Oscillometry and spirometry are not interchangeable when assessing the bronchodilator response in children and young adults born preterm

INTRODUCTION

The European Respiratory Society Oscillometry Taskforce identified that clinical correlates of bronchodilator responses are needed to advance oscillometry in clinical practice. The understanding of bronchodilator-induced oscillometry changes in preterm lung disease is poor. Here we describe a comparison of bronchodilator assessments performed using oscillometry and spirometry in a population born very preterm and explore the relationship between bronchodilator-induced changes in respiratory function and clinical outcomes.

METHODS

Participants aged 6-23 born ≤32 (N = 288; 132 with bronchopulmonary dysplasia) and ≥37 weeks' gestation (N = 76, term-born controls) performed spirometry and oscillometry. A significant bronchodilator response (BDR) to 400 μg salbutamol was classified according to published criteria.

RESULTS

A BDR was identified in 30.9% (n = 85) of preterm-born individuals via spirometry and/or oscillometry, with poor agreement between spirometry and oscillometry definitions (k = 0.26; 95% confidence interval [CI] 0.18-0.40, p < .001). Those born preterm with a BDR by oscillometry but not spirometry had increased wheeze (33% vs. 11%, p = .010) and baseline resistance (Rrs5 z-score mean difference (MD) = 0.86, 95% CI 0.07-1.65, p = .025), but similar baseline spirometry to the group without a BDR (forced expiratory volume in 1 s [FEV1 ] z-score MD = -0.01, 95% CI -0.66 to 0.68, p > .999). Oscillometry was more feasible than spirometry (95% success rate vs. 85% (FEV1 ), 69% (forced vital capacity) success rate, p < .001), however being born preterm did not affect test feasibility.

CONCLUSION

In the preterm population, oscillometry is a feasible and clinically useful supportive test to assess the airway response to inhaled salbutamol. Changes measured by oscillometry reflect related but distinct physiological changes to those measured by spirometry, and thus these tests should not be used interchangeably.

Inhaled corticosteroids to improve lung function in children (aged 6-12 years) who were born very preterm (PICSI): a randomised, double-blind, placebo-controlled trial

BACKGROUND

Despite the substantial burden of lung disease throughout childhood in children who were born very preterm, there are no evidence-based interventions to improve lung health beyond the neonatal period. We tested the hypothesis that inhaled corticosteroid improves lung function in this population.

METHODS

PICSI was a randomised, double-blind, placebo-controlled trial at Perth Children's Hospital (Perth, WA, Australia) to assess whether fluticasone propionate, an inhaled corticosteroid, improves lung function in children who had been born very preterm (<32 weeks of gestation). Eligible children were aged 6-12 years and did not have severe congenital abnormalities, cardiopulmonary defects, neurodevelopmental impairment, diabetes, or any glucocorticoid use within the preceding 3 months. Participants were randomly assigned (1:1) to receive 125 μg fluticasone propionate or placebo twice daily for 12 weeks. Participants were stratified for sex, age, bronchopulmonary dysplasia diagnosis, and recent respiratory symptoms using the biased-coin minimisation technique. The primary outcome was change in pre-bronchodilator forced expiratory volume in 1 s (FEV₁) after 12 weeks of treatment. Data were analysed by intention-to-treat (ie, all participants who were randomly assigned and took at least the tolerance dose of the drug). All participants were included in the safety analyses. This trial is registered at the Australian and New Zealand Clinical Trials Registry, number 12618000781246.

FINDINGS

Between Oct 23, 2018, and Feb 4, 2022, 170 participants were randomly assigned and received at least the tolerance dose (83 received placebo and 87 received inhaled corticosteroid). 92 (54%) participants were male and 78 (46%) were female. 31 participants discontinued treatment before 12 weeks (14 in the placebo group and 17 in the inhaled corticosteroid group), mostly due to the impact of the COVID-19 pandemic. When analysed by intention-to-treat, the change in pre-bronchodilator FEV₁ Z score over 12 weeks was -0·11 (95% CI -0·21 to 0·00) in the placebo group and 0·20 (0·11 to 0·30) in the inhaled corticosteroid group (imputed mean difference 0·30, 0·15-0·45). Three of 83 participants in the inhaled corticosteroid group had adverse events requiring treatment discontinuation (exacerbation of asthma-like symptoms). One of 87 participants in the placebo group had an adverse event requiring treatment discontinuation (inability to tolerate the treatment with dizziness, headaches, stomach pains, and worsening of a skin condition).

INTERPRETATION

As a group, children born very preterm have only modestly improved lung function when treated with inhaled corticosteroid for 12 weeks. Future studies should consider individual phenotypes of lung disease after preterm birth and other agents to improve management of prematurity-associated lung disease.

FUNDING

Australian National Health and Medical Research Council, Telethon Kids Institute, and Curtin University.

