Biomaterial Database

Relationship of phase IV to closing volume in lateral body positions. 1975

H F Don, and R H Ingram, and M Green

We studied the effect of body position in humans on the relationship between exhaled vital capacity (VC) and both helium (He) and nitrogen (N2) concentrations after delivery of an He bolus at residual volume (RV) followed by 100% oxygen to total lung capacity. Phase IV, defined as the % VC at the first sharp and permanent increase in N2 and He, occurred at a mean of 15.7% VC while seated, 60.0% VC in right lateral and 59.6% VC in left lateral positions. He bolus delivery above RV but well below 60% VC resulted in the disappearance of phase IV. Lung pressure-volume (PV) curves had inflections at the volume of phase IV in the seated position: but the inflections were well below phase IV in lateral positions. Phase IV increased to higher volumes at higher mouth pressures. The relationship between phase IV and mouth pressure fell near the respiratory system relaxation PV curves. The findings suggest the higher phase IV in lateral positions is due to sequence of emptying without airway closure and is influenced by active expiration.

UI	MeSH Term	Description	Entries
D008176	Lung Volume Measurements	Measurement of the amount of air that the lungs may contain at various points in the respiratory cycle.	Lung Capacities,Lung Volumes,Capacity, Lung,Lung Capacity,Lung Volume,Lung Volume Measurement,Measurement, Lung Volume,Volume, Lung
D009584	Nitrogen	An element with the atomic symbol N, atomic number 7, and atomic weight [14.00643; 14.00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth's atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells.
D011187	Posture	The position or physical attitude of the body.	Postures
D012119	Respiration	The act of breathing with the LUNGS, consisting of INHALATION, or the taking into the lungs of the ambient air, and of EXHALATION, or the expelling of the modified air which contains more CARBON DIOXIDE than the air taken in (Blakiston's Gould Medical Dictionary, 4th ed.). This does not include tissue respiration (	Breathing
D012123	Pulmonary Ventilation	The total volume of gas inspired or expired per unit of time, usually measured in liters per minute.	Respiratory Airflow,Ventilation Tests,Ventilation, Pulmonary,Expiratory Airflow,Airflow, Expiratory,Airflow, Respiratory,Test, Ventilation,Tests, Ventilation,Ventilation Test
D006371	Helium	A noble gas with the atomic symbol He, atomic number 2, and atomic weight 4.003. It is a colorless, odorless, tasteless gas that is not combustible and does not support combustion. It was first detected in the sun and is now obtained from natural gas. Medically it is used as a diluent for other gases, being especially useful with oxygen in the treatment of certain cases of respiratory obstruction, and as a vehicle for general anesthetics.	Helium-4,Helium 4
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man