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Biomedical subjects

G J Gibson

Publications and source records attributed to G J Gibson.

At least 37 records · Page 2Linked to original sources
PubMed2003

Subclinical aspirin sensitivity in subjects with nasal polyposis.

It is unclear whether subclinical airway responses to aspirin occur in subjects with nasal polyps and/or asthma without overt sensitivity. Sixty-three subjects without known aspirin sensitivity (13 controls, 17 nasal polyps alone, 15 nasal polyps and asthma and 18 asthma alone) inhaled increasing concentrations of nebulized lysine aspirin. Forced expiratory volume in 1 s (FEV1), symptoms and other potential markers of an airway response were measured. Four subjects (one polyps alone, one asthma alone, two with both) had a positive response to lysine aspirin predefined as symptoms plus a >10% fall in FEV1 from baseline. However, there was no evidence of a general subclinical response in any of the subject groups: mean (95% CI) change in FEV1; control 0.07 (-0.02,0.16) L, nasal polyps alone -0.05 (-0.16,0.05) L, nasal polyps with asthma -0.03 (-0.10,0.04) L, asthma alone -0.03 (-0.09,0.03) L. We concluded that in the absence of a suggestive clinical history, only a small proportion of patients with nasal polyposis are likely to be sensitive to aspirin. There is no evidence of general subclinical sensitivity to aspirin in subjects with nasal polyps and no relevant history.

Adult↗
PubMed2003

Erdheim-Chester disease: pulmonary infiltration responding to cyclophosphamide and prednisolone.

Erdheim-Chester disease is a rare multisystem histiocytic disorder in which death most commonly results from pulmonary or cardiac involvement. We report the case history of a 55 year old man with this condition with extensive and progressive pulmonary disease. He had no response to prednisolone alone, but treatment with prednisolone plus cyclophosphamide was associated with a rapid improvement in symptoms, lung function, and the chest radiographic appearance. He subsequently showed a symptomatic, functional, and radiological deterioration, followed by a marked slowing in the rate of decline. He currently remains stable 41 months after treatment was initiated. This is the first report of pulmonary Erdheim-Chester disease showing improvement in both lung function and symptoms with any form of treatment.

Anti-Inflammatory Agents↗
PubMed2002

Non-invasive ventilation in motor neuron disease: current UK practice.

OBJECTIVE: To evaluate the clinical application of non-invasive ventilation (NIV) in motor neuron disease (MND) in the UK. METHOD: We conducted a postal survey of the current clinical practice of all consultant neurologists in the UK, with a second mailing to non-responders after 6 weeks. The principal outcome measures assessed were: 1. the percentage of patients with MND receiving NIV, 2. access to a NIV service, 3. routine monitoring of respiratory function, and 4. influence of symptoms, respiratory function, rate of disease progression, level of disability and bulbar involvement on referral for NIV. RESULTS: The response rate was 76%, 1719 new patients had been diagnosed in the preceding 12 months and a total of 2280 patients were under review. Of these, 126 were currently receiving NIV (5.5% of patients under review, estimated 2.6-3.5% of all MND patients). Most neurologists (172/265) had referred no patients for NIV in the preceding year, while three neurologists made 30% of all referrals nationally. Referral was based primarily on symptoms, and was influenced by the number of MND patients under review, level of disability, rate of disease progression and availability of a NIV service. Bulbar involvement was considered a relative contra-indication to NIV by 51% of responders. CONCLUSIONS: In the UK, few patients with MND are treated with NIV. There is marked variation in clinical practice. This may reflect uncertainty about the role of non-invasive ventilation in MND, and emphasizes the need for a randomized controlled trial to assess the impact of NIV on quality of life and survival.

Humans↗
PubMed2002

Sleep-disordered breathing following acute stroke.

