I. Coping with Altitude. Coping with Altitude and Depth. I. Coping with altitude (air-breather) II. Coping with deep sea (diving airbreather)

Size: px

Start display at page:

Download "I. Coping with Altitude. Coping with Altitude and Depth. I. Coping with altitude (air-breather) II. Coping with deep sea (diving airbreather)"

Joseph Gregory
6 years ago
Views:

1 Coping with Altitude and Depth I. Coping with altitude (air-breather) II. Coping with deep sea (diving airbreather) Yuxiang Wang Chap 11.4, 11.6, 12.3, 15.4, 16.4 OT Chap. 9.4, 9.6, 9.10, 10.3, 13.4,14.4 I. Coping with Altitude O 2 and Hypobaric hypoxia? Hypocapnia-respiratory alkalosis 1

2 Challenges at high altitude Lower temperature (-0.6 o C/100m) - hypothermia Lower atmospheric pressure Exponential decrease air pressure (50% per 5500m) dehydration Reduced Po 2 Not a big issue to aquatic and tracheal animals Big problem for lung-breathing vertebrates Physiological Responses (non-birds) 1) Hyperventilation maintain alveolar Po 2 Conflicts with acid-base balance 2) Induce inorganic phosphates and 2,3-DPG in RBC to reduce Hb-O affinity unload O peripheral sites 3) Extra Hb and RBC in blood to increase O 2 carrying capacity* 4) Bohr Shift respiratory sites, higher affinity 5) increase functional lung volume* 6) Increase capillary density reduce diffusion distance* 7) Reduce muscle fibers diameter* *long term structural How do birds and insects cope with altitude? - Whooper swan 9,000m - Ruppell griffon 12,000m - Spider 7,300m Mount Makalu How do birds and insects cope with altitude? Whooper swan 9,000m Ruppell griffon 12,000m Spider 7,300m Mount Makalu 2

bar-headed Geese Annual migrations flying over the Himalayan mountain range. Flocks have been sighted above Mt.

3 How do birds fly high? More hypoxia tolerant Can fly over height 0 to 9,000m in 1 day (bar-headed geese cover 1000 miles) Flight requires more than 15x more energy Need to maintain O 2 supply! Migratory route of the bar-headed Geese Breed in Tibet- Qinghai Plateau ( m), Mongolia Gobi Desert Migratory route of the bar-headed Geese Annual migrations flying over the Himalayan mountain range. Flocks have been sighted above Mt. Everest (8848m) Winter in India How do birds stay in sane in thin air? Respiratory system Crosscurrent gas-blood flow arrangement and hyperventilation to increase gas exchange efficiency Extra thin gas-blood exchange barrier to overcome perfusion limit Greater PaO 2 under same Po 2 in inspired air greater blood O 2 content Low temp in inspired air increase O 2 diffusion 3

O 2 transport system High Hb oxygen affinity (P 50 =27mmHg) -> increase O 2 carrying capacity Hb Alpha chain Pro -> Ala Hb Beta chain Leu -> Ser Low Pco 2 and high ph -> left Bohr shift Lower Tb in

4 O 2 transport system High Hb oxygen affinity (P 50 =27mmHg) -> increase O 2 carrying capacity Hb Alpha chain Pro -> Ala Hb Beta chain Leu -> Ser Low Pco 2 and high ph -> left Bohr shift Lower Tb in hypoxic birds -> left Bohr shift Without hypocarpnia induced vasoconstriction Cardiovascular system Larger heart and stroke volume Great cardiac output scope (5-7x) Less redistribution of blood to critical tissue (brain and heart) under severe exercise because a higher O 2 content can be maintained in high altitude birds Cerebral circulation In mammals, cerebral blood vasodilation is caused by hypoxia Hypocapnia causes cerebral vasoconstriction Inhale CO 2 can increase blood flow to brain and alleviate mountain sickness (CA inhibitor does the same) In birds, Hypocapnia does not alter cerebral blood flow Hypercapnia significantly increase cerebral blood flow Severe hypocapnic hypoxia does not affect cerebral circulation Arterial blood from retes in the eyes has higher Po 2 to enhance O 2 in brain Individual tissues High capillary density in muscle and brain High MT density and aerobic enzymes activity in performance muscle High Mb O 2 affinity and concentration 4

(3,530) Different Adaptive Mechanisms? Increase RBC count in blood? Present only in Andean Higher hemoglobin concentrations? Change in carbonic anhydrase activity?

