Biomedical subjects

R Hejal

Publications and source records attributed to R Hejal.

6 recordsLinked to original sources

PubMed1998

Comparison of two dosage regimens of albuterol in acute asthma.

BACKGROUND: The standard therapy for acute episodes of asthma in the United States consists of three 2.5-mg doses of aerosolized albuterol given every 20 minutes. Whether this approach represents optimum therapy has never been tested. METHODS: This study employed a prospective, sequential design in which the effects of two doses of 5.0 mg of aerosolized albuterol administered during 40 minutes (high dose) were contrasted with the standard dose (three 2.5-mg doses). Improvements in pulmonary function, clinical resolution of the asthma attacks, and admission rates were used as primary endpoints. Both regimens were part of an overall care plan that involved objective, pretested decision algorithms. RESULTS: In an emergency department, 160 patients who presented with acute exacerbations of asthma received either standard (n = 80) or high-dose (n = 80) albuterol treatment. There were no significant baseline differences in gender, racial composition, clinical signs and symptoms, medication use, or peak expiratory flow (PEF) between the groups. Both treatment schedules were effective, but the high-dose regimen increased lung function more rapidly and to a greater extent than standard-dose therapy. It also resulted in lower charges to third party payers. More subjects attained the discharge criteria quicker and left the emergency department with peak expiratory flows closer to normal. Fewer patients in the high-dose group were admitted, but this trend did not quite reach statistical significance. CONCLUSIONS: Two 5.0-mg treatments of aerosolized albuterol at a 40-minute interval provide effective therapy for acute exacerbations of asthma. This combination of dose and frequency promotes maximum bronchodilatation, increases efficiency, and reduces the risks of undertreatment.

Acute Disease↗

PubMed1998

Lack of interaction of hyperpnoea with methacholine and histamine in asthma.

1. The thermal precipitants of asthma (exercise and hyperventilation) appear to have a unique pathogenesis that does not alter bronchial responsiveness. In the present work, we tested whether hyperpnoea interacts with other constrictor stimuli.2. To provide data on this issue, we exposed 17 subjects with asthma to isocapnic hyperventilation of frigid air (HV), methacholine (METH) and histamine (HIS) alone and in combination.3. With HV (mean ventilation=55.6+/-7.7 litres/min), METH (2.20+/-0.7 mmol/l) and HIS (10.35+/-5.04 mmol/l) alone, the decrements in forced expiratory volume in 1 s (FEV1) from baseline were 27.4+/-3.4, 27.4+/-3.8 and 32.4+/-3% respectively (n=9). Giving the agonists simultaneously did not produce additive effects (Delta FEV1 HV+METH=32.8+/-3.6%; HV+HIS=28.7+/-5.1%). None of the individual or combined responses was significantly different from each other. Changing the sequence of the experiments and giving METH at the height of the HV-induced bronchial narrowing, instead of during hyperpnoea, did not alter the findings (n=8). The maximum fall in FEV1 after both bronchoconstrictors in this experiment (Delta FEV1=32.3+/-4.3%) was not significantly different from either alone (HV=22.8+/-1.0%; METH=27.3+/-1.9%). When METH and HIS were administered together, however (n=5), a positive interaction ensued (METH=1.53+/-0.56 mmol/l, Delta FEV1=15.6+/-4.6%; HIS=4.77+/-2.07 mmol/l, Delta FEV1=18. 8+/-3.1%; METH+HIS Delta FEV1=33.4+/-5.2%; P<0.001 compared with the individual effects).4. These results indicate that HV does not interact with stimuli that directly or indirectly modulate airway calibre. It is unclear if this effect represents protection conferred from increased bronchial blood flow or derives from differences in effector mechanisms between the thermal and pharmacological agonists.

Adult↗

PubMed1997

Observations on the effects of aerosolized albuterol in acute asthma.