BACKGROUND: The reported prevalence of sleep apnoea following stroke varies between 44% and 72%, but its course and relations are unclear. AIM: To determine the prevalence and course of sleep-disordered breathing in acute stroke in-patients, and its relation to age, stroke subtype, pre-stroke handicap and post-stroke outcome. DESIGN: Prospective uncontrolled observational study. METHODS: Paired respiratory sleep studies were performed at week 2 and week 6-9 following stroke. Pre- and post-stroke handicap (modified Rankin Score) and week 2 and week 6-9 disability (Barthel Score) and impairment (Scandinavian Neurological Stroke Score) were assessed. Pre-stroke sleepiness was determined by Epworth Score. RESULTS: There were 68 patients in the week 2 study, and 50 in the week 6-8 study. Mean week 2 Apnoea Hypopnoea Index (AHI) was 30; 64 patients (94%) had an AHI > or =10. Mean AHI was higher in subjects with lacunar vs. cortical strokes (44 vs. 28, p<0.05), in subjects aged > or =65 years (32 vs. 21, p<0.05) and in those with greater pre-stroke handicap (modified Rankin Score 2 vs. <2) (41 vs. 27, p<0.05). In 50 paired studies, mean AHI fell from 31 to 24 (p<0.01) and the proportion with AHI > or =10 fell from 96% to 72%. Pre-stroke sleepiness was associated with post-stroke neurological impairment (r=-0.325, p<0.05) and disability (r=-0.377, p<0.05). DISCUSSION: Sleep-disordered breathing improves in the first 6-9 weeks following stroke, but remains highly prevalent. Worse sleep-disordered breathing was observed following lacunar stroke, and in older subjects or those with pre-stroke handicap.

Acute Disease↗
PubMed2002

A novel hypothesis to explain the bronchconstrictor effect of deep inspiration in asthma.

BACKGROUND: In healthy subjects deep inspiration transiently dilates the airways, while many asthmatic subjects show bronchoconstriction by a mechanism which is incompletely understood. We hypothesised that the negative intrathoracic pressure associated with deep inspiration occurring in the context of increased leakiness of the airway vasculature may temporarily increase airway oedema and thus reduce luminal diameter in subjects with asthma. METHODS: The effects of non-forced deep inspiration and forced deep inspiration through resistance (generating enhanced negative intrathoracic pressure) on specific airway conductance (sGaw) were compared in 10 asthmatic and 11 healthy subjects. Each performed two respiratory manoeuvres: (1) sGaw was measured immediately after three deep inspirations without added resistance, each performed at a predetermined rate (equal to that when performed maximally through resistance); and (2) sGaw was measured immediately after three forced inspirations through resistance. RESULTS: Compared with deep inspiration without added resistance, sGaw was significantly reduced after deep inspiration through resistance in the asthmatic group by a mean (SD) of -13.5 (11.0)% (p=0.003) but was unchanged in the control group (-0.5 (12.4)%, p=0.67). CONCLUSIONS: Given the similar time-volume relationship in the two manoeuvres, the reduction in sGaw is unlikely to be due to differences in smooth muscle behaviour. It is suggested that the enhanced negative intrathoracic pressure acting across the airway capillaries increases airway wall oedema and reduces airway calibre. Such a mechanism operational during normal rapid deep inspiration might contribute to bronchoconstriction after deep inspiration in subjects with asthma.

Adult↗
PubMed2002

Sleep and breathing in neuromuscular disease.

Respiratory muscle weakness in neuromuscular disease causes significant morbidity and mortality. The published data on respiratory muscle activity and breathing during sleep in normal subjects, the impact of respiratory muscle weakness on sleep and breathing and the relations to daytime respiratory function in neuromuscular disease are reviewed here. In normal subjects during sleep upper airway resistance increases, chemosensitivity is reduced and the wakefulness drive to breathe is lost, resulting in a fall in ventilation. During rapid eye movement (REM) sleep, ribcage and accessory breathing muscles are suppressed, particularly during bursts of eye movements, and breathing is more irregular, rapid and shallow, with a further fall in ventilation. In subjects with respiratory muscle weakness sleep is fragmented, with shorter total sleep time, frequent arousals, an increase in stage 1 sleep and a reduction in, or complete suppression of, REM sleep. Sleep-disordered breathing and nocturnal desaturation are common and most severe during REM sleep. Correlations between daytime respiratory function and nocturnal desaturation are moderate or weak, but daytime respiratory function has greater prognostic value than nocturnal measurements. Noninvasive ventilation improves sleep quality and breathing in subjects with respiratory muscle weakness. However, the optimal criteria for initiation of ventilation and its role in rapidly progressive neuromuscular diseases are unclear.

