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Biomedical subjects

A C Davidson

Publications and source records attributed to A C Davidson.

At least 19 recordsLinked to original sources
PubMed1996

A major outbreak of asthma associated with a thunderstorm: experience of accident and emergency departments and patients' characteristics. Thames Regions Accident and Emergency Trainees Association.

OBJECTIVE: To investigate the time course of an epidemic of asthma after a thunderstorm, characteristics of patients affected, and the demand on emergency medical resources. DESIGN: Study of registers and records in accident and emergency departments and questionnaire to staff. SETTING: London area. SUBJECTS: All patients presenting at 12 accident and emergency departments with asthma or other airway disease. MAIN OUTCOME MEASURES: Numbers of patients, clinical features, information on shortage of resources--equipment, drugs and staff. RESULTS: The epidemic had a sudden onset on 24 June 1994; 640 patients with asthma or other airways disease attended during 30 hours from 1800 on 24 June, nearly 10 times the expected number. Over half (365) the patients were aged 21 to 40 years. A history of hay fever was recorded in 403 patients; for 283 patients this was the first known attack of asthma; a history of chronic obstructive airways disease was recorded in 12 patients. In all, 104 patients were admitted (including five to an intensive care unit). Several departments ran out of equipment or drugs, called in additional doctors, or both. CONCLUSIONS: This study supports the view that this epidemic was larger than previously reported epidemics and the hypothesis that "thunderstorm associated asthma' is related to aeroallergens. Demands on resources were considerable; a larger proportion of patients needing intensive care would have caused greater problems.

Adult↗
PubMed1993

Thoracoscopy.

Explore the source record for details and available documents.

Humans↗
PubMed1992

Portable liquid oxygen and exercise ability in severe respiratory disability.

BACKGROUND: The development of portable liquid oxygen systems, capable of delivering high flow rate oxygen for long periods, justifies reassessment of the value of supplemental oxygen to aid exercise tolerance in patients with chronic respiratory insufficiency. The type of exercise test and the low oxygen flow rates previously used may account for the variable and often poor responses to supplemental oxygen reported in earlier studies. METHODS: The walking tolerance of 30 patients with severe respiratory disability was measured while they were breathing air and increasing doses of supplemental oxygen (2, 4, 6 1/min) by using both the standard six minute walking test and an endurance walking test. To assess the initial learning effect and repeatability of the walking tests, three six minute walks and three endurance walks were performed on day 1 and a single walk of each type on days 2, 3, and 14. In addition, oxygen dosing studies were performed on days 2 and 3 after the initial baseline walking tests. Each dosing study comprised four endurance walking tests or four six minute walking tests with patients breathing either air at a flow rate of 4 1/min from a portable cylinder or supplemental oxygen at a flow rate of 2, 4 or 6 1/min from a portable liquid oxygen supply. The order of the tests was randomised. Walking distance with each flow rate of oxygen was compared with walking distance with patients carrying cylinder air and for the initial unburdened walks. Breathlessness was assessed by visual analogue scoring on completion of each walk. RESULTS: Exercise ability and breathlessness were significantly improved with supplemental oxygen and this benefit outweighed the reduction in performance resulting from carrying the portable device. Supplemental oxygen at flow rates of 2, 4, and 6 1/min increased mean endurance walking distances by 37.9%, 67.7% and 85.0% and six minute walking distances by 19.2%, 34.5%, and 36.3% by comparison with distances when the patient was carrying air with a flow rate of 4 1/min. The additional work of carrying the portable gas supply reduced endurance walking distance by 22.2% and six minute walking distance by 14.1% by comparison with a baseline unburdened walk. Comparison of supplemental oxygen at 2, 4, and 6 1/min with the baseline unburdened performance showed increased endurance walking distances of 7.3%, 30.4%, and 43.9% and six minute walking distances of 2.3%, 15.5%, and 17.0%. Walking distance was increased by more than 50% by comparison with an unburdened walk in seven patients with the endurance walking test but in only three patients with the six minute walking test. The benefit was similar in patients with obstructive and with interstitial lung disease. Individual responses were variable and only desaturation during the baseline walk in patients with obstructive lung disease had any predictive value for benefit with oxygen. CONCLUSION: As there was no clear relation between response to oxygen therapy and the patients' characteristics, assessment for supplemental oxygen therapy will depend on exercise testing. It is suggested that portable oxygen should be considered only if a patient shows a 50% improvement in exercise ability with high flow rate oxygen (4-6 1/min) by comparison with an unburdened walk.

