The purpose of this study was to quantitatively evaluate paradoxical diaphragmatic motion using magnetic resonance (MR) imaging. A total of 27 subjects were examined, including 12 normal young adults, six control individuals, and nine patients with emphysema. With subjects in the supine position, 30 sequential sagittal MR images of the entire right lung were obtained during tidal and deep slow breathing. Diaphragmatic movement between sequential images was estimated as the displacement area and the total diaphragmatic movement in a respiratory cycle was calculated. The paradoxical motion of the diaphragm, representing the inverted movement to increase or decrease lung area, since paradoxical movement ratio (Mpr=(total paradoxical diaphragmatic movement/total diaphragmatic movement)x100), was evaluated. In patients with emphysema, paradoxical diaphragmatic motion was observed on MR images during deep breathing. The mean Mpr in emphysematous patients during deep breathing was 10+/-4%, which was significantly higher than 0.5+/-0.2% in young adults (p<0.05), and 1.2+/-0.6% in aged-matched controls (p<0.05). The present results indicate that magnetic resonance images could be used to detect paradoxical diaphragmatic motion in patients with emphysema.

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We have studied the effects and mechanism of fenoterol (a beta 2-agonist) on contractility of the fatigued canine diaphragm. Transdiaphragmatic pressure (Pdi) was measured by a pair of balloons, and diaphragmatic contractility was assessed from changes in tetanic contraction, produced by supramaximal electrical stimulation of the phrenic nerves. Diaphragmatic fatigue was developed by applying an inspiratory resistive load to a spontaneously breathing dog for approximately 30 min. Fenoterol improved the Pdi of the fatigued canine diaphragm at all stimulation frequencies, and the increases in Pdi at low frequencies were greater. The potentiation of Pdi by fenoterol occurred in a dose-dependent manner with doses of 2.5 to 10 micrograms/kg and was equal to that of aminophylline. Dibutyryl cyclic AMP did not have significant effect on the Pdi at all stimulation frequencies. The augmentation of Pdi in the fatigued diaphragm by fenoterol was abolished by administration of a calcium antagonist, verapamil, and fenoterol did not change the diaphragmatic contractility in nonfatigued dogs. We thus have concluded that fenoterol improves contractility in the fatigued canine diaphragm and the effect might be brought about by an increased influx of calcium to the muscle cell.

The authors evaluate paradoxical diaphragmatic motion using magnetic resonance (MR) imaging in patients with emphysema. The subjects were 12 healthy volunteers and 10 male patients with moderate to severe air flow obstruction. With subjects in the supine position, 30 sequential sagittal images of the bilateral lungs were obtained during quiet and forced breathing using a 1.5T MR unit with a body coil. The sequence was single shot fast spin echo (SSFSE) with half Fourier transformation. Subtraction images were made from the original images (by subtracting a given image from the preceding image), which visualized the chest wall motion as white or black bands on the edge of the lung fields. The authors evaluated both the original and subtraction images. MR imaging showed abnormal hemidiaphragmatic motion during forced breathing: the ventral portion of the hemidiaphragm moved downward while the dorsal part moved upward like a seesaw in 6 patients. MR images also revealed abnormal ribcage motion; the ventral ribcage moved anteriorly when the hemidiaphragm moved upward in 7 patients. No abnormal motion was observed in healthy volunteers. MR is a noninvasive and useful tool for evaluating the asynchronous respiratory motion in patients with emphysema.