Assessment of neonatal diaphragm function by magnetic stimulation of the phrenic nerves

TY - JOUR

T1 - Assessment of neonatal diaphragm function by magnetic stimulation of the phrenic nerves

AU - Rafferty, G.

AU - Dimitriou, G.

AU - Laubscher, B.

AU - Moxham, J.

AU - Greenough, A.

PY - 1997/12/1

Y1 - 1997/12/1

N2 - Impairment of diaphragmatic function is a cause of respiratory distress in the neonatal period. The aim of this study was to develop for neonates the novel technique of magnetic stimulation, a non-volitional test assessing diaphragm strength. Diaphragm force was determined by measuring transdiaphragmatic pressure (Pdi), obtained from balloons positioned in the mid-oesophagus and stomach. Pressure signals were measured by a Validyne MP 45 differential pressure transducer and displayed in real time on an Apple computer running Labview II software with analogue-to digital sampling at 100 Hz. Subjects were studied supine during periods of quiet sleep. Initially magnetic stimulation with a 90 mm double coil (P/N 8436) placed over the cervical spine and powered by a Magstim 200 stimulator was used in 7 neonates (mean gestational age 38 weeks, range 33-40). The mean twitch Pdi was 2.5 cmH2O (SD 0.8). These responses were thought not to be supramaximal or represent activation of the diaphragm alone. We therefore proceeded to stimulate the phrenic nerves using an anteriolateral approach, which allows both unilateral and bilateral stimulation. Nine neonates (mean GA 37 weeks, range 32-41) were studied; (5 unilateral and 4 bilateral stimulation) using two 90 mm double coils. The resulting mean diaphragm force was 3.1 cmH2O (SD 1.3) on the left, 2.9 cmH2O (SD 1.0) on the right and 7.4 cmH2O (SD 1.1) for both right and left together. In addition, the technique was used in a neonate in conjunction with electrical stimulation to demonstrate right hemidiaphragm paralysis and force responses from the left diaphragm of 3.9 cmH2O (SD 0.9) with magnetic and 3.3 cmH2O (SD 0.3) with electric stimulation. These results suggest magnetic stimulation of the phrenic nerve will be useful to assess diaphragm function in neonates and that anterolateral rather than cervical stimulation is more specific and supramaximal.

AB - Impairment of diaphragmatic function is a cause of respiratory distress in the neonatal period. The aim of this study was to develop for neonates the novel technique of magnetic stimulation, a non-volitional test assessing diaphragm strength. Diaphragm force was determined by measuring transdiaphragmatic pressure (Pdi), obtained from balloons positioned in the mid-oesophagus and stomach. Pressure signals were measured by a Validyne MP 45 differential pressure transducer and displayed in real time on an Apple computer running Labview II software with analogue-to digital sampling at 100 Hz. Subjects were studied supine during periods of quiet sleep. Initially magnetic stimulation with a 90 mm double coil (P/N 8436) placed over the cervical spine and powered by a Magstim 200 stimulator was used in 7 neonates (mean gestational age 38 weeks, range 33-40). The mean twitch Pdi was 2.5 cmH2O (SD 0.8). These responses were thought not to be supramaximal or represent activation of the diaphragm alone. We therefore proceeded to stimulate the phrenic nerves using an anteriolateral approach, which allows both unilateral and bilateral stimulation. Nine neonates (mean GA 37 weeks, range 32-41) were studied; (5 unilateral and 4 bilateral stimulation) using two 90 mm double coils. The resulting mean diaphragm force was 3.1 cmH2O (SD 1.3) on the left, 2.9 cmH2O (SD 1.0) on the right and 7.4 cmH2O (SD 1.1) for both right and left together. In addition, the technique was used in a neonate in conjunction with electrical stimulation to demonstrate right hemidiaphragm paralysis and force responses from the left diaphragm of 3.9 cmH2O (SD 0.9) with magnetic and 3.3 cmH2O (SD 0.3) with electric stimulation. These results suggest magnetic stimulation of the phrenic nerve will be useful to assess diaphragm function in neonates and that anterolateral rather than cervical stimulation is more specific and supramaximal.

UR - http://www.scopus.com/inward/record.url?scp=33750229104&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:33750229104

SN - 0040-6376

VL - 52

JO - Thorax

JF - Thorax

IS - SUPPL. 6

ER -