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Biomedical subjects

H Chai

Publications and source records attributed to H Chai.

At least 73 records · Page 4Linked to original sources
PubMed1984

Analysis of hyperventilation response in asthmatics.

We have tested seven young adult asthmatics (17-35 years) with two different tests of airway reactivity, i.e., treadmill exercise test and isocapnic hyperventilation test. To estimate the level of respiratory heat loss we standardized environmental conditions so that during these tests patients inhaled compressed air of 23 degrees and 0% of R.H. The level of ventilation during these tests thus determined the respiratory heat loss. It was found that five out of seven tested patients showed dose-response-like relationships between a change in FEF 25-75% (or FEV1) and minute ventilation as measured during exercise or voluntary hyperventilation (r = -.80 to -.97). However, in two patients this relationship could not be established. These two patients had the lowest baseline pulmonary function of the whole group, and by definition they had the most hyperreactive airways. When the change in pulmonary function observed after three to six minutes of isocapnic hyperventilation (both at the same level of minute ventilation) were compared it was found that the six minute test caused only slightly greater changes (P less than 0.01) than the three minute test. It is concluded that in asthmatics the relationship between a decrease in pulmonary function and respiratory heat loss varies among patients.

Adolescent↗
PubMed1984

Development of posterior subcapsular cataracts in asthmatic children.

Posterior subcapsular cataracts (PSCC) are known complications of systemic steroid therapy. Previous studies have not clearly identified the asthmatic children at risk for the development of PSCC. The possible factors associated with systemic steroid administration that may influence the development of PSCC in asthmatic children were evaluated: (1) duration of administered steroids, (2) dose, (3) number of steroid "bursts" in the preceding year, (4) degree of retardation of bone age, and (5) mode of administration (daily or alternate day) of steroids. Of the 40 asthmatic children requiring steroids, seven (17.5%) had PSCC. All of the children with PSCC had been receiving steroids on a daily or alternate-day basis for at least 2 years and all had markedly delayed bone age. Only one child with the concurrent occurrence of these two factors did not develop PSCC. None of the other risk factors considered could distinguish the group of patients with PSCC. It is concluded that asthmatic children receiving steroids for 2 years or longer and having markedly delayed bone age are at a greater risk for the development of PSCC.

Adolescent↗
PubMed1983

Effects of particulate air pollution on asthmatics.

Twenty-four asthmatic subjects in Denver were followed from January through March 1979, a three-month period in which Denver air pollution levels are generally high and variable. Dichotomous, virtual impactor samplers provided daily measurements (micrograms/m3) of inhaled particulate matter (total mass, sulfates, and nitrates) for coarse (2.5--15 micrograms in aerodynamic diameter) and fine fractions (less than 2.5 micrometers). Carbon monoxide, sulfur dioxide, ozone, temperature, and barometric pressure were also measured. Twice daily measurements of each subject's peak expiratory flow rates, use of as-needed aerosolized bronchodilators, and report of airways obstruction symptoms characteristic of asthma were tested for relationships to air pollutants using a random effects model across subjects. During the time actually observed, there were very few days in which high levels of suspended particulates were recorded. Of the environmental variables studied, only fine nitrates were associated with increased symptom reports and increased aerosolized bronchodilator usage.

Adult↗
PubMed1983

Two types of responses to exercise and isocapnic hyperventilation in asthmatics.

Seven young adult asthmatics (17-35 years old) with an established diagnosis of mild to severe bronchial asthma were tested twice per day on six different days. On these days, all of the subjects undertook the treadmill exercise test of varying intensity for a duration of 6 minutes. Four hours later a voluntary isocapnic hyperventilation challenge of 6 minutes duration was done with essentially the same level of minute ventilation as achieved during and immediately after the exercise. During exercise and voluntary isocapnic hyperventilation tested patients inhaled dry compressed air of 23 degrees C. Heart rate, minute ventilation and end tidal pCO2 were monitored before, during and after each test. Pulmonary functions were measured before and after each procedure including: spirometry, measurement of airway resistance (Raw) and thoracic gas volume (Tgv). We found that five out of seven patients showed a dose-response-like relationship between a change in pulmonary function (FEF25-75% and FEV1) and total ventilation as measured during treadmill exercise or isocapnic hyperventilation challenge. In two patients we failed to establish this relationship. In these two patients different levels of ventilation (as measured during exercise or isocapnic hyperventilation) induced a similar degree of bronchoconstriction. These two patients had the lowest baseline pulmonary function of the whole group and by definition they had the most reactive airways.

