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Biomedical subjects

J Moxham

Publications and source records attributed to J Moxham.

At least 19 recordsLinked to original sources
PubMed2006

The effect of noninvasive ventilation on ALS patients and their caregivers.

BACKGROUND: Noninvasive ventilation (NIV) reduces mortality and improves some aspects of quality of life (QoL) in ALS. However, concerns remain that progressive disability may negate these benefits and unnecessarily burden caregivers. METHODS: Thirty-nine patients requiring NIV were offered treatment. Twenty-six were established on NIV, but 13 declined or could not tolerate NIV. Fifteen patients without respiratory muscle weakness (RMW) but with similar ALS severity and age were studied in parallel. Caregivers of 21 NIV, 7 untreated, and 10 patients without RMW participated. Patients and caregivers had detailed QoL measurements for 12 months. NIV patients underwent cognitive testing before and after treatment. RESULTS: RMW correlated with lower QoL. The median survival of untreated patients (18 days; 95% CI 11 to 25 days) was shorter than for NIV patients (298 days; 95% CI 192 to 404 days) and non-RMW patients (370 days; 95% CI 278 to 462 days; log rank test [2 df] = 81, p = 0.00001). A wide range of QoL measures improved within 1 month of starting NIV, and improvements were maintained for 12 months. QoL of non-RMW patients declined as RMW progressed. Caregivers of NIV and non-RMW patients showed similar increases in burden, but NIV patient caregivers developed a deterioration in the Short Form-36 Vitality score. No improvements were found on measures of learning and recall in the NIV patients. CONCLUSIONS: Respiratory muscle weakness has a greater impact on quality of life (QoL) than overall ALS severity. Noninvasive ventilation (NIV) improves QoL despite ALS progression. NIV has no impact on most aspects of caregiver QoL and does not significantly increase caregiver burden or stress.

Adult↗
PubMed2006

Differences in motor activation of voluntary and reflex cough in humans.

OBJECTIVES: To study motor activation patterns of voluntary and reflex cough adjusted for cough flow rates. METHODS: Surface electromyography (EMG) and cough flow rate were measured in 10 healthy volunteers. Voluntary cough was assessed for 20 efforts in each quintile of increasing cough flow rate. Reflex cough was assessed for 25 efforts produced by nebulised l-tartaric acid. EMG was recorded over the expiratory (rectus abdominis, obliques, lower intercostals) and accessory (trapezius, pectoralis major, deltoid, latissimus dorsi) muscles. EMG activity, burst duration and onset were compared for each quintile of voluntary cough, and between voluntary and reflex cough matched for cough flow rate. RESULTS: EMG activity and burst duration of expiratory and accessory muscles during voluntary cough increased in proportion to cough flow. Expiratory muscles had longer EMG burst duration (difference 68 ms (95% CI 34 to 102), p<0.01) and earlier onset of EMG activity (difference 44 ms (95% CI 20 to 68), p<0.0001) compared with accessory muscles. EMG activity in all muscles was increased (mean 110.2% v 56.1%, p<0.001) and burst duration (mean 206 ms v 280 ms, p = 0.013) decreased in reflex cough compared with voluntary cough of equal flow rate. There were no differences in EMG onset (difference 8 ms (95% CI 25 to -9) or burst duration (difference 27 ms (95% CI 58 to -4) between expiratory and accessory muscles. CONCLUSIONS: Functional organisation of motor activity differs between voluntary and reflex cough. Voluntary cough is characterised by sequential activation whereas reflex cough is associated with early and simultaneous activation of expiratory and accessory muscles.

Adult↗
PubMed2006

Right hemi-diaphragm paralysis following cardiac radiofrequency ablation.

Diaphragm paralysis may occur after traumatic phrenic nerve injury. Here we report three patients in whom right hemi-diaphragmatic paralysis developed after cardiac radiofrequency ablation. We hypothesise that local focused thermal energy at the time of the ablation may have caused direct neuronal damage by axonal coagulation necrosis. The prognosis for this type of injury may be reasonably good; two of the three patients fully recovered diaphragm function by 1 year.

