| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 2 | 
                                    
                                    0.5%
                                 | 
| -7 | Does not apply | 8 | 
                                    
                                    2%
                                 | 
| 0 | No obstacle | 235 | 
                                    
                                    58.5%
                                 | 
| 1 | Minor obstacle | 74 | 
                                    
                                    18.4%
                                 | 
| 2 | Moderate obstacle | 59 | 
                                    
                                    14.7%
                                 | 
| 3 | Major obstacle | 15 | 
                                    
                                    3.7%
                                 | 
| 4 | Very severe obstacle | 9 | 
                                    
                                    2.2%
                                 |