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. Author manuscript; available in PMC: 2013 Aug 1.
Published in final edited form as: NMR Biomed. 2012 Sep 4;26(8):987–1003. doi: 10.1002/nbm.2847

Figure 3.

Figure 3

Schematic diagrams of the automated respiratory challenge apparatus currently in use with feedback (a) and feedforward (b) algorithms. The feedback algorithm works by analysing the gas composition of the preceding breath and adjusting the composition of the inflowing fresh gas to force the subject’s end-tidal values towards the targeted values in the following breath. The feedforward algorithm works by calculating the required gas composition to reach the given target end-tidal values using a model of alveolar gas exchange prior to the start of the experiment.