| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 8 | 
                                    
                                    7.2%
                                 | 
| -7 | Does not apply | 0 | 
                                    
                                    0%
                                 | 
| 0 | No obstacle | 45 | 
                                    
                                    40.5%
                                 | 
| 1 | Minor obstacle | 27 | 
                                    
                                    24.3%
                                 | 
| 2 | Moderate obstacle | 13 | 
                                    
                                    11.7%
                                 | 
| 3 | Major obstacle | 15 | 
                                    
                                    13.5%
                                 | 
| 4 | Very severe obstacle | 3 | 
                                    
                                    2.7%
                                 |