Ambulatory Care↗
PubMed1991

Non-invasive management of fever and breathlessness in HIV positive patients.

In a prospective study of 72 human immunodeficiency virus (HIV) positive patients presenting with fever and breathlessness, a non-invasive management protocol, incorporating a scanning technique using radioactively labelled diethylenetriamine penta acetate (DTPA) and sputum induction, was found to be highly sensitive and specific in the early detection of Pneumocystis carinii pneumonia (PCP). At presentation, the DTPA scan was abnormal in 34 of 36 cases of PCP, irrespective of smoking history, whilst the chest radiograph was diffusely abnormal in 21 cases. Sputum induction identified 7 of 14 patients with PCP in the first six months of its use and 7 of 10 patients over the last six months. The DTPA lung scan and induced sputum examination are non-invasive techniques which can be used to investigate out-patients. In combination they detected all cases of PCP at presentation, reduced the need for bronchoscopy, resulted in a low case fatality (5.4%) and reduced the need for admission.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Staphylococcal pneumonia, pneumatoceles, and the toxic shock syndrome.

A case of community acquired staphylococcal pneumonia is reported with the unusual complication, in an adult, of multiple pneumatoceles. Recognition of this prevented inappropriate management. The patient also developed the toxic shock syndrome. In contrast to infants with pneumatoceles, recovery of lung function has been poor.

Adult↗
PubMed1989

Atrial natriuretic peptide concentrations in hypoxic secondary pulmonary hypertension: relation to haemodynamic and blood gas variables and response to supplemental oxygen.

Plasma atrial natriuretic peptide concentrations, measured in samples drawn from the pulmonary artery, were raised in nine of 17 patients with hypoxic pulmonary hypertension but normal right atrial pressures at rest. No relationship was seen between atrial natriuretic peptide concentrations and mean pulmonary artery or right atrial pressure, or calculated pulmonary or systemic vascular resistance. Patients with the most severe hypoxaemia tended to have higher plasma atrial natriuretic peptide concentrations; three patients with no past history of oedema had concentrations more than twice the upper limit of normal. Treatment with supplementary oxygen for 30 minutes reduced pulmonary vascular resistance in all patients but had no significant effect on plasma atrial natriuretic peptide concentration. These findings suggest that atrial natriuretic peptide may be a factor in the control of sodium and water balance in hypoxic cor pulmonale, where the determinants of individual susceptibility to peripheral oedema are not well understood.

Aged↗
PubMed1988

Immunohistological localization of pregnancy-associated endometrial alpha 2-globulin (alpha 2-PEG) in endometrial adenocarcinoma and effect of medroxyprogesterone acetate.

Endometrium from postmenopausal women with endometrial adenocarcinoma was examined immunohistochemically using a monoclonal antibody to pregnancy-associated endometrial alpha 2-globulin (alpha 2-PEG), the major secretory protein of the glandular epithelium during the late luteal phase of the menstrual cycle and early pregnancy. Specimens were obtained at initial diagnostic curettage and at hysterectomy after medroxyprogesterone acetate (MPA) therapy. alpha 2-PEG was not detected in any malignant tissue irrespective of histological differentiation. Non-malignant endometrium obtained in association with malignant tissue was negative for alpha 2-PEG before treatment although after MPA therapy all specimens obtained exhibited marked alpha 2-PEG localization in glands. In four specimens endogenous alkaline phosphatase was observed consistently only in the malignant endometrium. Malignant endometrium does not appear to synthesize alpha 2-PEG nor is its synthesis induced by an oral progestogen, so that it does not represent a useful marker for endometrial carcinoma. Non-malignant endometrium in postmenopausal women appears to be fully capable of alpha 2-PEG production after stimulation with an oral progestogen.

