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S D Anderson

Publications and source records attributed to S D Anderson.

At least 55 records · Page 3Linked to original sources
PubMed1996

Airway responsiveness to hyperosmolar saline challenge in cystic fibrosis: a pilot study.

Hyperosmolar aerosols are used to assess airway responsiveness in subjects with asthma. Using a 10% NaCl aerosol, we investigated airway responsiveness in 23 cystic fibrosis (CF) subjects (12 females, 11 males; 19.1 +/- 3.3 years) who had asthma-like symptoms. The pre-challenge predicted forced expiratory volume in 1 second (FEV1) was 74.7 +/- 21.5. The aerosol was generated by a MistO2gen 143A ultrasonic nebulizer and inhaled for 0.5, 1, 2, 4, 8, 8, and 8 minutes or part thereof. Spirometry was performed before and 1 minute after each inhalation period. The challenge was stopped when a > or = 20% fall from the baseline FEV1 was recorded, after the last inhalation period, or when requested by the subject. We recorded different responses to 10% NaCl among subjects. In 7, the FEV1 fell progressively throughout the challenge in a manner similar to asthmatics. By contrast, in 15 subjects the FEV1 was higher at the completion of challenge compared to during challenge, i.e., the fall in FEV1 was transient. In 7 of these subjects, the final FEV1 at the end of the challenge was higher than the pre-challenge FEV1. We conclude that inhaled 10% hyperosmolar saline causes either progressive and sustained or transient airway narrowing during challenge in the majority of CF subjects. The cause of the transient airway narrowing requires further investigation.

Adolescent↗
PubMed1996

Challenge tests to assess airway hyperresponsiveness and efficacy of drugs used in the treatment of asthma.

Bronchial provocation tests are useful to diagnose and assess severity of asthma and to follow response to treatment. The tests used include those stimuli that act "directly" on receptors causing contraction of airway smooth muscle, e.g., pharmacological agents, and those stimuli that act "indirectly" by causing release of endogenous mediators that cause the airways to narrow. These "indirect" stimuli include physical ones such as airway drying from hyperpnea and changes in airway osmolarity from inhaling aerosols of water and hyperosmolar saline. Indirect stimuli cause the airways to narrow in response to endogenously released substances from inflammatory cells or nerves and responses are thought to reflect the presence and severity of inflammation of asthma. Challenge with hyperosmolar saline is now being used as an indirect test because it also identifies persons with exercise-induced asthma and is appropriate to assess suitability for diving with SCUBA. Hyperosmolar challenge is also useful to assess the effect of both the acute and chronic treatment with antiinflammatory drugs. This, combined with the potential to collect inflammatory cells in sputum induced by the same stimulus should result in this challenge being more widely used, not only in the hospital laboratory but also in epidemiology and occupational asthma.

Aerosols↗
PubMed1996

Hypertonic saline challenge in an adult epidemiological survey.

Bronchial provocation tests using pharmacological agents such as methacholine or histamine are used in epidemiological studies to identify asthma despite recognition of limitations in specificity, positive predictive value and availability of reagents. Hypertonic saline (4.5%) bronchial challenge (HSBC), although less sensitive than pharmacological challenges, is reportedly highly specific in diagnosing current asthma. Added advantages are that reagents are cheap, stable and recognized by participants. Thus, HSBC may offer benefits over pharmacological tests in epidemiological surveys. This paper reports on the second field survey using the test, a study of 99 adults from the timber industry in Western Australia. The test is described and critically appraised as a practical epidemiological tool for assessing asthma prevalence. At a cutoff point of 20% FEV, fall, HSBC was positive in 8% of subjects, appeared specific for asthma, was safe, well-accepted and easy to use in the field.

Adult↗
PubMed1996

Exercise-induced asthma and the use of hypertonic saline aerosol as a bronchial challenge.

