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Progressive augmentation and long‐term facilitation of ventilation is mitigated following a reduction in oxidative stress in individuals with obstructive sleep apnea
Author(s) -
Lee Dorothy,
D’Souza Anita,
Hadden Timothy,
Miller Richard,
Badr Safwan,
Mateika Jason
Publication year - 2007
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.21.6.a822-d
Subject(s) - intermittent hypoxia , anesthesia , medicine , ventilation (architecture) , oxidative stress , obstructive sleep apnea , hypoxia (environmental) , respiratory minute volume , apnea , placebo , trolox , respiratory system , antioxidant capacity , chemistry , oxygen , mechanical engineering , engineering , alternative medicine , organic chemistry , pathology
Purpose: To determine whether oxidative stress impacts on progressive augmentation (PA) and long‐term facilitation (LTF) of minute ventilation in subjects with obstructive sleep apnea (OSA) during wakefulness after exposure to intermittent hypoxia (IH). Methods: Six male OSA subjects were exposed to IH on two occasions. The IH protocol consisted of 12‐4 minute episodes of hypoxia (P ET O 2 −50 mmHg, P ET CO 2 ‐sustained at 4 mmHg above resting values) separated by 4 minute recovery periods. The recovery period following the last episode was 30 minutes. Prior to exposure to IH subjects were treated with an antioxidant cocktail (Aox) on one occasion and a placebo (Plb) on another. Peripheral venous blood was sampled before and after IH on both occasions to obtain measures of total antioxidant capacity. Results: Total antioxidant capacity was increased following treatment with Aox (Plb vs. Aox ‐ 2.6 ± 0.5 vs. 3.7 ± 0.7 mM Trolox Equivalents; p < 0.04). Baseline levels of minute ventilation and carbon dioxide following treatment with Plb and Aox were similar (19.9 ± 3.8 vs. 16.6 ± 1.1 L/min; 44.2 ± 1.1 vs. 44.2 ± 1.2 mmHg). The ventilatory response to the last IH episode was greater compared to the initial episode following Plb, but not after treatment with Aox (Plb ‐ 2.04 ± 0.13 vs. 1.70 ± 0.09 fraction of baseline, p < 0.001; Aox ‐ 1.86 ± 0.12 vs.1.80 ± 0.08 fraction of baseline). Moreover, LTF of minute ventilation was evident following IH on both occasions. However, LTF was significantly greater following Plb compared to Aox (1.48 ± 0.04 vs. 1.28 ± 0.03 fraction of baseline, p < 0.02). Conclusions: PA and LTF of minute ventilation are evident in subjects with OSA during wakefulness if carbon dioxide is sustained above resting levels. The emergence of these phenomena is impacted by levels of oxidative stress.