title: Effects of fasting and carbohydrate consumption on voluntary resting apnea duration.
abstract: Breath holding is normally terminated due to the urge to breathe, mainly caused by the increasing carbon dioxide level. It was recently shown that a combination of 18 h of carbohydrate-free diet and prolonged exercise prior to breath holding lowered the respiratory exchange ratio (RER) and end-expiratory PO(2 )at maximal breath-hold break-point (MBP). Current hypothesis: fasting will result in longer breath-hold duration than will fasting followed by carbohydrate intake. It was also hypothesized that breath-holds during carbohydrate supplementation would be ended at a higher alveolar PO(2). Ten male non-divers performed multiple breath-holds either to the first diaphragmatic contraction (PBP), or to MBP. The breath-holds were performed during normal diet (control; C), twice during fasting (F14 h, F18 h), followed by post fasting carbohydrate consumption (PFCC) and a repetition of the breath-hold testing 1-2 h after ingestion of carbohydrates. Duration, RER, end-tidal PO(2) and PCO(2), SaO(2) and blood glucose were determined. RER and blood glucose increased after PFCC compared with fasting and control conditions (P < 0.001). PBP breath-hold duration increased from 129 +/- 34 s at C to 148 +/- 33 s at F18 h, and was reduced during PFCC to 122 +/- 30 s (P < 0.001). End-tidal PO(2) was higher at PFCC compared to F18 h (10.4 +/- 1.2 vs. 9.5 +/- 1.2 kPa at PBP, P < 0.05). Similar trends in breath-hold duration and physiology were seen in breath-holds that were terminated at MBP. Dietary restriction can affect breath-hold duration. The lower O(2) level at breakpoint during fasting suggests that breath holding may be less safe during fasting; the increased risk may be mitigated by ingestion of carbohydrates before breath holding.
authors.affiliation: Center for Research and Education in Special Environments, University at Buffalo (SUNY), Buffalo, NY, USA. peter.lindholm@ki.se
authors.forename: Peter
authors.initials: P
authors.lastname: Lindholm
authors.forename: Mary
authors.initials: M
authors.lastname: Conniff
authors.forename: Mikael
authors.initials: M
authors.lastname: Gennser
authors.forename: David
authors.initials: D
authors.lastname: Pendergast
authors.forename: Claes
authors.initials: C
authors.lastname: Lundgren
mesh_terms: D000328:Adult; D001049:Apnea / Q000503:physiopathology*; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D004435:Eating / Q000502:physiology*; D005215:Fasting / Q000502:physiology*; D006801:Humans; D010100:Oxygen / Q000097:blood; D011659:Pulmonary Gas Exchange / Q000187:drug effects / Q000502:physiology; D012119:Respiration / Q000187:drug effects; D015656:Respiratory Mechanics / Q000187:drug effects* / Q000502:physiology*; D012143:Respiratory Physiological Phenomena; D012307:Risk Factors; D013990:Tidal Volume / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
chemical_list: D004040:Dietary Carbohydrates; D010100:Oxygen