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Biomedical subjects

S D Anderson

Publications and source records attributed to S D Anderson.

At least 91 records · Page 5Linked to original sources
PubMed1989

Inhalation provocation tests using nonisotonic aerosols.

The measurement of bronchial hyperresponsiveness with inhaled aerosols is now accepted as an objective measurement of the severity of asthma. The most commonly used agents administered as aerosols are methacholine and histamine, which are believed to cause airways to narrow by contracting bronchial smooth muscle via specific receptors. Patients with asthma may also have an attack provoked by inhaling aerosols that increase or decrease the osmolarity of the fluid lining the airways. There is evidence to suggest that a change in the osmolarity of the airways causes the release of mediators from inflammatory cells in the airways. Thus, inhalational challenge with nonisotonic aerosols, such as water and hyperosmolar saline, may be useful to assess bronchial hyperresponsiveness to endogenously released mediators. Described in this article are some of the techniques used to challenge with nonisotonic aerosols, and airway responses are discussed in relation to responses obtained with other bronchial provocation tests. The mechanisms whereby these aerosols cause airways to narrow are considered, and the clinical implications of identifying responsiveness to these aerosols are discussed. Specific recommendations are made with respect to equipment, technique, and choice of aerosol.

Aerosols↗
PubMed1989

Comparisons of planar and tomographic gamma scintigraphy to measure the penetration index of inhaled aerosols.

The quantitative measurement of regional aerosol deposition in human lungs using two-dimensional (2D) gamma scintigraphy has proven to be useful in therapeutic and diagnostic aerosol studies. The penetration index (PI) has been defined as the ratio of activity in a peripheral lung zone to a central lung zone, but the ability to discriminate between aerosol deposition in the large airways and lung parenchyma is reduced by the fact that the latter overlies the former in the central zone. To overcome this, we used a three-dimensional (3D) technique. Seven healthy subjects inhaled isotonic saline aerosols containing 99mTc-DTPA on two occasions. The droplets had a mass median aerodynamic diameter (MMAD) of either 2.6 or 5.5 microns (with geometric standard deviations [sigma g] of 1.4 and 1.7, respectively). Transmission tomography was performed on each subject to delineate lung boundaries in 2D and 3D. After inhalation, anterior (A) and posterior (P) images were collected and a tomographic study performed. Mid-lung slices were taken from coronal (CC) and transverse (TC) sections. PI was calculated on the 2D images (AP and P) and the 3D slices (CC and TC) using exactly defined regions. The PI values were smaller for the large droplet aerosol (5.5 microns) in all subjects and methods. The relative differences in PI between large and small (2.6 microns) droplet studies (d values) were greater and less variable for the 3D methods (TC, 56.5 +/- 11.4% and CC, 52.4 +/- 12.3%) compared to the 2D methods (P, 25.4 +/- 17.1% and AP, 38.3 +/- 15%; p less than 0.005). We found the 3D methods to be more sensitive for discriminating between aerosol deposition in large and small airways than were the conventional 2D methods.

Adult↗
PubMed1989

An investigation of the effects of heat and water exchange in the recovery period after exercise in children with asthma.

It has been reported that asthma provoked by breathing subfreezing air during exercise is enhanced when air at BTPS is inhaled in the recovery period (1). It was concluded that the rate of airway rewarming is an important event in asthma provoked by exercise. It is also possible, however, that the enhanced response was due to hypo-osmolarity caused by condensation of water from inspired air at BTPS on the cooled mucosa. We examined, in a group of boys with asthma, the response to rapid rewarming of the airways after exercise, with and without the potential for condensation. On two test days, two exercise tests were performed 4 h apart on a cycle ergometer. On Day 1 (n = 17), the inspired air during exercise was -5 degrees C, dry. During recovery, the air was either -5 degrees C, dry or 50 degrees C, 23 mg H2O/L. On Day 2 (n = 11), the inspired air during exercise was -15 degrees C, dry, and during recovery was either -15 degrees C, dry or at BTPS. We did not find enhancement of the response with either condition designed to cause rapid airway rewarming. On Day 1 the mean (+/- 1 SD) percent fall in FEV1 was 23 +/- 22 (-5 degrees C, dry) and 24 +/- 21 (50 degrees C, 23 mg H2O/L) (r = 0.92), and on Day 2 it was 19 +/- 17 (-15 degrees C, dry) and 18 +/- 17 (BTPS) (r = 0.96).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

A comparison between the airway response to isocapnic hyperventilation and hypertonic saline in subjects with asthma.

