Effect of abdominal compression on diaphragmatic tendon organ activity

Abstract

Previous studies suggest that afferents in the diaphragm participate in the reflex reduction in phrenic nerve efferent activation when the length of the diaphragm is increased by abdominal compression. The present study determined the response of tendon organ afferents in the diaphragm to increases in abdominal pressure. Five cats were anesthetized with thiopental sodium (60 mg/kg ip to induce, supplemented intravenously). Extracellular recordings from nine individual tendon organ afferents were made from right cervical dorsal root ganglia 5 and 6. Right crural electromyographic activity was recorded. The right extrathoracic phrenic nerve was isolated and stimulated to identify tendon organs on the basis of conduction velocity and response to twitch. The response to ramp-and-hold stretch of the diaphragm was used as an additional test to differentiate tendon organs from muscle spindles. The mean level of activity of the tendon organs during the 1st s of the inspiratory phase was 47 +/- 10 (SD) Hz. Abdominal compression was associated with a significant increase in the activity of these afferents to 61 +/- 11 Hz. Results indicate that increases in the activity of diaphragmatic tendon organs are associated with moderate increases in abdominal pressure and are likely the result of elevations in the active tension developed by the diaphragm. Combined with results from previous studies, it is possible that diaphragmatic tendon organs may play a role in the attenuation of respiratory muscle activation when abdominal pressure is increased.

Reflex inhibition of canine inspiratory intercostals by diaphragmatic tension receptors

“…Although it is virtually impossible to block selectively the afferent inputs from tendon organs or to stimulate them selectively (Jami, 1992), earlier studies on limb muscles in cats by Lundberg & Winsbury (1960) have shown that afferent volleys from tendon organs in an active muscle can be substantially increased by muscle stretch. Extracellular recordings from cervical dorsal root ganglia in cats by Revelette et al (1992) have also shown increased discharge frequencies from diaphragmatic tendon organs during stretching of the diaphragm by abdominal compression. This procedure, however, would affect a number of additional structures, such as the abdominal muscles, the abdominal viscera, and the large vessels in the abdominal cavity, and the confounding influence of these structures on inspiratory intercostal activity might be difficult to assess.…”

“…Although the primary effect of force application may be to elicit increased afferent volleys from tension receptors in the diaphragm (Lundberg & Winsbury, 1960; Revelette et al 1992), the procedure must also reduce or abolish the normal inspiratory shortening of the muscle fibres. Presumably, therefore, muscle spindles were triggered as well.…”

Functional classification of afferent phrenic nerve fibres and diaphragmatic receptors in cats.

“…There is unfortunately very little information about the function of diaphragmatic tendon organs. The available evidence suggests that they may be responsible for relaxation of the diaphragm during an increase in abdominal pressure (Revelette, Reynolds, Brown & Taylor, 1992). The unloading of diaphragmatic tendon organs may, in turn, lead to an increase in phrenic nerve discharges (Jammes, Buchler, Delpierre, Rasidakis, Grimaud & Roussos, 1986;Teitelbaum, Borel, Magder, Traystman & Hussain, 1993).…”

Influência da cinta abdominal elástica na avaliação da mecânica respiratória em pacientes cirróticos após paracentese

“…Estudos prévios sugerem que aferências diafragmáticas participam da ativação eferente do refl exo de redução do nervo frênico quando o diafragma é alongado pelo aumento da compressão abdominal. Assim, o aumento da atividade diafragmática está associado ao aumento da pressão abdominal [7]. O aumento da pressão diafragmática associado à compressão abdominal está relacionado com o alongamento desse músculo, e produzindo uma contração muscular máxima [8].…”