Premium
The effects of prior hyperventilation duration on central chemoreflex responses using the “Duffin” hyperoxic rebreathing test (1092.16)
Author(s) -
Boulet Lindsey,
Jamieson Alenna,
Day Trevor
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.1092.16
Subject(s) - hyperventilation , anesthesia , chemistry , central chemoreceptors , respiratory system , medicine , control of respiration
The effects of prior hyperventilation duration on central chemoreflex responses using the “Duffin” hyperoxic rebreathing test The “Duffin” hyperoxic rebreathing test was developed from the “Read” rebreathing test by the addition of a five‐minute hyperventilation (HV) prior to switching to the rebreathing circuit. This HV eliminates CO 2 stores, such that when the subject equilibrates with the rebreathing circuit, brainstem CO 2 is below the ventilatory recruitment threshold (VRT) of the central respiratory chemoreceptors. This allows investigators to quantify the VRT prior to eliciting a central chemoreflex to increases in CO 2 during rebreathing. An assumption of the test is that a full five minutes of prior HV is required. However, prolonged HV is uncomfortable for the subject, and there is no experimental evidence to validate this assumption. We aimed to test this assumption experimentally by comparing various durations of prior HV. We hypothesized that there would be no difference in central chemoreflex responses between randomized prior hyperventilation durations (HVD) of one, three and five minutes. Following instrumentation with a pneumotachometer and CO 2 and O 2 gas analyzers, 19 subjects underwent three hyperoxic rebreathing trials, each with randomized prior HV of one‐, three‐ and five‐minute durations, each coached to 18‐20 Torr PCO 2 . Rebreathing was carried out by switching to a circuit comprised of a 6L bag containing 7% CO 2 and 93% O 2 . For all three trials, we quantified the VRT (PCO 2 ; Torr), and respiratory frequency (min ‐1 /Torr CO 2 ), inspired tidal volume (L/Torr CO 2 ) and inspired ventilation (L/min/Torr CO 2 ) with linear regression. We found no differences between HVD in any respiratory variable, within‐subject. Our data suggest that when using the “Duffin” rebreathing test, a one‐minute HV is sufficient to drive CO 2 stores below the VRT, and the resulting central chemoreflex responses are no different than the standard five‐minute test. Grant Funding Source : NSERC