| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.2%
|
| -7 | Does not apply | 1 |
0.2%
|
| 0 | No obstacle | 16 |
2.7%
|
| 1 | Minor obstacle | 16 |
2.7%
|
| 2 | Moderate obstacle | 53 |
8.8%
|
| 3 | Major obstacle | 170 |
28.3%
|
| 4 | Very severe obstacle | 343 |
57.2%
|