Exercise induced asthma is a common complaint and the prevalence appears to be increasing worldwide. Once confined to the research domain of university teaching hospitals, the study of EIA has extended into the school playground, defence force establishments and sports institutions. Standardized protocols have been developed to study EIA in the laboratory and in the field. A surrogate challenge using eucapnic or isocapnic hyperventilation with dry air is becoming popular because it has advantages over exercise, at least for adults. The stimulus that leads the airways to narrow is caused by the inhalation of dry air during hyperventilation and exercise, during which water is evaporated from the airways in order to condition the inspired air. The mechanism whereby the airways narrow is thought to be due to the dehydrating effects of water loss, particularly in relation to its potential to cause the airways to become hyperosmolar. Mast cell mediators such as histamine and the leucotrienes are probably involved in EIA because specific antagonists reduce severity. As a result of the osmotic theory of EIA, studies were carried out to determine whether subjects with EIA were sensitive to the effects of increasing airway osmolarity by inhalation of hyperosmolar aerosols of sodium chloride. A challenge protocol using an aerosol of 4.5% sodium chloride, generated from an ultrasonic nebulizer, has been used to identify persons with asthma and to assess response to drug therapy. There are many similarities between responses to exercise, hyperventilation and hypertonic saline in the physiological and biochemical responses and the responses to drugs. Challenge with hypertonic saline is easier and cheaper to use because expensive equipment and a source of dry air is not required as with exercise or hyperventilation. The ability to obtain a dose-response curve rather than a single response and the ability to collect inflammatory cells at the same time make challenge with hypertonic saline an attractive technique to study patients suspected of having asthma.

Administration, Inhalation↗
PubMed1996

Mucociliary clearance during and after isocapnic hyperventilation with dry air in the presence of frusemide.

We have previously shown that mucociliary clearance (MCC) decreased during and increased after isocapnic hyperventilation (ISH) with dry air, both in asthmatic and healthy subjects. Inhaled frusemide, an inhibitor of the Na+/K+/2Cl- and NaCl co-transporters on the basolateral membrane of the epithelial cell, prevents the airway narrowing provoked by ISH with dry air. The co-transport system controls epithelial cell volume and chloride secretion and, thus, frusemide has the potential to modify the rate of recovery of periciliary fluid volume during and after ISH with dry air, and hence affect MCC. Frusemide also blocks mediator release from mast cells, which may also modify the increase in MCC after ISH. Eleven asthmatic and 11 healthy subjects inhaled frusemide (35.7 +/- 0.44 mg) or its vehicle, from a Fisoneb ultrasonic nebulizer 30 min before ISH with dry air, on two separate occasions. MCC was measured using 99mTc-sulphur colloid and a gamma camera. Frusemide, compared to its vehicle, did not affect MCC during or 45 min after ISH. However, in the presence of frusemide, the onset of the increase of MCC after ISH was significantly delayed for approximately 10 min in the whole right lung (p < 0.002) and central region (p < 0.01) in the asthmatic but not in the healthy subjects. These findings could be explained by frusemide delaying the recovery of the periciliary fluid volume after ISH with dry air and/or interfering with the stimulus that causes the increase in MCC in the asthmatic subjects after ISH.

Adult↗
PubMed1996

Inhalation of hypertonic saline aerosol enhances mucociliary clearance in asthmatic and healthy subjects.

Hyperosmolarity of the airway surface liquid (ASL) has been proposed as the stimulus for hyperpnoea-induced asthma. We found previously that mucociliary clearance (MCC) was increased after isocapnic hyperventilation (ISH) with dry air, and we proposed that the increase related to transient hyperosmolarity of the ASL. We investigated the effect of increasing the osmolarity of the ASL on MCC, by administering an aerosol of concentrated salt solution. MCC was measured using 99mTc-sulphur colloid, gamma camera and computer analysis in 12 asthmatic and 10 healthy subjects on three separate days, involving administration of each of the following: 1) ultrasonically nebulized 14.4% saline; 2) ultrasonically nebulized 0.9% saline; and 3) no aerosol intervention (control). The (mean +/- SD) volume of nebulized 14.4% saline was 2.2 +/- 1.2 mL for asthmatics and 3.2 +/- 0.7 mL for healthy subjects. This volume was delivered over a period of 5.4 +/- 1.3 and 6.4 +/- 0.7 min for asthmatic and healthy subjects, respectively. The airway response to 14.4% saline was assessed on a separate visit and the fall in forced expiratory volume in one second (FEV1) was 22 +/- 4% in the asthmatic and 3 +/- 2% in the healthy subjects. Compared to the MCC with the 0.9% saline and control, the hypertonic aerosol increased MCC in both groups. In asthmatic subjects, MCC of the whole right lung in 1 h was 68 +/- 10% with 14.4% saline vs 44 +/- 14% with 0.9% saline and 39 +/- 13% with control. In healthy subjects, MCC of the whole right lung in 1 h was 53 +/- 12% with 14.4% saline vs 41 +/- 15% with 0.9% saline and 36 +/- 13% with control. We conclude that an increase in osmolarity of the airway surface liquid increases mucociliary clearance both in asthmatic and healthy subjects. These findings are in keeping with our previous suggestion that the increase in mucociliary clearance after isotonic hyperventilation with dry air is due to a transient hyperosmolarity of the airway surface liquid.

