The chronicity of acute attacks of asthma--mechanical and therapeutic implications

Acute severe asthma

Acute severe asthma remains a major economic and health burden. The natural history of acute decompensations is one of resolution and only about 0.4% of patients succumb overall. Mortality in medical intensive care units is higher but is less than 3% of hospital admissions. "Near-fatal" episodes may be more frequent, but precise figures are lacking. However, about 30% of medical intensive care unit admissions require intubation and mechanical ventilation with mortality of 8%. Morbidity and mortality increase with socioeconomic deprivation and ethnicity. Seventy to 80% of patients in emergency departments clear within 2 hours with standardized care. The relapse rate varies between 7 and 15%, depending on how aggressively the patient is treated. The airway obstruction in the 20-30% of people resistant to adrenergic agonists in the emergency department slowly reverses over 36-48 hours but requires intense treatment to do so. Current therapeutic options for this group consist of ipratropium and corticosteroids in combination with beta2 selective drugs. Even so, such regimens are not optimal and better approaches are needed. The long-term prognosis after a near-fatal episode is poor and mortality may approach 10%.

Natural history of chronic asthma and its long-term effects on pulmonary function

Although asthma is a disease that has intrigued physicians since antiquity, its natural history has been incompletely determined. It has long been held that the presence of asthma, per se, does not carry with it any long-term deterioration in lung function, but recently this view has been challenged, and it has become fashionable to define asthma as being only partially reversible. At present, there are limited data to support such a view. All of the available information indicates that the vast majority of patients do not experience the development of a progressive decline in pulmonary mechanics or appear to be at risk for a diminution in life expectancy.

The acute asthmatic patient in the ED: to admit or discharge

Treating asthma in the emergency department (ED) always involves the potentially difficult decision as to whether to discharge the patient, to continue treatment, or to admit to the hospital. The following are useful guidelines. (1) The duration of the bronchospasm, frequency of visits, history of previous endotracheal intubation, pulse rate, and accessory muscle use are findings affecting successful discharge from the ED. (2) Patients with peak expiratory flow rate (PEFR) of < 20% and who do not respond to inhalant therapy, with PEFR values persisting at < 40% of predicted, will require 4 or more days to resolve and should be admitted to the hospital. (3) Patients with a PEFR between 40% and 70% of predicted after initial inhalant therapy may well be responsive to steroids in the ED, but an ED will adequately need to care for the patient for 5 to 12 hours while waiting for the onset of action of glucocorticoids. Discharged with glucocorticoids, this group has a 6% relapse rate within 10 days of the ED visit. (4) Patients with a PEFR of > or = 70% have a 14% relapse rate after discharge without glucocorticoids. Other reasons to consider admission are pneumonia, barotrauma, lability, prominent psychiatric difficulties, poor access to medications, poor educability, fear of steroids, patients on glucocorticoids or those who have recently stopped glucocorticoids, and evening discharges of patients from the ED, which all predispose to relapses of acute asthma. To decrease the relapse rate, provocative factors should be reviewed with the patient, as well as access to medication and use of spacers, inhaler techniques, PEFR meters, self-management plans, and referral to a defined appointment at 24 to 48 hours of the ED visit.

Protocol therapy for acute asthma: therapeutic benefits and cost savings

BACKGROUND

To evaluate the therapeutic and financial benefits of protocol therapy for acute asthma using standard medications.

MATERIALS AND METHODS

This study employed a sequential design in which the influence of an asthma care path on hospital admissions, length of stay (LOS) in the emergency department, and return visits were evaluated for 1 year. This information was contrasted with similar data obtained from the 8 months immediately before the protocol was implemented (preprotocol) and a 12-month period after strict adherence to it had declined (admixture).

