| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 3 | 
                                    
                                    0.3%
                                 | 
| -7 | Does not apply | 4 | 
                                    
                                    0.4%
                                 | 
| 0 | No obstacle | 391 | 
                                    
                                    40.9%
                                 | 
| 1 | Minor obstacle | 197 | 
                                    
                                    20.6%
                                 | 
| 2 | Moderate obstacle | 222 | 
                                    
                                    23.2%
                                 | 
| 3 | Major obstacle | 101 | 
                                    
                                    10.6%
                                 | 
| 4 | Very severe obstacle | 37 | 
                                    
                                    3.9%
                                 |