| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 7 | 
                                    
                                    0.7%
                                 | 
| -7 | Does not apply | 13 | 
                                    
                                    1.4%
                                 | 
| 0 | No obstacle | 453 | 
                                    
                                    47.4%
                                 | 
| 1 | Minor obstacle | 166 | 
                                    
                                    17.4%
                                 | 
| 2 | Moderate obstacle | 152 | 
                                    
                                    15.9%
                                 | 
| 3 | Major obstacle | 117 | 
                                    
                                    12.3%
                                 | 
| 4 | Very severe obstacle | 47 | 
                                    
                                    4.9%
                                 |