Administration, Inhalation↗
PubMed1996

The protective effect of nedocromil sodium and other drugs on airway narrowing provoked by hyperosmolar stimuli: a role for the airway epithelium?

The airways of persons with asthma are sensitive to acute changes in airway osmolarity and to dehydration. In reviewing the literature it is clear that airway narrowing provoked by these stimuli is blocked acutely by inhaling aerosols of nedocromil sodium, cromolyn sodium, frusemide, bumetanide, and antihistamines and by chronic use of aerosol corticosteroids. The responses are unaffected by inhalation of amiloride and verapamil. We have previously proposed that increases in the osmolarity of airway surface liquid (ASL) occur as a result of the water lost by evaporation during hyperpnea with dry air. An increase or decrease in osmolarity of the ASL will also occur with deposition of hyperosmolar and hypoosmolar droplets. Changes in osmolarity of the ASL result in the movement of water out of (shrinkage) and into (swelling) the epithelial cell, and this necessitates regulatory volume increase or decrease by the cell. We propose that nedocromil sodium and cromolyn sodium can affect water transport into and out of the epithelial cell by an action on chloride ion channels. A unifying hypothesis to explain the protective effect of these drugs may be their capacity to affect regulatory volume increase or decrease in a variety of cell types.

Adolescent↗
PubMed1996

Postconcussional disorder and loss of consciousness.

Postconcussional disorder (PCD) has been described in the psychiatric, neurological, neuropsychological, and rehabilitation medicine literature for many years. PCD has recently been introduced into DSM-IV, appearing in an appendix that contains a number of proposals for new categories and axes that were suggested for possible inclusion in DSM-IV. There are some major difficulties with the proposed criteria for PCD. This article explores some of these difficulties, particularly focusing on the criteria of loss of consciousness (LOC). A review of the literature demonstrates that LOC is not necessary for PCD to occur. The major difficulty with the DSM-IV criteria is the definition of concussion. The article suggests that, instead, the criteria for mild traumatic brain injury, as defined by the American Congress of Rehabilitation Medicine, may be more appropriate.

Brain Concussion↗
PubMed1995

An exercise challenge for epidemiological studies of childhood asthma: validity and repeatability.

We assessed the validity, repeatability and practicality of a standardized exercise challenge protocol for measuring airway responsiveness in epidemiological studies of asthma in children aged 8-11 yrs. The construct validity of the exercise challenge was assessed by comparing response to exercise with other measures of asthma, i.e. wheeze frequency, diagnosed asthma, asthma medication use, atopy and urgent doctor visits (n = 802), and by comparison with response to histamine challenge (n = 201). Repeatability was assessed by comparison of responsiveness to two exercise challenges within 3 days (n = 113), and practicality was assessed by measurement of consent, compliance and throughput rates (n = 802). There was a significant relationship between frequency of wheeze attacks and % fall in forced expiratory volume in one second (FEV1) to exercise. The correlation (r) between % fall in FEV1 to exercise challenge and dose-response ratio to histamine challenge was 0.59. The repeatability of the exercise challenge was +/- 12% fall in FEV1. Consent and compliance rates for exercise challenge were 78 and 99%, respectively, and the mean throughput rate was 45 children per school day for a team of seven researchers. In conclusion, this exercise challenge was found to have good validity and to be reliable and practical. Thus, this challenge could be used as a standardized epidemiological tool to investigate the prevalence, aetiology and mechanisms of asthma.

Asthma↗
PubMed1995

Changes in mucociliary clearance during and after isocapnic hyperventilation in asthmatic and healthy subjects.

