| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 2 | 
                                    
                                    0.3%
                                 | 
| -7 | Does not apply | 6 | 
                                    
                                    1%
                                 | 
| 0 | No obstacle | 381 | 
                                    
                                    63.5%
                                 | 
| 1 | Minor obstacle | 142 | 
                                    
                                    23.7%
                                 | 
| 2 | Moderate obstacle | 51 | 
                                    
                                    8.5%
                                 | 
| 3 | Major obstacle | 13 | 
                                    
                                    2.2%
                                 | 
| 4 | Very severe obstacle | 5 | 
                                    
                                    0.8%
                                 |