>> ptn = '# / TYPES OF OBSERV';
>> str = fileread('data.txt');
>> out = regexp(str, ['^[^\n]+(?=',ptn,'\s*$)'], 'match', 'lineanchors');
>> out = regexp([out{:}], '(?<=\s+)\S+', 'match')
out = '10' 'L1' 'A2' 'L5' 'C1' 'C2' 'P2' 'C5' 'S1' 'L2' 'S5'
where the first regexp call locates the required lines of text, and the second call extracts each individual group of characters.