| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 3 | 
                                    
                                    0.2%
                                 | 
| -7 | Does not apply | 6 | 
                                    
                                    0.4%
                                 | 
| 0 | No obstacle | 697 | 
                                    
                                    49.2%
                                 | 
| 1 | Minor obstacle | 200 | 
                                    
                                    14.1%
                                 | 
| 2 | Moderate obstacle | 265 | 
                                    
                                    18.7%
                                 | 
| 3 | Major obstacle | 140 | 
                                    
                                    9.9%
                                 | 
| 4 | Very severe obstacle | 105 | 
                                    
                                    7.4%
                                 |