| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 | 
                                    
                                    0.3%
                                 | 
| -7 | Does not apply | 2 | 
                                    
                                    0.5%
                                 | 
| 0 | No obstacle | 138 | 
                                    
                                    37.9%
                                 | 
| 1 | Minor obstacle | 57 | 
                                    
                                    15.7%
                                 | 
| 2 | Moderate obstacle | 83 | 
                                    
                                    22.8%
                                 | 
| 3 | Major obstacle | 59 | 
                                    
                                    16.2%
                                 | 
| 4 | Very severe obstacle | 24 | 
                                    
                                    6.6%
                                 |