| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 3 | 
                                    
                                    0.2%
                                 | 
| -7 | Does not apply | 2 | 
                                    
                                    0.1%
                                 | 
| 0 | No obstacle | 705 | 
                                    
                                    49.8%
                                 | 
| 1 | Minor obstacle | 246 | 
                                    
                                    17.4%
                                 | 
| 2 | Moderate obstacle | 150 | 
                                    
                                    10.6%
                                 | 
| 3 | Major obstacle | 117 | 
                                    
                                    8.3%
                                 | 
| 4 | Very severe obstacle | 193 | 
                                    
                                    13.6%
                                 |