Critical appraisal of three methods for measurement of nebuliser suction

Abstract

Three possible methods of measuring nebuliser suction were evaluated. The results obtained by each method for three nebulisers at different aspiration gas pressures are compared and apparent discrepancies discussed. The potential and limitations of each method are assessed for a variety of operating conditions and diagnostic purposes. Measurement with a mercury manometer via a T-piece during aspiration, but after correction for suction drops along all the nebuliser capillaries and across connections, appears to be the most reliable and generally applicable method. Measurement of suction with a manometer in the absence of sample solution may give rise to significantly different results from those obtained when a solution is being nebulised. A recently proposed procedure based upon the Poiseuille equation is shown to be unreliable under typical operating conditions because suction varies with aspiration rate.