Chest
Clinical InvestigationsNeuromuscular DiseaseBilateral Anterolateral Magnetic Stimulation of the Phrenic Nerves Can Detect Diaphragmatic Fatigue
Section snippets
Subjects
Twelve healthy subjects (eight men and four women) with a mean (± SE) age of 27.7 ± 2.0 years participated in the study. The mean height and weight of the subjects were 1.76 ± 0.03 m and 83.4 ± 5.3 kg, respectively. The study was approved by the appropriate institutional review boards, and informed consent was obtained from all subjects.
Phrenic Nerve Stimulation
The phrenic nerves were stimulated by the following three different techniques: TES, CMS, and BAMPS. Gastric pressure (Pga), esophageal pressure (Pes), and
Effect of Hyperpnea on Twitch Pressures
TwPdi values from before and after hyperpnea to task failure are shown in Figure 1 . TwPdi fell significantly after hyperpnea with all three stimulation techniques. In three subjects, maximal stimulation could not be achieved with transcutaneous stimulation. These subjects were not included in the analysis of the transcutaneous TwPdi data. Expressing the TwPdi after hyperpnea as a percentage of the baseline value (to normalize for differences in baseline TwPdi between stimulation techniques),
Discussion
The major findings of this study are the following: (1) TwPdi during BAMPS is as good at detecting diaphragmatic fatigue as the other stimulation techniques; (2) TwPdi during BAMPS is reproducible; 3) the results of measuring TwPdi during BAMPS in the fresh state were similar to those observed during CMS but were larger than those observed during TES; and (4) twitch pressure during BAMPS plateaued at power outputs well below the maximum.
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2011, Respiratory Physiology and NeurobiologyCitation Excerpt :TwPdi was calculated by online point-to-point subtraction of TwPes from TwPga. This study did not test for supramaximality, since it has already been shown that BAMPS is capable of reliably achieving supramaximal phrenic nerve stimulation (Mador et al., 2002; Mills et al., 1996). By the end of the first test session participants were thoroughly familiarized with the procedures (including BAMPS during exercise) for the second test session.