INFLUENCE OF AWARENESS OF THE RECORDING OF BREATHING ON RESPIRATORY PATTERN IN HEALTHY HUMANS

This study was designed to test whether awareness of the measurement o f breathing influences the breathing pattern in healthy subjects under routine laboratory conditions. Seventy four subjects (40 females and 34 males), aged 21-63 yrs, were studied under three different conditio ns whilst their breathing was being recorded for 5 min by means of ind uctance plethysmography (Respitrace): 1) subjects were misled into bel ieving that their breathing was not being recorded but that they had t o wait for 5 min whilst equipment was calibrated; 2) subjects were ins tructed that their breathing pattern was being recorded for 5 min; 3) the subject's breathing was recorded for 5 min with mouthpiece and pne umotachograph. The first two conditions were randomized. The Respitrac e was calibrated by means of multiple linear regression carried out du ring the 5 min period of quiet breathing through a mouthpiece. Awarene ss of the recording of breathing caused prolongation of inspiratory (t I) and expiratory time (tE). Breathing through the mouthpiece resulted in an increase of tI, tE and tidal volume (VT). The breathing irregul arities (sighs and end-expiratory pauses) decreased when subjects were aware of the recording of breathing and nearly disappeared when subje cts breathed through the mouthpiece. The end-tidal carbon dioxide conc entration was not significantly different between the three conditions . Mouthpiece breathing often induced some respiratory discomfort and e ven anxiety, particularly in females. Awareness by the subject that hi s or her breathing was being recorded altered the spontaneous breathin g pattern, mainly the breathing frequency, In addition, use of a mouth piece markedly increased tidal volume, particularly in females in whom mouthpiece breathing induced more complaints than in males.