Fig. 1.

Modified whole body plethysmography (WBP) open-system schematic. Positive and negative pressure sources were utilized in series with mass flow controllers and high-resistance elements to generate a continuous bias flow through the animal chamber while maintaining a sufficiently high time constant. The reference chamber served to filter ambient noise from the pressure signal. Slow leaks present on both chambers allowed for equilibration with atmospheric pressure. The sensor bladder (SB) transduced the mechanical pressure changes associated with mouse breathing, while the reference bladder (RB) signal allowed for cancellation of the contaminating chamber pressure signal via the differential pressure transducer. +, Pressurized air source; −, vacuum source; narrowed tubes, high resistance elements; arrow, bias flow; dashed line, platform; ΔP, differential pressure transducer.