| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 11 | 
                                    
                                    1.2%
                                 | 
| -7 | Does not apply | 42 | 
                                    
                                    4.4%
                                 | 
| 0 | No obstacle | 431 | 
                                    
                                    45.1%
                                 | 
| 1 | Minor obstacle | 191 | 
                                    
                                    20%
                                 | 
| 2 | Moderate obstacle | 166 | 
                                    
                                    17.4%
                                 | 
| 3 | Major obstacle | 68 | 
                                    
                                    7.1%
                                 | 
| 4 | Very severe obstacle | 46 | 
                                    
                                    4.8%
                                 |