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Life Sciences => Physiology & Medicine => Topic started by: Andrew K Fletcher on 13/06/2008 12:10:39

Title: The Lungs, Respiration and Fluid Loss
Post by: Andrew K Fletcher on 13/06/2008 12:10:39
I am trying to locate an estimate of the total amount of fluid in the lungs and respiratory tract of humans and animals in order to establish the change in density of the fluids from exhaling predominently water. Any help or pointers will be much appreciated.

The paper below realting to the controlled environment during regular flight gives us an ideal humidity level to estimate this.

The changes in respiration rate as we develo through our lives will play a very important roll later as I believe there is a correlation with the flow of coloids and solutes from the lungs down the main artery and the difference in length of the arteries that acomodate
It should be emphasized that sweat losses can exceed 2 litres/hour when in very hot conditions (pilots in full combat flight suits).  Meals taken at regular intervals in order to allow salt and glucose intake is a must. 
The cabin environment of commercial aircraft is warm and very dry (Relative Humidity 20-30%).  This results in significant insensible fluid loss from respiration.  Fluid loss of a sedentary person such as a pilot would be between 200-300mls per hour.  The loss from flight attendants would possibly be 300mls depending on their activity level.  Military pilots in full flight suits would conceivably be as high as 600mls per hr.
Sweating results in sodium and potassium loss.  Generally speaking this avenue for electrolyte loss would be minimal for pilots whilst flying,
The loss of sodium in sweat is around 30-50 mMol/L and potassium 3-6mMol/L.  Given these average losses it is not necessary to consume special fluids as long as regular food intake is maintained, this would be sufficient to replace all lost electrolytes.  Water is still the best replacement fluid.

Average respiratory rates, by age:
   Newborns: Average 44 breaths per minute
   Infants: 2040 breaths per minute
   Preschool children: 2030 breaths per minute
   Older children: 1625 breaths per minute
   Adults: 1220 breaths per minute
   Adults during strenuous exercise 3545 breaths per minute
Using 300mls per hour at 20-30% humidity at say 16 breaths per minute gives 5mls evaporative loss per exhale at rest.

Science 15 April 1966:
Vol. 152. no. 3720, pp. 384 - 386
DOI: 10.1126/science.152.3720.384
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Blood Pressure Responses of Wild Giraffes Studied by Radio Telemetry
Robert L. Van Citters 1, William S. Kemper 2, and Dean L. Franklin 2
1 Department of Physiology and Biophysics, University of Washington, Seattle 98105
2 Scripps Clinic and Research Foundation, University of California, La Jolla

Blood pressure was telemetered from transducers chronically implanted in the carotid arteries of two adult, wild, male giraffes captured and released near Kiboko, Kenya. Cerebral perfusion pressure ranged from 280/180 mm-Hg while the animal was lying with its head on the ground to 125/75 mm-Hg when it was standing erect; it varied between these levels during spontaneous activity such as walking, grazing, and running.

The above is interesting because it shows a reduction in blood pressure on standing and a significant increase in BP when the Giraffe was laying on the floor.
Title: The Lungs, Respiration and Fluid Loss
Post by: Andrew K Fletcher on 13/06/2008 17:33:33

The above link describes an inverted U tube theory to assist the flow of blood to and from the giraffes head. It is refered to as a siphon effect, which is part of the way there. I am aiming at the solute density changes from the respiration of the Giraffe both heat density changes and evaporative density chages combined to provide the motor for this flow and return system.