Forced expiratory volume in 1-second and blood gas analysis in children during asthma attacks

Background Asthma is the most common chronic disease in the world, with a high incidence in children. Blood gas analysis and pulmonary function test using spirometry are recommended to evaluate the degree of asthma in children. Spirometry test is non-invasive and easier to implement compared to blood gas analysis. Objective To evaluate for a possible correlation between forced expiratory volume in 1 second (FEV1) measured by spirometry test and blood gas analysis (pO2 and pCO2 levels) in children during an asthma attack. Methods This cross-sectional study was done in children with asthma attacks who were admitted to Sanglah Hospital, Denpasar, Bali, between November 2016 and April 2017. Subjects underwent spirometry tests and blood gas analyses. Potential correlations between FEV1 and pO2 and pCO2 levels were analyzed by Spearman’s correlation test. Results A total of 50 subjects, consisting of children aged 6 to 12 years, were diagnosed with asthma attacks during the study period. Subjects’ mean FEV1 level was 43.6%, mean pCO2 was 38.36 mmHg, and mean pO2 was 121.92 mmHg. There were no significant correlations between FEV1 and pCO2 level (r=0.206; P=0.152) or FEV1 and pO2 (r=0.157; P=0.277) found in this study. Conclusion FEV1 does not correlate with pCO2 and pO2 level in children during asthma attacks. [Paediatr Indones. 2018;58:221-6; doi: http://dx.doi.org/10.14238/ pi58.5.2018.221-6 } Keywords: spirometry; blood gas analysis; asthma; children Asthma remains a serious problem worldwide, since it is the most common chronic disease in children and adults.1 Approximately 300 million people around the world have been diagnosed with asthma. The asthma prevalence in children aged 5-14 years in the US reached 69.8 cases per 1,000 children.2 The prevalence in Indonesian children is unknown, but in adults approximately 10% of 25 million Indonesians have asthma with high morbidity and mortality.3 An asthma attack is an emergency requiring oxygenation, ventilation, and acid-base management.4 Optimal management includes not only symptom control, but lung function monitoring and blood gas analysis.1 Lung function test is necessary to assess severity, obstruction, reversibility, and diagnostic accuracy of the asthma. Spirometry is recommended at least once a year in children with asthma to assess respiratory function.5 Decreased FEV1 can be used to assess the degree of obstruction. Variation in FEV1 is also a good predictor of asthma severity.6 Dewa Ayu Dini Primashanti et al.: Forced expiratory volume in 1-second and blood gas analysis during asthma attacks 222 • Paediatr Indones, Vol. 58, No. 5, September 2018 Blood gas analysis is recommended for all asthma attack patients who come to the hospital. Blood gas analysis results are a good estimate of asthma severity. More severe obstruction tends to correlate with higher CO2 and lower pH in arterial blood.7 Blood gas analysis is more invasive and traumatic for children compared to spirometry. Several studies were done to assess for a correlation of FEV1 decrease with pO2 and pCO2 level in adults with obstructive respiratory diseases, but with varying results.8,9 We evaluated for correlations between FEV1 decrease and pO2 and pCO2 levels in children with asthma attacks. Methods This cross-sectional study was performed in the Emergency Department of Sanglah Hospital, Denpasar, Bali, from November 2016 - April 2017. Subjects were children diagnosed with asthma, aged >6 years, and brought to the Emergency Department due to asthma attacks. Study subjects were recruited using consecutive sampling until the minimum required sample size was achieved. The sample size was determined for a cross-sectional study with 5% significance level (a) and 80% power (b), and estimated to be 50 from minimal difference in previous studies.10,11 Subjects classified to mild-moderate and severe asthma attack based on clinical finding. The clinical findings of mild-moderate asthma attacks were shortness of breath, no exertion of additional respiratory muscle, spoke in sentence, prefer in sitting position, and a loud expiratory-inspiratory wheeze on auscultation. While in severe asthma attacks, the clinical findings were shortness of breath, exertion of additional respiratory muscles, difficulty speaking, leaning forward sitting position, irritable, and a loud expiratory-inspiratory wheeze can be heard without a stethoscope.12,13 Exclusion criteria were children diagnosed with impending respiratory failure, chronic lung disease, acute or chronic lung infection, congenital lung diseases, heart diseases, history of lung surgery, or systemic diseases that impaired lung function. Subjects’ parents provided written informed consent. This study was approved by the Human Study Ethics Committee of Sanglah Hospital. Subjects underwent history-taking and physical examinations. Spirometry and blood gas analysis were performed after assessment before bronchodilator therapy. Blood specimens were collected in containers with anti-coagulant (heparin) for blood gas analyses using Siemens RapidLab 348Ex®. Diagnoses of asthma and degree of severity were made based on National Pediatric Asthma Guidelines (Pedoman Nasional Asma Anak Indonesia). 12 Characteristics of subjects were described in tables. Differences in FEV1, pO2, and pCO2 were analyzed using independent T-test or Mann-Whitney test, depending on data normality. Spearman’s test was performed to analyze abnormal data distributions. Analyses were performed with SPSS 22.0 software.