Determination of 1,7,7-Trimethyl-bicyclo(2,2,1)heptan-2-one in a Cream Pharmaceutical Formulation by Reversed-phase Liquid Chromatography

A reversed-phase liquid chromatographic method for the determination of 1,7,7-trimethyl-bicyclo(2,2,1)heptan-2-one in a cream formulation is developed and validated. The separation was achieved using an isocratic mobile phase, on a Lichrosorb C8 column. The calibration curve is linear (r²= 0.9999) from 25-175% of the analytical concentration of 1.0 mg/ml. The mean percent standard deviation values for intra-day and inter-day precision studies were <1%. The recovery ranges 99.80-100.06% from a cream formulation. The method can be used reliably in quality control for the analysis of bulk cream samples and final product release.

Development and Validation of a RPLC Method for the Determination of 2-Phenoxyethanol in Senselle Lubricant Formulation

A new and simple reversed-phase liquid chromatographic method has been developed and validated for the determination of 2-phenoxyethanol preservative (0.3%, w/w) in senselle lubricant formulation. The separation was achieved with acetonitrile-tetrahydrofuran-water (21:13:66, v/v/v) as mobile phase, a C(8) column, and UV detection at 258 nm. The calibration curve is linear (r(2)= 0.9999) from 20-140% of the analytical concentration of 0.75 mg/ml. The mean percent relative standard deviation values for intra- and inter-day precision studies are <1%. The recovery of 2-phenoxyethanol ranged between 99.76 and 100.03% from lubricant formulation. The limits of detection and quantitation are determined to be 0.094 and 0.15 mg/ml, respectively. The method was found to be robust and can be successfully and reliably used to determine the 2-phenoxyethanol preservative content of marketed formulations.

DNA single-strand breaks in adult and embryonic avian erythrocytes

We have investigated the possibility that the reactivation rate of adult avian erythrocytes, which is slower than that of embryonic erythrocytes, after fusion with metabolically active cells, is due to a greater number of single-strand breaks (ssb) in the DNA of the former. We have assayed ssb by measuring the template activity of the erythrocyte nuclei for added Escherichia coli DNA polymerase. We have found that differences in the numbers of ssb within polymerase-accessible regions between adult and embryonic cells are within experimental error. We conclude that, unless very localized clusters of damage exist within the DNA (which would not be detectable by this or other techniques), the difference in reactivation rate is not attributable to differences in ssb numbers.

Effect of N-methyl-N-nitrosourea on avian erythrocyte nuclei reactivation

Avian erythrocytes are terminally differentiated cells but they can be reactivated by fusion with actively metabolising cells. We have examined the effects of treating the erythrocytes with a carcinogenic methylating agent, N-methyl-N-Nitrosourea (MNU), on the process of reactivation of adult and embryonic nuclei. We have found that the rate of nuclear enlargement is slightly lower in nuclei from MNU-treated cells than from control cells and that there is a marked delay of about 24 h in the appearance of nucleoli in both adult and embryonic cells. This is not due to an effect of MNU on ribosomal (r)DNA: the number of rDNA genes appears to be similar in treated and control cells. Also, the number of rDNA genes appears to be similar in adult and embryonic cells and in unreactivated and reactivated embryonic nuclei: thus, differences in reactivation rate between adult and embryonic cells, observed by us and others, can not be attributed to a gross difference in their ribosomal DNA contents, and reappearance of nucleoli on reactivation can not be due to an amplification of rDNA (i.e., to recovery of such genes if lost on terminal differentiation). We suggest that MNU, although a monofunctional alkylating agent, may cause increased association--possibly cross-linkage--between DNA and protein in chromatin, thereby hindering access of host cell reactivating proteins, especially to the nucleolar regions.

Chromatin characteristics of carcinogen-treated avian erythrocyte nuclei and effects of reactivation

We have examined nucleosome repeat length and accessibility of erythrocyte nuclei to micrococcal nuclease before and after reactivation of the erythrocytes by fusion with A9 cells, and also after treatment with the alkylating agent N-methyl-N-nitrosourea (MNU). We have found that the repeat length is higher for adult than for embryonic nuclei (227 and 202 base pairs, respectively) and after reactivation the value decreases (to 183 +/- 2 bp and 172 +/- 4 bp, respectively). Values for MNU-treated, reactivated nuclei are slightly (but probably not significantly) higher (188 bp and 176 +/- 1 bp) than for corresponding untreated nuclei. However, the rate of digestion is lower in MNU-treated erythrocytes, both unreactivated and reactivated, than in the corresponding untreated nuclei.

Cell transformation: the role of oncogenes and growth factors

An attempt is made to draw together diverse areas of biological research which have recently converged and opened up new experimental approaches to understanding the nature of cancer. In particular, the powerful techniques of molecular biology have been brought to bear on tissue culture systems. The case is made for the continued use of cell transformation in vitro as a real and useful model for cancer development. The hallmark of all cancer cells is loss of control over the cell cycle and the cellular elements involved, growth factors, growth factor receptors and signal transducers have been identified and in some instances shown to be encoded in cellular oncogenes. Moreover, as the molecular mechanisms underlying cell growth control are unravelled, those aspects involved in neoplastic change will be identified and this will lead to the development of definitive short-term tests for the detection of chemical carcinogens.

