| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 5 |
0.5%
|
| -7 | Does not apply | 12 |
1.2%
|
| 0 | No obstacle | 146 |
14.3%
|
| 1 | Minor obstacle | 103 |
10.1%
|
| 2 | Moderate obstacle | 198 |
19.4%
|
| 3 | Major obstacle | 300 |
29.4%
|
| 4 | Very severe obstacle | 255 |
25%
|