| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 2 | 
                                    
                                    0.3%
                                 | 
| -7 | Does not apply | 50 | 
                                    
                                    8.2%
                                 | 
| 0 | No obstacle | 271 | 
                                    
                                    44.3%
                                 | 
| 1 | Minor obstacle | 97 | 
                                    
                                    15.8%
                                 | 
| 2 | Moderate obstacle | 86 | 
                                    
                                    14.1%
                                 | 
| 3 | Major obstacle | 60 | 
                                    
                                    9.8%
                                 | 
| 4 | Very severe obstacle | 46 | 
                                    
                                    7.5%
                                 |