title: Exercise-induced depression of the diaphragm motor evoked potential is not affected by non-invasive ventilation.
abstract: Whole body exercise is followed by a depression of the diaphragm motor evoked potential (MEP). It is unknown whether the change is due to diaphragm activity or whole body exercise. To test the hypothesis that exercise-induced MEP depression was related to diaphragm activity, we performed two experiments. The first examined the effect of whole body exercise, performed with and without the use of non-invasive ventilation (NIV). NIV resulted in significant unloading of the diaphragm (pressure time product 101+/-68 cm H(2)O/s/min versus 278+/-95 cm H(2)O/s/min, p<0.001). Both conditions produced significant MEP depression compared to the control condition (% drop at 5 min, after exercise and exercise with NIV: 29 and 34%, p=0.77). Study 2 compared exercise with isocapnic hyperventilation. At 20 min the MEP had fallen by 29% in the exercise session versus 5% with hyperventilation (p=0.098). We conclude that the work of breathing during whole body exercise is not the primary driver of exercise-induced diaphragm MEP depression.
authors.affiliation: Respiratory Muscle Laboratory, Royal Brompton Hospital, London SW3 6NP, United Kingdom.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Dayer
authors.forename: Sophie
authors.initials: S
authors.lastname: Jonville
authors.forename: Michelle
authors.initials: M
authors.lastname: Chatwin
authors.forename: Elisabeth B
authors.initials: EB
authors.lastname: Swallow
authors.forename: Raphael
authors.initials: R
authors.lastname: Porcher
authors.forename: Tarek
authors.initials: T
authors.lastname: Sharshar
authors.forename: Ewen T
authors.initials: ET
authors.lastname: Ross
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Hopkinson
authors.forename: John
authors.initials: J
authors.lastname: Moxham
authors.forename: Michael I
authors.initials: MI
authors.lastname: Polkey
mesh_terms: D000328:Adult; D000399:Air Pressure; D002245:Carbon Dioxide / Q000494:pharmacology; D003627:Data Interpretation, Statistical; D003964:Diaphragm / Q000502:physiology*; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D005267:Femoral Nerve / Q000502:physiology; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010791:Phrenic Nerve / Q000502:physiology; D012121:Respiration, Artificial; D016683:Supine Position; D050781:Transcranial Magnetic Stimulation
chemical_list: D002245:Carbon Dioxide