We compared the response to isocapnic hyperventilation (ISH), where both cooling and drying of the mucosa occur, with the response to inhaling aerosols of hypertonic saline (HS), where airway osmolarity increases without airway cooling. We studied nine subjects on two days. For ISH, subjects ventilated at 70% of their estimated maximum voluntary ventilation (MVV). For HS, they inhaled aerosols of 2.7, 3.6, or 4.5% saline. The concentration that was used depended on the rate of ventilation during ISH. For both challenges the stimulus was given for one minute. Forced expiratory volume in one second (FEV1) was measured once between each minute, and the challenge ceased when the FEV1 did not change for two successive minutes. A plateau in FEV1 occurred after 8.1 +/- 2.4 (mean +/- 1 SD) min of ISH, and 8.3 +/- 2.4 min of HS. The lowest FEV1 (% predicted) after ISH was 45 +/- 16% and after HS was 51 +/- 18% (r = 0.93). However, the maximum responses occurred after the final challenge and were not the same as the plateau. For HS, the plateau represented 89 +/- 11% of the maximum response which developed within one minute of the final challenge. For ISH, the plateau was only 56 +/- 26% of the maximum response, which developed within 5.2 +/- 2.9 min after challenge. The similarities in the response to these challenges are consistent with the hypothesis that ISH induces asthma via hyperosmolarity. The delayed response to ISH suggests that cooling may delay the response to hyperosmolarity.

Adolescent↗
PubMed1988

The effect on airway function of inspired air conditions after isocapnic hyperventilation with dry air.

The magnitude of postexercise or posthyperventilation bronchoconstriction in patients with asthma is related to the temperature and the water content of the inspired air during the exercise or hyperventilation period. Recent studies have suggested that the inspired air conditions during recovery from exercise may also be important in determining the magnitude of postexercise airway narrowing. In the present study, normal subjects (n = 8) and patients with asthma (n = 12) were studied on separate days. On day 1 the subjects performed isocapnic hyperventilation with warm dry air and recovered breathing warm dry air. On the second day, an identical warm dry air challenge was administered, but recovery occurred while they were breathing warm humid air. There was no significant bronchoconstriction in the normal subjects, irrespective of the inspired air conditions during recovery. The patients with asthma showed greater bronchoconstriction during recovery in warm, humid air (maximal decrease in FEV1 31% +/- 17%) than in dry air (maximal decrease in FEV1 19% +/- 20%; p less than 0.05). These results suggest that the inspired air condition during recovery from isocapnic hyperventilation of dry air is also a determinant of the magnitude of the bronchoconstrictor response.

Adult↗
PubMed1988

The duration of action of the combination of fenoterol hydrobromide and ipratropium bromide in protecting against asthma provoked by hyperpnea.

We compared the duration of the protective effect of two beta-adrenoceptor agonists, fenoterol (200 micrograms) and salbutamol (200 micrograms), the anticholinergic agent ipratropium (80 micrograms), and the combination of fenoterol (200 micrograms) and ipratropium (80 micrograms) against challenge by eucapnic voluntary hyperventilation (EVH). Twelve patients with asthma performed EVH for two or four min at 60 percent maximal voluntary ventilation, 30 min, 2 and 4 h after treatment. All treatments (Rx) produced significant bronchodilation after 30 min. The Rx containing a beta-adrenoceptor agonist maintained this bronchodilation for at least 2 h. While all the Rx with a beta-adrenoceptor agonist significantly reduced the fall in forced expiratory volume in one second after EVH at 30 min, only the combination of fenoterol and ipratropium provided significant protection after 2 h. We advise that the duration of protective effect of beta-adrenoceptor agonists is short and patients with moderate to severe exercise-induced asthma may be better controlled by combination therapy.

Administration, Inhalation↗
PubMed1987

Effect of propranolol and verapamil on oxygen utilization, acidosis and fatigue during exercise in stable angina pectoris.

