Relationship among EMG and contractile responses of the diaphragm elicited by hypotension |
| |
Authors: | Hussain S N; Marcotte J E; Burnet H; Collett P; Roussos C |
| |
Institution: | Department of Medicine, Royal Victoria Hospital, Montreal, Quebec, Canada. |
| |
Abstract: | In a canine model, we investigated the effects of severe hypotension on the indexes of diaphragmatic failure. We measured 1) the transdiaphragmatic pressure obtained in response to 20- and 100-Hz stimulation of phrenic nerves (Pdi20 and Pdi100), 2) the power spectrum of diaphragmatic electromyogram (EMG), 3) the ratio of integrated diaphragmatic EMG to Pdi (Edi/Pdi), and 4) the rate of relaxation of Pdi100 and Pdi20. Arterial blood pressure (Pa) was reduced to 40-50 mmHg by a balloon inflated in the inferior vena cava and was maintained at this level until Pdi100 declined to 75% of the control value (100% shock time, ST). A recovery period of 60 min at normal Pa was allowed. During hypotension, Pdi100 and Pdi20 declined only at 100% ST 95.0 +/- 13.0 (SE) min]; however, only Pdi100 recovered within 15 min. The power spectrum shifted to low frequencies early and progressively during shock period. Edi/Pdi rose significantly at 80 and 100% ST and recovered within 15 min. The relaxation rate of Pdi20 and Pdi100 increased significantly at 100% ST only. We conclude that 1) diaphragmatic contractility is depressed during severe hypotension, 2) changes in the power spectrum occurred first in the shock state, followed by alterations in Edi/Pdi, and subsequently both changes in the frequency-pressure curve and relaxation rate occurred last. |
| |
Keywords: | |
|
| 点击此处可从《Journal of applied physiology (Bethesda, Md. : 1985)》浏览原始摘要信息 |
| 点击此处可从《Journal of applied physiology (Bethesda, Md. : 1985)》下载免费的PDF全文 |
|