hold your breath and stay fat: sleep apnea as a water and ... ppt on sleep apnea.pdf · sleep apnea...

Cambria, CA, 16 November 2013

Hold your Breath and Stay Fat: Sleep Apnea as a Water and Energy-Saving

Strategy in Elephant Seals

Presented by Susanna B. BlackwellWednesday, November 20, 13


Wednesday, November 20, 13


Elephant seals are desert animals!


Dehydration = problem for all mammals. Loss of 15-20% body

water is fatal to most species.

Options if living in a dry environment:

- get better at extracting water from the environment

- evolve ways

of reducing water loss

- develop the ability to withstand temporary imbalances

Desert animals generally use a combination of physiological and

behavioral adaptations


Physiological adaptations

Efficient kidneys

Hopping mouse (25x body fluids)Kangaroo ratSand ratSpringbok antelope

Nasal heat exchanger Giraffe

Reduction in metabolic rate

Springbok antelopeElandOryxOstrich

Use body as a heat sink

Camel (6° => 5 liters)Eland OryxSpringbok antelopeGrant’s gazelle


Physiological adaptations

Efficient kidneys

Hopping mouse (25x body fluids)Kangaroo ratSand ratSpringbok antelope

✓

Nasal heat exchanger Giraffe ✓

Reduction in metabolic rate

Springbok antelopeElandOryxOstrich

✓

Use body as a heat sink

Camel (6° => 5 liters)Eland OryxSpringbok antelopeGrant’s gazelle

E. seals


Two-sentence summary of what I will tell you today?

Elephant seals have an

unusual breath-holding ability, likely

acquired for procuring prey at sea.

They use this breath-holding

ability during long fasts on land to

save both water and energy.


Apnea (apnoea) = suspension of external breathing. No movement of respiratory muscles and no change in lung volume.

Eupnea (eupnoea) = “normal” breathing

Sleep apnea in humans is a disorder (includes obstructive and central sleep apnea)

Terrestrial sleep apnea in seals is “normal”!

Weddell seal

Southern elephant

seal

Northern elephant

seal

Gray seal

Harbor seal

Hawaiian monk seal


OUTLINE


http://www.racerocks.com/racerock/archives_08/vidslashsleep.htm




While on land, elephant seals abstain from food and water ...

~ 100 days in breeding males, particularly top-ranking males

Mass loss: 7.1 kg / day(average, ad. ♂)

Over entire season:41% top ♂34% low- ranking ♂



~ 100 days in breeding males, particularly top-ranking males~ 30 days in adult females that are nursing a pup



~ 100 days in breeding males, particularly top-ranking males~ 30 days in adult females that are nursing a pup

Day: 1 21 Day: 1 21

88%

75 %

35 %

15 %

4.5 %

55 %

Human

Elephant seal

Water FatWednesday, November 20, 13


~ 100 days in breeding males, particularly top-ranking males~ 30 days in adult females that are nursing a pup~ 70 days in weaned pups, before their first trip to sea


No eating, no drinking => very small fecal and urinary water losses In addition, urine is concentrated Evaporation from the skin is minimal So what’s left?



Respiratory water loss!


Nasal turbinates = counter-current heat exchanger

Huntley et al. 1985


Respiratory water loss!


Nasal turbinates = counter-current heat exchanger

Adult ♂


Nasal turbinate: how it works

Air

OUTSIDE

---->

---->

---->

---->

LUNGS

Bone

Vascularized flesh (w / mucous)

NASAL TURBINATE

- Estimated surface area of 3140 cm2 in adult males- Allows 92% respiratory water recovery (sheep: 24%)


Elephant seals do long fasts

They have a well-developed adaptation (the nasal turbinates) to cut down on their biggest water loss (respiratory water loss)

All their water is obtained from burning fat

Saving (water) would be a good idea, because you then also loose less weight!


Elephant seals do long fasts

They have a well-developed adaptation (the nasal turbinates) to cut down on their biggest water loss (respiratory water loss)

All their water is obtained from burning fat

Saving (water) would be a good idea, because you then also loose less weight!

Sleep apnea = suspected of playing a role

Do all age groups use it?

Is it an ability that gets developed with age?

What difference does it end up making over days and weeks?


N SP Yg W Old W J Sa M Ad F Ad M0

2

4

6

8

10

12

14M

ea

n A

pn

ea

Du

ratio

n (

min

)20

21

34

18

11

2020

19

N = neonates (1-4 d)SP = suckling pups (5-28 d)Yg W = young weanlings (25-60 d)Old W = old weanlings (61-100 d)J = juveniles (1-2 y)Sa M = subadult males (5-7 y)Ad F = adult females (3-10 y) Ad M = adult males (8-14 y)

Longest apnea:5.5 min



2

4

6

8

10

12

14M

ea

n A

pn

ea

Du

ratio

n (

min

)20

21

34

18

11

2020

19



Terrestrial neonates: more resistant to asphyxiation

than adults; this tolerance to asphyxia disappears early in development.