Hyperpnoea with dry air could lead to a reduction in depth and hyperosmolarity of the periciliary fluid layer (PFL) as a consequence of evaporative water loss. We investigated whether mucociliary clearance (MCC) is likely to be affected by dry air hyperpnoea, which also results in airway narrowing in asthmatics. MCC was measured by radioaerosol technique, for about 1 h, in 10 asthmatic and 8 healthy subjects on 3 separate days: 1) nasal resting breathing with ambient air; 2) isocapnic hyperventilation (ISH) with dry air; and 3) ISH with warm humid air. Analysis of the initial and post-intervention lung radioactivity for the whole right lung and for defined regions of interest showed that, compared to ISH with warm humid air and nasal resting breathing, MCC was reduced during and increased post-ISH with dry air in the whole right lung of both groups. The mean reduction in clearance (+/- 95% confidence interval (95% CI)) was -9.3% (-3.1 to -15.6%) and -3.6% (-2.0 to -9.1%), and the mean increase (+/- 95% CI) was 19.2% (11.8 to 26.6%) and 14.8% (7.1 to 22.5%), compared to warm humid air, in asthmatic and healthy subjects, respectively. However, regional analysis showed that the changes were present in all lung regions of the asthmatics, whilst only in the central region of the healthy subjects. The duration of the increased clearance rates post-ISH was also different in both groups. The changes in mucociliary clearance during and after isocapnic hyperventilation with dry air was probably related to the water content of the inspired air, causing transient changes in the periciliary fluid layer.

Adult↗
PubMed1994

An exercise challenge protocol for epidemiological studies of asthma in children: comparison with histamine challenge.

We investigated whether an exercise challenge protocol is suitable for measuring bronchial responsiveness in epidemiological studies of asthma in children, and determined its comparability with histamine challenge. The exercise challenge was 6 minutes of outdoor, free-range running at 85-90% of maximum heart rate, measured by heart rate monitor. Nose clips were worn. Distance run was measured to estimate oxygen consumption. Water content of the inspired air was < 10 mg H2O.l-1. Histamine challenge was by the rapid method. We used questionnaires to measure respiratory symptoms and skin prick tests to measure atopy. A total of 96 children aged 8-11 years were studied. Bronchial hyperresponsiveness (BHR) to exercise challenge was defined as a fall in forced expiratory volume in one second (FEV1) of 13% of greater. Eleven children had a positive response to exercise challenge and 11 to histamine challenge but 12 responded to one challenge and not to the other. The correlation coefficient between the two tests was 0.65 (p = 0.0001). Exercise challenge thus proved to be a practical epidemiological tool for objective measurements of bronchial responsiveness in children. In this sample, some children responded to one challenge and not to the other which suggests that the two challenges identify different abnormalities of the airways.

Asthma↗
PubMed1994

Regional deposition of saline aerosols of different tonicities in normal and asthmatic subjects.

Nonisotonic aerosols are frequently used in the diagnosis and therapy of lung disease. The purpose of this work was to study the difference in the pattern of deposition of aerosols containing aqueous solutions of different tonicities. 99mTechnetium-diethyltriaminepentaacetic acid (99mTc-DTPA)-labelled saline aerosols, with mass median aerodynamic diameter 3.7-3.8 microns and geometric standard deviation 1.4, were inhaled under reproducible breathing conditions on two occasions. Hypotonic and hypertonic solutions were used in 11 normals subjects, isotonic and hypertonic solutions in 9 asthmatics. The regional deposition was quantified by a penetration index measured with the help of a tomographic technique. There was a small but significant increase (6.7%) in the penetration index of the hypotonic as compared to the hypertonic aerosols in the normal subjects. The region that was markedly affected was the trachea. The differences in the penetration of the isotonic and hypertonic aerosols in the asthmatics appeared to be strongly dependent on the state of the airways at the time of the study. These findings can be interpreted in terms of effects of growth or shrinkage of nonisotonic aerosols, as well as of airway narrowing, on regional deposition of aerosols. Tonicity of aerosols appears to affect their deposition both through physical and physiological mechanisms. This should be taken into account when interpreting the effects of inhaled aqueous solutions of various tonicities in patients in vivo.

Administration, Inhalation↗
PubMed1994

Acute effect of sodium cromoglycate on airway narrowing induced by 4.5 percent saline aerosol. Outcome before and during treatment with aerosol corticosteroids in patients with asthma.

