is present if there was an increase in altitude and the person has headache or at least one other symptom and a total score equal to or above 5. The minimum score indicates that the subject is healthy; the maximum score is 25. Finally, the d2 test was administered. The test consists of 14 rows with 47 characters each (total of 658 items), as shown in Figure 3. There is a time limit of 20 seconds for each row. The task is to differentiate the characters d or p with 1 to 4 dashes. Every d with 2 dashes has to be crossed out with a pencil; no other signs should be marked. Each row contains 21 or 22 targets (i.e. characters to be crossed out) in random order. Each row is a small test in and of itself and allows evaluation of performance over time. The test counts the number of items processed (TN), the percentage of errors (E%), the concentration performance (CP – the number of correctly processed items minus the incorrectly crossed items), the errors (E) and the TN minus E (TN-E) as well as the fluctuation rate (FR). About 5 minutes are needed to complete the test. An important advantage is that the test can be administered to a group.
Fig. 3. First 3 lines of the d2 test showing the processed items. After arrival at a new altitude, the subjects rested at least for 1 hour prior to testing.
R E S U LT S Table 1 shows the results of the d2 test for all 8 subjects at the three measurement time points. The mean CP value decreased from 242.6 at sea level (SL) to 194.1 at 3,500 m and again increased to 212.3 at 4,640 m. The same trend can be seen for female and male participants with slightly more reduced values for females at altitude, but no significance analysis was performed because of the limited number of subjects. The maximum CP at SL was achieved from S8 (283), at 3,500 m from S6 and S8 (212) and at 4,640 m from S3 (245). S4 showed a CP performance that was well under the performance of all other subjects. The most characters (TN) were processed at SL, followed by 4,640 m and 3,500 m. The most errors (E) were made at 3,500 m, followed by SL and 4,640 m.
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