5 Birds have very low myoglobin P 50 values. Eg. Melanotrochilus fuscus 2.5 mmhg Human ~5 mmhg Myoglobin is very good at holding onto oxygen. Cardiac musculature in birds has higher concentrations of myoglobin, Myoglobin Human adaptations to high altitudes Tibetans (4,200m) Andean (3,900m) Ethiopian (3,530) Different Adaptive Mechanisms? Increase RBC count in blood? Present only in Andean Higher hemoglobin concentrations? Change in carbonic anhydrase activity? Different hemoglobin P 50 values? Nitric Oxide? Tibetan Andean Beall et al, 2006 At 4000m, Andean has 21% higher Hb than Tibetan and Ethiopian Tibetans need stronger stimuli to boost Hb (5000m) 5

Ethiopean Andean Tibetan Andeans: high Hb, high Hct, high Arterial O 2, low O 2 Sat% Tibetans: Low O 2 Sat %, low arterial O 2 O 2 Sat% indicate hypoxia stress Tibetans show clear altitude

6 Ethiopean Andean Tibetan Andeans: high Hb, high Hct, high Arterial O 2, low O 2 Sat% Tibetans: Low O 2 Sat %, low arterial O 2 O 2 Sat% indicate hypoxia stress Tibetans show clear altitude dose-response Ethiopians show no sign of stress Ethiopians: NO EFFECTS! High O 2 sat% phenotype has greater infant survival rate suggest that natural selection is favor high Sat% allele at this major gene locus Nitric oxide Tibetans and Andean populations have higher pulmonary nitric oxide concentrations, but not in Ethiopian p.p.b. 9.5 p.p.b. 7.4 p.p.b. Tibetans and Viagra - the missing link? November 23, 2001 Posted: 4:04 AM EST (0904 GMT) Could the blockbusting anti-impotency drug Viagra and high altitude living Tibetans possibly have anything in common? Scientists think the link being nitric oxide. Recent research shows that the same chemical that increases blood flow in Tibetan's lungs allowing them to breathe at high altitudes, also gives lift to a flagging penis. Nature 414, (22 November 2001) 6

Nitric oxide as an adaptive mechanism Endogenous nitrates (NO) are produced by blood vessels. Relax smooth muscle -vasodilation Nitroglycerin relieves Angina pectoris.

7 Nitric oxide as an adaptive mechanism Endogenous nitrates (NO) are produced by blood vessels. Relax smooth muscle -vasodilation Nitroglycerin relieves Angina pectoris. Giving low altitude individuals NO, increases their O 2 content during hypoxia. NO dilates pulmonary blood vessels, increases pulmonary blood flow. NO facilitates oxygenation of hemoglobin. II. Coping with Deep Sea (pressure) Fish Relatively straightforward in stable ocean environment, no direct depth effect except in the anaerobic zone. Respiratory pigments can be affected by pressure and low temperature in the species living in this zone. Left-shift of O 2 dissociation curve, high O 2 extraction efficiency (~50%) Hb can be temperature insensitive in some species (tuna) Organic phosphate and lactic acid are used to modify the pigment O 2 -affinity. Diving Tetrapods and birds Physiological Challenges Hypoxia, store sufficient O 2 to support metabolism. Hydrostatic pressure on air-filled cavities (1 atmospheric pressure/10m) The bends and air bubbles due to changing pressure (decompression) N 2 Low temperature Free-radicals formed during repeat diving Champion divers Seals, max 1600m Emperor penguins, m,2-10min, max 22min Weddell seals, m, 10-20min, max 82min Elephant seals, m, 20-30min 7

A Hallmark of diving animals Substantial elevation of muscle myoglobins concentration Two diving strategies Seals, rely on aerobic metabolism (< Aerobic Diving Limit, ADL) Birds, rely on anaerobic

8 A Hallmark of diving animals Substantial elevation of muscle myoglobins concentration Two diving strategies Seals, rely on aerobic metabolism (< Aerobic Diving Limit, ADL) Birds, rely on anaerobic metabolism (>ADL) Physiological responses to diving Apnoea regulate respiratory muscles Increase O 2 storage RBS, Hb, Mb, Hypoperfusion to visceral organs Hypometabolism, lower Tb Increase anaerobic metabolism and withhold lactate in ICF till finishing the dive Bradycardia and reduce cardiac output Neuronal and hormonal control of cardiac and spleen action (via catecholamine.) Smaller lung (some deep diving mammals) in comparison to upper airways to reduce bubble formation and the bends Decrease Tb to reduce metabolic rate critical Fig OT Fig

Comparison of O 2 storage between seal and human Mb O 2 capacity Schmidt-Nielsen

characteristics Spleen, RBC and blood volume adjustments are diver-specific.

increased gas absorption into tissues Dissolved gas tension is higher than ambient

9 Comparison of O 2 storage between seal and human Mb O 2 capacity Schmidt-Nielsen Schmidt-Nielsen Effects of pressure Bradycardia and hypoperfusion are ancestral characteristics Spleen, RBC and blood volume adjustments are diver-specific. Mechanical distortion and compression of tissues High gas tension in lung results in increased gas absorption into tissues Dissolved gas tension is higher than ambient pressure during ascent gas bubble in blood and tissue High pressure nerve syndrome What is diving bents? 9

Lung is a liability for deep divers Reduce lung volume or allow it to collapse to reduce N 2 absorption (challenge to re-inflate surfactant) Reinforcement of upper airway to prevent collapse Shorten

frequent short-shallow dives after long-deep dive- decompression Diving Challenges Pressure Oxygen/Nitrogen temperature L.

