| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 4 | 
                                    
                                    0.4%
                                 | 
| -7 | Does not apply | 5 | 
                                    
                                    0.5%
                                 | 
| 0 | No obstacle | 291 | 
                                    
                                    30.5%
                                 | 
| 1 | Minor obstacle | 149 | 
                                    
                                    15.6%
                                 | 
| 2 | Moderate obstacle | 252 | 
                                    
                                    26.4%
                                 | 
| 3 | Major obstacle | 187 | 
                                    
                                    19.6%
                                 | 
| 4 | Very severe obstacle | 67 | 
                                    
                                    7%
                                 |