Adenocarcinoma↗
PubMed1988

Supplemental oxygen and exercise ability in chronic obstructive airways disease.

The influence of supplemental oxygen on exercise performance was assessed in 17 patients with severe airflow obstruction. Exercise capacity was measured by the six minute walking distance, by an endurance walking test, and by an endurance cycling test and comparison was made with performance when the patient was breathing air. In addition, the relation between the flow rate of supplemental oxygen and cycling endurance time was studied. Portable oxygen (41 min-1) carried by the patient increased the mean endurance walking time by 59% and the six minute walking distance by 17%. The endurance time for cycling at a constant work load was increased by 51% with oxygen at a flow rate of 21 min-1, by 88% at 41 min-1, and by 80% at 61 min-1. Supplemental oxygen prolonged the length of time that the patients were able to walk at a fixed speed. It also increased the mean speed achieved during a six minute walk but this was variable and did not occur in all the subjects. The benefit from supplemental oxygen was not cancelled by the effort of carrying the portable cylinder.

Adult↗
PubMed1988

Thoracoscopy: assessment of a physician service and comparison of a flexible bronchoscope used as a thoracoscope with a rigid thoracoscope.

The practicality of physicians performing thoracoscopy for diagnostic purposes was assessed in 30 patients with pleural effusions of unknown cause. A rigid thoracoscope was compared with a fibreoptic bronchoscope used as a flexible thoracoscope and the diagnostic adequacy of biopsy specimens obtained with the two instruments assessed. The two instruments were inserted by a physician in the bronchoscopy suite using local anaesthesia. The procedure proved safe, acceptable, and diagnostically effective. The rigid thoracoscope proved a more satisfactory instrument but the fibreoptic bronchoscope, with minor adaptations, may be used for thoracoscopy.

Biopsy↗
PubMed1987

Distal intestinal obstruction syndrome in cystic fibrosis treated by oral intestinal lavage, and a case of recurrent obstruction despite normal pancreatic function.

An oral intestinal lavage solution has been successfully used in the treatment of six patients with chronic distal intestinal obstruction syndrome (previously referred to as meconium ileus equivalent) complicating cystic fibrosis and a further case of recurrent small bowel obstruction. The patient with recurrent obstruction is unusual in having no evidence of pancreatic maldigestion, which previously has been considered a prerequisite for the syndrome.

Acute Disease↗
PubMed1986

The influence of topical anaesthetic agent at bronchoalveolar lavage upon cellular yield and identification and upon macrophage function.

The influence of cocaine and lignocaine as local anaesthetic agent upon the results obtained at bronchoalveolar lavage was investigated. No differences were found. A functional activity of macrophages was assessed when the cells were stored in lavage fluid. A time-dependent decrease occurred which was related to lack of nutrients rather than the anaesthetic concentration.

Bronchi↗
PubMed1985

Ventilatory control in normal man following five minutes' exposure to hypoxia.

Ventilatory control was studied in normal subjects following brief (5 min) exposure to hypoxia (inhalation 7-8% O2). The ventilatory response to rebreathing CO2 (hyperoxic) was assessed 20 min before and after 5 min exposure to (a) 7-8% O2, (b) 7-8% O2 rebreathing CO2, (c) rebreathing CO2 during hyperoxia, and (d) 10% O2, normocapnic. The slope of the V-PCO2 response (S) was increased for up to 40 min following (a) and (b) by 25-34%, but was unchanged following (c) and (d). Resting ventilation was unchanged throughout. The ventilatory response to normocapnic progressive hypoxia was measured as the slope of the V-Hb% SaO2 relationship (H); this was increased by 26%. The mechanism underlying this change in ventilatory control in man is unknown; it may relate to the process of acclimatization to hypoxia whereby chronic hypoxia is a greater stimulus to ventilation than acute hypoxia.

Acclimatization↗