| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.1%
|
| -7 | Does not apply | 18 |
1%
|
| 0 | No obstacle | 373 |
21.6%
|
| 1 | Minor obstacle | 271 |
15.7%
|
| 2 | Moderate obstacle | 380 |
22%
|
| 3 | Major obstacle | 364 |
21.1%
|
| 4 | Very severe obstacle | 318 |
18.4%
|