2

4

6

8

10

12

14M

ea

n A

pn

ea

Du

ratio

n (

min

)20

21

34

18

11

2020

19




What have we learned?

All age and sex categories of

elephant seals breathe apneustically.

Most of the development of this

behavior takes place during the post-

weaning fast.

==> therefore focus, in second part, on the period from weaning to the return to land after the first trip to sea


Goal: to prove that sleep apnea makes a difference

How to do that: compare water loss between




CharlieUses sleep apnea

HugoDoes not use sleep apnea






How many breaths per

day

How much water lost per breath

+ ==>Water loss for Charlie

Water loss for HugoΔ

(diff.)

Remember: breathing is the biggest avenue of water loss during the fast



How much time in

terrestrial apnea

How much time in aquatic apnea

+ ==> Total amount of time per day in eupnea



How much time in

terrestrial apnea



x

Breathing rate

==>Total number of breaths per day



How much time in

terrestrial apnea



x

Breathing rate


Temperature and relative humidity

==>Water loss per breath



How much time in

terrestrial apnea



x

Breathing rate


+

Temperature and relative humidity

==>Water loss per breath

==>

Water loss for CharlieWater loss for Hugo


Problem: how to record apneas day and night


Problem: how to record apneas day and night

Hea

rt R

ate

(BP

M)

Time (min)

We’re in luck: there is a relationship between heart rate and breathing!


Tattletale Lite Data Logger- Heart rate (modified Polar jogger’s system)- Activity (motion switch)- Temperature (thermistor)- Presence in and out of the water (salt switch)


Yearling JET2


Example records: yearling 1 on the beach

Time (minutes)Hea

rt R

ate

(BP

M) a

nd T

empe

ratu

re (°

C)


Example records: yearling 2 on the beach

Time (minutes)Hea

rt R

ate

(BP

M) a

nd T

empe

ratu

re (°

C)


Example records: weaner coming out of the water

Time (minutes)Hea

rt R

ate

(BP

M) a

nd T

empe

ratu

re (°

C)


Percentage time spent in terrestrial apnea vs time-of-dayM

ean

% o

f eac

h H

our S

pent

in T

erre

stria

l Apn

ea

Time of Day (hrs)

Time of Day (hrs)Wednesday, November 20, 13

Percentage time spent in the water vs time-of-dayM

ean

% o

f eac

h H

our S

pent

in th

e W

ater

Time of Day (hrs)

Time of Day (hrs)Wednesday, November 20, 13

Percentage time spent in terrestrial apnea vs age

Age (days)

Mea

n %

of e

ach

Day

Spe

nt in

Ter

r. A

pnea


Percentage time spent in the water vs ageM

ean

% o

f eac

h D

ay S

pent

in th

e W

ater

Age (days)Wednesday, November 20, 13

Total percentage time spent in apnea vs ageM

ean

% o

f eac

h D

ay S

pent

in A

pnea


OUTLINE So does sleep apnea make a difference?

We still need:- water loss per breath- breathing rates

Then we can compare daily respiratory water loss between



&


Eupneic breathing rateB

reat

hing

Rat

e (b

reat

hs /

min

)


Eupneic breathing rateB

reat

hing

Rat

e (b

reat

hs /

min

)

Age (days)

Humans?


Breaths / day

AgeAge Br / day apnea Br / day no apnea Increase (%)

W 50 days 9630 12,850 33

65 days 7860 10,260 31

80 days 6410 8670 35

95 days 5240 7850 50

Y ~290 days 6640 11,680 76


Water loss / breath- Varies with temperature and humidity

Hours of the Day

Tem

p. (°

C)

Rel

. Hum

. (%

)

- Where weanlings spend 80% of their time:50 mg H2O / breath (26-80 mg / breath)


Respiratory water loss for Charlie and Hugo (“average weaners”, 131 kg, 68 days old)

Hours of the Day

Gra

ms

H2O

lost

/ hr


Respiratory water loss for Charlie and Hugo (“average weaners”, 131 kg, 68 days old)

Hours of the Day

Gra

ms

H2O

lost

/ hr



378 g

529 g121%87%

As a % of the H2O available for respiratory water loss:


AcknowledgmentsFor the use of pictures I thank the Pinniped Cognition and Sensory Systems Laboratory (UCSC), in particular Colleen Reichmuth and Caroline Casey, as well as my former advisor Burney Le Boeuf. Images obtained with authorization from NMFS. Do not use or post this material without permission from the author.


hold your breath and stay fat: sleep apnea as a water and ... ppt on sleep apnea.pdf · sleep apnea...

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