Effect of respiratory muscle training on load sensations in people with chronic tetraplegia: a secondary analysis of a randomised controlled trial.

STUDY DESIGN: Secondary analysis of a randomised controlled trial. OBJECTIVES: Our primary study showed that increasing inspiratory muscle strength with training in people with chronic (>1 year) tetraplegia corresponded with reduced sensations of breathlessness when inspiration was loaded. This study investigated whether respiratory muscle training also affected the respiratory sensations for load detection and magnitude perception. SETTING: Independent research institute in Sydney, Australia. METHODS: Thirty-two adults with chronic tetraplegia participated in a 6-week, supervised training protocol. The active group trained the inspiratory muscles through progressive threshold loading. The sham group performed the same protocol with a fixed threshold load (3.6 cmH2O). Primary measures were load detection threshold and perceived magnitudes of six suprathreshold loads reported using the modified Borg scale. RESULTS: Maximal inspiratory pressure (PImax) increased by 32% (95% CI, 18-45) in the active group with no change in the sham group (p =  0.51). The training intervention did not affect detection thresholds in the active (p =  0.24) or sham (p =  0.77) group, with similar overall decreases in Borg rating of 0.83 (95% CI, 0.49-1.17) in active and 0.72 (95% CI, 0.32-1.12) in sham group. Increased inspiratory muscle strength reduced slope magnitude between Borg rating and peak inspiratory pressure (p =  0.003), but not when pressure was divided by PImax to reflect contraction intensity (p =  0.92). CONCLUSIONS: Training reduces the sensitivity of load sensations for a given change in pressure but not for a given change in contraction intensity.

Impact of respiratory muscle training on respiratory muscle strength, respiratory function and quality of life in individuals with tetraplegia: a randomised clinical trial.

BACKGROUND: Respiratory complications remain a leading cause of morbidity and mortality in people with acute and chronic tetraplegia. Respiratory muscle weakness following spinal cord injury-induced tetraplegia impairs lung function and the ability to cough. In particular, inspiratory muscle strength has been identified as the best predictor of the likelihood of developing pneumonia in individuals with tetraplegia. We hypothesised that 6 weeks of progressive respiratory muscle training (RMT) increases respiratory muscle strength with improvements in lung function, quality of life and respiratory health. METHODS: Sixty-two adults with tetraplegia participated in a double-blind randomised controlled trial. Active or sham RMT was performed twice daily for 6 weeks. Inspiratory muscle strength, measured as maximal inspiratory pressure (PImax) was the primary outcome. Secondary outcomes included lung function, quality of life and respiratory health. Between-group comparisons were obtained with linear models adjusting for baseline values of the outcomes. RESULTS: After 6 weeks, there was a greater improvement in PImax in the active group than in the sham group (mean difference 11.5 cmH2O (95% CI 5.6 to 17.4), p<0.001) and respiratory symptoms were reduced (St George Respiratory Questionnaire mean difference 10.3 points (0.01-20.65), p=0.046). Significant improvements were observed in quality of life (EuroQol-Five Dimensional Visual Analogue Scale 14.9 points (1.9-27.9), p=0.023) and perceived breathlessness (Borg score 0.64 (0.11-1.17), p=0.021). There were no significant improvements in other measures of respiratory function (p=0.126-0.979). CONCLUSIONS: Progressive RMT increases inspiratory muscle strength in people with tetraplegia, by a magnitude which is likely to be clinically significant. Measurement of baseline PImax and provision of RMT to at-risk individuals may reduce respiratory complications after tetraplegia. TRIAL REGISTRATION NUMBER: Australian New Zealand Clinical Trials Registry (ACTRN 12612000929808).

Optimal electrode position for abdominal functional electrical stimulation.