Adult↗
PubMed2006

Diaphragm electromyograms recorded from multiple surface electrodes following magnetic stimulation.

The diaphragm compound-muscle action potential (CMAPdi), elicited by unilateral magnetic stimulation (UMS) of the phrenic nerve can be recorded using surface electrodes. However, there is no consensus on the best positioning of surface electrodes and there are no data on the reproducibility of the signal. Using 36 surface electrode pairs, in five healthy subjects, the CMAPdi elicited by UMS and electrical stimulation (ES) were compared and 12 pairs were identified as providing acceptable signals. The latency and amplitude were measured for each CMAPdi, following UMS at 60-100% of maximal stimulator output, in 12 healthy subjects, on two occasions. Latencies obtained using UMS and ES ranged between 6.1-7.33 and 6.25-7.17 ms, respectively. Optimum CMAPdi were not recorded from the same electrode pair in all subjects, or for both hemidiaphragms in each subject. However, the optimal recording site for a particular individual remained unchanged on subsequent testing. When recorded from the optimal site, latencies and amplitudes of CMAPdi elicited on the two occasions were not significantly different. The current study suggests that the use of multiple chest wall electrodes can identify an optimal electrode pair, from which it is possible to obtain reproducible compound-muscle action potential signals.

Action Potentials↗
PubMed2005

Mechanisms of improvement of respiratory failure in patients with restrictive thoracic disease treated with non-invasive ventilation.

BACKGROUND: Nocturnal non-invasive ventilation (NIV) is an effective treatment for hypercapnic respiratory failure in patients with restrictive thoracic disease. We hypothesised that NIV may reverse respiratory failure by increasing the ventilatory response to carbon dioxide, reducing inspiratory muscle fatigue, or enhancing pulmonary mechanics. METHODS: Twenty patients with restrictive disease were studied at baseline (D0) and at 5-8 days (D5) and 3 months (3M). RESULTS: Mean (SD) daytime arterial carbon dioxide tension (Paco(2)) was reduced from 7.1 (0.9) kPa to 6.6 (0.8) kPa at D5 and 6.3 (0.9) kPa at 3M (p = 0.004), with the mean (SD) hypercapnic ventilatory response increasing from 2.8 (2.3) l/min/kPa to 3.6 (2.4) l/min/kPa at D5 and 4.3 (3.3) l/min/kPa at 3M (p = 0.044). No increase was observed in measures of inspiratory muscle strength including twitch transdiaphragmatic pressure, nor in lung function or respiratory system compliance. CONCLUSIONS: These findings suggest that increased ventilatory response to carbon dioxide is the principal mechanism underlying the long term improvement in gas exchange following NIV in patients with restrictive thoracic disease. Increases in respiratory muscle strength (sniff oesophageal pressure and sniff nasal pressure) correlated with reductions in the Epworth sleepiness score, possibly indicating an increase in the ability of patients to activate inspiratory muscles rather than an improvement in contractility.

Carbon Dioxide↗
PubMed2005

Abdominal muscle and quadriceps strength in chronic obstructive pulmonary disease.

BACKGROUND: Quadriceps muscle weakness is common in chronic obstructive pulmonary disease (COPD) but is not observed in a small hand muscle (adductor pollicis). Although this could be explained by reduced activity in the quadriceps, the observation could also be explained by anatomical location of the muscle or fibre type composition. However, the abdominal muscles are of a similar anatomical and fibre type distribution to the quadriceps, although they remain active in COPD. Cough gastric pressure is a recently described technique that assesses abdominal muscle (and hence expiratory muscle) strength more accurately than traditional techniques. A study was undertaken to test the hypothesis that more severe weakness exists in the quadriceps than in the abdominal muscles of patients with COPD compared with healthy elderly controls. METHODS: Maximum cough gastric pressure and quadriceps isometric strength were measured in 43 patients with stable COPD and 25 healthy elderly volunteers matched for anthropometric variables. RESULTS: Despite a significant reduction in mean quadriceps strength (29.9 kg v 41.2 kg; 95% CI -17.9 to -4.6; p = 0.001), cough gastric pressure was preserved in patients with COPD (227.3 cm H(2)O v 204.8 cm H(2)O; 95% CI -5.4 to 50.6; p = 0.11). CONCLUSIONS: Abdominal muscle strength is preserved in stable COPD outpatients in the presence of quadriceps weakness. This suggests that anatomical location and fibre type cannot explain quadriceps weakness in COPD. By inference, we conclude that disuse and consequent deconditioning are important factors in the development of quadriceps muscle weakness in COPD patients, or that activity protects the abdominal muscles from possible systemic myopathic processes.

