5. DISCUSSION
This study demonstrated that intraoral mask has more easy ventilation rate than classic face mask according to Han Scale (123(85.4), 84(58.3); n(%); respectively; p=0.000). Also it has higher expiratory tidal volume (481.92±173.99, 430.85±154.87 mL; respectively; p=0.000) and decreased air leak volume (71.50±91.17, 159.38±146.31 mL; respectively; p=0.000) than classic face mask.
There are very few studies in the scientific literature that discuss the effectiveness of the intraoral mask 12-15,17,22. The comparisons in terms of the effectiveness of masks in our study are consistent with previous cadaver studies 13,15,17,22.
According to these results it can be assumed that intraoral mask may have some advantages in difficult mask ventilation situations caused by air leakage due to improper seal. Society of Airway Management recommended using a well-sealed facemask with HEPA filter in suspected COVID-19 patients for pre-oxygenation and ventilation4. It can be assumed that decreased air leakage may result less aerosol formation and reduce the likelihood of virus transmission in the COVID-19 era.
Secondly our study demonstrated that practitioners’ situational anxiety level obtained from STAI FORM TX1 were similar between intraoral and classic face mask. Despite of these results workload measurements of the practitioners with the NASA task load index (NASA TLX) were higher for intraoral mask than classic facemask. This can be attributed to the users not being familiar with the intraoral mask and their routine use of the classic mask.
There are conflicting results in the literature regarding users’ evaluation of intraoral and classic masks. In the study of Riggle et al.12 conducted on the airway training manikin, the average muscle pain perceived by the practitioners for both masks was statistically insignificant and most of the practitioners preferred the classical mask; stated that it is easier to grasp, less fatigue and easier to use with the classical mask. The practitioners’ evaluations in this study 12 are consistent with the results of our study.
However, in terms of workload, the results of our study are contradicted by the fact that McCroy et al.13 found the workload of the intraoral mask higher in their study. The reason for this situation may be that practitioners may evaluate the workload of a real mask ventilation application on the patient higher than the workload of a mask ventilation scenario on a cadaver. In addition, in our study, each doctor was given the opportunity to try the mask on 4 different patients instead of a single cadaver, and this situation may have changed the workload assessment due to encountering different patient characteristics.
The main difference of our study from others12,13,15,17,22 is that it was performed on real patients under operating room conditions and both masks were used in a large series of patients. Although there are many studies investigating the risk factors for difficult mask ventilation in the literature3,8,9, to our knowledge our study is the first study investigating these risk factors for intraoral mask together with the classic mask in the same patient group. Since we have a large patient series, we were able to secondarily investigate the predictors of difficult mask ventilation for both of the masks. We comprehensively investigated the risks of difficult mask ventilation, including the STOP-BANG score, which evaluates the risk of obstructive sleep apnea syndrome along with anthropometric features. The most significant factor among the possible risks for difficult mask ventilation was the neck circumference for the classical mask (other significant factors were body weight, mallampati and stop-bang score). For NuMask the most significant risk factor was BMI and the other was mallampati score. Our results are compatible with a number of risk factors in studies involving a larger number of patients for classic mask3,9 and additionally determines risk factors for intraoral mask.
However, there are many limited aspects of our study. It is an important deficiency that the risk factors for difficult mask ventilation are calculated according to the Han scale for patients with> I (II = Needs oral airway, III = requiring two care providers) and do not include real difficult mask ventilation. According to Orbany23, the aspects in which Han scale is limited; not validated, not sensitive enough for data comparisons and research purposes, and it is not reproducible. Evaluation is also subjective and observer dependent. Orbany 23 emphasized that there is no standard definition of difficult mask ventilation based on precise and objective criteria, therefore it is difficult to compare studies and share clinical information. He points out that due to the subjective and practitioner-dependent nature of success in mask ventilation, making such a precise definition is also a difficult goal. However, the risk factors found in our study when considered causally were rational and this limitation is common in other studies 8.