| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 | 
                                    
                                    0.1%
                                 | 
| -7 | Does not apply | 4 | 
                                    
                                    0.4%
                                 | 
| 0 | No obstacle | 663 | 
                                    
                                    69.4%
                                 | 
| 1 | Minor obstacle | 84 | 
                                    
                                    8.8%
                                 | 
| 2 | Moderate obstacle | 92 | 
                                    
                                    9.6%
                                 | 
| 3 | Major obstacle | 65 | 
                                    
                                    6.8%
                                 | 
| 4 | Very severe obstacle | 46 | 
                                    
                                    4.8%
                                 |