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The "88% saturation test": a simple lung function test for young children
C L Wagner1, J G Brooks, S E Richter
1Department of Pediatrics, Children's Hospital, Medical University of South Carolina, Charleston 29425.
Insights
The 88% saturation test (88%-SAT) shows promise for identifying reactive airways disease in young children who cannot perform standard spirometry. This test demonstrated higher sensitivity and specificity than spirometry in detecting this condition.
Area of Science:
- Pediatric Pulmonology
- Respiratory Medicine
- Diagnostic Testing
Background:
- Standard spirometry is challenging for young children unable to perform forced expiratory maneuvers.
- The 88% saturation test (88%-SAT) was developed as an alternative for assessing respiratory function.
- Previous adult studies indicated 88%-SAT's potential in identifying asthma-related desaturation.
Purpose of the Study:
- To evaluate the efficacy of the 88%-SAT in identifying reactive airways disease in young children.
- To compare the performance of 88%-SAT with standard spirometry in this pediatric population.
Main Methods:
- The study enrolled 33 former premature infants (5-7 years old) at a tertiary care hospital.
- The 88%-SAT involved breathing a 12% oxygen/nitrogen mixture until oxygen saturation (SaO2) dropped to 88% or for 10 minutes.
- Results were compared with standard spirometry and parental questionnaires.
Main Results:
- The 88%-SAT identified reactive airways disease in all 7 children with a history of the condition, showing 100% sensitivity and 87% specificity.
- Spirometry had lower sensitivity (75%) and specificity (63%) for reactive airways disease.
- Children unable to complete spirometry often could complete the 88%-SAT, suggesting its utility in uncooperative or developmentally delayed children.
Conclusions:
- The 88%-SAT appears more effective than spirometry for diagnosing reactive airways disease in young, uncooperative, or developmentally delayed children.
- The hypoxic gas mixture in the 88%-SAT may act as an airway challenge, revealing decreased oxygenation in those with reactive airways.
Objective:
The 88% saturation test (88%-SAT) was developed as an alternative to standard spirometry for those young children unable to perform standard forced expiratory maneuvers. In adults, this test revealed rapid desaturation in those persons with a history of asthma when compared with healthy control subjects. Similar findings in children were tested.
Setting:
Tertiary care hospital.
Patients:
Thirty-three former premature infants (28.3 +/- 2.3 weeks gestation), aged 5 to 7 years, who were participating in a follow-up study, were enrolled in this study.
Design:
The study compared the 88%-SAT with standard spirometry and respiratory health characteristics ascertained through a parental questionnaire. The 88%-SAT consists of continuous measurement of hemoglobin saturation by pulse oximetry (SaO2) while the subject breathes a nonhumidified 12% oxygen and nitrogen mixture for 10 minutes or until SaO2 decreases to 88%, whichever occurs first. Abnormal 88%-SAT was defined as a decrease of SaO2 to 88% within the 10-minute period, and abnormal spirometry was defined using standardized values.
Results:
Of the 20 children who successfully completed both spirometry and the 88%-SAT, 10 had normal spirometry results and did not desaturate to 88%, and 5 had abnormal spirometry and 88%-SAT results. Four children did not desaturate during the 88%-SAT, but had abnormal spirometry results, and one child had abnormal 88%-SAT results, but normal spirometry. Ten additional children completed the 88%-SAT, but not standard spirometry. Three children were unable to complete either test. Of those 30 children tested, 7 (23%) had a history of reactive airways disease, and all 7 had abnormal 88%-SAT results. The 88%-SAT had greater sensitivity (100% vs 75%) and specificity (87% vs 63%) than spirometry in identifying children with known reactive airways disease. The mean McCarthy general cognitive index (GCI) of the group performing both spirometry and the 88%-SAT (n = 20) achieved a mean (+/- SD) GCI of 96.2 +/- 16.7, and the group (n = 30) that completed the 88%-SAT had a mean (+/- SD) GCI of 75.2 +/- 26.3 (chi 2 P < .012). The 10 children able to perform only the 88%-SAT had a mean GCI (+/- SD) of 72.8 +/- 26.9, and the 3 children unable to perform either test had a mean GCI (+/- SD) of 63 +/- 11.
Conclusions:
Our data suggest that the 88%-SAT may be more effective than spirometry for identifying reactive airways disease in young, uncooperative, or developmentally delayed children. The dry air of the hypoxic inspired gas may function as an airway challenge, leading to decreased oxygenation in patients with reactive airways.