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Human ventilatory efficiency and respiratory sinus arrhythmia during head-up tilt. 2008

S J Brown, and M Bryant, and T Mundel, and S R Stannard
Institute of Food, Nutrition and Human Health, Massey University, New Zealand. s.j.brown@massey.ac.nz

Cardiac vagal withdrawal when moving from supine to an upright posture may be independent of respiratory sinus arrhythmia. Further, ventilatory efficiency of an upright lung may improve with clustering of heart beats during inhalation. We studied healthy human subjects (n=8, 6 male) during supine rest (SUP) and 80 degrees head-up tilt (HUT). ECG and expired breath were sampled continuously to determine heart rate, mean and end-tidal (ET) fractional content (F) of O2 and CO2, tidal volume (V(T)) and breathing frequency (Bf). HUT increased heart rate (47+/-3 vs. 59+/-9 beats min(-1), p<0.01), decreased the high frequency component of heart rate variability (8.76+/- vs. 7.07+/-1.12, p<0.05), and increased the ratio of low to high frequency components in the heart rate (0.62+/-0.6 vs. 1.79+/-2.07, p<0.05). HUT did not change VT, Bf, or minute ventilation (V'E), but decreased FCO2 (4.90+/-0.48 vs. 4.56+/-0.42 %, p<0.05) and FETCO2 (6.64+/-0.24 vs. 6.30+/-0.27 %, p<0.01). HUT increased the CO2 ventilatory equivalent (24.88+/-2.50 vs. 26.74+/-2.61, p<0.01). Mean heart rate during inhalation increased with HUT (26+/-3 vs. 34+/-6 beats min-1), with no change during exhalation. Increased clustering of heart beats during inhalation independent of a decrease in HF cardiac variability may partly offset decreases in ventilatory efficiency of an upright lung.

UI MeSH Term Description Entries
D008297 Male Males
D010100 Oxygen An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration. Dioxygen,Oxygen-16,Oxygen 16
D012129 Respiratory Function Tests Measurement of the various processes involved in the act of respiration: inspiration, expiration, oxygen and carbon dioxide exchange, lung volume and compliance, etc. Lung Function Tests,Pulmonary Function Tests,Function Test, Pulmonary,Function Tests, Pulmonary,Pulmonary Function Test,Test, Pulmonary Function,Tests, Pulmonary Function,Function Test, Lung,Function Test, Respiratory,Function Tests, Lung,Function Tests, Respiratory,Lung Function Test,Respiratory Function Test,Test, Lung Function,Test, Respiratory Function,Tests, Lung Function,Tests, Respiratory Function
D002245 Carbon Dioxide A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals. Carbonic Anhydride,Anhydride, Carbonic,Dioxide, Carbon
D004562 Electrocardiography Recording of the moment-to-moment electromotive forces of the HEART as projected onto various sites on the body's surface, delineated as a scalar function of time. The recording is monitored by a tracing on slow moving chart paper or by observing it on a cardioscope, which is a CATHODE RAY TUBE DISPLAY. 12-Lead ECG,12-Lead EKG,12-Lead Electrocardiography,Cardiography,ECG,EKG,Electrocardiogram,Electrocardiograph,12 Lead ECG,12 Lead EKG,12 Lead Electrocardiography,12-Lead ECGs,12-Lead EKGs,12-Lead Electrocardiographies,Cardiographies,ECG, 12-Lead,EKG, 12-Lead,Electrocardiograms,Electrocardiographies, 12-Lead,Electrocardiographs,Electrocardiography, 12-Lead
D005260 Female Females
D006339 Heart Rate The number of times the HEART VENTRICLES contract per unit of time, usually per minute. Cardiac Rate,Chronotropism, Cardiac,Heart Rate Control,Heartbeat,Pulse Rate,Cardiac Chronotropy,Cardiac Chronotropism,Cardiac Rates,Chronotropy, Cardiac,Control, Heart Rate,Heart Rates,Heartbeats,Pulse Rates,Rate Control, Heart,Rate, Cardiac,Rate, Heart,Rate, Pulse
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000328 Adult A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available. Adults
D001146 Arrhythmia, Sinus Irregular HEART RATE caused by abnormal function of the SINOATRIAL NODE. It is characterized by a greater than 10% change between the maximum and the minimum sinus cycle length or 120 milliseconds. Sinus Arrhythmia,Arrhythmia, Sinoatrial,Sinoatrial Arrhythmia,Arrhythmias, Sinoatrial,Arrhythmias, Sinus,Sinoatrial Arrhythmias,Sinus Arrhythmias

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