INTRODUCTION AND OBJECTIVES: Eccentric contractions are those that occur after a muscle has been stretched, and they can predispose the muscle to damage. Most previous studies have been performed on limb muscles, and the potential consequences of eccentric contractions on the respiratory muscles are therefore unknown. The aim of this study was to evaluate the effects of repeated eccentric contractions on diaphragmatic function. METHODS: In 6 dogs, the diaphragm was stretched by applying pressure on the abdominal wall, and consecutive series of eccentric contractions were induced by bilateral supramaximal stimulation. The effect of these contractions on the diaphragm was then evaluated by applying bilateral twitch and tetanic stimulation of the phrenic nerves and measuring the changes in abdominal pressure and the shortening of the right and left hemidiaphragms (by sonomicrometry). Structural study of the muscle was also performed in 4 animals. RESULTS: Eccentric contractions were successfully achieved in all cases. Stimulation-induced diaphragmatic pressures became lower immediately after these contractions: twitch pressure fell by 53% and tetanic pressure by 67% after the first 10 eccentric contractions (P<.001 in both cases). Tetanic stimulation also demonstrated an early deterioration in contractility, which fell by 29% in the right hemidiaphragm (P<.05) and by 14% in the left hemidiaphragm (P<.001). Functional impairment was persistent, lasting at least 12 hours, and was associated with sarcomeric and sarcolemmal damage. CONCLUSIONS: This experimental model, which enabled the effects of eccentric contractions to be studied in the diaphragm, revealed a deterioration of muscle function that persisted for hours and that appeared to be partly due to structural damage. In the clinical setting, physiologic or therapeutic maneuvers that increase the resting length of the diaphragm should be used with caution.
INTRODUCTION AND OBJECTIVES: Eccentric contractions are those that occur after a muscle has been stretched, and they can predispose the muscle to damage. Most previous studies have been performed on limb muscles, and the potential consequences of eccentric contractions on the respiratory muscles are therefore unknown. The aim of this study was to evaluate the effects of repeated eccentric contractions on diaphragmatic function. METHODS: In 6 dogs, the diaphragm was stretched by applying pressure on the abdominal wall, and consecutive series of eccentric contractions were induced by bilateral supramaximal stimulation. The effect of these contractions on the diaphragm was then evaluated by applying bilateral twitch and tetanic stimulation of the phrenic nerves and measuring the changes in abdominal pressure and the shortening of the right and left hemidiaphragms (by sonomicrometry). Structural study of the muscle was also performed in 4 animals. RESULTS: Eccentric contractions were successfully achieved in all cases. Stimulation-induced diaphragmatic pressures became lower immediately after these contractions: twitch pressure fell by 53% and tetanic pressure by 67% after the first 10 eccentric contractions (P<.001 in both cases). Tetanic stimulation also demonstrated an early deterioration in contractility, which fell by 29% in the right hemidiaphragm (P<.05) and by 14% in the left hemidiaphragm (P<.001). Functional impairment was persistent, lasting at least 12 hours, and was associated with sarcomeric and sarcolemmal damage. CONCLUSIONS: This experimental model, which enabled the effects of eccentric contractions to be studied in the diaphragm, revealed a deterioration of muscle function that persisted for hours and that appeared to be partly due to structural damage. In the clinical setting, physiologic or therapeutic maneuvers that increase the resting length of the diaphragm should be used with caution.
Authors: Francesco Mojoli; Marco Pozzi; Anita Orlando; Isabella M Bianchi; Eric Arisi; Giorgio A Iotti; Antonio Braschi; Laurent Brochard Journal: Crit Care Date: 2022-01-30 Impact factor: 9.097
Authors: Elias Baedorf Kassis; Henry K Su; Alexander R Graham; Victor Novack; Stephen H Loring; Daniel S Talmor Journal: Am J Respir Crit Care Med Date: 2021-01-01 Impact factor: 21.405
Authors: Ewan C Goligher; Martin Dres; Bhakti K Patel; Sarina K Sahetya; Jeremy R Beitler; Irene Telias; Takeshi Yoshida; Katerina Vaporidi; Domenico Luca Grieco; Tom Schepens; Giacomo Grasselli; Savino Spadaro; Jose Dianti; Marcelo Amato; Giacomo Bellani; Alexandre Demoule; Eddy Fan; Niall D Ferguson; Dimitrios Georgopoulos; Claude Guérin; Robinder G Khemani; Franco Laghi; Alain Mercat; Francesco Mojoli; Coen A C Ottenheijm; Samir Jaber; Leo Heunks; Jordi Mancebo; Tommaso Mauri; Antonio Pesenti; Laurent Brochard Journal: Am J Respir Crit Care Med Date: 2020-10-01 Impact factor: 30.528