Humans↗
PubMed2001

Respiratory function vs sleep-disordered breathing as predictors of QOL in ALS.

BACKGROUND: Most patients with ALS have evidence of respiratory muscle weakness at diagnosis, and death is usually due to respiratory failure. Sleep disruption, possibly due to apneas, hypopneas, orthopnea, or REM-related desaturation, is common. The relative impact of these factors on quality of life has not been established. METHODS: The authors recruited 23 subjects with probable or definite ALS. Quality of life was assessed using generic and specific instruments, and respiratory muscle strength by measurement of vital capacity, maximum static pressures, and sniff nasal inspiratory pressure. Twenty-two subjects underwent polysomnography. Overall limb and axial muscle strength was estimated using a summated muscle score based on the Medical Research Council clinical scale. RESULTS: On univariate analysis, there were moderate to strong correlations between quality of life and all measurements of respiratory muscle function (R = 0.42-0.82). The correlations with selected polysomnographic indices were weaker and less consistent (R = 0.44-0.59). Multivariate analysis showed that maximum static inspiratory pressure was the strongest independent predictor of quality of life. CONCLUSION: Quality of life was strongly and independently related to respiratory muscle function. Relations with polysomnographic indices were weaker and were attributable to respiratory muscle weakness. Respiratory muscle weakness is much more important than the frequency of apneas and hypopneas in determining quality of life in ALS.

Adult↗
PubMed2001

Comparing approximations to spatio-temporal models for epidemics with local spread.

Analytical methods for predicting and exploring the dynamics of stochastic, spatially interacting populations have proven to have useful application in epidemiology and ecology. An important development has been the increasing interest in spatially explicit models, which require more advanced analytical techniques than the usual mean-field or mass-action approaches. The general principle is the derivation of differential equations describing the evolution of the expected population size and other statistics. As a result of spatial interactions no closed set of equations is obtained. Nevertheless, approximate solutions are possible using closure relations for truncation. Here we review and report recent progress on closure approximations applicable to lattice models with nearest-neighbour interactions, including cluster approximations and elaborations on the pair (or pairwise) approximation. This study is made in the context of an SIS model for plant-disease epidemics introduced in Filipe and Gibson (1998, Studying and approximating spatio-temporal models for epidemic spread and control, Phil. Trans. R. Soc. Lond. B 353, 2153-2162) of which the contact process [Harris, T. E. (1974), Contact interactions on a lattice, Ann. Prob. 2, 969] is a special case. The various methods of approximation are derived and explained and their predictions are compared and tested against simulation. The merits and limitations of the various approximations are discussed. A hybrid pairwise approximation is shown to provide the best predictions of transient and long-term, stationary behaviour over the whole parameter range of the model.

Cluster Analysis↗
PubMed2001

Nutritional status of patients undergoing lung cancer operations.

BACKGROUND: Patients referred for lung cancer operations were reported to be nutritionally depleted. This may be relevant in determining patient outcome after surgical procedures. A study was undertaken to measure a range of nutritional variables including dietary intake of patients referred to a regional cardiothoracic center for curative lung cancer operations. METHODS: Anthropometric measurements, grip strength, fat-free mass (FFM), serum protein concentrations, lymphocyte count, creatinine-height index, subjective global assessment, and data on daily intakes of energy, protein, and vitamin C were collected prospectively. Anthropometric indices were also measured in a group of control patients with mild chronic obstructive pulmonary disease. RESULTS: Sixty patients and 22 control patients were recruited. Weight, skin-fold thickness, and grip strength were not significantly different between patients and control patients, and both groups were similar to the general population. However, 8 patients (13.3%) had a body mass index (BMI) less than 20, and 14 patients (24.1%) had a fat-free mass index less than 15. Serum albumin and transferrin concentrations and lymphocyte count were very rarely depressed but prealbumin and retinol-binding protein levels were below normal in 11.9% and 8.3% of patients, respectively. Thirty percent of patients reported low energy intake, 13% reported a low protein intake, and 61.7% had reduced vitamin C intake. CONCLUSIONS: Severe nutritional depletion was uncommon in patients referred for operations for lung cancer and its frequency may have been overestimated in some previous reports. A low intake of vitamin C was common in our patients but its clinical significance is unclear.

