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Biomedical subjects

A K Simonds

Publications and source records attributed to A K Simonds.

At least 19 recordsLinked to original sources
PubMed2001

Impact of age on breathing and resistive pressure in people with and without sleep apnea.

We investigated the effect of age on breathing and total pulmonary resistance (RL) during sleep by studying elderly (>65 yr) and young (25-38 yr) people without sleep apnea (EN and YN, respectively) matched for body mass index (BMI). To determine the impact of sleep apnea on age-related changes in breathing, we studied elderly and young apneic patients (EA and YA, respectively) matched for apnea and BMI. In all groups (n = 11), breathing during periods of stable sleep was analyzed to evaluate the intrinsic variability of respiratory control mechanisms. In the absence of sleep apnea, the variability of the breathing was similar in the elderly and young [mean (+/- SD) coefficient of variation (CV) of tidal volume (VT); wake: EN 21.0 +/- 14.9%, YN 14.7 +/- 5.5%; sleep: EN 14.0 +/- 6.0%; YN 11.5 +/- 6.4%]. In patients with sleep apnea, breathing during stable sleep was more irregular, but there were no age-related differences (CV of VT; wake: EA 22.0 +/- 11.6%, YA 16.7 +/- 11.3%; sleep: EA 32.8 +/- 24.9%, YA 25.2 +/- 16.3%). In addition, EN tended to have a higher RL (n = 6, RL midinspiration, wake: EN 7.1 +/- 3.0; YN 9.1 +/- 6.4 cmH(2)O. l(-1). s, sleep: EN 17.5 +/- 11.7; YN 9.8 +/- 2.0 cmH(2)O. l(-1). s). We conclude that aging per se does not contribute to the intrinsic variability of respiratory control mechanisms, although there may be a lower probability of finding elderly people without respiratory instability.

Adult↗
PubMed2000

Outcome of paediatric domiciliary mask ventilation in neuromuscular and skeletal disease.

Noninvasive positive pressure ventilation delivered by nasal mask or facemask has been used widely in the last decade to manage chronic ventilatory failure in adults with neuromuscular and chest wall disease. However, it has been thought that paediatric patients would not be able to tolerate masks, and previous anecdotal reports on the paediatric application of mask ventilation have not assessed the effects on nocturnal and arterial blood gas control. Domiciliary mask ventilation has been used in 40 children with ventilatory insufficiency due to congenital neuromuscular and skeletal disease aged 9 months-16 yrs. Eighteen patients had symptomatic nocturnal hypoventilation, 17 had diurnal ventilatory failure, three were referred for weaning and two had frequent chest infections associated with sleep-disordered breathing. Thirty eight of the 40 patients tolerated mask ventilatory support long-term. Diurnal mean+/-SD oxygen tension in arterial blood (Pa,O2) increased from 8.5+/-1.8-10.9+/-1.7 kPa (p<0.001) and mean carbon dioxide tension in arterial blood (Pa,CO2) fell from 7.0+/-1.6-5.9+/-0.8 kPa (p=0.01) following initiation of ventilatory support. Mean and minimum nocturnal Pa,O2 and peak transcutaneous carbon dioxide tension (Ptc,CO2) (n=21) improved significantly. Mask ventilation can be used successfully in young children and reverses ventilatory insufficiency due to congenital neuromuscular and skeletal disease.

Adolescent↗
PubMed2000

Nasal ventilation in progressive neuromuscular disease: experience in adults and adolescents.

A nihilistic approach to ventilatory support in progressive neuromuscular disorders is no longer acceptable. Noninvasive ventilation may improve survival and quality of life in some patients. In other situations, worthwhile palliation of symptoms of nocturnal hypoventilation and dyspnoea may be achieved. Noninvasive ventilation combined with cough assistance may obviate the need for tracheostomy ventilation, or can be employed as part of a staged approach. Individual titration of ventilatory support to meet the needs of the individual and family is vital. The participation of the patient, family and carers in decision-making is crucial and advanced directives are likely to be used increasingly.

Adolescent↗
PubMed1999

Magnetic resonance navigator echo diaphragm monitoring in patients with suspected diaphragm paralysis.

