| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 | 
                                    
                                    0.2%
                                 | 
| -7 | Does not apply | 1 | 
                                    
                                    0.2%
                                 | 
| 0 | No obstacle | 419 | 
                                    
                                    69.8%
                                 | 
| 1 | Minor obstacle | 111 | 
                                    
                                    18.5%
                                 | 
| 2 | Moderate obstacle | 48 | 
                                    
                                    8%
                                 | 
| 3 | Major obstacle | 14 | 
                                    
                                    2.3%
                                 | 
| 4 | Very severe obstacle | 6 | 
                                    
                                    1%
                                 |