E
COHb
C G Level
(0)
>3%, but <10%
Level
(1)
≥10%, but<20%
Level
(2)
≥20%, but<25%
Level
(3)
≥25%
No % No % No % No %
Normal ECG 1 25 0 0 1 10 0 0
Tachycardia 3 75 12 57.1 4 40 8 53.3
ST segment  changes with inverted T wave 0 0 10 47.6 2 20 0 0
Prolonged Q-T interval 0 0 8 38 5 50 3 20
Prolonged Q-T interval, ST segment  changes & inverted T wave 0 0 0 0 0 0 3 20
Premature ventricular contractions 0 0 0 0 0 0 3 20
Table 5: Frequency of ECG changes with different COHb levels in the study group