| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 9 | 
                                    
                                    1.5%
                                 | 
| -7 | Does not apply | 1 | 
                                    
                                    0.2%
                                 | 
| 0 | No obstacle | 396 | 
                                    
                                    64.7%
                                 | 
| 1 | Minor obstacle | 139 | 
                                    
                                    22.7%
                                 | 
| 2 | Moderate obstacle | 51 | 
                                    
                                    8.3%
                                 | 
| 3 | Major obstacle | 10 | 
                                    
                                    1.6%
                                 | 
| 4 | Very severe obstacle | 6 | 
                                    
                                    1%
                                 |