Abdominal Muscles↗
PubMed2005

Measurement of neural respiratory drive in patients with COPD.

Assessment of neural respiratory drive may be useful in patients with chronic obstructive pulmonary disease (COPD) for diverse clinical and academic reasons. We hypothesised that the oesophageal diaphragm EMG during CO2 rebreathing and treadmill exercise could be used for this purpose. The oesophageal catheter consisted of nine consecutive recording electrode coils, which formed five pairs of electrodes with an inter-electrode distance 3.2 cm within a recording pair. Each coil was 1cm in length and the gap between adjacent coils was 0.5 mm. Maximal isometric contractions at functional residual capacity (FRC) and maximal voluntary inspirations from FRC to total lung capacity (TLC) were performed. All subjects performed CO2 rebreathing until end-tidal CO2 was approximately 9% or they became intolerably breathless. There was a good linear relationship between peak of root mean square (RMS) of the diaphragm EMG and end-tidal CO2 (r = 0.92 +/- 0.06) during CO2 rebreathing. The method was also shown to be feasible during exercise. It is concluded that the diaphragm EMG recorded from an oesophageal electrode is a useful technique to assess neural respiratory drive in patients with COPD.

Aged↗
PubMed2004

Inspiratory muscle load and capacity in chronic heart failure.

BACKGROUND: Although breathlessness is common in chronic heart failure (CHF), the role of inspiratory muscle dysfunction remains unclear. We hypothesised that inspiratory muscle endurance, expressed as a function of endurance time (Tlim) adjusted for inspiratory muscle load and inspiratory muscle capacity, would be reduced in CHF. METHODS: Endurance was measured in 10 healthy controls and 10 patients with CHF using threshold loading at 40% maximal oesophageal pressure (Poes(max)). Oesophageal pressure-time product (PTPoes per cycle) and Poes(max) were used as indices of inspiratory muscle load and capacity, respectively. RESULTS: Although Poes(max) was slightly less in the CHF group (-117.7 (23.6) v -100.0 (18.3) cm H(2)O; 95% CI -37.5 to 2.2 cm H(2)O, p = 0.1), Tlim was greatly reduced (1800 v 306 (190) s; 95% CI 1368 to 1620 s, p<0.0001) and the observed PTPoes per cycle/Poes(max) was increased (0.13 (0.05) v 0.21 (0.04); 95% CI -0.11 to -0.03, p = 0.001). Most of this increased inspiratory muscle load was due to a maladaptive breathing pattern, with a reduction in expiratory time (3.0 (5.8) v 1.1 (0.3) s; 95% CI 0.3 to 3.5 s, p = 0.03) accompanied by an increased inspiratory time relative to total respiratory cycle (Ti/Ttot) (0.43 (0.14) v 0.62 (0.07); 95% CI -0.3 to -0.1, p = 0.001). However, log Tlim, which incorporates the higher inspiratory muscle load to capacity ratio caused by this altered breathing pattern, was >/=85% predicted in seven of 10 patients. CONCLUSIONS: Although a marked reduction in endurance time was observed in CHF, much of this reduction was explained by the increased inspiratory muscle load to capacity ratio, suggesting that the major contributor to task failure was a maladaptive breathing pattern rather than impaired inspiratory muscle endurance.

Aged↗
PubMed2004

Effect of salmeterol on respiratory muscle activity during exercise in poorly reversible COPD.

