Poor standardisation of plethysmographic specific airways resistance measurement despite widespread use.

Plethysmographic specific airways resistance (sRaw) has remained the most recognised measure of airway resistance for almost 60 years [1]. Studies in both adults and children (including preschoolers) suggest clinical utility across important obstructive lung diseases [2–5]. Measurement protocols based on rapid panting or tidal breathing exist, and are incorporated into many current commercial plethysmographs. Tidal breathing measurement offers feasibility across a wide age range, and a relatively stable index with which to distinguish effects of disease from those of growth and development [6]. Both adult and paediatric reference data exists [7, 8]; however, the wide variation in methodology existing between centres has recently been highlighted [8], and sRaw remains one of the few lung function measurements without formal standardisation guidelines [9]. Despite the wide availability of plethysmographic equipment in lung function laboratories, its use is frequently confined to lung volume measurements. Although simultaneous measures of airway resistance can easily be recorded at no extra cost, the clinical applications of sRaw remain unclear. As part of ongoing sRaw standardisation work, we sought to describe current international use of sRaw across paediatric and adult respiratory laboratories.