| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 6 | 
                                    
                                    1.5%
                                 | 
| -7 | Does not apply | 9 | 
                                    
                                    2.2%
                                 | 
| 0 | No obstacle | 239 | 
                                    
                                    59.5%
                                 | 
| 1 | Minor obstacle | 69 | 
                                    
                                    17.2%
                                 | 
| 2 | Moderate obstacle | 38 | 
                                    
                                    9.5%
                                 | 
| 3 | Major obstacle | 28 | 
                                    
                                    7%
                                 | 
| 4 | Very severe obstacle | 13 | 
                                    
                                    3.2%
                                 |