Oxygen utilization, arterial and venous blood gas levels, hemodynamic values and exercise tolerance were compared before and after administration of propranolol and verapamil in 10 patients with stable angina pectoris. During exercise, propranolol decreased cardiac output (CO) by 22%; O2 extraction was increased and O2 consumption (VO2) did not change. With verapamil treatment, CO modestly increased (7%), O2 extraction decreased and VO2 did not change. In contrast to O2 utilization, the drugs produced opposite changes in mixed venous and arterial blood gas levels. Propranolol decreased mixed venous pH, increased CO2 tension and decreased the pH of arterial blood. Verapamil increased venous pH and decreased CO2 tension; pH of arterial blood did not change. The drugs yielded similar levels of antianginal efficacy, but patients exercised longer during verapamil therapy and were less fatigued. The hemodynamic and metabolic differences suggest that muscle perfusion during exercise influences the onset of fatigue and may help determine the choice of therapy.

Adult↗
PubMed1987

The effect of non-isotonic solutions on human isolated airway smooth muscle.

In patients with asthma, bronchoconstriction can be provoked by the inhalation of aerosols of non-isotonic solutions. In order to determine if this bronchoconstriction results from a direct effect on airway smooth muscle we decided to examine the effects of non-isotonic solutions on the resting tone of human isolated bronchi and on responses to carbachol, histamine and field stimulation. Human bronchi were obtained from thoracotomy and dose-response relationships for each agonist were obtained for bronchial rings suspended in isotonic Krebs-Henseleit solution (290 mOsm). A second curve was then obtained with half the rings immersed in a solution made hypotonic (145 mOsm) or hypertonic (440 mOsm) by the addition of NaCl or salts and glucose. The other half remained in isotonic solutions as controls. In a separate series of experiments, field stimulation responses to a submaximal frequency (15 Hz) were measured before and after a change from isotonic to non-isotonic bathing solution. The resting tone of the preparations was transiently reduced by hypertonic solutions and increased by hypotonic solutions. Contractile responses to agonists were significantly diminished by non-isotonic solutions. Agonist potency was unaffected by hypertonic solutions but the potency of carbachol was reduced by hypotonic solutions. Responses to field stimulation were unaffected by the hypertonic solution but reduced by the hypotonic solution. We conclude that the bronchoconstrictor actions of non-isotonic solutions and their effects on airway reactivity are unlikely to be due to direct effects on airway smooth muscle.

Bronchi↗
PubMed1987

Methacholine responsiveness increases after ultrasonically nebulized water but not after ultrasonically nebulized hypertonic saline in patients with asthma.

Airway obstruction can be induced in patients with asthma by the inhalation of ultrasonically nebulized aerosols of nonisotonic solutions. It is the change in osmolarity of the periciliary fluid that is believed to be the stimulus for bronchoconstriction. However, it is not known whether hyperosmolar and hypo-osmolar aerosols induce asthma via the same mechanism. We have previously reported that patients with asthma have a reduction in the dose of provoking agent that induces a 20% fall in FEV1 (PD20) for methacholine after challenge with nebulized water. To determine whether hyperosmolar aerosols also increase sensitivity to methacholine, we studied 13 subjects with asthma on 3 days. On day 1, the PD20 to methacholine was determined. On day 2, a challenge with nebulized 4.5% saline was followed by a challenge with methacholine 40 to 60 minutes later. On day 3, a challenge with nebulized water was followed by a methacholine challenge. Sensitivity to methacholine was significantly increased after water (p less than 0.02) but not after 4.5% saline. Furthermore, there was no relationship between the PD20 to water and to 4.5% saline. When the Spearman's correlation coefficient was used to compare sensitivity to the challenges, there was a significant relationship between the PD20 to 4.5% saline and methacholine (p less than 0.01) but not between the PD20 to water and methacholine. These results suggest that the mechanism of asthma induced by hyperosmolar and hypo-osmolar solutions is different.

Adolescent↗
PubMed1987

Cromolyn sodium inhibits the increased responsiveness to methacholine that follows ultrasonically nebulized water challenge in patients with asthma.

We have previously reported that airway responsiveness to inhaled methacholine in subjects with asthma is increased 40 to 60 minutes after challenge with ultrasonically nebulized water. This study reveals that increased responsiveness to methacholine is abolished by administration of cromolyn sodium before the water challenge. The mean dose of methacholine (95% confidence limits) inducing a 20% fall in FEV1 (PD20) was 1.10 mumol (0.43 to 2.80). The PD20 after water challenge was 0.42 mumol (0.17 to 1.01) that was significantly lower (p less than 0.005) than that observed for the initial challenge. Administration of cromolyn before the water challenge abolished this increased responsiveness to methacholine. The mean PD20 was 1.32 mumol (0.47 to 3.68) that was not significantly different from that measured for the initial methacholine challenge. Methacholine responsiveness was unchanged when challenge was performed 40 to 60 minutes after cromolyn alone or after methacholine itself. We conclude that cromolyn abolishes the increased responsiveness to methacholine and probably does so by inhibiting the release of mediators.

