Diurnal variability of peak expiratory flow

One-day systemic corticosteroid administration for asthma and future "short bursts" risk in real clinical practice

OBJECTIVE

Systemic corticosteroid administration, also called short bursts (SB), is harmful for patients with asthma; however, the actual burden of one-day SB remains unsolved. This study aimed to elucidate the characteristics of patients requiring one-day SB against asthma in clinical practice.

METHODS

Consecutive patients who regularly visited our hospital for asthma treatment between January 2019 and December 2020 were reviewed and followed for one year. SB was defined as ≥3 days of systemic corticosteroid treatment for an exacerbation. One-day SB was defined as one-day of systemic corticosteroid to treat an exacerbation. The one-day SB group included patients who received only one-day SB but no SB during the preceding year. Frequent SB was defined as that occurring ≥2 times/year.

RESULTS

Data on 229 patients were analyzed. Among them, 2.6% (95% confidence interval 1.2-5.6%) were in the one-day SB group. The one-day SB group was female-dominant, obese, non-eosinophilic, and non-atopic. The median one-day SB was 1.5 times/year and almost half of one-day SB were performed by patients themselves. Independent of the low pulmonary function, high blood eosinophil count, and inhaled corticosteroid dose, one-day SB was associated with future frequent SB (adjusted odds ratio = 18.2, 95% confidence interval 1.1-288, P = 0.040, compared to the no SB group).

CONCLUSIONS

Although one-day SB was not frequently experienced, even one-day SB without conventional SB was associated with future frequent SB. It is important to grasp the actual condition of one-day SB and to reinforce the treatment used.

Redox regulation of circadian molecular clock in chronic airway diseases

At the cellular level, circadian timing is maintained by the molecular clock, a family of interacting clock gene transcription factors, nuclear receptors and kinases called clock genes. Daily rhythms in pulmonary function are dictated by the circadian timing system, including rhythmic susceptibility to the harmful effects of airborne pollutants, exacerbations in patients with chronic airway disease and the immune-inflammatory response to infection. Further, evidence strongly suggests that the circadian molecular clock has a robust reciprocal interaction with redox signaling and plays a considerable role in the response to oxidative/carbonyl stress. Disruption of the circadian timing system, particularly in airway cells, impairs pulmonary rhythms and lung function, enhances oxidative stress due to airway inhaled pollutants like cigarette smoke and airborne particulate matter and leads to enhanced inflammosenescence, inflammasome activation, DNA damage and fibrosis. Herein, we briefly review recent evidence supporting the role of the lung molecular clock and redox signaling in regulating inflammation, oxidative stress, and DNA damage responses in lung diseases and their exacerbations. We further describe the potential for clock genes as novel biomarkers and therapeutic targets for the treatment of chronic lung diseases.

Effects of altered airway function on exercise ventilation in asthmatic adults

PURPOSE

Variable airway function is a central feature of the asthmatic condition. Thus, habitually active asthmatics are certain to exercise under conditions of variable airway (dys)function. The purpose of this study was to determine the effects of variable preexercise airway function on ventilation during whole-body exercise in asthmatic adults.

METHODS

Eight mild asthmatic (age = 26 yr; V˙O2peak = 49 mL·kg·min) and nine nonasthmatic (age = 30 yr; V˙O2peak = 46 mL·kg·min) adults performed constant workrate cycling exercise to exhaustion after four separate interventions: 1) a control trial (CON); 2) inhalation of fast-acting β2-agonist (BD); 3) eucapnic voluntary hyperpnea challenge (BC); and 4) sham to the hyperpnea (SHAM). Pulmonary function was assessed at baseline and after each intervention. Exercise ventilation and operating lung volumes were compared among the four exercise trials in both control and asthmatic subjects.

RESULTS

Baseline pulmonary function was significantly lower in asthmatic subjects compared with control subjects. In asthmatic subjects, postintervention (i.e., preexercise) forced expiratory volume 1.0 s was significantly different among the four exercise trials (CON = 3.5 ± 0.4, BD = 4.1 ± 0.4, SHAM = 3.6 ± 0.3, BC = 2.8 ± 0.3 L, P < 0.05), whereas it was not different in control subjects. There were no differences in exercise ventilation or operating lung volumes during exercise among the four trials either within asthmatic subjects or between control and asthmatic subjects.

CONCLUSIONS

These findings suggest that the state of airway function-whether bronchodilated or bronchoconstricted-before exercise in the mild asthmatic does not affect the exercise ventilatory response. Thus, ventilatory system function in the asthmatic appears to be responsive to the acute requirement for increased airflow during whole-body exercise.

Assessing the exacerbations risk of influenza-associated chronic occupational asthma

The purpose of this article was to conduct a risk-based study based on a linkage of experimental human influenza infections and fluctuation analysis of airway function to assess whether influenza viral infection was risk factor for exacerbations of chronic occupational asthma. Here we provided a comprehensive probabilistic analysis aimed at quantifying influenza-associated exacerbations risk for occupational asthmatics, based on a combination of published distributions of viral shedding and symptoms scores and lung respiratory system properties characterized by long-range peak expiratory flow (PEF) dynamics. Using a coupled detrended fluctuation analysis-experimental human influenza approach, we estimated the conditional probability of moderate or severe lung airway obstruction and hence the exacerbations risk of influenza-associated occupational asthma in individuals. The long-range correlation exponent (alpha) was used as a predictor of future exacerbations risk of influenza-associated asthma. For our illustrative distribution of PEF fluctuations and influenza-induced asthma exacerbations risk relations, we found that the probability of exacerbations risk can be limited to below 50% by keeping alpha to below 0.53. This study also found that limiting wheeze scores to 0.56 yields a 75% probability of influenza-associated asthma exacerbations risk and a limit of 0.34 yields a 50% probability that may give a representative estimate of the distribution of chronic respiratory system properties. This study implicates that influenza viral infection is an important risk factor for exacerbations of chronic occupational asthma.

