| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 2 | 
                                    
                                    0.9%
                                 | 
| -7 | Does not apply | 3 | 
                                    
                                    1.4%
                                 | 
| 0 | No obstacle | 102 | 
                                    
                                    47.4%
                                 | 
| 1 | Minor obstacle | 69 | 
                                    
                                    32.1%
                                 | 
| 2 | Moderate obstacle | 22 | 
                                    
                                    10.2%
                                 | 
| 3 | Major obstacle | 14 | 
                                    
                                    6.5%
                                 | 
| 4 | Very severe obstacle | 3 | 
                                    
                                    1.4%
                                 |