)
- Caused by [2,3-DPG] - Left shifted O2-Hb dissociation curve (high altitudes)
- Better loading at the pulmonary capillaries
- Caused by respiratory alkalosis - Improved diffusion capacity via:
- Expanded surface area via greater lung volume on inflation
- Increased tissue capillarisation (angiogenesis) (days) - Endothelial cells release up to 10 times more nitric oxide (NO)
- Reduced skeletal muscle fibre size (weeks)
- In conjunction with increased oxidative capacity & mitochondria numbers
What do athletes often take?
EPO
What happens at high altitude to arterial O2 and the Hb saturation via the O2 Hb dissociation curve?
Despite low levels of arterial O2 and lower Hb saturation via O2 Hb dissociation curve
What is the total O2 content at higher altitudes?
Polycthemia
blood is more cellular more viscoisty, so more work for the cardiac system leading to hypertrophy and blood flow distribution can be uneven as well
What does the O2 HB dissociation curve at moderation altitudes look like?
S shaped curve
Why is the diffusion capacity increased at moderate altitudes?
increased diffusion capacity as we need to breathe more
actual size of skeletal muscle fibres is reduced and shrinks due to losing appetite and lose sustantial amount of weight?
sleeping is affected, chemoreceptros are reduced
particualr changing initially to sleep at moderate altitudes as heart rate is icnreased and breathing is more dificult
What is a mild sickness at moderate-higher altirtudes?
Acute mountain sickness: AMS
Does AMS affect men or women more?
AMS is higher in women
some people just adapt better than others
Symptoms of AMS
- Headaches, Loss of appetite & Insomnia, Nausea, Vomiting, Dyspnea
- Begin from 6 to 48 h after arrival to altitude (most severe days 2 and 3)
- Worse at night (as respiratory drive is reduced)
What does AMS incidence vary with ?
altitude, rate of ascent & individual’s susceptibility
AMS incidence varies with altitude, rate of ascent & individual’s susceptibility - explain:
Elevations 2,500–3,500 m: incidence ~15% (higher in women)
* Maybe linked to low ventilatory response to hypoxia
* Physical conditioning little protection against effect of hypoxia
* Elevations >3,500 m : ~ 75% of individuals at least mild symptoms
What is high altitude pulmonary/ cerebral oedema?
Linked to pulmonary vasoconstriction (hypoxia): high [protein] oedema fluid from damaged capillaries.
- Fluid accumulation leads to persistent cough, shortness of breath, cyanosis of lips & fingernails and loss of consciousness.
- Could lead to High altitude cerebral oedema (fluid accumulation in cranial cavity)
Treatment for high altitude pulmonary/cerebral oedema?
Descending to lower altitude and supplemental oxygen.
Example of inspired pressures at extreme altitude?
Took them just before summit called the balcony
Arterial samples - harder to get then venous
People were not acclimitised before hands
base camp of Everest - 5000m
Must acclimitase propelry
camp 4 is highest camp: 8000m
beyond this point we cannot acclimitise
must climb very slowly at final climb
chances of survivibg are slim if you do not realise the summit by early afternoon
often people use artificial O2 when climbing Everest
Can technically do it without artifical O2 - 25 years ago
Who was the 1st person to climb Everest without O2
Reinhold Andreas Messner
He made the first solo ascent of Mount Everest and, along with Peter Habeler, the first ascent of Everest without supplemental oxygen
How many climb without O2
Less than 5%
O2 content in blood was almost same at sea level due to extra Hb in blood
Case study - Kilian Jornet what did he do?
He was well aclimitased
He also climbed another 8000m peak near Everest before the actual summit - he was very fit and very strong
He did not have any helpers
Climbed Everest twice (May 2017)
Without artificial O2
In a single climb (each ascent)
New speed record (first ascent)
Both ascents within a week
He had some stomach issues in climb
he decided from Tebit side which is longer and steeper
He went up and down within 7 days
Human Bodies can do it if you properly adapt and are super careful
2000-300m: What are some altitude/hypoxic training strategies to maximise sea-level performance? 4 examples
- live high - train high
- Live (or sleep) high and train low
- Live low - train high
- Intermittent hypoxia at rest
How is it good for performacne?
Increase RBCs and so can increase O2 carrying capcityies making someone stromger, able to go on for longer, etc
What is the issue with live high-train high?
cannot maintain benefits of actual training programme - difficult to train at same volume/intensity as at sea level
There a few well controlled studies on athletes
Benefit of live high- train high: LHTH or HiHi
Increased RBC volume (>2000m x 3-4 weeks)
What effect does intermittent hypoxia training strategy have for increasing performance?
Weak effect - if any
What effect does live low-train high (LLTH or LoHi) training strategy have on performance?
Weak effect if any
Which type of training is the most effective to maximise sea-level performance?
Live (or sleep) high - train low (LHTH or HiLo)
Problem with LHTL?
Logistics and finance
What are some other ways to do LHTL?
Hypoxic tents (sleeping devices) or even hypoxic living apartments (>2000m x 3 weeks x >12h/day)
Treatment for decompression sickness?
Recompression - issue is we need recompression chamber which are very sophisticated often need to get someone to hospital and can be issue if someone is diving in a remote place they will not be able to get access to this
What is decompression sickness?
Refers to injuries caused by a rapid decrease in the pressure that surrounds you, of either air or water. It occurs most commonly in scuba or deep-sea divers, although it also can occur during high-altitude or unpressurized air travel
COPD - intermittent hypoxia?
beneficial to COPD for some patients
what happens when you go underwater?
Pressure increases - 1 atmosphere every 10m which is 33ft
What happens to N2 under water with pressure?
N2 solubility in blood increases when pressure is higher and this creates problem
Gas cavities increase compress when we descend in H20 and they decrease, expand when we ascend
important to pinch nose to pop ears to equalise pressure to avoid compression of gas cavities
Since the total pressure increases when you go under water, what does that mean for gas partial pressures?
Therefore, Gas partial pressures also increase when under water
euphoric feeling under depper water
can lose coridnationa dn consciouness and this can be fatal under
how to avoid?
use less N2 - use helium instead as it has 1/2 the solubility
getting 100% O2 is not useful as O2 can be toxic to brain, etc
mix of O2 and He is most recommended
What happens if we ascend too quickly in water?
if we ascend too quickly can increase N2 bubbles in the blood - decompression sickness
BENDS
can affect myelination, can affect muscle joints, can induce dizziness and paralysis
so painful that people bend over due to the pain
can break tissue
similar effect to opening champagne bottle or fizzy drink
How do we prevent decompression sickness
Slow ascent - according to prescribed tables
N2 gas replacement: Helium which has 1/2 the solubility of N2 , molecular weight is lower exhale during ascent
What does this prevention for decompression sickness depend on?
Depends on Dept, Time, N2 wash-in & wash-out times and Tissue types