Real-time magnetic resonance (MR) navigator echo (NE) monitoring of the diaphragm is now possible. Using this technique, temporal changes in diaphragm position can be analyzed in a non-invasive fashion, without x-ray exposure. In this preliminary study, we have optimized three NE parameters (the NE column area, the NE repeat time, and the location of the NE on the diaphragm surface), and demonstrated the clinical application of MR NE diaphragm monitoring in patients with suspected diaphragm paralysis. The NE parameters were defined in 10 healthy volunteers, and diaphragm traces were scored for variance in NE diaphragm position registration. Using the optimal NE column parameters, we investigated four patients with diaphragm paralysis, one of whom required positive pressure ventilation while in the MR scanner, to show the utility of this technique. The NE diaphragm position registration was significantly affected by the area of the NE column, with poor position registration for the smallest column area (2.25 cm2 vs. 4 cm2 vs. 6.25 cm2, variance 6.3 vs. 0.6 vs. 0.3, P = 0.006). Diaphragm position registration was also significantly affected by the NE repeat time, with misregistration for the shortest repeat time (250 msec vs. 500 msec vs. 1000 msec, variance 11.9 vs. 0.6 vs. 1.0, P = 0.02), and data clipping, with loss of end-expiratory and end-inspiratory position registration, for the longest repeat time. Finally, if the NE was positioned too anteriorly, the diaphragm traces were of poor quality (anterior vs. dome vs. posterior, variance 11.8vs. 0.6vs. 3.2, P < 0.001). Application of the technique confirmed diaphragm paralysis in all four patients. The technique can be applied during positive pressure ventilation if necessary. The optimal NE parameters for diaphragm monitoring at 0.5 T were: column area, 400 mm2; NE repeat time; 500 msec; NE column positioned on the diaphragm dome. MR NE diaphragm monitoring provides a safe, non-invasive method of assessing diaphragm motion in patients with suspected diaphragm paralysis and may prove useful for long-term follow-up and monitoring of therapeutic interventions in these subjects.

Adult↗
PubMed1999

A three-centre prospective pilot study to elucidate the effect of uvulopalatopharyngoplasty on patients with mild obstructive sleep apnoea due to velopharyngeal obstruction.

In this paper we describe the outcome of a prospective study designed to investigate the role of uvulopalatopharyngoplasty in the management of mild obstructive sleep apnoea. A group of 21 patients fulfilling strict inclusion and exclusion criteria underwent uvulopalatopharyngoplasty performed by a single surgeon using a modified technique. Specifically designed daily pain questionnaires were completed by the patients for 2 weeks after surgery and the morbidity associated with the procedure was assessed at 2, 6 and 12 weeks after operation. Thirteen of the 21 patients underwent a postoperative sleep study at 3 months after operation. The outcome measures used were the apnoea/hypopnoea index, the minimum O2 saturation, the sleep arousal index, the sleep architecture the Epworth Sleepiness Scale score, the subjective improvement in both the patient's and their partner's sleep and the morbidity associated with uvulopalatopharyngoplasty. We conclude that the patients with mild obstructive sleep apnoea most likely to obtain significant benefit from uvulopalatopharyngoplasty are those with a body mass index of between 27 and 30 with no cephalometric disproportion, those with frequent arousals not associated with periodic limb movements, those whose sleep related breathing disorder is not positional and most importantly those with symptomatic day time sleepiness.

Adult↗
PubMed1998

Nasal ventilation.

Nasal intermittent positive pressure ventilation is likely to have an increasing role in the management of acute ventilatory failure, weaning, and chronic ventilatory problems. Further improvements in ventilator and mask design will be seen. Appropriate application is likely to reduce both mortality and admissions to intensive care, while domiciliary use can improve life expectancy and/or quality of life in chronic ventilatory disorders. As with any new technique, enthusiasm should not outweigh clear outcome information, and possible new indications should always be subject to careful assessment.

Acute Disease↗
PubMed1998

Impact of nasal ventilation on survival in hypercapnic Duchenne muscular dystrophy.

BACKGROUND: Respiratory failure is the commonest cause of death in patients with Duchenne muscular dystrophy (DMD). Life expectancy is less than one year once diurnal hypercapnia develops. This study examines the effects of nasal intermittent positive pressure ventilation (NIPPV) on survival in symptomatic Duchenne patients with established ventilatory failure. METHODS: Nocturnal NIPPV was applied in 23 consecutive patients with DMD of mean (SD) age 20.3 (3.4) years who presented with diurnal and nocturnal hypercapnia. RESULTS: One year and five year survival rates were 85% (95% CI 69 to 100) and 73% (95% CI 53 to 94), respectively. Early changes in arterial blood gas tensions following NIPPV occurred with mean (SD) PO2 increasing from 7.6 (2.1) kPa to 10.8 (1.3) kPa and mean (SD) PCO2 falling from 10.3 (4.5) kPa to 6.1 (1.0) kPa. Improvements in arterial blood gas tensions were maintained over five years. Health perception and social aspects of SF-36 health related quality of life index were reported as equivalent to other groups with nonprogressive disorders using NIPPV. CONCLUSIONS: Nasal ventilation is likely to increase survival in hypercapnic patients with Duchenne muscular dystrophy and should be considered as a treatment option when ventilatory failure develops.

