| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 | 
                                    
                                    0.7%
                                 | 
| -7 | Does not apply | 0 | 
                                    
                                    0%
                                 | 
| 0 | No obstacle | 108 | 
                                    
                                    72%
                                 | 
| 1 | Minor obstacle | 21 | 
                                    
                                    14%
                                 | 
| 2 | Moderate obstacle | 4 | 
                                    
                                    2.7%
                                 | 
| 3 | Major obstacle | 6 | 
                                    
                                    4%
                                 | 
| 4 | Very severe obstacle | 10 | 
                                    
                                    6.7%
                                 |