RESULTS

In all, 526 acute exacerbations of asthma were treated with the care path, and 429 and 558 episodes were evaluated during the preprotocol and admixture periods, respectively. There were no significant differences between the presenting clinical or physiologic features of any group. With the protocol, 77% of the patients resolved their symptoms within 1:47 +/- 0.02 hours:minutes of arrival in the emergency department with a 2% return rate within 24 hours. The algorithms used quickly identified those needing hospitalization. Patients not meeting the criteria for discharge after receiving the treatments employed typically did not resolve their symptoms for days (average hospital stay 4.1 +/- 0.2 days). Compared with the preprotocol period, the care path significantly reduced the LOS by 50 minutes, the number of urgent and intensive care unit admissions by 27% and 41%, respectively, and the frequency of return visits within 24 hours by 66%. Charges to patients and third-party payors decreased $395,000. When adherence to the protocol diminished, LOS, admissions, and returns rose significantly toward preprotocol values and the financial benefits were lost.

CONCLUSIONS

Asthma protocol therapy, based primarily upon aggressive use of sympathomimetics in association with serial monitoring of key indices of improvement, provides prompt and efficient relief for acute exacerbations of asthma. Such an approach yields significant financial benefit while quickly identifying individuals who require hospitalization, and it also detects physician practice patterns that can have potentially detrimental impacts on patient care.

Clinical and symptom measures

We present a review of specific health status measures, including symptoms, physical examination, and laboratory tests (exclusive of lung function tests), in terms of their suitability for assessing the presence and severity of asthma in epidemiologic and clinical research. We focus on the validity, reliability, and responsiveness to clinical intervention of these measures. Several adult questionnaires designed for epidemiologic research include questions on asthma and wheezing that have demonstrated repeatability and validity against concurrent measurements of nonspecific airway responsiveness. The International Union Against Tuberculosis Bronchial Symptoms Questionnaire was designed specifically to detect asthma and airway hyperresponsiveness in adult populations, and its reliability and validity have been well documented. A childhood questionnaire developed by Australian investigators has been demonstrated to provide information on asthma and wheezing that is reliable and valid against the criterion of concurrently measured nonspecific airway responsiveness. Although suitable for epidemiologic research, these questionnaires do not provide sufficient data on the severity of current asthma symptoms (aspects of which include intensity, duration, and frequency of symptoms) to be useful for clinical research involving subjects with established asthma. Many different methods of obtaining and analyzing symptom data have been used in clinical trials, but these have not received the methodologic scrutiny that allow the recommendation of a "best" approach for evaluating symptoms in clinical trials of interventions for asthma. The use of daily symptom diaries in short-term drug trials is common, but the optimal symptom-reporting interval for such studies has not been established. Similarly, a particular approach to integrating different symptoms (wheeze, dyspnea, cough, sputum) and the different aspects of these symptoms (intensity, duration, frequency) cannot be recommended on the basis of available data. Physical examination findings have little utility as asthma outcome measures because they may be normal between symptom episodes, they have relatively poor interobserver reliability, and they are relatively poor predictors of the outcome of emergency room visits for asthma. The finding of an elevated arterial PCO2 has utility as an indicator of a severe asthma attack, but arterial blood gas measurements have little other utility as asthma outcome measures. The chest radiograph is generally normal in patients with asthma and therefore not useful as an asthma outcome measure.(ABSTRACT TRUNCATED AT 400 WORDS)

Expired breath hydrogen peroxide is a marker of acute airway inflammation in pediatric patients with asthma

Airway inflammation is important in the development and progression of many pulmonary disorders, including asthma. We hypothesized that the hydrogen peroxide (H2O2) concentration in expired breath may be a marker of airway inflammation. Expired breath condensate was collected by cooling and the H2O2 concentration was measured fluorimetrically. Thirty-five samples were collected from 22 pediatric patients with asthma who were 7 to 18 yr of age and from 11 healthy, nonasthmatic controls. Asthmatic subjects were determined to be well or sick (acute disease of the upper or lower respiratory tract) by clinical examination. Pulmonary function tests were determined to be abnormal if there was a > 15% reduction in FEV1 or > 20% reduction in FEF25-75 compared with baseline values. Expired breath H2O2 was elevated in asthmatic subjects compared with controls (0.81 +/- 0.70 versus 0.25 +/- 0.27 mumol/L). The difference was primarily due to elevation of H2O2 in sick asthmatic subjects, whose expired breath H2O2 level of 1.5 +/- 0.5 (n = 10) was different from that of well asthmatics (0.54 +/- 0.56, n = 25). There was a high correlation between expired breath H2O2 and clinical status. Elevation of expired H2O2 occurred with either acute upper or lower respiratory tract disease. There was no statistically significant correlation between expired breath H2O2 level and pulmonary function test results. We conclude that elevation of H2O2 in the expired breath condensate is a simple, noninvasive method that can be used as a biochemical marker of airway inflammation.