Adolescent↗
PubMed1998

Weaning difficulties.

All units providing ventilatory support will experience patients with weaning difficulties. The factors which contribute to weaning problems include the pathophysiology of the illness, the extent of underlying chronic disease, and equipment, physician-related and organisational issues. In this article ways to resolve these problems are outlined.

Female↗
PubMed1995

Outcome of domiciliary nasal intermittent positive pressure ventilation in restrictive and obstructive disorders.

BACKGROUND: Nasal intermittent positive pressure ventilation (NIPPV) is a new technique which has rapidly supplanted other non-invasive methods of ventilation over the last 5-10 years. Data on its effectiveness are limited. METHODS: The outcome of long term domiciliary NIPPV has been analysed in 180 patients with hypercapnic respiratory failure predominantly due to chest wall restriction, neuromuscular disorders, or chronic obstructive lung disease. One hundred and thirty eight patients were started on NIPPV electively, and 42 following an acute hypercapnic exacerbation. Outcome measures were survival (five year probability of continuing NIPPV), pulmonary function, and health status. A crossover study from negative pressure ventilation to NIPPV was carried out in a subgroup of patients. RESULTS: Five year acturial probability of continuing NIPPV for individuals with early onset scoliosis (n = 47), previous poliomyelitis (n = 30), following tuberculous lung disease (n = 20), general neuromuscular disorders (n = 29), and chronic obstructive pulmonary disease (n = 33) was 79% (95% CI 66 to 92), 100%, 94% (95% CI 83 to 100), 81% (95% CI 61 to 100), 43% (95% CI 6 to 80), respectively. Most of the patients with bronchiectasis died within two years. One year after starting NIPPV electively the mean (SD) PaO2 compared with the pretreatment value was +1.8 (1.9) kPa, mean PaCO2 -1.4 (1.3) kPa in patients with extrapulmonary restrictive disorders, and PaO2 +0.8 (1.0) kPa, PaCO2 -0.9 (0.8) kPa in patients with obstructive lung disease. Arterial blood gas tensions improved in patients transferred from negative pressure ventilation to NIPPV. Health status was ranked highest in patients with early onset scoliosis, previous poliomyelitis, and following tuberculous lung disease. In the group as a whole health perception was comparable to outpatients with other chronic disorders. CONCLUSIONS: The long term outcome of domiciliary NIPPV in patients with chronic respiratory failure due to scoliosis, previous poliomyelitis, and chest wall and pulmonary disease secondary to tuberculosis is encouraging. The results of NIPPV in patients with COPD and progressive neuromuscular disorders show benefit in some subgroups. The outcome in end stage bronchiectasis is poor.

Administration, Intranasal↗
PubMed1995

Nocturnal assisted ventilation using bilevel positive airway pressure: the effect of expiratory positive airway pressure.

Increasing expiratory positive airway pressure (EPAP) has theoretical advantages during overnight nasal ventilation. We wanted to evaluate the effect of the addition of EPAP upon the control of nocturnal hypoventilation. Seven patients with neuromuscular/skeletal (NMS) disorder (mean +/- SD forced vital capacity (FVC) 1.06 +/- 0.28 l, arterial oxygen tension (PaO2) 9.1 +/- 0.6 kPa, and arterial carbon dioxide tension (PaCO2) 6.9 +/- 0.9 kPa), and seven patients with chronic obstructive pulmonary disease (COPD) (FEV1 0.46 +/- 0.14 l, PaO2 6.2 +/- 0.6 kPa, and PaCO2 8.4 +/- 1.1 kPa) all underwent full polysomnography on two nights during bilevel positive airway pressure (BiPAP) ventilation, with and without the addition of expiratory positive airway pressure, which was matched to the level of dynamic positive end-expiratory pressure (PEEP) or set at a minimum value of 5 cmH2O. In the group with neuromuscular/skeletal disorders the maximum transcutaneous carbon dioxide tension (PtcCO2) overnight was lower (inspiratory positive airway pressure (IPAP) 8.1 +/- 1.4 kPa, IPAP/EPAP 7.3 +/- 0.9 kPa) and the minimum level of arterial oxygen saturation (SaO2 min) increased (IPAP 77.1 +/- 6.7%, IPAP/EPAP 83.6 +/- 4.2%) when expiratory positive airway pressure was added. There were no differences in mean PtcCO2 or mean oxygen saturation, but sleep quality was worse (non-rapid eye movement (non-REM) sleep IPAP 266 +/- 44 min, IPAP/EPAP 226 +/- 32 min). In the patients with COPD, expiratory positive airway pressure conferred no advantage.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