| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 2 | 
                                    
                                    0.2%
                                 | 
| -7 | Does not apply | 2 | 
                                    
                                    0.2%
                                 | 
| 0 | No obstacle | 514 | 
                                    
                                    53.8%
                                 | 
| 1 | Minor obstacle | 153 | 
                                    
                                    16%
                                 | 
| 2 | Moderate obstacle | 145 | 
                                    
                                    15.2%
                                 | 
| 3 | Major obstacle | 92 | 
                                    
                                    9.6%
                                 | 
| 4 | Very severe obstacle | 47 | 
                                    
                                    4.9%
                                 |