| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 3 |
0.5%
|
| -7 | Does not apply | 19 |
3.1%
|
| 0 | No obstacle | 451 |
73.7%
|
| 1 | Minor obstacle | 49 |
8%
|
| 2 | Moderate obstacle | 49 |
8%
|
| 3 | Major obstacle | 29 |
4.7%
|
| 4 | Very severe obstacle | 12 |
2%
|