| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 5 | 
                                    
                                    4.5%
                                 | 
| -7 | Does not apply | 1 | 
                                    
                                    0.9%
                                 | 
| 0 | No obstacle | 46 | 
                                    
                                    41.4%
                                 | 
| 1 | Minor obstacle | 26 | 
                                    
                                    23.4%
                                 | 
| 2 | Moderate obstacle | 17 | 
                                    
                                    15.3%
                                 | 
| 3 | Major obstacle | 12 | 
                                    
                                    10.8%
                                 | 
| 4 | Very severe obstacle | 4 | 
                                    
                                    3.6%
                                 |