Is combined therapy of sympathomimetics and theophylline indicated?

Bronchodilator effect and toxicity of theophylline 300 mg twice a day (R1), salbutamol 4 mg tid (R2), their combination in higher (200/4mg, R3), and lower doses (100/2mg R4), and placebo (calcium lactate 300 mg) tid (R5) were compared in 25 patients with bronchial asthma in a randomized crossover trial. Statistically significant improvement in forced expiratory volume in one second (FEV1) was observed in all the active treatment groups (R1 to R4) compared with placebo (R5). The mean improvement in FEV1 was 29.0%, 22.0%, 28.0%, 30.0%, and 0.73% in regimen R1, R2, R3, R4, and R5, respectively day 1, and corresponding improvement was 30.0%, 24.0%, 29.0%, 34.0%, and 4.4% on completion of one week therapy. On intergroup statistical comparison, mean improvement in pulmonary function test values were statistically significant or highly significant in regimens R1 to R4, as compared with placebo. However, improvement between any two regimens was not statistically significant in any of the regimens (R1-R4). Almost all the regimens were tolerated well and no patient showed major adverse reactions or cardiotoxicity necessitating withdrawal of the drug. On the other hand, minor adverse reactions were common and the high dose combination (R3) was found to have more adverse reactions than the low dose combination and either drug used alone.

Influence of baseline lung function on exercise-induced response in childhood asthma

The dependence of bronchial reactivity to exercise on baseline lung function was studied in 84 asthmatic children aged 7-16 years. The percentage fall in PEF values after a standard exercise running test was 8.4 +/- 8.6% in the 39 children with an attack rate of less than 10 per year and 29.6 +/- 23.2% in the 45 children with an attack rate of 10 or more per year (p less than 0.001). A significant negative correlation (r = -0.46, p less than 0.001) was found for pre-exercise MMEF and other sensitive tests of airway calibre with the response to exercise, but no such correlation was found between baseline PEF or SGaw values and the exercise response. These results show that bronchial hyperreactivity to exercise is dependent on residual airway obstruction, but a wide variety of reactivity can occur. If the baseline flow-values are less than three standard deviations below the mean reference, however, a clinically significant response to exercise can be predicted.

Effects of exercise on gas exchange in patients recovering from acute severe asthma

The effect of exercise on gas exchange was studied in 17 patients (seven male and 10 female) recovering in hospital from acute severe asthma. On admission the patients (mean age 26 (SD 8) years) had a mean peak expiratory flow (PEF) of 26.8% (5.7%) predicted, a mean arterial oxygen tension (PaO2) of 8.63 (1.26) kPa, and a mean alveolar-arterial oxygen difference (A-aDO2) of 5.98 (1.34) kPa. Once resting symptoms had resolved (after 3.7 (1.6) days) patients performed a constant load exercise test (100 watts for men, 75 watts for women) on a bicycle ergometer for five minutes. PEF was measured before exercise and at five minute intervals for 30 minutes after exercise. Blood gas tensions were measured on capillary blood before, during, and 10 minutes after exercise. Treatment was not interrupted for this study. Mean PEF at rest was 87.6% (21.1%) predicted and showed no significant change after exercise. Mean PaO2 was 13.13 (1.37) kPa before exercise; it showed no significant change during exercise (13.93 (1.34) kPa) or 10 minutes after exercise (13.50 (2.15) kPa). Mean A-aDO2 also showed no change, being 1.82 (1.31) kPa before exercise, 1.79 (1.27) kPa during exercise, and 2.53 (0.93) kPa after exercise. It is concluded that moderate exercise carried out shortly after treatment for acute severe asthma is unlikely to result in worsening gas exchange during or after exercise if resting PEF, PaO2 and A-aDO2 have attained normal or near normal values.

