Transdiapragmatic pressure and contractile properties of the human diaphragm following standardized magnetic stimulation

Background: Twitch transdiaphragmatic pressure (twPdi) following magnetic stimulation (MS) of the phrenic nerves reflects inspiratory muscle strength. Since specific protocols are heterogeneous, we present normal values derived from standardized cervical and cortical MS of the diaphragm in a large cohort of healthy adults. Methods: 63 subjects (24 men, 39 women; 34±13 years) underwent transcortical and posterior cervical MS of the diaphragm with simultaneous recording of twitch esophageal and gastric pressures (twPes, twPgas). MS was performed both at functional residual capacity (FRC) and using an inspiratory pressure trigger (–0.5 kPa). Results: Following cortical MS at FRC, twPdi amplitudes showed high intra-individual variability which was markedly reduced when an inspiratory pressure trigger was applied. Lower limit of normal (LLN) was 12 cmH2O, independent of gender or age. Following cervical MS of the phrenic nerves, twPdi amplitudes were well reproducible and unaffected by gender, but age-dependent (age 18-29: LLN 23 cmH2O; age = 30: LLN 16 cmH2O; p 30 years; p Conclusions: The peripheral portion of the inspiratory pathway can be assessed using cervical MS of the phrenic nerves. Dynamics of diaphragm contraction appear to be age-dependent.