One of the most common errors in plethysmography is allowing inadequate time for thermal equilibration to occur (Fig 1, bottom right, D). The patient is requested to sit upright, support the cheeks with his/her hands, and firmly seal his/her lips around the mouthpiece. Nose clips should be used. During open-shutter panting maneuvers, the Pbox and flow results are displayed and measured to determine the slope of the relationship (Fig 1, top left, A). Immediately after the open-shutter panting, the shutter is closed while the patient continues to pant (Fig 1, top right, B). Changes in mouth pressure and Pbox are displayed and measured to determine the slope of the relationship (Fig 1, bottom left, C). During Raw measurements, patients are allowed to select the most comfortable lung volume for the panting efforts. The final results are lung volume adjusted (specific resistance and conductance). Raw is calculated by the ratio of the slope shown in Figure 1, bottom left, C, to that shown in top left, A.