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P ET CO 2 In Women at Sea‐Level and Upon Acute Exposure to Normobaric Hypoxic Environments Simulating 3,500 m
Author(s) -
Kambis Ken,
Yasukawa Michio,
Moran Thomas,
Pleasant Austen,
Hafner Gabriella,
Barbour Veronique,
Duckworth Courtney,
Muza Stephen,
LooftWilson Robin
Publication year - 2016
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.30.1_supplement.1007.1
Subject(s) - effects of high altitude on humans , medicine , tidal volume , altitude (triangle) , hypobaric chamber , ventilation (architecture) , hypoxia (environmental) , sea level , anesthesia , hypoxic ventilatory response , zoology , oxygen , respiratory system , chemistry , mathematics , biology , physics , meteorology , anatomy , geometry , organic chemistry , physical geography , geography
A prior study in men (Reeves, J. Appl. Physiol. 75: 1993) demonstrated that the ventilatory response to high altitude is highly variable among sea level residents, but the sea level end‐tidal PCO 2 (P ET CO 2 , a measurement of effective alveolar ventilation) is highly predictive of subsequent ventilation at high altitude. While prior work suggests that women and men have similar ventilatory responses to high altitude (Muza, J. Appl. Physiol. 91: 2001), no studies have determined if women's sea level P ET CO 2 is predictive of subsequent ventilation at high altitude. As part of a larger study examining individual variability upon acute exposure to normobaric hypoxia, P ET CO 2 was measured while subjects rested for >30 minutes at sea level (SL) and, no sooner than two days later, for >30 minutes in a normobaric hypoxia chamber at 13.55% FiO 2 approximating oxygen partial pressures equivalent to those found at 3,500 m, or at a FiO 2 of 20.93% in the case of control subjects. METHODS Informed volunteer female subjects participated in this IRB approved study. 47 (20.6±1.5 yr.; 165.6±6.9 cm; 62.9±10.4 kg; 22.9±3.4 kg/m 2 ; VO 2peak 42.6±7.4 ml/kg −1 /min −1 ) subjects were assigned to the treatment group who were tested at SL then entered the normobaric chamber where the FiO 2 =13.55% (HYPO) and 9 subjects (21.8±4.3 yr.; 166.5±6.1 cm; 57.9 ±7.0 kg; 20.9 ±2.1 kg/m 2 ; VO 2peak 40.9 ±6.5 ml/kg −1 /min −1 ) acted as controls (SHAM) who were in the normobaric chamber at a FiO 2 = 20.93%. At both SL and chamber conditions, subjects rested for >30 minutes. P ET CO 2 was measured during the final 14 minutes of each rest period as was percent hemoglobin O 2 saturation (SpO 2) , respiratory rate (RR), and heart rate (HR). RESULTS Two‐way RM ANOVA revealed that there was no difference (P>0.5) in P ET CO 2 between the HYPO vs SHAM groups at SL (37.9±2.7 vs 36.0±2.9) but, as expected, there was a difference (P<0.001) between the SL and chamber conditions (P ET CO 2 = 37.9±2.7 vs 36.0±2.2) in the HYPO group. A significant (P < 0.001) Pearson correlation (r = 0.759) was also observed between SL P ET CO 2 and HYPO P ET CO 2 while no difference was observed between the SHAM conditions. A multiple regression model [Y = 79.617 – 0.452 X 1 – 0.207 X 2 – 0.016 X 3 (Where Y= P ET CO 2 _HYPO, X 1 = SpO 2 _HYPO, X 2 = RR_HYPO, X 3 = HR_HYPO; R 2 = 0.500, F = 19.15, P < 0.001)] was used to plot the actual and predictive values for P ET CO 2 at 3,500 m ( Fig. 1). CONCLUSIONS Women's SL P ET CO 2 is predictive of their ventilatory response to acute normobaric hypoxia and may be useful in predicting an individual's ventilation during travel to moderately high altitudes. Support or Funding Information The Doug Morton/Marilyn Brown Endowment for Biomedical Research, The Foundation for Aging Studies and Exercise Science Research, and The Borgenicht Program