Electrocardiographic prediction of hyperinflation in children.

The mean frontal P wave axis in an electrocardiogram (ECG), which reflects the atrial orientation in the thorax, is altered by the relationship between atria and the diaphragm and, therefore, by hyperinflation. To examine this relationship, 102 children (ages 6-18) with asthma were prospectively studied. Lung volumes were estimated by plethysmography and a standard ECG obtained before and after bronchodilator. The mean thoracic gas volume (TGV) was 120.7 +/- 2.1% of predicted and the mean P axis was 54.9 +/- 1.5 degrees. Sixty-two subjects (61%) had a "vertical" P axis (> or = 60 degrees). Of 27 subjects with moderate or severe hyperinflation (TGV > or = 130% predicted), 23 (85%) had a vertical P axis. As a measure of significant hyperinflation, a vertical P axis had a sensitivity of 85%, specificity of 49%, positive predictive value of 38% and a negative predictive value of 90%. After nebulized albuterol, the mean TGV decreased to 96.4 +/- 1.3% predicted and the mean P axis decreased by 7.1 +/-1.6 degrees. Sixty-two of 76 subjects (82%) with > or = 15% decrease in TGV also had a decrease in P axis, and 62/67 subjects (93%) with a decrease in P axis also had > or = 15% decrease in TGV. The sensitivity was 82%, specificity 81%, and positive predictive value 93% for a decrease in P axis as a measure of decrease in TGV. A vertical P axis combined with a decrease in P axis after bronchodilator is highly sensitive and predictive for hyperinflation in children.