| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 9 | 
                                    
                                    0.9%
                                 | 
| -7 | Does not apply | 17 | 
                                    
                                    1.8%
                                 | 
| 0 | No obstacle | 535 | 
                                    
                                    56%
                                 | 
| 1 | Minor obstacle | 166 | 
                                    
                                    17.4%
                                 | 
| 2 | Moderate obstacle | 110 | 
                                    
                                    11.5%
                                 | 
| 3 | Major obstacle | 80 | 
                                    
                                    8.4%
                                 | 
| 4 | Very severe obstacle | 38 | 
                                    
                                    4%
                                 |