A calibrated measuring tape accurately predicts tidal volumes from ulna length.

BACKGROUND: Low tidal volume ventilation improves outcomes in acute respiratory distress syndrome. Calculation of this volume requires knowledge of a patient's gender, and height, which may not be available in emergency admissions, and the subsequent application of a nomogram. The objective of this study was to test the accuracy of a calibrated measuring tape that reads in mL of tidal volume when the ulna is measured.

METHODS: The measuring tape was used to obtain an estimate of a subject's tidal volume from their ulna length, and standing height was then measured (reference method).

RESULT: A total of 100 healthy volunteers were included. Mean tidal volume was 450 mL for males and 372 mL for females when calculated from the height. Comparing tidal volumes from the tape with those from the reference method, Bland Altman analysis showed a bias of -10 mL (limits of agreement (2SD) -74 mL to 54 mL) for males and a bias of -36 mL (limits of agreement (2SD) -88 mL to 16 mL) for females. Predicted mean tidal volumes were 5.7 mL/kg (95% CI: 5.1-6.3 mL/kg) for males and 5.8 mL/kg (95% CI: 5.3-6.2 mL/kg) for females.

CONCLUSIONS: Usage of a calibrated measuring tape produced accurate estimates of tidal volumes required for lung protective ventilation in healthy volunteers.