Adult↗
PubMed2001

The influence of nutritional status on complications after operations for lung cancer.

BACKGROUND: Nutritional status is known to play an important role in determining outcome after many types of operations but its importance relative to nonnutritional indices in patients undergoing an operation for lung cancer is unclear. METHODS: Detailed nutritional and nonnutritional assessment of 52 patients undergoing surgical resection of lung cancer was performed. The frequency of postoperative complications and length of intercostal drainage time were recorded, and the relation between preoperative indices and postoperative outcome was assessed. RESULTS: Patients who died or needed reventilation had poorer nutritional status, worse lung function, and lower maximum expiratory pressures than those who did not. Using multiple logistic regression, the best model (R2 = 0.39) to predict death combined operation type, preoperative carbon monoxide transfer factor (% predicted), and maximum expiratory pressure (% predicted). Operation type and the fat-free mass index (FFMI) alone were only slightly less informative (R2 = 0.35). For reventilation the best model (R2 = 0.80) combined operation type, body mass index (BMI), and maximum expiratory pressure (% predicted). Intercostal drainage time after lobectomy was significantly related only to preoperative lymphocyte count (p = 0.004) and subjective global assessment score (p = 0.02). CONCLUSIONS: Impaired nutrition is an important predictor of death and the need for reventilation after an operation for lung cancer, and the selection of patients for lung resection might be improved by measuring simple nutritional indices such as BMI and the FFMI.

Aged↗
PubMed2001

Lung volumes and elasticity.

The respiratory system is an elastic structure changing volume when pressures are generated by inspiratory or expiratory muscles. If the muscles are relaxed the respiratory system returns to its relaxation volume (Vr) (referred to in the pediatric literature as the elastic equilibrium volume [EEV]), which in normal subjects is the end-expired volume or functional residual capacity, FRC, where alveolar pressure is equal to atmospheric pressure.

Elasticity↗
PubMed2001

Degradation of the cartilage collagen matrix associated with changes in chondrocytes in osteoarthrosis. Assessment by loss of background fluorescence and immunodetection of matrix components.

Articular cartilage damage and eventual loss is the primary pathological change seen in osteoarthrosis (OA). In this study we have investigated the link between turnover of the collagen matrix and changes in chondrocytes. The background fluorescence of articular cartilage, as indicated by its emission spectrum and resistance to extraction was generated by the slow non-enzymic modification of the collagen matrix by advanced glycation end products (AGEs). Assessment of changes in background fluorescence in sections of articular cartilage provided a narrative of collagen degradation. Patients without OA pathology typically had a uniform strong background fluorescence throughout the depth of the cartilage. Cartilage from OA patients showed a range of changes in background fluorescence dependent on depth from the articular surface and proximity to overt lesions. Loss of background fluorescence was centered on chondrocytes, more extensive near the surface and associated with detection of the proteoglycan epitope 7D4. Expression of type X collagen was seen in articular cartilage in the region of the interface of with subchondral bone in most OA patients but was not associated with prominent, pericellular, loss of background fluorescence. These observations are consistent with progressive cartilage damage in OA, whereby collagen turnover and loss of surface integrity is associated with chondrocyte activity similar to that seen in immature articular cartilage.

Aged↗
PubMed2001

Influence of nonenzymatic glycation on biomechanical properties of cortical bone.

In this study, the influence of nonenzymatic glycation (NEG) on the mechanical properties of bone and bone collagen were investigated. Bovine cortical bone specimens were incubated in ribose to cause collagen cross-links in vitro, and nondestructive mechanical testing was used to determine tensile and compressive elastic modulus as a function of incubation time. Mechanical properties associated with yield, postyield, and final fracture of bone were determined at the end of the incubation period. The stiffness of the collagen network was measured using stress relaxation tests of demineralized bone cylinders extracted periodically throughout the incubation period. It was found that accumulation of nonenzymatic glycation end-products in cortical bone caused stiffening of the type I collagen network in bone (r2 = 0.92; p < 0.001) but did not significantly affect the overall stiffness of the mineralized bone (p = 0.98). The ribosylated group had significantly more NEG products and higher yield stress and strain than the control group (p < 0.05). Postyield properties including postyield strain and strain energy were lower in the ribosylated group but were not significantly different from the control group (p = 0.24). Compared with the control group, the ribosylated group was characterized by significantly higher secant modulus and lower damage fraction (p < 0.05). Taken together, the results of this study suggest that collagen in bone is susceptible to the same NEG-mediated changes as collagen in other connective tissues and that an increased stiffness of the collagen network in bone due to NEG may explain some of the age-related increase in skeletal fragility and fracture risk.