STUDY OBJECTIVE: To investigate the acute effect of sodium cromoglycate on airway responses to 4.5 percent saline aerosol challenge, before and during treatment with inhaled budesonide--a corticosteroid. DESIGN: Open study, with a total of five visits, two before budesonide treatment, and three follow-up visits, two between 5 and 6 weeks and one at more than 11 weeks. SETTING: Referral-based Respiratory Investigation Unit at Royal Prince Alfred Hospital, a major Sydney-based teaching hospital. PATIENTS: Eleven patients with asthma (ten atopic), with a PD20 FEV1 to 4.5 percent saline aerosol challenge and about to commence inhaled budesonide for treatment of their asthma. INTERVENTIONS: The 40 mg of sodium cromoglycate was inhaled before a 4.5 percent NaCl challenge, both before and after regular (36 +/- 9 d) treatment with budesonide (1,000 micrograms/d). The final challenge was repeated in ten subjects after 11 weeks or more of treatment with budesonide. MEASUREMENTS AND RESULTS: Sensitivity to 4.5 percent saline aerosol was measured as the dose of saline aerosol required to induce a 20 percent fall in FEV1 (PD20). Reactivity was measured as the dose-response slope by taking the percent fall in FEV1 and dividing it by the dose required to induce the fall. On the control day the geometric mean PD20 (95 percent CI) for 4.5 percent saline aerosol was 2.8 (1.4 to 5.4) and the dose response slope (DRS) 5.6 (2.9-11.1). An acute dose of sodium cromoglycate reduced sensitivity (PD20) by 8-fold and reactivity (DRS) 12.3-fold. This effect was similar in magnitude to that measured after regular treatment with budesonide alone. When sodium cromoglycate was given during treatment with budesonide, the PD20 was reduced 16-fold and the DRS 42-fold, and this was greater than the reduction with budesonide taken for 3 months (p < 0.03, p < 0.05 respectively). CONCLUSIONS: Sodium cromoglycate inhibits responses to 4.5 percent saline aerosol and has additional benefits to those conferred by aerosol steroids. The mechanism for responsiveness to saline aerosol and efficacy of these drugs may relate to alteration in chloride ion channel regulation by inflammation.

Adolescent↗
PubMed1993

Compressed air diving and respiratory disease. A discussion document of the Thoracic Society of Australia and New Zealand.

OBJECTIVE: To review the pathophysiology and respiratory complications of compressed air diving, and to formulate guidelines for assessing respiratory fitness to dive so that diving candidates can be advised of the risks associated with respiratory disease, in particular asthma. DATA SOURCES: Specialist medical journals in the areas of respiratory medicine, physiology and diving medicine. Morbidity and mortality statistics were obtained from international diving bodies, diving medicine scientific meetings, and papers. SYNTHESIS: The major complications of underwater diving in subjects with compromised respiratory function are drowning, pulmonary barotrauma and arterial gas embolism. Diving candidates with a history of asthma, pneumothorax, obstructive or restrictive lung disease, lung cysts or thoracic trauma should be advised not to dive in view of these risk factors. CONCLUSIONS: Several respiratory diseases carry an increased risk of morbidity and mortality from compressed air diving. An accurate history and measurement of lung function are an essential part of assessing fitness to dive, both to advise potential divers appropriately and to reduce risks associated with this increasingly popular recreational activity.

Asthma↗
PubMed1993

The effect of inhaled frusemide on airway sensitivity to inhaled 4.5% sodium chloride aerosol in asthmatic subjects.

BACKGROUND: Frusemide inhaled by asthmatic subjects before a variety of indirect bronchial challenges inhibits the airway response to these challenges. Since inhalation of hyperosmolar saline is an indirect bronchial challenge, the effect of inhaled frusemide and its vehicle on airway sensitivity to a 4.5% sodium chloride (NaCl) aerosol challenge was investigated. METHODS: Eleven asthmatic subjects (five females, six males) who had a 20% fall in forced expiratory volume in one second after 4.5% NaCl challenge were enrolled in this double blind controlled crossover trial. Sensitivity was measured as the dose of aerosol required to provoke a 20% fall in FEV1. Frusemide (33.2 mg) or its vehicle was delivered through a Fisoneb ultrasonic nebuliser and inhaled 10 minutes before challenge with 4.5% NaCl. A Mistogen ultrasonic nebuliser was used to generate the 4.5% NaCl aerosol and FEV1 was measured before and one minute after each challenge period of 0.5, one, two, four, eight, eight and eight minutes. The doubling dose difference for PD20 was calculated. RESULTS: Frusemide or vehicle had no effect on baseline lung function. The geometric mean PD20 after vehicle was 1.3 ml with a 95% confidence interval of 0.7-2.3 and after frusemide was 8.2 ml with a 95% confidence interval of 4.7-14.1. This represented a 2.6 doubling dose increase in PD20 after frusemide inhalation. In five of the 11 subjects an increase from baseline FEV1 occurred after exposure to 4.5% NaCl challenge in the presence of frusemide. This transient bronchodilatation may be caused by the release of prostaglandin E2. CONCLUSION: Inhalation of frusemide is very effective in delaying airway narrowing induced by an aerosol of 4.5% NaCl in asthmatic subjects.

Administration, Inhalation↗