Table 4.

Parameters of gas exchange

Symbol	Parameter	Value	Units	Reference
${\rho }^{O_2}$	Density of oxygen	1.429	$\text{kg}{\text{m}}^{-3}$	Known
${\rho }^{C{O}_2}$	Density of carbon dioxide	1.98	$\text{kg}{\text{m}}^{-3}$	Known
$D^{C{O}_{2}a},D^{C{O}_2\widehat{a}}$	Diffusion coefficient of carbon dioxide in air	$1.48\times {10}^{-5}$	${\text{m}}^2{\text{s}}^{-1}$	Known
$D^{C{O}_{2}b},D^{C{O}_2\widehat{b}}$	Diffusion coefficient of carbon dioxide in blood	$1.48\times {10}^{-9}$	${\text{m}}^2{\text{s}}^{-1}$	Known1
$D^{O_{2}a}{D}^{O_2\widehat{a}}$	Diffusion coefficient of oxygen in air	$1.76\times {10}^{-5}$	${\text{m}}^2{\text{s}}^{-1}$	Known
$D^{O_{2}b}{D}^{O_2\widehat{b}}$	Diffusion coefficient of oxygen in blood	$2.18\times {10}^{-9}$	${\text{m}}^2{\text{s}}^{-1}$	Known
${\alpha }^{O_2}$	Solubility of oxygen in water	$0.21\times {10}^{-6}$	${\text{Pa}}^{-1}$	Klinke et al. (2010)2
${\alpha }^{C{O}_2}$	Solubility of carbon dioxide in water	$5.06\times {10}^{-6}$	${\text{Pa}}^{-1}$	Klinke et al. (2010)2
$N·MCHC$	Max. hemoglobin-bound oxygen	0.5	−	Possenti et al. (2021)
H	Discharge hematocrit	0.5	−	Possenti et al. (2021)
$p_{50}^2$	Partial pressure of oxygen at 50 % oxygen Saturation	3600	Pa	Klinke et al. (2010)
$\gamma$	Hill exponent	3	Pa	Possenti et al. (2021)
d	Thickness of blood gas barrier	$1.0\times {10}^{-6}$	m	Klinke et al. (2010)
$D^{O_{2}t}$	Diffusion coefficient of oxygen in tissue	$2.41\times {10}^{-9}$	${\text{m}}^2{\text{s}}^{-1}$	Possenti et al. (2021)
$D^{C{O}_{2}t}$	Diffusion coefficient of carbon dioxide in tissue	$2.41\times {10}^{-9}$	${\text{m}}^2{\text{s}}^{-1}$	Assumed3
S	Gas exchange surface	120	${\text{m}}^2$	Klinke et al. (2010)
V	Total lung capacity	$6.2\times {10}^{-3}$	${\text{m}}^3$	Known4
${ϵ}^{\mathit{Healthy}}$	Healthy blood volume fraction	0.1	−	Assumed
pH	pH-value	7.352	−	Loeppky et al. (1983)

¹ In the same order of magnitude as in Wang et al. (1976)

² The solubility of water is used to account for the solubility in blood, as well as in the alveolar epithelium and capillary endothelium, whose cytoplasm primarily consists of water (Klinke et al. 2010)

³ The same value as for oxygen is used, as the diffusion coefficient is determined by the molecular diameter, which is nearly identical for both gases (Klinke et al. 2010)

⁴ Physiological value for a 25-year-old 1.80 m tall woman (Klinke et al. 2010)