Animals↗
PubMed2001

The apparent response of airway function to deep inspiration depends on the method of assessment.

The response to deep inspiration (DI) has been reported in terms of specific airway conductance (SGaw) pre- and post-DI, and by comparing forced expiratory flows following both maximal and partial inspiration (M/P ratio). The lung volume at which M/P has been obtained has varied between studies. We have investigated how the method of assessment affects the apparent response to DI. In 16 asthmatic and 16 control subjects both SGaw and M/P were measured, the latter at various lung volumes from 40 to 15% vital capacity (VC) (remaining). In each group M/P increased as lung volume decreased (r=-0.98, P<0.001 for each group). In contradistinction to M/P ratio, the SGaw ratio (post-DI: pre-DI) suggested a bronchoconstrictor asthmatic response (mean 0.938, SEM 0.029) and a bronchodilator control response (mean 1.063, SEM 0.029). SGaw ratio and M/P were correlated strongly in normals but not in asthmatics. These results confirm that the observed response to DI depends on the method used to measure it. The results in normals are explicable by DI-induced smooth muscle stretch increasing unstressed airway calibre, but also increasing compressibility on forced expiration. The results in asthma suggest the existence of an additional DI-related bronchoconstricting mechanism.

Adult↗
PubMed2001

Ex-vivo product performance of Diskus and Turbuhaler inhalers using inhalation profiles from patients with severe chronic obstructive pulmonary disease.

Dosing performance of dry powder inhalers is dependent on patient's inspiratory effort. This study compares the inhalation profiles generated by patients with severe obstructive lung disease using Diskus and Turbuhaler inhalers. The patient profiles are subsequently used to determine the dosing performance of fluticasone propionate Diskus and budesonide Turbuhaler inhalers. Inhalation profiles were recorded in COPD patients (FEV1 < or = 30% predicted) as they inhaled with maximal effort through the inhalers. The profiles were used in an inhalation simulator to assess the dosing performance by measuring the total emitted dose and the fine particle mass for each inhaler type. Peak inspiratory flow was significantly higher through the Diskus (mean 82.31 min(-1)) compared with Turbuhaler (mean 53.51 min(-1), difference = 28.8 l min(-1); P < 0.0001). In addition, in direct comparison of the two devices. the Diskus was shown to deliver a more consistent dose irrespective of flow than the Turbuhaler in this patient population. These findings may be of importance in optimising selection of devices for patients with severe airway obstruction.

Aged↗
PubMed2001

Pharyngoesophageal pressure monitoring in sleep apnea syndrome.

OBJECTIVES: This study tests the sensitivity and the specificity of overnight pharyngoesophageal pressure measurement for identification and classification of obstructive sleep apnea (OSA). METHODS: Fifty-nine snoring patients undergoing polysomnography were invited to have simultaneous pharyngoesophageal manometry. We used a soft silicone catheter with 4 microtip pressure sensors at different levels. RESULTS: The apnea hypopnea indexes (AHIs) measured by the 2 methods were highly correlated (r = 0.971). Manometry was 100% sensitive and specific in excluding OSA and identifying severe OSA. It was 90% sensitive in identifying moderate OSA and 80% sensitive in identifying mild OSA. CONCLUSION: Overnight ambulatory pharyngoesophageal manometry is a reliable tool for the exclusion of OSA and identification of severe OSA. It has additional advantages of localizing the level of obstruction and identifying the upper airway resistance syndrome and can be performed at home. It is cost-effective when compared with polysomnography and may aid in treatment selection for individual patients.

Adult↗