Whole Body Flow Derived Parameters

In whole body plethysmography, the entire subject resides in a single chamber. So, unlike other methods (FDP and NAM), the measured flow is the sum (or net) of nasal and thoracic flows. These flows are nearly equal and opposite.

In fact, flows in and out of a whole body plethysmograph are approximately one-tenth the magnitude of either nasal or thoracic flow. This smaller "box flow" signal must be mathematically scaled back to proper physiological values.

Two algorithms are provided in BioSystem XA for converting "box flow" parameters to "direct flow" parameters:

• Drorbaugh and Fenn
• Epstein and Epstein

The difference between "box flow" and "direct flow" is sensitive to chamber temperature, core body temperature, temperature at the nares, humidity, and pressure. These values are defined in the software analyzer setup. For accuracy, temperature and humidity should be monitored real-time unless aerosols are being introduced.

Only flow derived parameters (tidal volume, peak flows, etc.) are affected by temperatures, humidity, and pressure. Enhanced Pause (Penh) does not substantially change within normal operating ranges.

Chamber options

• Chambers for unrestrained subjects are available in sizes ranging from mouse to dog and large NHPs
• Chambers for restrained subjects are available for mouse and rat

Reported Parameters

• Enhanced pause (Penh)
• Breath frequency
• Tidal volume
• Total volume breathed
• Minute ventilation
• Inspiratory time
• Expiratory time
• Peak inspiratory flow
• Peak expiratory flow
• End inspiratory pause
• End expiratory pause
• Relaxation time
• Others