Adult↗
PubMed1987

Prevalence of bronchial hyperresponsiveness and asthma in a rural adult population.

The prevalence of bronchial hyperresponsiveness in adult populations is not known. To document its prevalence and distribution and to determine the factors associated with it, a random sample of the adult population of Busselton, Western Australia, was studied. Spirometric function, bronchial responsiveness to histamine, and atopic responses to skin prick tests were measured. Respiratory symptoms were determined by questionnaire. Data were obtained from 916 subjects. Of these, 876 underwent a histamine inhalation test and bronchial hyperresponsiveness to histamine (defined as a dose of histamine provoking a 20% fall in FEV1 equal to or less than 3.9 mumol) was found in 10.5%. Another 40 subjects with poor lung function were tested with a bronchodilator and 12 were found to have bronchial hyperresponsiveness (defined as a greater than 15% increase in FEV1), making the total prevalence of bronchial hyperresponsiveness 11.4%. The prevalence of current asthma, defined as bronchial hyperresponsiveness plus symptoms consistent with asthma in the last 12 months, was 5.9%. The distribution of bronchial hyperresponsiveness in the studied population was continuous. There was a significant association between it and respiratory symptoms, atopy, smoking, and abnormal lung function (p less than 0.001 for all associations). There was no association with age, sex, or recent respiratory tract infection.

Adult↗
PubMed1987

Review of iliopsoas anatomy and pathology.

The iliopsoas compartment acts as a conduit for the spread of disease within the body. Knowledge of its anatomy facilitates the early diagnosis of some potentially fatal lesions.

Abscess↗
PubMed1986

Hyperosmolarity as the stimulus to asthma induced by hyperventilation?

Hyperosmolarity of the epithelial fluid of the large airways caused by evaporative water loss (wloss) has been proposed as the stimulus to exercise-induced asthma. The aim of this study was to compare the wloss during hyperpnea with a theoretical wloss from a known hypertonic stimulus in order to determine whether comparable volumes of wloss will induce the same response. Since wloss also occurs during isocapnic hyperventilation (ISH), we decided to compare the airway response to ISH with the response obtained after inhaling 4.5% NaCl aerosol. Changes in FEV1 were measured in 17 subjects with asthma in response to increasing rates of ventilation (ISH) and increasing doses of 4.5% NaCl aerosol. For ISH, wloss was calculated at 29 mg/L of expired air and for 4.5% NaCl, at 4.0 ml/l ml of aerosol inhaled, as this is the volume of water that will bring the periciliary fluid to normal tonicity. Two dose-response curves were drawn for each subject. These curves were similar both in position (PD20) and in shape (i.e., the slope of the curve as estimated by the ratio of wloss for maximum recorded percent fall in FEV1 [PDmax] to PD20). There was no significant difference in the PD20 (ISH, 10.3 ml, 95% confidence limits 7.5 and 13.9; 4.5% NaCl, 12.3 ml, 95% confidence limits 8.9 and 17.1) or between the ratio of log PDmax:log PD20 (ISH, 1.19 +/- 1 SD, 0.14; 4.5% NaCl, 1.17 +/- 1 SD, 1.17; p = not significant). These findings support the concept that airway hyperosmolarity may be the mechanism for ISH and exercise-induced asthma.

Adolescent↗
PubMed1986

Effects of nifedipine on arterial oxygenation at rest and during exercise in patients with stable angina.