To determine the dose of albuterol required to terminate acute episodes of asthma, 92 acutely ill subjects received three doses of 2.5 mg each by nebulization every 20 min. Peak expiratory flow rates (PEFR) and signs and symptoms were serially monitored. A dose-response increase in pulmonary function was found, but only 66% of the subjects improved sufficiently to be sent home. Of these, 56% required < or = 5.0 mg of drug to reach the discharge threshold, whereas the remainder needed 7.5 mg. In 34% of participants, albuterol was ineffectual. These individuals were characterized by more severe obstruction at presentation, and after three doses of medication their PEFR still did not exceed 40% of the expected value. Further treatment in the emergency department (ED) or hospital was not immediately helpful, and these patients ultimately required 3.8 +/- 0.4 d of inpatient care to become asymptomatic. There were no discernible differences between responders and nonresponders in the type or quantity of medications used. However, the nonresponders had more severe disease as measured by recurrent hospitalizations and ED visits. This study demonstrates that, in emergency situations, albuterol does not relieve acute airway obstruction in all asthmatic individuals with equal efficacy. Two-thirds of patients are sensitive, and in these patients 5 to 7.5 mg of albuterol provides optimal treatment. In the remainder, albuterol, even in high doses, has little effect for days.

Acute Disease↗

PubMed1995

Asthma.

Explore the source record for details and available documents.

Acute Disease↗

PubMed1995

Effect of hypoxia on reflex responses of tracheal submucosal glands.

The effects of moderate sustained normocapnic hypoxia on tracheal submucosal gland reflex responses were studied. Experiments were performed in anesthetized, paralyzed, and mechanically ventilated dogs. The changes in the number of secreting glands and volume of secreted fluid in the subsequent period of time were recorded after 15-30 min of controlled ventilation with room air [arterial PO2 (PaO2) 86 +/- 3 Torr], hypoxic gas mixture (PaO2 49 +/- 4 Torr), or 100% O2 (PaO2 339 +/- 39 Torr), under isocapnic and isohydric conditions. The hillocks method was used to quantify the changes in submucosal gland secretion. The changes in secretion 30 s after stimulation of pulmonary C-fiber receptors by right atrial injection of capsaicin (10 micrograms/kg; n = 10) were markedly lower during moderate hypoxia than in normoxia or hyperoxia. Differences in the number of liquid droplets and the volume of secreted fluid were statistically significant (P < 0.05 and P < 0.001, respectively). Stimulation of airway rapidly adapting receptors by lung deflation increased airway secretion; the number of "hillocks" and the volume of secreted fluid were lower in hypoxic than in hyperoxic state. Differences between response curves for the number of glands activated and secreted volume were statistically significant (P < 0.05 and P < 0.001). The number of glands activated by substance P given locally by arterial infusion was not affected by the state of oxygenation, but the calculated volume of secreted fluid was lower during the hypoxic state than under hyperoxic condition (P = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Pathways and mechanisms involved in neural control of laryngeal submucosal gland secretion.

The purpose of this study was to define the pathways and mechanisms involved in the neural regulation of laryngeal mucosal gland functions. In anesthetized, paralyzed, and artificially ventilated dogs, the responses of laryngeal submucosal glands to stimulation of laryngeal mechanoreceptors and peripheral chemoreceptors were examined by measuring the number of hillocks and volume of secreted fluid before and after activation of sensory nerve endings. Compared with a control period, the number of hillocks and volume of secreted fluid significantly increased (P < 0.05) with mechanical stimulation of the vocal folds (n = 13) and with chemical activation of peripheral chemoreceptors by systemic administration of sodium cyanide (100 micrograms/kg; n = 11). The reflex responses induced by vocal fold stimulation and activation of peripheral chemoreceptors were slightly decreased by interrupting transmission in the recurrent laryngeal nerves (P > 0.05) and were abolished by subsequent sectioning of superior laryngeal nerves or prior intravenous administration of atropine methylnitrate (P < 0.05). In denervated animals, topical application of nicotine on laryngeal epithelium caused significant activation of submucosal glands (P < 0.05). We conclude that laryngeal secretion can be significantly altered reflexly by stimulation of laryngeal sensory nerve endings and peripheral chemoreceptors, that both superior and recurrent laryngeal nerves convey cholinergic outflow to laryngeal submucosal glands, and that nicotine acting locally activates laryngeal submucosal glands.

Animals↗