Molecular phenotyping of non-transformed and chemically transformed C3H10T1/2 mouse fibroblasts

A systematic molecular phenotyping approach based on two-dimensional gel electrophoresis is being applied in an attempt to identify protein changes associated with malignant transformation. Using the C3H10T1/2 mouse cell line, two-dimensional polypeptide maps of the non-transformed cell line, several chemically transformed lines and a tumour cell line were compared. Although there is a large degree of similarity between the protein profiles of all cell lines, clear differences are evident. Initial results are consistent with the view that many of the protein changes are incidental to malignant transformation. Changes induced by 3-methylcholanthrene are retained after transplantation of the cells into nude mice.

Alterations in the enzyme activity and polypeptide composition of rat hepatic endoplasmic reticulum during acute exposure to 2-acetylaminofluorene

Studies have been made of the morphology, enzyme activity and protein composition of liver endoplasmic reticulum in rats exposed to acute doses of the carcinogen, 2-acetylaminofluorene (2-AAF). Electron microscopic examination revealed numerous ultrastructural changes in the hepatocyte; most consistent alterations were the disorganisation of endoplasmic reticulum system with apparent increase of smooth endoplasmic reticulum. Administration of 2-AAF to rats immediately depressed microsomal glucose-6-phosphatase activity and eventually induced epoxide hydratase activity 6--7-fold over control activity. The induction was time-dependent and maximal rates of induction were observed at dosages greater than 40 mg/kg body wt. The treatment also induced cytochrome b5 content, NADH and NADPH cytochrome c reductase activities (1.0--1.5-fold). Only very small changes in the total content of cytochrome P-45- were noted. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of microsomal proteins from 2-AAF pretreated animals showed time-dependent induction of two polypeptides which differed slightly in migration, in the region of Mr = 48000; the fast-migrating induced polypeptide has been identified as epoxide hydratase. Two-dimensional PAGE analysis of microsomal proteins from 2-AAF exposed rats showed a reproducible deletion of a protein with molecular weight in the region of 67000. The basis for the alterations in the protein composition of endoplasmic reticulum in response to 2-AAF treatment is discussed.

Specific labelling of microsomal proteins by reactive intermediates generated from 2-acetylaminofluorene in vitro

Incubation of 2-[9-14C]acetylaminofluorene (2-[9-14C]AAF) in vitro with rat liver microsomes, leads to covalent binding of label to microsomal proteins. The binding is NADPH-dependent, increases linearly with time, and is inhibited by SKF-525A and 7,8-benzoflavone (7,8-BF). Binding is increased more than 8-fold in microsomes from 3-methylcholanthrene(MC)-pretreated rats, but only less than 2-fold in those from phenobarbital(PB)-pretreated rats. In the presence of cytosolic proteins, there is slight enhancement of the labelling of microsomes and some labelling of the cytosolic proteins. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and 2-dimensional gel electrophoresis indicate that covalent labelling by 2-AAF derivatives is concentrated in specific proteins. The pattern of labelling varies between microsomes from animals pretreated with PB, MC and 2-AAF. Factors which may contribute to the specificity of labelling are discussed.

The effect of 5-bromodeoxyuridine on interferon production in human cells

5-Bromodeoxyuridine (BrdUrd) increased interferon production by the Namalwa line of human lymphoblastoid cells treated with Sendai virus, but inhibited their growth. Thymidine, which also inhibited cell growth had no effect on interferon production, so that growth inhibition per se was not the cause of the stimulation. BrdUrd was incorporated into cellular DNA; 5-chlorodeoxyuridine and 5-iododeoxyuridine (which are also incorporated) increased the interferon yield, but 5-fluorodeoxyuridine (which is not incorporated) did not. Thymidine reduced both the incorporation of BrdUrd and its stimulatory effect on interferon production. Deoxycytidine (which prevents the cytotoxic effects of BrdUrd) had no effect on the stimulation. BrdUrd also stimulated interferon production in response to poly(rI) . poly(rC) in growing human diploid fibroblasts but not in SV40 virus-transformed human cells. Since BrdUrd was incorporated into the DNA of all these cells, we concluded that incorporation is necessary, but not sufficient for the stimulation of interferon formation.

Electron impact studies. LVI. The fluorenyl and phenalenyl cations. The application of metastable characteristics

A study of the abundances of certain metastable peaks formed by the de- composition of ions in the first and second field-free regions of a double-focusing mass spectrometer has shown that the M-1 ions (m/e 165) in the mass spectra of fluorene and phenalene have different structures. Correlations based on these structures have been obtained for C13H9+ species formed from different systems.