| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 4 | 
                                    
                                    0.3%
                                 | 
| -7 | Does not apply | 1 | 
                                    
                                    0.1%
                                 | 
| 0 | No obstacle | 808 | 
                                    
                                    57.1%
                                 | 
| 1 | Minor obstacle | 249 | 
                                    
                                    17.6%
                                 | 
| 2 | Moderate obstacle | 151 | 
                                    
                                    10.7%
                                 | 
| 3 | Major obstacle | 128 | 
                                    
                                    9%
                                 | 
| 4 | Very severe obstacle | 75 | 
                                    
                                    5.3%
                                 |