| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 24 |
2.3%
|
| 0 | No obstacle | 304 |
29.7%
|
| 1 | Minor obstacle | 210 |
20.5%
|
| 2 | Moderate obstacle | 238 |
23.2%
|
| 3 | Major obstacle | 201 |
19.6%
|
| 4 | Very severe obstacle | 47 |
4.6%
|