Biomedical subjects
R S Howard
Publications and source records attributed to R S Howard.
Surface EMG in the recording of fasciculations.
The usefulness of multichannel surface recording of fasciculations was evaluated by a retrospective study of 116 patients with various neurological disorders. Eight channels of a conventional electroencephalograph were used with plate electrode recordings from the upper arms and legs. Wide-spread fasciculations (defined as five or more of the eight muscle groups) were recorded in 48 of 54 patients with motor neuron disease, spinal muscular atrophy or postpolio syndrome, but noted on routine clinical examination at presentation in only 6. Eleven of 23 patients with peripheral neuropathy or myelopathy had fasciculations in five or more leads compared to one clinically, and 3 of 39 with other neurological diseases had fasciculations electrically but in only one were they clinically observed. The method is a noninvasive and sensitive adjunct to clinical examination for detecting fasciculations. Its diagnostic value is limited by the relatively high incidence of fasciculations in neuropathies and myelopathies. However, this study suggests that "false negatives" are rare and that the diagnosis of motor neuron disease should be reconsidered when less than five leads shows fasciculations.
Respiratory involvement in multiple sclerosis.
Respiratory complications occur in advanced multiple sclerosis (MS) but may also complicate acute relapses earlier in the disease. We present 19 patients with MS who developed respiratory complications at a mean of 5.9 (range 1-12) yrs after the onset of neurological symptoms. Fourteen patients developed severe respiratory insufficiency presenting with a combination of reduced forced vital capacity (FVC), hypoxaemia or hypercapnia (12 patients) and respiratory arrest (four patients). Two patients presented with apneustic breathing, one with paroxysmal hyperventilation, one with obstructive sleep apnoea and one with bulbar weakness leading to aspiration pneumonia. Respiratory muscle weakness was a major factor in 14 patients (predominantly diaphragm involvement in six), bulbar weakness in seven patients, impaired voluntary control in three and impaired automatic control in three. Twelve patients received mechanical respiratory support of whom seven have subsequently died. The methods of support used were intermittent positive pressure ventilation (nine patients), iron lung (three), cuirass (two) and rocking bed (one). Six patients were maintained on respiratory support until they died after intervals varying from 24 h to 6 yrs (mean 17.7 mths). Five patients received temporary ventilation for between 6 d and 42 d: of these four remain alive at up to 4 yrs and one died after 16 yrs. One patient remains on domiciliary nasal intermittent positive pressure ventilation (IPPV) after 1 yr.
Ice cream scooper's hand. Report of an occupationally related stress fracture of the hand.
Stress fracture of the hand is uncommon but can be a significant source of morbidity if not promptly diagnosed. The authors present a case of metacarpal stress fracture in which the occupational history was key to the diagnosis and management of long-standing hand pain.
Transient amnesia heralding brain stem infarction.
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Glomerulonephritis in sarcoidosis: causal relationship unproven.
Two patients with sarcoidosis and glomerular mesangial proliferative lesions are described. Although a causative relationship between sarcoidosis and glomerulonephritis has been suggested, critical review of the literature fails to confirm this.
Bronchial vasodilation by histamine in sheep: characterization of receptor subtype.
Histamine has been shown to mediate features of pulmonary allergic reactions including increased tracheobronchial blood flow. To determine whether the increase in blood flow was due to stimulation of H1- or H2-histamine receptors, we gave histamine base (0.1 micrograms/kg iv) or histamine dihydrochloride as an aerosol (10 breaths of 0.5% "low dose" or 5% "high dose") before and after H1- or H2-receptor antagonists. Blood velocity in the common bronchial branch of the bronchoesophageal artery (Vbr) was continuously measured using a chronically implanted Doppler flow probe. Pretreatment with H2-receptor antagonists cimetidine, ranitidine, or metiamide did not affect the increase in Vbr induced by intravenous histamine [106 +/- 45% (SD)]. Addition of the H1-receptor antagonists diphenhydramine or chlorpheniramine, however, reduced the Vbr response to 16 +/- 22, 21 +/- 28, 23 +/- 23, and 37 +/- 32% of the unblocked responses (P less than 0.05) when intravenous histamine was given at 3, 10, 20, and 30 min, respectively, after the H1 antagonist. At 40, 50, and 60 min the H1-receptor blockade appeared to attenuate, but subsequent continuous infusion of chlorpheniramine (2 mg.kg-1.min-1) then blocked the histamine response for 60 min. Low-dose histamine aerosol did not change mean arterial or pulmonary arterial pressures, cardiac output, or arterial blood gases but increased Vbr transiently from 15.2 +/- 3.4 to 37.6 +/- 8.4 (SE) cm/s. After chlorpheniramine, the Vbr response to histamine, 16.3 +/- 2.2 to 22.6 +/- 3.6 cm/s, was significantly reduced (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Sensitivity and specificity of bronchial provocation testing. An evaluation of four techniques in exercise-induced bronchospasm.