BACKGROUND: Some patients with irreversible chronic obstructive pulmonary disease (COPD) experience subjective benefit from long acting bronchodilators without change in forced expiratory volume in 1 second (FEV(1)). Dynamic hyperinflation is an important determinant of exercise induced dyspnoea in COPD. We hypothesised that long acting bronchodilators improve symptoms by reducing dynamic hyperinflation and work of breathing, as measured by respiratory muscle pressure-time products. METHODS: Sixteen patients with "irreversible" COPD (<10% improvement in FEV(1) following a bronchodilator challenge; mean FEV(1) 31.1% predicted) were recruited into a randomised, double blind, placebo controlled, crossover study of salmeterol (50 micro g twice a day). Treatment periods were of 2 weeks duration with a 2 week washout period. Primary outcome measures were end exercise isotime transdiaphragmatic pressure-time product and dynamic hyperinflation as measured by inspiratory capacity. RESULTS: Salmeterol significantly reduced the transdiaphragmatic pressure-time product (294.5 v 348.6 cm H(2)O/s/min; p = 0.03), dynamic hyperinflation (0.22 v 0.33 litres; p = 0.002), and Borg scores during endurance treadmill walk (3.78 v 4.62; p = 0.02). There was no significant change in exercise endurance time. Improvements in isotime Borg score were significantly correlated to changes in tidal volume/oesophageal pressure swings, end expiratory lung volume, and inspiratory capacity, but not pressure-time products. CONCLUSIONS: Despite apparent "non-reversibility" in spirometric parameters, long acting bronchodilators can cause both symptomatic and physiological improvement during exercise in severe COPD.

Aged↗
PubMed2004

Dynamic dead space in face masks used with noninvasive ventilators: a lung model study.

The aim of this study was to determine what the influence of different designs of face masks and different noninvasive ventilator modes would be upon total dynamic dead space. Using a spontaneous breathing model, total dynamic dead space was measured when using 19 commercially available face masks and a range of ventilators in various ventilation modes. Total dynamic dead space during spontaneous ventilation was increased above physiological dead space from 32% to 42% of tidal volume by using face masks. The use of noninvasive ventilation modes such as bilevel and continuous positive airway pressure, with continuous pressure throughout the expiratory phase, reduced total dynamic dead space to approach physiological dead space with most face masks. Pressure assist and pressure support ventilation decreased total dynamic dead space to a lesser degree, from 42% to 39% of tidal volume. Face masks with expiratory ports over the nasal bridge resulted in beneficial flow characteristics within the face mask and nasal cavity, so as to decrease total dynamic dead space to less than physiological dead space from 42% to 28.5% of tidal volume. Exhaust ports over the nasal bridge in face masks effect important decreases in dynamic dead space provided positive pressure throughout the expiratory phase is used.

Equipment Design↗
PubMed2004

Magnetic stimulation for the measurement of respiratory and skeletal muscle function.

Respiratory and skeletal muscle function is of interest in many areas of pulmonary and critical care medicine. The capacity of the respiratory muscle pump to respond to the load imposed by disease is the basis of an understanding of ventilatory failure. Over the last four decades, considerable progress has been made in quantifying the capacity of the respiratory muscles, in terms of strength, endurance and fatigue. With the development of magnetic stimulation, it has recently become possible to nonvolitionally assess the respiratory muscles in a clinically acceptable way. This is of particular interest in the investigation of patients receiving critical care, those with neuromuscular disease, and in children where volitional efforts are either not possible or likely to be sub-maximal. Furthermore, the adaptation of these techniques to quantify the strength of peripheral muscles, such as the quadriceps, has allowed the effects of muscle training or rehabilitation, uninfluenced by learning effect, to be assessed. This article focuses on the physiological basis of magnetic nerve stimulation, and reviews how the technique has been applied to measure muscle strength and fatigue, with particular emphasis upon the diaphragm. The translation of magnetic stimulation into a clinical tool is described, and how it may be of diagnostic, prognostic and therapeutic value in several areas of pulmonary medicine. In particular, the use of magnetic stimulation in neuromuscular disease, the intensive care setting, chronic obstructive pulmonary disease and paediatrics will be discussed.

