| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 7 | 
                                    
                                    0.5%
                                 | 
| -7 | Does not apply | 9 | 
                                    
                                    0.6%
                                 | 
| 0 | No obstacle | 893 | 
                                    
                                    63.1%
                                 | 
| 1 | Minor obstacle | 161 | 
                                    
                                    11.4%
                                 | 
| 2 | Moderate obstacle | 121 | 
                                    
                                    8.5%
                                 | 
| 3 | Major obstacle | 125 | 
                                    
                                    8.8%
                                 | 
| 4 | Very severe obstacle | 100 | 
                                    
                                    7.1%
                                 |