The thresholds used to define a positive result for bronchial provocation challenges (BPC) are arbitrary. Requiring smaller decrements in expired flow to define a positive study would capture more cases of reactive airways (increased sensitivity) but would include some "normal" responses (decreased specificity). To examine the relationship between threshold definition and the ability to correctly classify subjects as either normal or as having airways hyperresponsiveness (AHR), four different BPC tests were administered on different days to 20 patients with a clinical diagnosis of exercise-induced bronchospasm (EIB) and 20 control subjects. The four BPC tests were indoor exercise on a cycle ergometer, methacholine inhalation challenge (MIC), eucapnic voluntary hyperventilation (EVH) with dry gas, and EVH with cold gas. Our results indicate that the thresholds which best separate the two groups are different for each of the four BPC techniques. For methacholine inhalation (MIC), a fall in FEV1 (d%FEV1) of 15 percent or greater at 188 cumulative breath units was 100 percent specific for AHR but had a sensitivity of only 55 percent. Eucapnic voluntary hyperventilation (EVH) with room temperature dry gas was 100 percent specific at a d%FEV1 of 11 percent, but, at that threshold, sensitivity was only 50 percent. EVH with cold air was 100 percent specific at a d%FEV1 of 12 percent but sensitivity was only 35 percent. The bicycle ergometer challenge was far too insensitive to be of value in evaluating AHR. Based on their respective receiver operating characteristic curves, the best separation of the two subject groups occurred at a d%FEV1 of 5 percent and 12 percent for the two EVH techniques and MIC, respectively. An individual's response to one test was highly correlated with the response to either of the other two (r = 0.66, p less than 0.001 for dry vs cold gas EVH; r = 0.56, p less than 0.001 for dry gas EVH vs methacholine; and r = 0.69, p less than 0.001 for cold gas EVH vs methacholine). Thus, MIC and EVH techniques are equally useful in defining AHR and each has its optimal threshold for a positive test result.
Long-term followup of asymptomatic microhematuria.
We present a 10 to 20-year followup assessment of 191 patients with unexplained microhematuria (including persons with insignificant lesions). Genitourinary malignancies did not develop in any of the patients (128 alive and 27 dead) evaluated after the first diagnostic investigation. Patient and physician compliance with followup protocols was poor. We currently recommend renal ultrasound and cystoscopy for the first diagnostic survey, have abandoned routine periodic studies and advise diagnostic studies only for patients in whom symptoms develop.
Mycobacterium fortuitum pulmonary infection complicating achalasia.
Achalasia is a cause of chronic aspiration pneumonia that may be complicated by pulmonary infection with Mycobacterium fortuitum. In any patient with achalasia, the presence of a pulmonary infiltrate that does not respond to routine antibiotic therapy should suggest the possibility of M fortuitum pulmonary infection, and sputum should be cultured for these organisms.
The effects of opiates on the respiratory activity of thoracic motoneurones in the anaesthetized and decerebrate rabbit.