Abdominal functional electrical stimulation (abdominal FES) improves respiratory function. Despite this, clinical use remains low, possibly due to lack of agreement on the optimal electrode position. This study aimed to ascertain the optimal electrode position for abdominal FES, assessed by expiratory twitch pressure. Ten able-bodied participants received abdominal FES using electrodes placed: 1) on the posterolateral abdominal wall and at the motor points of 2) the external oblique muscles plus rectus abdominis muscles, and 3) the external obliques alone. Gastric (Pga) and esophageal (Pes) twitch pressures were measured using a gastroesophageal catheter. Single-stimulation pulses were applied at functional residual capacity during step increments in stimulation current to maximal tolerance or until Pga plateaued. Stimulation applied on the posterolateral abdominal wall led to a 71% and 53% increase in Pga and Pes, respectively, compared with stimulation of the external oblique and rectus abdominis muscles ( P < 0.001) and a 95% and 56% increase in Pga and Pes, respectively, compared with stimulation of the external oblique muscles alone ( P < 0.001). Stimulation of both the external oblique and rectus abdominis muscles led to an 18.3% decrease in Pga compared with stimulation of only the external oblique muscles ( P = 0.040), with inclusion of the rectus abdominis having no effect on Pes ( P = 0.809). Abdominal FES applied on the posterolateral abdominal wall generated the highest expiratory twitch pressures. As expiratory pressure is a good indicator of expiratory muscle strength and, thus, cough efficacy, we recommend this electrode position for all therapeutic applications of abdominal FES. NEW & NOTEWORTHY While abdominal functional electrical stimulation (abdominal FES) can improve respiratory function, clinical use remains low. This is at least partly due to lack of agreement on the optimal electrode position. Therefore, this study aimed to ascertain the optimal electrode position for abdominal FES. We show that electrodes placed on the posterolateral abdominal wall generated the highest expiratory twitch pressures. As such, we recommend this electrode position for all therapeutic applications of abdominal FES.

Electrical stimulation of abdominal muscles to produce cough in spinal cord injury: effect of stimulus intensity.

BACKGROUND: Surface electrical stimulation of the abdominal muscles, with electrodes placed in the posterolateral position, combined with a voluntary cough can assist clearance of airway secretions in individuals with high-level spinal cord injury (SCI). OBJECTIVE: To determine whether an increase in stimulus intensity of the trains of electrical stimuli delivered to the expiratory muscles has an increasing effect on a stimulated voluntary cough and to determine at which stimulus intensity a plateau of cough peak expiratory flow occurs. METHODS: In 7 healthy individuals with a SCI at and above C7, gastric pressure (P(ga)), esophageal pressure (P(es)), peak expiratory cough flow (PEF(cough)), and expiratory volume were measured as participants coughed voluntarily with simultaneous trains of electrical stimuli delivered over the abdominal muscles (50 Hz, 1-s duration). The intensity of the stimulation was increased incrementally. RESULTS: A plateau in PEF(cough) occurred in all 7 individuals at a mean of 211 ± 29 mA (range 120-360 mA). Peak values reached for P(ga), P(es), and PEF(cough) were 83.0 ± 8.0 cm H2O, 66.1 ± 5.6 cm H2O, and 4.0 ± 0.4 l/s respectively. CONCLUSIONS: The plateau in expiratory cough flow that was associated with increasing expiratory pressures is indicative of dynamic airway compression. This suggests that the evoked cough will be effective in creating more turbulent airflow to further assist in dislodging mucus and secretions.

Abdominal muscle training can enhance cough after spinal cord injury.

BACKGROUND: Respiratory complications in people with high-level spinal cord injury (SCI) are a major cause of morbidity and mortality, particularly because of a reduced ability to cough as a result of abdominal muscle paralysis. OBJECTIVE: . We investigated the effect of cough training combined with functional electrical stimulation (FES) over the abdominal muscles for 6 weeks to observe whether training could improve cough strength. METHODS: Fifteen SCI subjects (C4-T5) trained for 6 weeks, 5 days per week (5 sets of 10 coughs per day) in a randomized crossover design study. Subjects coughed voluntarily at the same time as a train of electrical stimulation was delivered over the abdominal muscles via posterolaterally positioned electrodes (50 Hz, 3 seconds). Measurements were made of esophageal (Pes) and gastric (Pga) expiratory pressures and the peak expiratory flow (PEFcough) produced at the 3 time points of before, during, and after the training. RESULTS: During voluntary coughs, FES cough stimulation improved Pga, Pes, and PEFcough acutely, 20-fold, 4-fold, and 50%, respectively. Six weeks of cough training significantly increased Pga (37.1 ± 2.0 to 46.5 ± 2.9 cm H2O), Pes (35.4 ± 2.7 to 48.1 ± 2.9 cm H2O), and PEFcough (3.1 ± 0.1 to 3.6 ± 0.1 L/s). Cough training also improved pressures and flow during voluntary unstimulated coughs. CONCLUSIONS: FES of abdominal muscles acutely increases mechanical output in coughing in high-level SCI subjects. Six weeks of cough training further increases gastric and esophageal cough pressures and expiratory cough flow during stimulated cough maneuvers.

