| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 5 | 
                                    
                                    0.8%
                                 | 
| -7 | Does not apply | 3 | 
                                    
                                    0.5%
                                 | 
| 0 | No obstacle | 494 | 
                                    
                                    80.7%
                                 | 
| 1 | Minor obstacle | 66 | 
                                    
                                    10.8%
                                 | 
| 2 | Moderate obstacle | 25 | 
                                    
                                    4.1%
                                 | 
| 3 | Major obstacle | 9 | 
                                    
                                    1.5%
                                 | 
| 4 | Very severe obstacle | 10 | 
                                    
                                    1.6%
                                 |