Flow in the Lungs - Biofluidmechanics: An Introduction to Fluid Mechanics Macrocirculation and Microcirculation - page 276

9.11 Using Table 9.1 , calculate the solubility coefficients for nitrogen and carbon monoxide,
assuming that the cross-sectional area and diffusion distance is the same.
9.12 In the upper atmosphere, the oxygen concentration drops to 15% of the total composition
of air at an air temperature of 5 C. Assume that the nitrogen concentration makes up the
difference in air composition. Calculate the respiratory rate needed to maintain the body
oxygen requirements of 250 mL/min. Assume that the tidal volume remains the same and
that 35% of the tidal volume enters the bloodstream and that all of this would be used to
meet the body's oxygen requirements. Also, assume that the pressure drops to 700 mmHg.
9.13 Assume at particular atmospheric conditions, a person's respiratory rate increases to
25 breaths/min because the body needs 350 mL/min of oxygen. If the oxygen concentra-
tion in the atmosphere is 21% and that percent usage of oxygen is 40%, calculate the air
pressure if the temperature is 32 C.
*9.14 The carbon dioxide concentration in the gas at the inlet of a semipermeable oxygenator is
5 mmHg and that in the blood is 45 mmHg. Assume that the radius of the channel is 4 cm
and that the thickness of the boundary is 100 m. Calculate the change in carbon dioxide

concentration with distance if the diffusion coefficient is 2

μ

10 2 4 cm 2 /s, the gas velocity is

3

5 cm/s, and the blood velocity is 10 cm/s.
9.15 Air is flowing from the alveoli to the trachea and is following an isentropic flow conditions.
Calculate the velocity that air is leaving the alveoli if the temperature within the alveoli is
37 C and that in the trachea is 33 C. The velocity of air within the alveoli is 50 mm/s and
the specific heat for air (c p ) is equal to 30.02 mJ/(kg mol K).
9.16 Is there heat being transferred under the conditions in problem 9.15 if you can assume stea-
dy flow and the alveoli radius is equal to 100 m? What is the rate of heat transfer?

9.17 What is the change in entropy under the conditions in problem 9.15, if the pressure is
1.1 atm in the trachea and 1.15 atm in the alveoli?

μ

References

[1] E. Agostoni, E. D'Angelo, G. Roncoroni, The thickness of the pleural liquid, Respir. Physiol. 5 (1968) 1.
[2] E. Agostoni, Mechanics of the pleural space, Physiol. Rev. 52 (1972) 57.
[3] E. Agostoni, E. D'Angelo, Pleural liquid pressure, J. Appl. Physiol. 64 (1988) 1760.
[4] A. Al-Tinawi, J.A. Madden, C.A. Dawson, J.H. Linehan, D.R. Harder, D.A. Rickaby, Distensibility of small
arteries of the dog lung, J. Appl. Physiol. 71 (1991) 1714.
[5] H. Bachofen, J. Hildebrandt, M. Bachofen, Pressure-volume curves of air- and liquid-filled excised lungs-
surface tension in situ, J. Appl. Physiol. 29 (1970) 422.
[6] H. Bachofen, J. Hildebrandt, Area analysis of pressure-volume hysteresis in mammalian lungs, J. Appl.
Physiol. 30 (1971) 493.
[7] J.S. Brody, E.J. Stemmler, A.B. DuBois, Longitudinal distribution of vascular resistance in the pulmonary arter-
ies, capillaries, and veins, J. Clin. Invest. 47 (1968) 783.
[8] P.J. Dale, F.L. Matthews, R.C. Schroter, Finite element analysis of lung alveolus, J. Biomech. 13 (1980) 865.
[9] A.P. Fishman, The syndrome of chronic alveolar hypoventilation, Bull. Physiopathol. Respir. (Nancy) 8 (1972)
971.
[10] A.P. Fishman, Pulmonary edema. The water-exchanging function of the lung, Circulation 46 (1972) 390.
[11] E. Flicker, J.S. Lee, Equilibrium of force of subpleural alveoli: implications to lung mechanics, J. Appl.
Physiol. 36 (1974) 366.
[12] Y.C. Fung, S.S. Sobin, Theory of sheet flow in lung alveoli, J. Appl. Physiol. 26 (1969) 472.
[13] Y.C. Fung, S.S. Sobin, Elasticity of the pulmonary alveolar sheet, Circ. Res. 30 (1972) 451.