Posterolateral surface electrical stimulation of abdominal expiratory muscles to enhance cough in spinal cord injury.

BACKGROUND: Spinal cord injury (SCI) patients have respiratory complications because of abdominal muscle weakness and paralysis, which impair the ability to cough. OBJECTIVE: This study aims to enhance cough in high-level SCI subjects (n = 11, SCI at or above T6) using surface electrical stimulation of the abdominal muscles via 2 pairs of posterolaterally placed electrodes. METHODS: From total lung capacity, subjects performed maximum expiratory pressure (MEP) efforts against a closed airway and voluntary cough efforts. Both efforts were performed with and without superimposed trains of electrical stimulation (50 Hz, 1 second) at a submaximal intensity set to evoke a gastric pressure (P(ga)) of 40 cm H(2)O at functional residual capacity. RESULTS: In the MEP effort, stimulation increased the maximal P(ga) (from 21.4 ± 7.0 to 59.0 ± 5.7 cm H(2)O) and esophageal pressure (P(es); 47.2 ± 11.7 to 65.6 ± 13.6 cm H(2)O). During the cough efforts, stimulation increased P(ga) (19.5 ± 6.0 to 57.9 ± 7.0 cm H(2)O) and P(es) (31.2 ± 8.7 to 56.6 ± 10.5 cm H(2)O). The increased expiratory pressures during cough efforts with stimulation increased peak expiratory flow (PEF, by 36% ± 5%), mean expiratory flow (by 80% ± 8%), and expired lung volume (by 41% ± 16%). In every subject, superimposed electrical stimulation improved peak expiratory flow during cough efforts (by 0.99 ± 0.12 L/s; range, 0.41-1.80 L/s). Wearing an abdominal binder did not improve stimulated cough flows or pressures. CONCLUSIONS: The increases in P(ga) and PEF with electrical stimulation using the novel posterolateral electrode placement are 2 to 3 times greater than improvements reported in other studies. This suggests that posterolateral electrical stimulation of abdominal muscles is a simple noninvasive way to enhance cough in individuals with SCI.

Preliminary screening study of reproductive outcomes after exposure to yarrow in the pregnant rat.

BACKGROUND: Yarrow (Achillea millefolium) is used for the treatment of diarrhea, as a urinary antiseptic, hypotensive, and diuretic. Yarrow also has traditionally been used as an abortifacient, emmenagogue, contraceptive, and for stimulating uterine contractions. For this reason, it is contra-indicated for use in pregnancy. There has, however, been little scientific research carried out to either confirm or refute this recommendation. METHODS: Female rats were dosed, orally by gavage using 56 times the human dose of yarrow daily on either gestation days (GD) 1-8 or GD 8-15. Two groups of controls were included; the first received water and the second received an equivalent dose of ethanol to that found in the yarrow preparation over the two gestation periods. On GD 20, rats were sacrificed, placentae were weighed, and corpora lutea counted. The fetuses were weighed and examined for signs of external, internal or skeletal malformations. RESULTS: The dose used was not materno-toxic. There was no increase in pre- or post-implantation losses suggesting that yarrow was neither an abortifacient nor a contraceptive. Placental weights were increased in rats treated with yarrow on GD 8-15 compared to water and ethanol controls and on GD 1-8 compared to water control fetuses. Body weight was reduced in fetuses exposed to yarrow on GD 8-15 compared to water control fetuses. There was no difference in incidence of external or internal malformations. CONCLUSIONS: In the present study it was found that yarrow, when administered to rats at 56 times the human dose, was associated with reduced fetal weight and increased placental weight. In the absence of a no observable effect level for these variables it must be concluded that the consumption of yarrow is contraindicated during pregnancy until further investigations have been carried out.