Adolescent↗
PubMed1982

Linear growth of chronic asthmatic children: the effects of the disease and various forms of steroid therapy.

The effects of asthma per se and of various oral steroid-treatment schedules on linear growth in 231 children with chronic severe asthma (6.2-16.2 years of age) were evaluated. Asthmatic children who had never received steroids and those who received occasional steroids, had comparable growth retardation, averaging approximately 1 standard deviation (s.d.) below their age- and sex-specific predicted means. Children who had been treated for 2 years or longer with alternate-day or daily steroids also did not differ from each other, with both groups averaging approximately 2 s.d. below their predicted means. Growth stunting, intermediate in severity, was found in children treated with frequent intermittent steroids. For groups with steroid medication-histories of never, occasional, intermittent, alternate-day and daily, the percentage of children with 2 or more s.d. below their predicted heights were 25, 17.4, 28, 50 and 45.5 respectively. The duration and dosage of daily steroid-treatment correlated positively with severity of growth retardation. In addition to norms, the children were also compared with a healthy, same-sex sibling and with predictions from their parents' heights. Regardless of the comparison used, the results were similar. Since genetic and socio-economic factors are controlled by the latter two comparisons, the data indicate that these factors played no role in growth retardation in these children. Growth retardation in asthma appears to be due to the disease itself, and is accelerated by steroid therapy.

Adolescent↗
PubMed1982

Airway cooling and nocturnal asthma.

It has long been recognized that asthma often worsens at night. The nature of nocturnal asthma is unclear. Previously we have demonstrated that acute asthma attacks can be induced by exposing the body to cold, and that such attacks can be prevented by breathing warm, humidified air (WHA). Since body temperature begins to decrease late at night and continues through the early morning hours, we suspected that part if not all of nocturnal asthma may be triggered by the same mechanism as asthma induced by body cooling. To test this hypothesis, eight asthmatic patients were studied on four occasions. The subjects breathed either ambient room air (RA; 23 degrees C, 20 percent relative humidity) or WHA (37 degrees C, 100 percent relative humidity) for eight hours during the night with or without taking their regular evening medication. Each night, oral temperature and pulmonary function were measured at 9:45 PM (baseline measurement) and again at 6:15 AM (morning measurement). Results showed that when RA was used, morning pulmonary function and oral temperature decreased significantly from baseline. Using WHA in conjunction with regular evening medication completely prevented both nocturnal asthma and changes in oral temperature. Using WHA without regular evening medication did not prevent but substantially reduced bronchoconstriction compared with RA. These results suggest that airway cooling, which occurs as a consequence of body cooling, plays a significant role in triggering nocturnal asthma.

Adolescent↗
PubMed1982

Intravenous maintenance aminophylline dosage in patients with asthma on regular oral theophylline.

Intravenous maintenance aminophylline infusion rate can be calculated from the previously received equivalent oral dosage in children with chronic asthma with considerable accuracy. This method is expected to be more effective than that calculated from the body weight-based recommended guidelines. Reducing the intravenous aminophylline infusion rate in patients who have an upper respiratory infection is likely to reduce the risk of theophylline toxicity.

Administration, Oral↗
PubMed1981

Effect of erythromycin on theophylline clearance in asthmatic children.

Fifteen asthmatic children (mean age = 14.5 years) who required daily theophylline therapy were studied for effect of erythromycin ethyl-succinate on theophylline clearance. After a one week course of EES, there was 25.8 +/- 18.4% reduction in theophylline clearance rate (P less than 0.001), and a concomitant elevation in steady-state serum theophylline concentration of 40.0 +/- 35.3% (P less than 0.01). Three subjects reached serum theophylline concentrations greater than 20 micrograms/ml. Patients receiving therapeutic doses of theophylline are at considerable risk of theophylline toxicity if EES is co-administered.

Adolescent↗
PubMed1981

Atropine and exercise-induced bronchoconstriction.

