Respiratory muscle length measured by sonomicrometry

Abstract

The use of sonomicrometry to study the mechanical properties of the diaphragm in vivo is presented. This method consists of the implantation of piezoelectric transducers between muscle fibers to measure the fibers' changes in length. Ultrasonic bursts are produced by one transducer upon electrical excitation and sensed by a second transducer placed 1-2 cm away. The time elapsed between the generation of the ultrasound burst and its detection is used to calculate the intertransducer distance. Excitation and sampling are done at 1.5 kHz and the output is a DC signal proportional to the length change between the transducers. Neither irreversible injury to the diaphragm nor regional differences within an anatomical part or segment were noted. Measurements were stable within the physiological range of temperature. We measured costal and crural length and velocity of contraction in anesthetized dogs during spontaneous breathing, occluded inspirations, passive lung inflation, and supramaximal phrenic nerve stimulation. We found that shortening during spontaneous breathing was 11 and 6% for crural and costal, respectively. The crural leads the costal in velocity of shortening. Supramaximal stimulation results in a velocity of shortening of 5 resting lengths X s-1. During an occluded inspiration crural shortens as much as in the nonoccluded breath, whereas costal shortens less. During passive lung inflation there is a nearly linear relationship between lung volume and diaphragm length; however, the relationships of chest wall dimensions with diaphragm length are nonlinear and cannot be described by any simple function. Some of the implications of these data on the present understanding of diaphragmatic mechanics are discussed.

Cancellation of Cardiac Interference in Diaphragm EMG Signals Using an Estimate of ECG Reference Signal

“…The EMGdi signal was measured via internal electrodes inserted into the costal diaphragm, as described in [8]. The dog was anesthetized and remained in supine position during the acquisition.…”

Effects of controlled and pressure support mechanical ventilation on rat diaphragm muscle

“…During MV, the diaphragm is intermittently and repetitively shortened by cyclical lung inflation 34 . Therefore, changes in the respiratory rate and tidal volume applied during mechanical ventilation will necessarily alter the speed and extent of diaphragmatic shortening.…”

“…During CMV, there is a complete absence of neural activation and diaphragm mechanical activity 2,4 , and a passive shortening of this muscle during lungs inflation 34,36 . This trauma has been implicated in the origin of VIDD 12,42 , particularly during sarcomere injury 36,37 and during decreased force-generating capacity of diaphragm 8,11 .…”

Effects of Lung Volume on Parasternal Pressure‐Generating Capacity in Dogs

“…The sternomastoid muscle was left intact since this muscle was found to be electrically silent during SCS in previous studies and therefore does not contribute to changes in airway pressure generation during upper thoracic SCS. Pairs of piezoelectric crystals (Triton Technology, San Diego, CA, USA), oriented along the axis of muscle fibres, were sewn directly into the medial portion of the parasternal muscle (3rd intercostal space) to monitor changes in muscle length according to a previously described technique (Newman et al 1984). The fibres of the external intercostal (EI) and levator costae (LC) muscles were separated from their points of insertion using a blunt instrument from the first to the sixth intercostal space.…”