Postprandial effects on twitch transdiaphragmatic pressure

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Abstract
Twitch transdiaphragmatic pressure (Pdi,tw), measured following magnetic stimulation of the phrenic nerves, is used to assess diaphragm strength, contractility and fatigue. Although the effects of posture, lung volume and potentiation onPdi,tware well described, it is not known whether the degree of gastric filling affects the measurement.Pdi,twwas recorded in seven healthy volunteers on two occasions with antero-lateral magnetic stimulation of the phrenic nerves. On the first occasion, the subjects had fasted for at least 8 h, whilst on the second occasion, measurements were made after each subject had eaten a substantial meal sufficient to produce a feeling of satiation.Mean postprandial unpotentiated and potentiatedPdi,twwere significantly greater than corresponding fastingPdi,twin all seven volunteers (29.8versus25.7 cmH2O and 38.9versus34.4 cmH2O, respectively). This was due to a significantly increased gastric pressure component (1.10versus0.84 and 0.94versus0.78, respectively), and reduced abdominal compliance (36versus62 mL·cmH2O−1). Twitch oesophageal pressure was preserved (15.0versus15.4 cmH2O).The postprandial state increases twitch transdiaphragmatic pressure, and this should be taken into account when using twitch transdiaphragmatic pressure to follow-up patients or to assess the effects of interventions on diaphragm contractility.