Nebulization and selective deposition of LTD4 in human lungs

The process of nebulization and deposition of LTD4 was studied in detail. The concentration of LTD4 in a saline solution decreased by approximately 90% after 2 min of nebulization in a DeVilbiss 35B ultrasonic nebulizer. This decrease was prevented by diluting LTD4 in a phosphate buffer, pH 7.4. Nebulization of tritiated LTD4 in this phosphate buffer did not cause any appreciable deterioration of the leukotriene, as demonstrated by an unchanged ratio between radioactivity and LTD4 concentration in the test solution before and after nebulization as well as in the condensed aerosol. The aerosol generated by the DeVilbiss 35B ultrasonic nebulizer was shown to generate particles with a mass median diameter of 1.3 microns (dry particle size). Interposition of a settling bag reduced the amount of large particles, reducing the mass median diameter to 0.84 microns (dry particle size). Nine healthy volunteers were challenged on separate days with 40 nmol LTD4 or 100 mumol histamine, and the changes in FEV1 and partial flow volume curves initiated at 50% of vital capacity (Vmax30) were measured. A relative diffuse deposition pattern was ensured by inhalation via a settling bag. These results were compared to challenges with a relatively central deposition pattern as ensured by inhalation directly from the nebulizer with brisk inhalation maneuvers. The diffuse deposition pattern caused minimal changes in FEV1 but pronounced effect in Vmax30. The effects of LTD4 and histamine on FEV1 and Vmax30 changed in parallel when the deposition of the mediators was changed to a more central pattern. This indicates that the two mediators do not differ with respect to any selective effects on different parts of the airways.

Mechanisms of glucocorticoid action in pulmonary disease

This article reviews the multiple mechanisms by which glucocorticoids influence the pathophysiology of pulmonary disease. Particular emphasis is given to the influence of glucocorticoids on the release and action of mediators that promote inflammation and that modulate other pathophysiologic processes in the lung. The time course and mechanisms of action that contribute to glucocorticoid effects on pulmonary function are also discussed.

Leukotrienes and prostaglandins in asthma

Leukotrienes and prostaglandins possess properties which are central in the asthmatic reaction. They are bronchoconstrictors, they inhibit the mucociliary clearance, increase blood flow and permeability and thereby induce edema formation, and they attract and activate leukocytes. They are formed partly by allergic reactions and partly by a large number of other more non-specific reactions. Finally, the concentration of prostanoids has been found increased in the asthmatic reaction in vivo. The leukotrienes have not been traced in vivo in asthmatic attacks so far, but have been found in vivo in man in a specific type I allergic conjunctival reaction. Much evidence suggests that these mediators are relevant in asthmatic diseases, even though prostaglandin inhibitors have no effect in asthma. There still remains the need to investigate the influence on asthmatic diseases by as yet unavailable leukotriene blocking agents. Even though leukotrienes are judged today to be important mediators in asthma, it does not seem reasonable to expect that a single mediator is responsible for asthmatic diseases. Rather, it seems quite likely that asthma is caused by a complex interplay of a large number of mediators, circulating hormones, nervous mechanisms, receptor abnormalities, intracellular metabolic defects, etc. Despite this complexity, investigations in recent years have increased the knowledge of the biochemistry and human physiological effects of leukotrienes and prostaglandins which has created an improved understanding of the asthmatic reaction's pathophysiology, contributed a pharmacological rationale for previously used therapy, and stimulated new perspectives for specific pharmacological research.

Leukotriene D4 induces bronchoconstriction in man

The effect of leukotriene D4 (LTD4) on lung function was investigated in a controlled study on four normal subjects. A pronounced decrease in airflow was found after inhalation of less than 0.5 nmol, and was most pronounced in the variables generally accepted as indicators of the function of the small airways. No subjective symptoms were experienced.

Bronchoconstrictor effects of leukotriene C in humans

Maximum expiratory flow rate at 30 percent of vital capacity above residual volume served as an index of airway obstruction in comparing the effects of leukotriene C and histamine administered by aerosol to five normal persons. Leukotriene C was 600 to 9500 times more potent than histamine on a molar basis in producing an equivalent decrement in the residual volume. The leukotriene C response was slow in onset and prolonged, reminiscent of the effects of aerosol allergen challenge in asthmatic allergic subjects.