10 Lung is a liability for deep divers Reduce lung volume or allow it to collapse to reduce N 2 absorption (challenge to re-inflate surfactant) Reinforcement of upper airway to prevent collapse Shorten airway to allow quick air exhalation/inhalation during resurfacing How do animal divers perform quick ascent without the bends? frequent short-shallow dives after long-deep dive- decompression Diving Challenges Pressure Oxygen/Nitrogen temperature L. Martin, 1997 Depth, volume and density, Boyle s law Depth (msw) Pressure (atm) Air vol in a balloon (l) () x x x x x Density Relative size Four types of diving (human) a) Breath-hold diving ("breath-hold") b) Diving in a heavy-walled vessel ("vessel") c) Diving with compressed air or other gas supplied from the surface ("surface air") d) Diving with compressed air or other gas in a container carried by the diver ("scuba") 10

Human diving technology evolved mirroring our understanding of diving physiology of Animal Human use external air carrying device to expand diving range and extend time underwater Decompression

2nd stage demand regulator and mouthpiece, a face mask an extra second stage regulator and mouthpiece, carried by the diver in case of emergency two submersible gauges, accurate depth air remains in

11 Human diving technology evolved mirroring our understanding of diving physiology of Animal Human use external air carrying device to expand diving range and extend time underwater Decompression chamber allow human divers to perform deeper dive without decompression sickness Scuba is an acronym for 'self-contained underwater breathing apparatus - SCUBA compressed air tank 1st stage regulator. 2nd stage demand regulator and mouthpiece, a face mask an extra second stage regulator and mouthpiece, carried by the diver in case of emergency two submersible gauges, accurate depth air remains in the tank an inflatable vest (buoyancy compensator, BC) a weight belt and weights fins to facilitate self-propulsion in the water. a wet suit or other type of body protection Compressed gas to increase oxygen storage during diving Major events in diving history marks our understanding of diving physiology New technology Nitrox (32% O 2 balance N 2 ) Heliox, helium to replace N 2, avoid narcosis Heliox, helium to replace N 2, avoid narcosis Trimix O 2 under high pressure can be toxic Pure O 2 treatment for bubble disease L. Martin,

12 Ana (Pearl) Diver of Japan and South Korea A practice with >1,500yr history Funado (assisted) meters, 30sec/dive, 30 dives/hr Cachido (un-assisted) 3-5meter, 25-30sec/dive, 60 dives/hr Go Snorkeling Why do elephants have long nostril trunk? 12

Elephants Aquatic ancestral (Manatee s cousin) whenever they have to traverse the water, they lift the nostril trunk above the the water surface and breath through it in De Partibus Animalium,

Physiological consequences: 2m water = 150mmHg (20kPa) above atmospheric pressure Alveolar pressure remains at atmospheric level (open to air) Systemic vascular pressure increase to 150mmHg to

13 Elephants Aquatic ancestral (Manatee s cousin) whenever they have to traverse the water, they lift the nostril trunk above the the water surface and breath through it in De Partibus Animalium, Aristotle, 4 th century B.C.E. Elephants are champion snorkellers! How could elephants snorkel beyond 2 meters depth? Physiological consequences: 2m water = 150mmHg (20kPa) above atmospheric pressure Alveolar pressure remains at atmospheric level (open to air) Systemic vascular pressure increase to 150mmHg to maintain tissue perfusion Pressure in thoracic cavity remain low Negative pressure between lung and the rest of body blood vessels in the pleura is at risk of tearing Boyle s law P 1 xv 1 = P 2 xv 2. Water Surface <30cm 100mmHg Human snorkeling ~7x Elephants -150mmHg (West, 2001) Pa + hydraulic pressure 13

Sheep: the parietal pleura and endothoracic fascia Elephant s solution Structure - function: Dense connective tissue to replace pleura

sliding movement lubricating Thickening of pleura is primary evolutionary change to protect microvessels (2mm, 4x thicker), the

africana). Parietal pleura Viscerel pleura What happens when elephants raise their trunk to drink water?

14 Sheep: the parietal pleura and endothoracic fascia Elephant s solution Structure - function: Dense connective tissue to replace pleura tissue to obliterate cavity preventing rapture of blood vessel Separated parietal and visceral pleura with connective tissue to allow sliding movement lubricating Thickening of pleura is primary evolutionary change to protect microvessels (2mm, 4x thicker), the addition layer of connective tissue is secondary response Thickening of diaphragm (3mm) to 10x of other s African elephant (Loxodonta africana). Parietal pleura Viscerel pleura What happens when elephants raise their trunk to drink water? Hydraulic pressure in trunk = 200cm H 2 0 Alveolar pressure is below atmospheric pressure? Open mouth, no low pressure exerted by buccal muscle Only last for several seconds 14

4/18/2012. Northern Fur Seal Three Foraging Patterns. Thermocline. Diving Physiology and Behavior

4/18/2012. Northern Fur Seal Three Foraging Patterns. Thermocline. Diving Physiology and Behavior Northern Fur Seal Three Foraging Patterns Thermocline Diving Physiology and Behavior 1 Fundamental Constraint on Foraging Behavior Return to Surface to Breathe 2 Studies of Dive Behavior Dive depths from