| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 4 | 
                                    
                                    0.4%
                                 | 
| -7 | Does not apply | 1 | 
                                    
                                    0.1%
                                 | 
| 0 | No obstacle | 629 | 
                                    
                                    65.9%
                                 | 
| 1 | Minor obstacle | 183 | 
                                    
                                    19.2%
                                 | 
| 2 | Moderate obstacle | 79 | 
                                    
                                    8.3%
                                 | 
| 3 | Major obstacle | 43 | 
                                    
                                    4.5%
                                 | 
| 4 | Very severe obstacle | 16 | 
                                    
                                    1.7%
                                 |