ObjectiveThe aim was to determine the effect on end-tidal carbon dioxide (ETCO2) of spinal immobilization (SI) at a conventional 0° angle and to investigate the usefulness of immobilization at a 20° angle for preventing possible hypoventilation. MethodsThe study included 80 healthy volunteers, randomly divided into two groups. Spinal backboards and cervical collars were applied in Group 1 using a 0° angle and in Group 2 using a 20° angle, with the head up. SI was continued for 1 h, and ETCO2 values were measured at the 0th, 30th and 60th minute. ResultsThere were no significant differences between the groups in 0th and 30th minute ETCO2. However, after 60th minute, results showed a statistically significant increase in ETCO2 in Group 1 (35.5 mmHg [IQR 25–75:35–38]) compared to Group 2 (34 mmHg [IQR 25–75:33–36]) (p < 0.001). During SI, there was a statistically significant increase in ETCO2 in Group 1 (35 mmHg [IQR 25–75:34–36], 35.5 mmHg [IQR 25–75:34–37] and 36 mmHg [IQR 25–75:35–38] respectively at the 0th, 30th and 60th minute after SI) (p < 0.001) and no change in Group 2. Also, we found statistically significant differences between ΔETCO2 levels in Groups 1 and 2 at all 3 time intervals. ConclusionConventional SI with an angle of 0° led to an increase in ETCO2 while subjects immobilization at a 20° angle maintained their initial ETCO2 values. Immobilization at 20° may prevent decompensation in patients who have thoracic trauma or lung diseases or those who are elderly, pregnant, or obese.