Study of the role of exhaled nitric oxide (NO) in predicting controlled or uncontrolled asthma in asthmatic children

Effects of different nitric oxide synthases on pulmonary and systemic hemodynamics in hypoxic stress rat model

BACKGROUND

Under hypoxia, exaggerated compensatory responses may lead to acute mountain sickness. The excessive vasodilatory effect of nitric oxide (NO) can lower the hypoxic pulmonary vasoconstriction (HPV) and peripheral blood pressure. While NO is catalyzed by various nitric oxide synthase (NOS) isoforms, the regulatory roles of these types in the hemodynamics of pulmonary and systemic circulation in living hypoxic animals remain unclear. Therefore, this study aims to investigate the regulatory effects of different NOS isoforms on pulmonary and systemic circulation in hypoxic rats by employing selective NOS inhibitors and continuously monitoring hemodynamic parameters of both pulmonary and systemic circulation.

METHODS

Forty healthy male Sprague-Dawley (SD) rats were randomly divided into four groups: Control group (NG-nitro-D-arginine methyl ester, D-NAME), L-NAME group (non-selective NOS inhibitor, NG-nitro-L-arginine methyl ester), AG group (inducible NOS inhibitor group, aminoguanidine), and 7-NI group (neurological NOS inhibitor, 7-nitroindazole). Hemodynamic parameters of rats were monitored for 10 min after inhibitor administration and 5 min after induction of hypoxia [15% O2, 2200 m a. sl., 582 mmHg (76.5 kPa), Xining, China] using the real-time dynamic monitoring model for pulmonary and systemic circulation hemodynamics in vivo. Serum NO concentrations and blood gas analysis were measured.

RESULTS

Under normoxia, mean arterial pressure and total peripheral vascular resistance were increased, and ascending aortic blood flow and serum NO concentration were decreased in the L-NAME and AG groups. During hypoxia, pulmonary arterial pressure and pulmonary vascular resistance were significantly increased in the L-NAME and AG groups.

CONCLUSIONS

This compensatory mechanism activated by inducible NOS and endothelial NOS effectively counteracts the pulmonary hemodynamic changes induced by hypoxic stress. It plays a crucial role in alleviating hypoxia-induced pulmonary arterial hypertension.

Objective monitoring tools for improved management of childhood asthma

Asthma is a common chronic disease amongst children. Epidemiological studies showed that the mortality rate of asthma in children is still high worldwide. Asthma control is therefore essential to minimize asthma exacerbations, which can be fatal if the condition is poorly controlled. Frequent monitoring could help to detect asthma progression and ensure treatment effectiveness. Although subjective asthma monitoring tools are available, the results vary as they rely on patients' self-perception. Emerging evidence suggests several objective tools could have the potential for monitoring purposes. However, there is no consensus to standardise the use of objective monitoring tools. In this review, we start with the prevalence and severity of childhood asthma worldwide. Then, we detail the latest available objective monitoring tools, focusing on their effectiveness in paediatric asthma management. Publications of spirometry, fractional exhaled nitric oxide (FeNO), hyperresponsiveness tests and electronic monitoring devices (EMDs) between 2016 and 2023 were included. The potential advantages and limitations of each tool were also discussed. Overall, this review provides a summary for researchers dedicated to further improving objective paediatric asthma monitoring and provides insights for clinicians to incorporate different objective monitoring tools in clinical practices.

Clinical and functional characteristics of OSA in children with comorbid asthma treated by leukotriene receptor antagonist: A descriptive study

Background

Obstructive sleep apnea (OSA) is the most common form of respiratory disorders during sleep in children, especially those with severe asthma. However, optimal treatment of asthma might significantly improve OSA severity.

Methods

It was a cohort study including children aged >5 years old and diagnosed with asthma according to GINA (Global Initiative for Asthma). The data related to age, gender, height, weight, body mass index (BMI), clinical symptoms and medical history of asthma, spirometry (FEV₁: forced expiratory in 1 s), and exhaled nitric oxide (F_ENO) were recorded for analysis. Respiratory polygraphy (RPG) was done for each study subject to diagnose OSA and its severity.

Results

Among 139 asthmatic children, 99 patients with OSA (71.2%) were included in the present study (9.3 ± 0.2 years): 58.6% with uncontrolled asthma and 32.3% with partial controlled asthma. The mean ACT (asthma control testing) score was 19.0 ± 3.4. The most frequent night-time symptoms were restless sleep (76.8%), snoring (61.6%), sweating (52.5%), and trouble breathing during sleep (48.5%). The common daytime symptoms were irritable status (46.5%) and abnormal behavior (30.3%). The mean AHI (apnea-hypopnea index) was 3.5 ± 4.0 events/h. There was a significant correlation between BMI and snoring index (R = 0.189 and P = 0.027), bronchial and nasal F_ENO with AHI (R = 0.046 and P < 0.001; R = 0.037 and P < 0.001; respectively). There was no significant correlation between asthma level, FEV₁ and AHI. The severity of asthma and respiratory function were improved significantly after 3 months and 6 months of asthma treatment in combination with leukotriene receptor antagonist (LRA) treatment. The symptoms related to OSA were significantly improved after treatment with LRA. The severity of OSA was decreased significantly after 3 months and 6 months of treatment.

Conclusion

The treatment of asthmatic children with comorbid OSA by LRA in combination with standard therapy for asthma could improve the control of asthma and the symptoms and severity of OSA.

Study of the Correlation between HRCT Semi-quantitative Scoring, Concentration of Alveolar Nitric Oxide, and Clinical-functional Parameters of Systemic Sclerosis-induced Interstitial Lung Disease

Introduction: The correlation between alveolar nitric oxide (CANO) and the severity of interstitial lung disease (ILD) evaluated by high resolution computed tomography (HRCT) has not been well demonstrated. Methods: It was a perspective and observational study, including patients with diagnosed systemic sclerosis (SSc). They performed lung function testing (LFT), exhaled nitric oxide (NO) measurements, exercise testing, chest X-ray, and HRCT. Study patients were divided into SSc with ILD (SSc-ILD+) or without ILD (SSc-ILD-). SSC-ILD+ patients were revisited after 6 months and 12 months to complete the study. Results: Thirty-one control subjects and 74 patients with SSc (33 SSc-ILD- and 41 SSc-ILD+) were included. Forty-one SSc-ILD+ patients were followed-up at 6 months and 12 months. Lung functional parameters of patients with SSc-ILD+ were lower than that of SSc-ILD- patients. The level of CANO was significantly higher in SSc-ILD+ than SSc-ILD- patients (8.6 ± 2.5 vs 4.2 ± 1.3 ppb and P<0.01). Warrick and Goldin scores of patients with SSc-ILD+ were respectively 16.5 ± 5.2 and 12.7 ± 4.3. Warrick scores were reduced after 6 and 12 months of follow-up vs at inclusion (12.4 ± 4.3 and 9.1 ± 3.2 vs 16.5 ± 5.2; P<0.05, P<0.01, and P<0.05; respectively). ΔWarrick and ΔGoldin scores were significantly and inversely correlated with ΔFVC, ΔTLC, ΔTLCO, ΔVO₂ max; that was also correlated with ΔCANO (R= 0.783, P<0.01 and R= 0.719 and P<0.05). Conclusion: CANO is a relevant biomarker for the diagnosis of ILD in patients with SSc, especially in combination with HRCT.