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Compensating for RQ:  One of the many troublesome complications in respirometry is that organisms seldom exchange just one gas at a time: instead, they are simultaneously consuming oxygen and producing CO₂ (we'll leave water out of this discussion because -- usually -- it can easily be scrubbed from air streams prior to gas analysis).  Since the ratio of CO₂ produced / oxygen consumed (the Respiratory Quotient, or RQ) is seldom exactly equal to 1.0, respiration causes a net change in the total gas volume.  As a result, gas concentrations are affected.  For example, consider a calculation of oxygen consumption:   If more oxygen is consumed than CO₂ is produced, the total gas volume is slightly reduced, which results in an increase in the concentration of O₂.  This seemingly trivial imbalance will influence exchange calculations and needs to be accounted for (startlingly large errors can result if you don't do this correctly).  The necessary equations can be derived from simple algebra, but are tedious in practice.  Fortunately, equations for most respirometry systems are built into LabAnalyst (see below for details).

If you are calculating oxygen consumption and you use a flow configuration that requires compensation for CO₂ production, you are asked if you want to use a constant RQ value, or a previously computed channel containing VCO₂ (note that VCO₂ must be in units of ml/min, or you may get extremely inaccurate results), or CO₂ concentration data (in % deflection from ambient CO₂ concentration).  If you elect to use VCO₂ or %CO₂ , you will be asked to select the channel containing CO₂ data.  For maximal precision, be sure to use the lag correction function to synchronize the timing of oxygen and CO₂ data (especially important if there are large short-term fluctuations in gas concentrations).

Similarly, if you are calculating CO₂ production, you will always need to compensate for oxygen consumption (since animals rarely produce CO₂ unless they are also consuming O₂) and you are asked if you want to use a constant RQ value, or oxygen concentration data (in % deflection from ambient O₂ concentration), or a previously computed channel containing VO₂ in units of ml/min.

In most cases, use of a constant RQ will produce quite good accuracy.