The purpose of this study was to compare the effect of two types of cervical collars (Philadelphia and Miami-J) on pulmonary function and ventilation in healthy volunteers through spirometry, peak flow meter, and capnograph.

Initially, subjects were randomized into two groups in which the sequence of collars' fixation was reversed. Afterward, we assessed the pulmonary parameters without a cervical collar in all participants. Each group underwent two additional test conditions, including measurements after wearing a Philadelphia and Miami-J cervical collar. In any case, we took the measurements half an hour after the collar fixation.

The mean age of participants was 48.34 ± 1.35 years. Following either type of collars application, there was a statistically significant decrease in FEV1, FEV1/FVC, FEF25–75%, and PEF (p < .001). However, FVC was not significantly changed (p = .157).

In summary, we noted a statistically significant expiratory flow obstruction after both the Philadelphia and Miami-J cervical collar. These changes were not clinically significant in healthy volunteers, albeit may have ramifications in patients with pre-existing respiratory compromise.