Controlled trial of slow-release aminophylline in childhood asthma: are short-term trials valid?

Slow-release aminophylline, although widely used for the prophylaxis of childhood asthma, has had only limited formal assessment. A four-month double-blind cross-over trial of slow-release aminophylline (14 mg/kg twice daily) was carried out in 24 children with perennial asthma. Satisfactory serum theophylline concentrations were obtained in 17 children, with few side effects. There was a significant improvement in mild daytime and night-time symptoms. The incidence of more severe symptoms was unaffected. Treatment did not improve the mean peak expiratory flow or reduce the incidence of use of bronchodilators. It is concluded that slow-release aminophylline has a place in the prophylaxis of perennial childhood asthma but is unsuitable for children who suffer from severe attacks. The cross-over trial design has severe limitations.

The Basenji-Greyhound dog: antigen-induced changes in lung volumes

Subdivisions of lung volume, closing volume (CV), pulmonary resistance (RL) and dynamic pulmonary compliance (Cdyn) were measured before and after bronchial challenge with Ascaris suum in seven ascaris-sensitive Basenji-Greyhound (BG) crossbreed dogs. RL increased from a control value of 1.41 +/- 0.43 (mean +/- SE) cm H2O/L/sec to 21.4 +/- 5.15 (P Less Than 0.01) and Cdyn decreased from 163 +/- 32 ml/cm H2O to 43 +/- 11 (P Less Than 0.01) in the first 15 min following ascaris-antigen aerosol (AAA) challenge. Vital capacity (VC) decreased from 1581 +/- 147 ml to 944 +/- 86 (P Less Than 0.005) ml and residual volume (RV) increased from 381 +/- 63 to 577 +/- 68 ml (P Less Than 0.005) following AAA challenge. We conclude that the pulmonary mechanical changes in the BG dog following antigen challenge more closely resemble the changes observed in acute human asthma than do changes occurring in the mongrel dog.

Slow reacting substances of anaphylaxis: identification of leukotrienes C-1 and D from human and rat sources

Slow reacting substance(s) of anaphylaxis (SRS-A) was isolated from both human (lung) and rat sources and compared with three synthetic SRS-As of known structure-leukotrienes (LTs) C-1, C-2, and D. Reversed-phase liquid chromatography was used both as a final purification step and a means of comparison of biologically derived and synthetic substances. Two major peaks of SRS-A activity of both rat and human origin corresponded chromatographically with LTC-1 and LTD, respectively, and had equivalent specific activities on the guinea pig ileum. With guinea pig ileum, the specific activities (units/pmol) for synthetic leukotrienes and anaphylactic peaks were (mean +/- SEM): synthetic LTC-1, 1.93 +/- 0.13; SRS-A(rat) peak I, 1.69 +/- 0.43; synthetic LTD, 6.10 +/- 1.15; SRS-A(rat) peak II, 7.14 +/- 0.51; and SRS-A(hu) peak II, 1.90. Both synthetic LTC-1 and LTD and their SRS-A natural counterparts had a preferential contractile activity on guinea pig peripheral airway compared to central airways and were at least 200 times more active than histamine on peripheral airways on a molar basis. Leukotriene D is the major SRS-A of human lung and accounts for almost all of the biological activity. It likely is formed from leukotriene C-1 in vivo by an enzymic process of the well-known gamma-glutamyltransferase type.

Controlled assessment of oral bronchodilators for asthmatic children

Various pulmonary function changes were determined in twenty paediatric patients after a single oral dose of theophylline, ephedrine, or their combination in a double-blind crossover study. The possible contributions of guaifenesin and butabarbital, components of some formulations in clinical use, were also examined. Bronchodilatory efficacy in decreasing order, when compared to placebo, was observed for theophylline-ephedrine and theophylline (nearly comparable), and for ephedrine-butabarbital and ephedrine (nearly comparable). Butabarbital and guaifenesin did not enhance or decrease bronchodilatory effect. Adverse reactions appeared to be more frequently related to ephedrine intake, although no serious reactions were noted.