| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 3 | 
                                    
                                    0.2%
                                 | 
| -7 | Does not apply | 21 | 
                                    
                                    1.5%
                                 | 
| 0 | No obstacle | 984 | 
                                    
                                    69.5%
                                 | 
| 1 | Minor obstacle | 159 | 
                                    
                                    11.2%
                                 | 
| 2 | Moderate obstacle | 92 | 
                                    
                                    6.5%
                                 | 
| 3 | Major obstacle | 96 | 
                                    
                                    6.8%
                                 | 
| 4 | Very severe obstacle | 61 | 
                                    
                                    4.3%
                                 |