| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 7 | 
                                    
                                    0.5%
                                 | 
| -7 | Does not apply | 5 | 
                                    
                                    0.4%
                                 | 
| 0 | No obstacle | 908 | 
                                    
                                    64.1%
                                 | 
| 1 | Minor obstacle | 213 | 
                                    
                                    15%
                                 | 
| 2 | Moderate obstacle | 113 | 
                                    
                                    8%
                                 | 
| 3 | Major obstacle | 103 | 
                                    
                                    7.3%
                                 | 
| 4 | Very severe obstacle | 67 | 
                                    
                                    4.7%
                                 |