Child↗
PubMed2004

Acute effect of oral steroids on muscle function in chronic obstructive pulmonary disease.

Prospective data to support the hypothesis that corticosteroids are a significant cause of muscle weakness in patients with chronic obstructive pulmonary disease (COPD) are lacking. The authors studied respiratory and quadriceps muscle function, using both volitional techniques and magnetic nerve stimulation, as well as measuring metabolic parameters during incremental cycle ergometry, in 25 stable COPD patients. The forced expiratory volume in one second was 37.6 +/- 21.4% predicted, before and after a 2-week course of o.d. prednisolone 30 mg. Quadriceps strength was also assessed in 15 control patients on two occasions. Only two patients met the British Thoracic Society definition of steroid responsiveness. There was no change either in sniff transdiaphragmatic pressure (pre: 96.8 +/- 19.7 cmH2O; post: 98.6 +/- 22.4 cmH2O) or in twitch transdiaphragmatic pressure elicited by bilateral anterolateral magnetic phrenic-nerve stimulation (pre: 16.8 +/- 9.1 cmH2O; post: 17.9 +/- 10 cmH2O). Quadriceps twitch force did not change significantly either in the steroid group (pre: 9.5 +/- 3.1 kg; post: 8.9 +/- 3.7 kg) or in the control patients (pre: 8.1 +/- 2.7 kg; post: 7.9 +/- 2.2 kg). There were no changes in either peak or isotime ventilatory and metabolic parameters during exercise. In conclusion, in stable patients with chronic obstructive pulmonary disease, a 2-week course of 30 mg prednisolone daily does not cause significant skeletal muscle dysfunction or alter metabolic parameters during exercise.

Adrenal Cortex Hormones↗
PubMed2003

Cough augmentation in amyotrophic lateral sclerosis.

Cough flows and pressures were measured during cough augmentation in healthy subjects and patients with bulbar and nonbulbar amyotrophic lateral sclerosis. Manual assistance increased flow 11% in bulbar (p < 0.01) and 13% in nonbulbar (p < 0.001) patients. Mechanical insufflation-exsufflation increased flow 17% in healthy subjects (p < 0.05), 26% (p < 0.001) in bulbar, and 28% (p < 0.001) in nonbulbar patients. The greatest improvements were in patients with the weakest coughs. Patient group and level of weakness influenced the effect of augmentation.

Amyotrophic Lateral Sclerosis↗
PubMed2003

Clinical trial comparing nicotine replacement therapy (NRT) plus brief counselling, brief counselling alone, and minimal intervention on smoking cessation in hospital inpatients.

BACKGROUND: Guidelines recommend that smoking cessation interventions are offered in all clinical settings to all smokers willing to make a quit attempt. Since the effectiveness of routine provision of behavioural counselling and nicotine replacement therapy (NRT) to smokers admitted to hospital has not been established, a randomised controlled trial of these interventions given together compared with counselling alone or minimal intervention was performed in hospital inpatients. METHODS: Medical and surgical inpatients who were current smokers at the time of admission were randomised to receive either usual care (no additional advice at admission), counselling alone (20 minute intervention with written materials), or NRT plus counselling (counselling intervention with a 6 week course of NRT). Continuous and point prevalence abstinence from smoking (validated by exhaled carbon monoxide <10 ppm) was measured at discharge from hospital and at 3 and 12 months, and self-reported reduction in cigarette consumption in smokers was assessed at 3 and 12 months. RESULTS: 274 inpatient smokers were enrolled. Abstinence was higher in the NRT plus counselling group (n=91) than in the counselling alone (n=91) or usual care (n=92) groups. The difference between the groups was significant for validated point prevalence abstinence at discharge (55%, 43%, 37% respectively, p=0.045) and at 12 months (17%, 6%, 8%, p=0.03). The respective differences in continuous validated abstinence at 12 months were 11%, 4%, 8% (p=0.25). There was no significant difference between counselling alone and usual care, or in reduction in cigarette consumption between the treatment groups. CONCLUSIONS: NRT given with brief counselling to hospital inpatients is an effective routine smoking cessation intervention.

Administration, Intranasal↗