Sleep deprivation influences diurnal variation of human time perception with prefrontal activity change: a functional near-infrared spectroscopy study

Human short-time perception shows diurnal variation. In general, short-time perception fluctuates in parallel with circadian clock parameters, while diurnal variation seems to be modulated by sleep deprivation per se. Functional imaging studies have reported that short-time perception recruits a neural network that includes subcortical structures, as well as cortical areas involving the prefrontal cortex (PFC). It has also been reported that the PFC is vulnerable to sleep deprivation, which has an influence on various cognitive functions. The present study is aimed at elucidating the influence of PFC vulnerability to sleep deprivation on short-time perception, using the optical imaging technique of functional near-infrared spectroscopy. Eighteen participants performed 10-s time production tasks before (at 21:00) and after (at 09:00) experimental nights both in sleep-controlled and sleep-deprived conditions in a 4-day laboratory-based crossover study. Compared to the sleep-controlled condition, one-night sleep deprivation induced a significant reduction in the produced time simultaneous with an increased hemodynamic response in the left PFC at 09:00. These results suggest that activation of the left PFC, which possibly reflects functional compensation under a sleep-deprived condition, is associated with alteration of short-time perception.

Monosodium glutamate 'allergy': menace or myth?

Monosodium glutamate (MSG) is a salt form of a non-essential amino acid commonly used as a food additive for its unique flavour enhancing qualities. Since the first description of the 'Monosodium glutamate symptom complex', originally described in 1968 as the 'Chinese restaurant syndrome', a number of anecdotal reports and small clinical studies of variable quality have attributed a variety of symptoms to the dietary ingestion of MSG. Descriptions of MSG-induced asthma, urticaria, angio-oedema, and rhinitis have prompted some to suggest that MSG should be an aetiologic consideration in patients presenting with these conditions. This review prevents a critical review of the available literature related to the possible role of MSG in the so-called 'Chinese restaurant syndrome' and in eliciting asthmatic bronchospasm, urticaria, angio-oedema, and rhinitis. Despite concerns raised by early reports, decades of research have failed to demonstrate a clear and consistent relationship between MSG ingestion and the development of these conditions.

Effect of fetal sex on airway lability in pregnant women with asthma

The authors investigated the association between sex of the fetus and maternal airway lability among pregnant women with asthma. Data were prospectively collected among 702 pregnant women with a diagnosis of asthma who were recruited in southern New England between 1997 and 2000 and followed through pregnancy. Peak expiratory flow lability, defined as percent daily maximum minus the minimum divided by the mean, was assessed at enrollment and at 21, 29, and 37 weeks' gestation. There was a -9.9 percent (95 percent confidence interval: -19.4, -0.4) difference in airway lability observed between women carrying female fetuses and those carrying male fetuses. This difference persisted throughout pregnancy. Among pregnant asthmatic women, carrying a female fetus is associated with worse maternal asthma, as assessed by greater airway lability, than is carrying a male fetus.

Underestimation of the peak flow variability in asthmatic children: evaluation of a new formula

Asthma guidelines suggest evaluation of peak expiratory flow (PEF) variability, but timing for the two PEF measurements is not mentioned. Usual formula calculates amplitude as percentage of mean day-night PEF values. Since PEF circadian changes follow a sinusoidal function, we reasoned that variability might be calculated by measuring PEF at 4 pm (PEF(1)) and either at 10 am or 10 pm (PEF(2)) with the formula %variability = 200 . |PEF(1)-PEF(2)|/PEF(2). Children with stable, mild intermittent asthma were recruited from an Asthma Clinic and asked to perform PEF measurements at even hours during a week, until 12 measurements covering a 24-h period were accomplished. From these measurements we calculated PEF variability through several methods. Accuracy of such methods to predict actual PEF variability was assessed through the concordance correlation coefficient (r(c)). Thirty five asthmatic children were recruited. Actual PEF variability, calculated with the usual formula using the highest and lowest PEF obtained at any time of the 24 h cycle had a median of 37.3% (range, 0-88.5%). Variability calculated through other methods was: usual formula with highest and lowest PEF obtained from the sinusoidal curve, 21.4% (r(c) = 0.79); usual formula with PEF measured at 4 pm and 4 am, 17.8% (r(c) = 0.67); proposed formula using PEF measured at 4 pm and either 10 pm, 15.9% (r(c) = 0.68), or 10 am, 17.4% (r(c) = 0.69). Some examples with PEF measured in the morning (8 am or 10 am) and at night (8 pm or 10 pm) yielded median PEF variability from 4.0% (r(c) = 0.18) to 8.7% (r(c) = 0.38). Current methods for calculating PEF variability seemed not to be accurate enough as to be confident, suggesting that an in-deep reevaluation of the usefulness of PEF variability or, conversely, of the methods to assess it, should be done.