| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 4 | 
                                    
                                    1.1%
                                 | 
| -7 | Does not apply | 4 | 
                                    
                                    1.1%
                                 | 
| 0 | No obstacle | 205 | 
                                    
                                    56.3%
                                 | 
| 1 | Minor obstacle | 50 | 
                                    
                                    13.7%
                                 | 
| 2 | Moderate obstacle | 57 | 
                                    
                                    15.7%
                                 | 
| 3 | Major obstacle | 20 | 
                                    
                                    5.5%
                                 | 
| 4 | Very severe obstacle | 24 | 
                                    
                                    6.6%
                                 |