| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 3 |
0.3%
|
| 0 | No obstacle | 70 |
7.6%
|
| 1 | Minor obstacle | 86 |
9.4%
|
| 2 | Moderate obstacle | 224 |
24.4%
|
| 3 | Major obstacle | 258 |
28.1%
|
| 4 | Very severe obstacle | 277 |
30.1%
|