Table 2

Respiratory muscle strength and resting levels of neural respiratory drive measured in healthy subjects and patients with cystic fibrosis (CF)

HealthyCFp Value
PImax Pmouth (cm H2O)129.4 (41)83.8 (19)0.010
PImax Pdi (cm H2O)119.7 (38)92 (32)0.080
Sniff Poes (cm H2O)110.8 (28)95.8 (36)0.273
Sniff Pdi (cm H2O)142.4 (38)112.1 (46)0.105
PEmax Pmouth (cm H2O)124.5 (27)106.5 (22)0.108
PEmax Pgas (cm H2O)125.1 (38)135.3 (52)0.602
Cough Pgas (cm H2O)170.8 (48)237 (70)0.018
Tidal RMS sEMGpara per breath (μV)4.8 (2)21.7 (17)0.001
Tidal RMS EMGdi per breath (μV)20.08 (6.6)46.6 (15)0.001
RMS sEMGpara max (μV)147.5 (43)130 (35)0.283
RMS EMGdi max (μV)305.5 (59)280.8 (64)0.343
sEMGpara% max (%)5.8 (3)13.14 (7)0.001
EMGdi%max (%)7.54 (2)18.5 (7.5)0.001
(Vt%VC predicted)/sEMGpara%max (AU)2.06 (0.89)0.90 (0.50)0.001
(Vt%VC predicted)/EMGdi%max (AU)1.34 (0.43)0.63 (0.27)0.001
  • Data expressed as mean (SD).

  • AU, arbitrary units; EMGdi, diaphragm electromyogram; EMGdi%max, resting diaphragm EMG activity normalised to the maximal EMG evoked during maximal inspiratory manoeuvres; Pdi, transdiaphragmatic pressure; PEmax, maximal expiratory pressure; Pgas, gastric pressure; PImax, maximal inspiratory pressure; Pmouth, mouth pressure; Poes, oesophageal pressure; RMS, root mean square; RMS EMGdi max, peak RMS of EMGdi recorded during a maximal inspiratory manoeuvre; RMS sEMGpara max, peak RMS of sEMGpara recorded during maximal inspiratory manoeuvre; sEMGpara%max, resting parasternal EMG activity normalised to the maximal EMG evoked during maximal inspiratory manoeuvres; sEMGpara, surface parasternal electromyogram; VC, vital capacity; Vt, tidal volume; (Vt%VC predicted)/sEMGpara%max, tidal volume expressed as a percentage of predicted vital capacity per unit sEMGpara%max; (Vt%VC predicted)/EMGdi%max, tidal volume expressed as a percentage of predicted vital capacity per unit EMGdi%max.