An algebraic solution to dead space determination according to Fowler's graphical method

Area of Science:

• Physiology
• Respiratory Mechanics
• Pulmonary Function Testing

Background:

• Anatomical dead space (VD) is crucial for assessing respiratory function.
• Fowler's method is a standard technique for VD determination, involving graphical analysis of expirograms.
• Existing methods can be time-consuming and require manual interpretation.

Purpose of the Study:

• To develop a more efficient and accurate algebraic method for determining anatomical dead space (VD).
• To provide a generalized solution encompassing existing methods like Bohr's and Fowler's.
• To facilitate computer-aided, on-line VD measurements.

Main Methods:

• Utilizing phase III of the fraction-volume expirogram (F(V)) and back-extrapolation with a straight line (R(V)).
• Setting the area between F(V) and R(V) equal to a trapezoid with VD as one side.
• Deriving algebraic equations for non-sloping and sloping alveolar plateaus, and a general equation.

Main Results:

• Two algebraic equations were derived for specific alveolar plateau conditions.
• A generalized third equation was developed, unifying Bohr's and Fowler's solutions.
• Experimental validation confirmed the algebraic solution's equality with the graphical method for VD values.

Conclusions:

• The new algebraic formulas accurately represent Fowler's graphical method.
• These formulas are applicable to all gases used in dead space determination.
• The primary advantage is the facilitation and acceleration of computer-aided, on-line VD determinations.