Usefulness of the flow volume loop.

We have read with interest the article by Guntupalli et al (February 1997)l on the usefulness of the flow volume loop (FVL) in emergency and ICU settings. The selection of cases where the FVL can easily help to establish the level of flow impairment was well chosen by the authors. In emergency situations, the FVL is especially helpful in identifying certain abnormalities quickly by visual pattern recognition. With respect to this, we were particularly interested in the two cases of variable upper airway obstruction: case 1 with bilateral vocal cord paral¬ ysis (BVCP) and case 5 with vocal cord dysfunction (VCD). The clinical description of BVCP was adequate, with a patient being able to speak almost normally but having tremendous difficulty breathing in, especially on the slightest effort. Therefore, the FVL will show a severely reduced forced inspiratory flow but almost normal expiratory flow, with the exception of an ampu¬ tated peak flow, and usually a plateau following the peak flow (Fig 1). Contrary to the loop shown by Guntupalli et al, there usually is no restrictive pattern if the patient has normal lungs. In the patient shown, one can see that she did not inhale completely from residual volume to total lung capacity because the inspira¬ tory flow is clearly not zero at the y-intercept. Thus, the FVL shown is compatible with, but not typical for, BVCP. We previously published a typical loop in a patient with BVCP, with a perfectly normal FEV2 and FVC.2