Six asthmatic children were studied to determine whether supplemental, parenteral atropine would increase the effects of bronchodilation and protection against exercise-induced bronchoconstriction after maximal effects had been achieved by inhalation. First, we determined the amount of inhaled atropine sulfate that would give maximal bronchodilation for each patient at rest. This quantity of atropine was designated as "A." Then all subjects exercised for five sessions with the following pre-exercise treatments in a random order: (a) inhaled distilled water plus intramuscular (IM) saline solution; (b) inhaled A dose of atropine plus IM saline solution; (c) inhaled distilled water plus 0.35 mg IM atropine; (d) inhaled A dose of atropine plus 0.35 mg IM atropine; and (e) inhaled double the A dose plus IM saline solution. The results showed that the combination of inhaled and IM atropine had the greatest bronchodilation effect and the greatest protection against exercise-induced bronchoconstriction. Atropine inhalation alone (A dose) or IM injection (0.35 mg) was not as effective in bronchodilation or in alleviation of exercise-induced bronchoconstriction. Doubling the dose of inhalation (2A) did not increase the effects of the A dose. These results support the hypothesis that inhaled atropine does not reach all the airways where cholinergic receptors are present.

Adolescent↗
PubMed1981

Efficacy of rush immunotherapy in decreasing bronchial sensitivity to inhaled antigens in perennial childhood asthma.

Rush Immunotherapy (IT) was given to 13 children with asthma, positive skin tests (ST), bronchial provocation tests (BPT) and compatible histories. ST was done by prick or intradermal technique, using commercially available antigens (Ag). BPT was done after an eight-hour medication hold for oral bronchodilators (BD) and four hours for inhaled BD. A Fisons/Vaponephrine nebulizer with an air compressor was used to deliver the Ag. A persistent 25% decrease in peak expiratory flow rate was considered a positive test. Rush IT consisted of four Ag dilutions: 10, 100, 1000 and 5000 pnu/ml. The maintenance dose of 0.5 ml of the 5000 pnu/ml solution was achieved in from seven to 18 weeks (mean 12 weeks). The total cumulative dose of Ag ranged from 3000--14000 pnu (mean 7200 pnu) when the BPT was repeated. Two patients had mild wheezing post-injections and rush IT was discontinued; one of these was later restarted and tolerated the IT well. Three were discharged from the Center prior to repeat BPT. Nine completed the protocol to a total of 14 Ags. One had increased bronchial sensitivity (BS) to both Ags tested. One had no change in BS. Seven subjects had decreased BS on 11 post-rush IT BPTs, four by an unknown degree as the BPT was negative on re-challenge. The mean pre-rush IT BPT was positive at 900 pnu (range 190--2200 pnu); the mean post-RI BPT was positive at 2600 pnu (range 20--7200 pnu). Five patients who had repeat BPT's to the same Ag without IT served as controls. The results showed that (1) Rush IT is a safe and effective method of IT and (2) a marked change in BS can be achieved rapidly and after a relatively low administered dose of Ag in a majority of patients.

Adolescent↗
PubMed1981

Calibration and stability of Standard and Mini-Wright peak flow meters.

Periodic checks of peak flow meter (PFM) stability is essential to ensure meaningful application even when the PFMs are only used to measure the relative changes in patient peak flow rate. Calibration of PFMs becomes necessary, however, when peak flow readings are to be interpreted precisely. Techniques and flow systems which offer ease and accuracy in calibrating and/or checking PFMs were tested on Standard Wright and Mini-Wright PFMs. Individual Wright PFMs were found to be stable over a six-month testing period. The PFM readings varied from actual flow, however, and the variation from actual flow was greatest among the Mini-Wright PFMs.

Forced Expiratory Flow Rates↗
PubMed1980

Corticosteroids in the treatment of acute exacerbations of asthma.

In a 72-hour double-blind study 16 moderately to severely asthmatic subjects received either oral prednisone 2 mg/kg/day or placebo in addition to their regular medication as treatment for an acute exacerbation of asthma. The group receiving prednisone demonstrated significant increases in the PEFR and decreased need for beta-2 agonist nebulization or injections the first 12 hours of the study period and these improvements were maintained over the 72 hours. The placebo-treated group showed minimal reduction in nebulization and injection requirements and minimal increase in PEFR. Oral prednisone was found to be effective in controlling acute exacerbations of asthmatic symptoms.

Acute Disease↗