Impaired voluntary drive tobreathe: apossible link between depression andunexplained ventilatory failure inasthmatic patients

Background - Although psychological distresspredicts mortality inasthma, an underlying physiological linkhasnot been shown.Thisstudyexaminedrelations betweenimpaired voluntary drive tobreathe andmeasures ofmood states. Methods - Thelevel ofmaximalvoluntary activation ofthediaphragmand elbow flexors was measuredina previous study using asensitive modification ofthetwitch interpolation technique in11asthmatic and10control subjects. Inthisstudy psychological distress was assessed usingthe Profile ofMood States questionnaire and measures ofdistress were comparedwith themusclevoluntary activation results. Results - Fortheasthmatic subjects, depressedmood increased theriskofimpaired maximalvoluntary activation ofthe diaphragmby35times(95%CI 109to 11.3). Nosuchassociation was observed in control subjects. Conclusions - Theseresults suggestthat depressedmood may predispose an asthmatic patient toimpairedvoluntary activation ofthediaphragm. Such individuals wouldbe at increased riskof rapidly developing ventilatory failure if facedwithsevere airway narrowing.