From the Guidelines
Normal spirometry values for a 6-year-old child are not well-established, but the forced expiratory volume at 1 second to forced vital capacity (FEV/FVC) ratio is approximately 90 to 95%. When interpreting spirometry in young children, it's essential to consider the physiological developmental stage of the respiratory system, as they have proportionally larger airways relative to lung size compared to adults, resulting in higher FEV1/FVC ratios 1. Children this age can usually perform acceptable spirometry with proper coaching, though they may need more attempts than adults. The test requires the child to take a deep breath and blow out as hard and fast as possible into a mouthpiece.
Key Considerations
- The FEV1/FVC ratio in healthy 5- to 6-year-old children is approximately 90 to 95% 1
- Children in the preschool age group may not have the chest wall muscle strength to maintain flow limitation to lung volumes as low as 90% of exhaled vital capacity 1
- Measurements that can be made during tidal breathing, such as forced oscillation, the interrupter technique, and gas washout techniques, may be more suitable for young children who cannot accurately perform spirometry 1
Clinical Implications
- Normal results indicate healthy lung function with no evidence of airflow obstruction or restriction
- Abnormalities detected should be interpreted in the clinical context, as transient changes can occur with respiratory infections or environmental exposures
- Systematic research is needed to determine the appropriate outcome variables for spirometry in this age group and to standardize how these tests are performed 1
From the Research
Normal Spirometry Values for a 6-Year-Old
To determine normal spirometry values for a 6-year-old, we need to consider the standards for interpreting pulmonary function tests in children.
- The American family physician study 2 states that an obstructive defect is indicated by a low forced expiratory volume in one second/forced vital capacity (FEV1/FVC) ratio, which is defined as less than 85% in patients five to 18 years of age.
- A restrictive pattern is indicated by an FVC below the fifth percentile based on NHANES III data in adults, or less than 80% in patients five to 18 years of age 2.
- For children, a well-performed spirometry using a change in forced expiratory volume in one second (FEV1) after albuterol is commonly used to support the likelihood of an asthma diagnosis 3.
- The current standard for a significant change in FEV1 in children is a 12% improvement after a bronchodilator 3.
Interpreting Spirometry Results
When interpreting spirometry results for a 6-year-old, consider the following:
- A normal FEV1/FVC ratio is above 85% 2.
- A normal FVC is above 80% of the predicted value 2.
- A positive bronchodilator response is defined as a 12% improvement in FEV1 after albuterol 3.
- Spirometry is a simple, non-invasive test that can detect obstruction with high sensitivity and specificity, and classify the severity and response to the bronchodilator 4.
Bronchodilator Response
The frequency of a positive bronchodilator response in patients with normal baseline spirometry is low, around 3.1% 5.
- Bronchodilator testing can be omitted in patients with normal spirometry and an FEV1 above 90% of predicted, as they have a low probability of a positive response 5.
- Airway reversibility in bronchodilation tests and fractional exhaled nitric oxide can predict the response to anti-asthma therapy in patients with suspected asthma and normal FEV1 6.