Biomaterial Database

Fall in specific airway conductance at residual volume in small airway obstruction. 1980

K P Agrawal, and A Kumar

A technique of body plethysmography has been developed for measuring specific airway conductance (SGaw) at residual volume (RV). Box pressure variations were recorded as difference between chest volume change and air volume respired at atmospheric pressure, delta(V1--V2). They could easily be related to alveolar pressure change per liter of lung volume and SGaw could directly be calculated without breathing against a closed shutter. To eliminate 'temperature-humidity artifact', calculations were made near end-tidal points where air movement in and out of lungs is minimal. For that purpose airflow changes were related to box pressure changes over a period of 0.2 sec from the beginning of inspiratory effort. SGaw was measured at FRC as well as at RV. Excessive air trapping at RV in some cases resulted in some chest expansion unaccompanied by any airflow at mouth. This has been termed pre-flow work (PFW). Any abnormal fall in SGaw at RV or the presence of PFW could be used as an indicator of small airway obstruction. Using this method obstruction in small airways was found in all smokers with smoking history of 5 to 30 packs years (mean 13.1 pack years) and in 4 patients who had a history of cough and/or dyspnoea or exertion. Simultaneous measurements of SGaw at FRC and SGaw 0.2 sec and PFW at RV could be of great help in determining the degree and site of airflow obstruction.

UI	MeSH Term	Description	Entries
D008168	Lung	Either of the pair of organs occupying the cavity of the thorax that effect the aeration of the blood.	Lungs
D008875	Middle Aged	An adult aged 45 - 64 years.	Middle Age
D010993	Plethysmography, Whole Body	Measurement of the volume of gas in the lungs, including that which is trapped in poorly communicating air spaces. It is of particular use in chronic obstructive pulmonary disease and emphysema. (Segen, Dictionary of Modern Medicine, 1992)	Whole Body Plethysmography,Body Plethysmographies, Whole,Body Plethysmography, Whole,Plethysmographies, Whole Body,Whole Body Plethysmographies
D012115	Residual Volume	The volume of air remaining in the LUNGS at the end of a maximal expiration. Common abbreviation is RV.	Residual Volumes,Volume, Residual,Volumes, Residual
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
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
D000402	Airway Obstruction	Any hindrance to the passage of air into and out of the lungs.	Choking,Airway Obstructions,Obstruction, Airway,Obstructions, Airway
D012907	Smoking	Willful or deliberate act of inhaling and exhaling SMOKE from burning substances or agents held by hand.	Smoking Behaviors,Smoking Habit,Behavior, Smoking,Behaviors, Smoking,Habit, Smoking,Habits, Smoking,Smoking Behavior,Smoking Habits