| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 2 | 
                                    
                                    0.9%
                                 | 
| -7 | Does not apply | 1 | 
                                    
                                    0.5%
                                 | 
| 0 | No obstacle | 145 | 
                                    
                                    67.4%
                                 | 
| 1 | Minor obstacle | 39 | 
                                    
                                    18.1%
                                 | 
| 2 | Moderate obstacle | 19 | 
                                    
                                    8.8%
                                 | 
| 3 | Major obstacle | 8 | 
                                    
                                    3.7%
                                 | 
| 4 | Very severe obstacle | 1 | 
                                    
                                    0.5%
                                 |