The effects of nifedipine on arterial oxygenation and hemodynamics were studied at rest and during bicycle exercise in 12 men (mean age 55 years, range 41 to 67) with stable exertional angina. The study was conducted double-blind on 2 days, 1 week apart, using a placebo-controlled crossover design. On each day, measurements at rest were made before and 20 minutes after 20 mg sublingual nifedipine or placebo and were followed by measurements made during exercise. Compared with placebo, nifedipine reduced mean arterial pressure, systemic vascular resistance and pulmonary vascular resistance, and increased heart rate and cardiac output at rest and during exercise. It did not alter mean pulmonary artery or pulmonary artery wedge pressures at rest, but decreased them during exercise. Nifedipine decreased arterial oxygen tension (PaO2) from 96 +/- 10 to 90 +/- 13 mm Hg (p less than 0.05) at rest and from 99 +/- 11 to 92 +/- 12 mm Hg (p less than 0.005) at submaximal exercise (33 +/- 21 W), but did not alter it (100 +/- 12 versus 100 +/- 16 mm Hg, p = NS) at maximal exercise (68 +/- 30 W). The reduction in PaO2 was not due to alveolar hypoventilation, because nifedipine did not alter arterial carbon dioxide tension, or to changes in mixed venous oxygen tension, which nifedipine increased at rest (39 +/- 2 versus 43 +/- 3 mm Hg, p less than 0.001) and during submaximal exercise (31 +/- 4 versus 33 +/- 4 mm Hg, p less than 0.03) and maximal exercise (27 +/- 3 versus 31 +/- 3 mm Hg, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Causes of jaundice during hepatic artery infusion chemotherapy.

Jaundice develops in many patients with liver metastases from colorectal adenocarcinoma during hepatic arterial infusion chemotherapy (HAIC). The usual cause is thought to be hepatotoxicity from the chemotherapeutic agent or biliary obstruction from progressive neoplastic disease. The authors evaluated the abdominal computed tomography and ultrasound examinations performed on 49 patients who were jaundiced during long-term HAIC. In only one patient was diffuse intrahepatic biliary dilatation caused by an obstructing mass in the porta. Two patients had metastatic hepatic lesions causing focal biliary obstruction. Intrahepatic dilatation without an obstructing mass occurred in 20 patients. Percutaneous or endoscopic cholangiograms were commonly interpreted prospectively as showing extrinsic compression by metastases, but no mass was confirmed on imaging studies. Seven patients had focal intrahepatic ductal dilatation from stricture without an associated mass. The remaining 19 patients had normal-caliber ducts; their jaundice was caused by chemical hepatitis. This series suggests that the most common causes of jaundice in these patients are chemical hepatitis and common bile duct stricture, complications of intraarterial chemotherapy, rather than neoplastic obstruction. Stricture formation may be confused with extrinsic compression on direct cholangiograms.

Adenocarcinoma↗
PubMed1985

Issues in exercise-induced asthma.

It is concluded that challenge by exercise and ISH induces asthma by the same mechanism, the protective effect of water vapor is evidence that the events that lead to bronchial smooth muscle contraction begin in the airway lumen, it is the loss of water rather than the loss of heat from the airways that is the primary stimulus to EIA and HIA, the mechanism by which water loss induces asthma is by increasing the osmolarity of the epithelial fluid, in some subjects with asthma, cooling of the airways enhances the response to water loss, the increase in osmolarity stimulates the production and release of bronchoactive substances from mast cells and epithelial cells, vagal afferent pathways are activated by changes in osmolarity and by the released mediators, and vagal efferent activity may be modified by alpha-adrenoceptor antagonists and SCG.

Asthma↗
PubMed1985

Mediators of hypersensitivity and "fog"-induced asthma.

Seven asthmatic and five normal subjects inhaled increasing amounts of nebulized water ("fog"). Neutrophil chemotactic activity (NCA), histamine and FEV1 measurements were undertaken before and at time intervals after challenge. In asthmatics, the mean maximal reduction in FEV1 (+/- 1 SD) was 46.6% +/- 11.5; whereas, in normal subjects, the reductions were less than 20% of pre-challenge values after the inhalation of 33 ml of water. There were no significant differences in the pre-challenge values for NCA between the asthmatics and the normal controls. When the highest values for NCA during the 30 min after challenge in the asthmatics were compared with controls there was a significant increase (P less than 0.02). The percentage change in NCA was also significantly greater in the asthmatics compared with the controls at 10 min after challenge (P less than 0.05). Fog-induced NCA was shown to be associated with proteins with approximate molecular weight of 600,000 daltons (as assessed by gel filtration chromatography on Sephacryl-S400). There was an increase in plasma histamine in the asthmatics after challenge but this was not significantly greater than the controls. These findings support the view that mediators might be involved in fog-induced asthma, possibly as a result of mast cell degranulation by "osmotic shock".

Adult↗