Figure 2

A tabular display of the characteristics of diagnostic tests. Readings for respiratory frequency/tidal volume ratio (fR/VT) ≤100 are classified as positive test results and readings >100 are classified as negative test results. The relationship of these binary results to the outcome of a T-tube weaning trial forms a decision matrix, which has four possible combinations. TP: true positive; test predicts weaning success and patient actually succeeds. TN: true negative; test predicts weaning failure and patient actually fails. FP: false positive; test predicts weaning success and patient actually fails. FN: false negative; test predicts weaning failure and patient actually succeeds. PPV: positive predicted value; NPV: negative predicted value; R: rate. Reproduced from [2] with permission from the publisher.