Biomaterial Database

Prediction of the physiological dead space/tidal volume ratio during anaesthesia/IPPV from simple pre-operative tests. 1981

R Fletcher, and B Jonson

It can be shown that the assumption of an arbitrary value for VDphys/VT during IPPV can lead to unacceptable degrees of hypo- or hyperventilation. We investigated 33 adult patients scheduled for major non-thoracic surgery, to see if any simple tests could be used to predict VDphys/VT during anaesthesia/IPPV. Fifteen were smokers and 18 non- or ex-smokers. The tests were spirometry, and the single breath tests for CO2 and for N2 (SBT-CO2: SBT-N2). Patients were ventilated during anaesthesia with a Servo Ventilator 900 B, and SBT-CO2 was recorded from a CO2 Analyzer 930. During anaesthesia/IPPV, smokers had significantly greater VDphys/VT (0.40 +/- 0.10 vs. 0.31 +/- 0.07 [P less than 0.01]), and they had more steeply sloping phase IIIs of SBT-CO2 (P less than 0.01) than non- and ex-smokers. For smokers, VDphys/VT was correlated to age (r = 0.75, P less than 0.01), to the slope of phase III of both SBT-CO2 and SBT-N2, and to the ratio of FEV% to its predicted value. For non- and ex-smokers, only one variable, efficiency, describing the shape of SBT-CO2, was correlated to VDphys/VT (r = 0.53, P less than 0.05). Pre-operative prediction of VDphys/VT based on age, smoking history, and SBT-CO2 can reduce the uncertainty in estimating VDphys/VT and therefore ventilatory requirements. It appears to offer the greatest benefits amongst smokers, who show a large variation in VDphys/VT.

UI	MeSH Term	Description	Entries
D007385	Intermittent Positive-Pressure Ventilation	Application of positive pressure to the inspiratory phase when the patient has an artificial airway in place and is connected to a ventilator.	BIPAP Biphasic Intermittent Positive Airway Pressure,IPPV,Inspiratory Positive-Pressure Ventilation,Ventilation, Intermittent Positive-Pressure,Biphasic Intermittent Positive Airway Pressure,Inspiratory Positive Pressure Ventilation,Intermittent Positive Pressure Ventilation,Positive-Pressure Ventilation, Inspiratory,Positive-Pressure Ventilation, Intermittent,Ventilation, Inspiratory Positive-Pressure,Ventilation, Intermittent Positive Pressure
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
D010313	Partial Pressure	The pressure that would be exerted by one component of a mixture of gases if it were present alone in a container. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Partial Pressures,Pressure, Partial,Pressures, Partial
D011175	Positive-Pressure Respiration	A method of mechanical ventilation in which pressure is maintained to increase the volume of gas remaining in the lungs at the end of expiration, thus reducing the shunting of blood through the lungs and improving gas exchange.	Positive End-Expiratory Pressure,Positive-Pressure Ventilation,End-Expiratory Pressure, Positive,End-Expiratory Pressures, Positive,Positive End Expiratory Pressure,Positive End-Expiratory Pressures,Positive Pressure Respiration,Positive Pressure Ventilation,Positive-Pressure Respirations,Positive-Pressure Ventilations,Pressure, Positive End-Expiratory,Pressures, Positive End-Expiratory,Respiration, Positive-Pressure,Respirations, Positive-Pressure,Ventilation, Positive-Pressure,Ventilations, Positive-Pressure
D012126	Respiratory Dead Space	That part of the RESPIRATORY TRACT or the air within the respiratory tract that does not exchange OXYGEN and CARBON DIOXIDE with pulmonary capillary blood.	Dead Space, Respiratory,Dead Spaces, Respiratory,Respiratory Dead Spaces,Space, Respiratory Dead,Spaces, Respiratory Dead
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000367	Age Factors	Age as a constituent element or influence contributing to the production of a result. It may be applicable to the cause or the effect of a circumstance. It is used with human or animal concepts but should be differentiated from AGING, a physiological process, and TIME FACTORS which refers only to the passage of time.	Age Reporting,Age Factor,Factor, Age,Factors, Age
D000768	Anesthesia, General	Procedure in which patients are induced into an unconscious state through use of various medications so that they do not feel pain during surgery.	Anesthesias, General,General Anesthesia,General Anesthesias
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
D013990	Tidal Volume	The volume of air inspired or expired during each normal, quiet respiratory cycle. Common abbreviations are TV or V with subscript T.	Tidal Volumes,Volume, Tidal,Volumes, Tidal