# 2CompLung_Air

Airflow between atmosphere and lung modeled with 2 compartments representing the non-exchanging space (bronchus) and exchanging space (alveolus).

Model number: 0004

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## Description

This model represents a simple 2-compartmental respiratory system, consisting of one bronchi compartment and one alveoli compartment. This model is driven by external pressure (Pventil)as with positive pressure ventilation. There is no exchange between the alveoli and blood. The fluid (air) is assumed incompressible. AMOUNT OF MATERIAL IN Vbronch: If Fbronch is positive, the material added is Fbronch*Cair. Note that Fbronch*Cair is positive when Fbronch is positive. If Fbronch is negative, the material subtracted is Fbronch*Cbronch. Note that Fbronch*Cbronch is negative when Fbronch is negative. If Falv is positive, the material being subtracted is -Falv*Cbronch. If Falv is negative, the material being added is -Falv*Calv. AMOUNT OF MATERIAL IN Valv: If Falv is positive, the material being added is Falv*Cbronch. If Falv is negative, the material being subtracted is Falv*Calv. VERIFICATION: The verification test consists in modifying the parameters so that Vbronch is very small, and the solution for Calv corresponds to a solution from the model Lung_RC_Air which has been imported as a data file. See Notes for Figure 4 for complete details.

## Equations

where *P*_{mouth} is the pressure at the mouth;
*P* _{scalar} multiplies *P*_{ventil}, a function representing
inhalation pressure;
*P*_{bronch } is the pressure in the bronchi;
*P*_{alv } is the pressure in the alveoli;
*P*_{ref} is the reference pressure;
*P*_{FRC} is the pressure when the alveoli volume is the functional residual capacity;
and *P*_{VT} is the pressure required to inflate the tidal volume in the alveoli.
*a*_{1} governs the decrease in pressure in the alveoli near the residual volume and
*a*_{2} governs the increase in pressure in the alveoli near the total lung capacity;

*V*_{bronch} is the volume of air in the bronchi;
*V*_{bronch0} is the initial volume of air in the bronchi;
*V*_{alv } is the volume of air in the alveoli;
*V*_{RV} is the residual volume;
*V*_{FRC} is the volume of the functional residual capacity;
*V*_{T} is the tidal volume;
and *V*_{TLC} is the total lung capacity.

*Q*_{bronch} is the amount of material in the bronchi;
*Q*_{alv } is the amount of material in the alveoli;
*C*_{air} is the concentration of material in the air;
*C*_{bronch} is the concentration of material in the bronchi;
*C*_{bronch0} is the initial concentration of material in the bronchi;
*C*_{alv } is the concentration of material in the alveoli; and
*C*_{alv0} is the initial concentration of material in the alveoli.

*F*_{bronch} is the air flow at the mouth;
*F*_{alv} is the air flow between the bronchi and alveoli;
*R*_{bronch} is the resistance to the air flow in the bronchi;
*R*_{alv} is the resistance to the air flow in the alveoli;
and *Com*_{alv} is the compliance of the alveoli.

### Amount of Material in *V*_{bronch} :

If *F*

_{bronch}is positive, the material added is

*F*

_{bronch}*

*C*

_{air}. Note that

*F*

_{bronch}*

*C*

_{air}is positive when

*F*

_{bronch}is positive.

If

*F*

_{bronch}is negative, the material subtracted is

*F*

_{bronch}*

*C*

_{bronch}. Note that

*F*

_{bronch}*

*C*

_{bronch}is negative when

*F*

_{bronch}is negative.

If

*F*

_{alv}is positive, the material being subtracted is -

*F*

_{alv}*

*C*

_{bronch}. If

*F*

_{alv}is negative, the material being added is -

*F*

_{alv}*

*C*

_{alv }.

### Amount of Material in *V*_{alv: }

If *F*

_{alv}is positive, the material being added is

*F*

_{alv}*

*C*

_{bronch}. If

*F*

_{alv}is negative, the material being subtracted is

*F*

_{alv}*

*C*

_{alv }.

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## References

Lutchen, K. R., F. P. Primiano, and G. M. Saidel. A nonlinear model combining pulmonary mechanics and gas concentration dynamics. IEEE Trans. Biomed. Eng. 29: 629-641, 1982. Lutchen KR, Saidel GM, Estimation of mechanical parameters in multicompartment models applied to normal and obstructed lungs during tidal breathing, IEEE Trans. Biomed. Eng., vol. BME-33, no. 9, pp. 878-887, Sept. 1986. M.G. Levitzky, Lange Physiology Series: Pulmonary Physiology, 6th edition. McGraw Hill, 2003.

## Related Models

- One compliant lung compartment
- One compliant lung with positive pressure ventilator
- Non-linearly compliant lung with resistance to air flow

## Key Terms

lung, non-linear, compliance, resistance, RC circuit, mechanics, airflow, trachea, tidal volume, positive pressure, ventilation

## Model History

Get Model history in CVS.Posted by: BEJ

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[This page was last modified 02Nov16, 2:18 pm.]

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