1. Efferent discharges were recorded from inspiratory and expiratory intercostal nerve filaments (T2-T10) in artificially ventilated, anaesthetized or decerebrate rabbits with or without vagotomy. 2. Hypocapnic apnoea was used to study the fractional end-tidal CO2 (FET,CO2)-dependent tonic discharges of the expiratory motoneurones, the FET,CO2 threshold for rhythm generation and the FET,CO2 response curve of both inspiratory and expiratory burst activity. 3. Incremental doses of morphine (e.g. 1 mg kg-1 I.V.) produced slowing of the respiratory rhythm due to prolongation of the expiratory duration and an elevation of the FET,CO2 threshold for rhythm generation. Eventually apnoea supervened with associated tonic firing of the expiratory motoneurones. At the elevated levels of FET,CO2 bursts of inspiratory activity, with concomitant phasic inhibition of the tonic expiratory activity, could occur either spontaneously or following sensory stimulation. The peak integrated activities of these bursts were closely similar to the values obtained for corresponding levels of FET,CO2 before the administration of morphine. 4. Tonic expiratory activity responded to increased levels of FET,CO2, as it had during hypocapnic apnoea prior to morphine, by an increased discharge frequency of single units or recruitment of new units. 5. All of these effects of morphine were immediately reversed by naloxone (100 micrograms kg-1). 6. Naloxone (greater than 100 micrograms kg-1), without pre-treatment with morphine, led to an increase in respiratory frequency due to a shortening of the expiratory duration and a dose-dependent reduction in the FET,CO2 threshold for rhythm generation. There was little alteration either in the inspiratory response to FET,CO2 during rhythm or in the FET,CO2 response of the expiratory output whether expressed as tonic activity during hypocapnic apnoea or phasic activity following the onset of rhythm. 7. Thus opiates act upon the mechanisms of rhythm generation without depressing the FET,CO2 drive as expressed either as phasic or tonic activation of the motoneurones.
Congenital tracheobronchomegaly (Mounier-Kuhn syndrome): a report of 10 cases and review of the literature.
Mounier-Kuhn syndrome is a congenital abnormality of the trachea and main bronchi characterized by atrophy or absence of elastic fibers and thinning of muscle, which allows the trachea and main bronchi to become flaccid and markedly dilated on inspiration with narrowing or collapse on expiration or cough. The abnormal airway dynamics and pooling of secretions in broad outpouchings of redundant musculomembranous tissue between the cartilaginous rings predispose to the development of chronic pulmonary suppuration, bronchiectasis, emphysema, and pulmonary fibrosis. A broad spectrum of clinical abnormalities has been documented in Mounier-Kuhn syndrome, ranging from minimal disease with good preservation of pulmonary function to progressive disease leading to respiratory failure and death. In the appropriate clinical setting, Mounier-Kuhn syndrome is diagnosed in women from chest radiographs when the transverse and sagittal diameters of the trachea exceed 21 mm and 23 mm, respectively, and when the transverse diameters of the right and left main bronchi exceed 19.8 mm and 17.4 mm, respectively. In men it is diagnosed when the transverse and sagittal diameters of the trachea exceed 25 mm and 27 mm, respectively, and when the transverse diameters of the right and left main bronchi exceed 21.1 mm and 18.4 mm, respectively. The diagnosis can be confirmed easily by computed tomography.
EEG appearances in acute carbamazepine toxicity.
A 16-year-old woman deliberately took a large, toxic overdose of carbamazepine and recovered despite a high plasma level. During the acute phase the EEG was dominated by occipital delta activity suggestive of a brainstem disorder. Following 24-h treatment with activated charcoal the plasma carbamazepine was cleared and the EEG returned to normal.
Respiratory complications and their management in motor neuron disease.
Although respiratory insufficiency is common in the advanced stages of motor neuron disease, some patients may develop distressing respiratory symptoms early in the course of the disease or even present with respiratory failure or arrest. We describe 14 patients with motor neuron disease who were considered for respiratory support; 11 received such support and all derived significant symptomatic improvement without distressing prolongation of life. Of the 8 patients with typical features of amyotrophic lateral sclerosis, 7 had predominant diaphragm weakness and 1 generalized respiratory muscle weakness; 7 received negative pressure ventilation by cuirass which improved both the quality of sleep and exercise tolerance. Three patients with predominantly bulbar disease had nocturnal apnoea or hypoventilation. Two received no support. One, who also developed diaphragm weakness, was treated by a cuirass, continuous positive airway pressure (CPAP), and later nocturnal intermittent positive pressure ventilation (IPPV). Three patients with progressive muscular atrophy had predominant diaphragm weakness or nocturnal apnoea. These patients received nocturnal CPAP, cuirass or IPPV with symptomatic benefit. This series shows that some patients with motor neuron disease, mainly those with symptoms due to respiratory muscle weakness in the absence of severe bulbar impairment, derive symptomatic benefit from supported ventilation.
On the relaxation of orthodontic elastic threads.
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Clinic information system fills teaching, audit, managerial needs.
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The VA/Q resolution of inert gas data.
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Theory of evaluation of the single pneumatic resistor decompression computer.
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