| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 4 | 
                                    
                                    0.4%
                                 | 
| -7 | Does not apply | 0 | 
                                    
                                    0%
                                 | 
| 0 | No obstacle | 342 | 
                                    
                                    35.8%
                                 | 
| 1 | Minor obstacle | 200 | 
                                    
                                    20.9%
                                 | 
| 2 | Moderate obstacle | 245 | 
                                    
                                    25.7%
                                 | 
| 3 | Major obstacle | 135 | 
                                    
                                    14.1%
                                 | 
| 4 | Very severe obstacle | 29 | 
                                    
                                    3%
                                 |