Respiration 33: 104-111 (1976)
Differential Diagnosis of Ventilatory Disorders with the Help of Volume/Flow Diagram1 M . S. Islam Institut für Lungenfunktionsforschung, Bochum, in Verbindung mit der Westfälischen Wilhelms-Universität, Münster (Chefarzt: Prof. Dr. W. T. U lmer)
Key Words. Lung mechanics • Volume/flow curve • Differential diagnosis Abstract. Volume/flow (V/v) diagrams obtained from 82 healthy and pulmonary diseased subjects were analyzed. A formula had been worked out on the basis of determined slow vital capacity, for the calculation of maximum forced expiratory flow (VEmax). The expiratory volume/flow curves were used for the computation of lung conpliance (Ci). These calculated values of VEmax and Ci were highly correlated to the measured values. It is concluded that these calculated values would provide a good index for the preliminary differential diagnosis of the pulmonary disorders.
H yatt et al. [3] and H yatt and F lath [5] introduced the volume/flow (V/y) diagram for the assessment of ventilatory status in health and pul monary disorders. According to them the rising phase of the diagram is effort dependent, whereas the falling limb is controlled by the geometry of the bronchial system. Since then it has been studied and reported by various working groups [1, 6-8]. This study is projected mainly to find out the relationship between the V/^ diagram and vital capacity (VC), airway resistance (Raw ) and lung compliance (Ci). And on that concept, the V/y diagram is used for the dif ferential diagnosis of ventilatory disorders. 1 Supported by Europäische Gemeinschaft für Kohle und Stahl, Hohe Behörde, Luxemburg.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/14/2018 4:06:46 AM
Received: January 23, 1975; accepted: April 12, 1975.
I slam
105
Theory (a) The V/y diagram provides maximum expiratory flow (VEmax) and forced vital capacity (FVC). The FVC and VEmax are highly related to each other. With smaller compliance and resistance, the system may empty quicker, i.e. requires shorter time. Whereas increased resistance and compli ance may produce slow emptying. Therefore, it may be said that the same VC can produce greater VEmax, when Ci and Raw are smaller but reverse in increased Ci and Raw. The relation of VC and VEmax of healthy subjects as well as patients are worked out as given below: VEmix ml/sec = {1,310 + 0.148 x VC ml)}
From the above analogy we can expect that the computed VEmax will be greater than the measured one in patients with obstruction (greater Raw), smaller in patients with restrictive disorder (smaller Q). (b) V/^ diagram is really the expression of emptying rate or, in other words, it has the dimension of time (t). It can be derived as follows:
V = volume, V = (low, t = time
Resistance (R) x compliance (C), also providing the factor with a dimension of time, can be derived as follows: R C R •C
P •t ~ V P P-t-V V •P
= t
Therefore, R • C and V/$ have the same dimension and can be written as: R • C = V/v or: V = -/R V V V
= v'p _ V ~ P Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/14/2018 4:06:46 AM
C
106
I slam
Table I. Subjects categorized into four groups according to airway resistance and lung compliance Group II
III
IV
3.00
>0.160 22
0.160 13
Differential Diagnosis of Ventilatory Disorders with the Help of Volume/Flow Diagram1 M . S. Islam Institut für Lungenfunktionsforschung, Bochum, in Verbindung mit der Westfälischen Wilhelms-Universität, Münster (Chefarzt: Prof. Dr. W. T. U lmer)
Key Words. Lung mechanics • Volume/flow curve • Differential diagnosis Abstract. Volume/flow (V/v) diagrams obtained from 82 healthy and pulmonary diseased subjects were analyzed. A formula had been worked out on the basis of determined slow vital capacity, for the calculation of maximum forced expiratory flow (VEmax). The expiratory volume/flow curves were used for the computation of lung conpliance (Ci). These calculated values of VEmax and Ci were highly correlated to the measured values. It is concluded that these calculated values would provide a good index for the preliminary differential diagnosis of the pulmonary disorders.
H yatt et al. [3] and H yatt and F lath [5] introduced the volume/flow (V/y) diagram for the assessment of ventilatory status in health and pul monary disorders. According to them the rising phase of the diagram is effort dependent, whereas the falling limb is controlled by the geometry of the bronchial system. Since then it has been studied and reported by various working groups [1, 6-8]. This study is projected mainly to find out the relationship between the V/^ diagram and vital capacity (VC), airway resistance (Raw ) and lung compliance (Ci). And on that concept, the V/y diagram is used for the dif ferential diagnosis of ventilatory disorders. 1 Supported by Europäische Gemeinschaft für Kohle und Stahl, Hohe Behörde, Luxemburg.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/14/2018 4:06:46 AM
Received: January 23, 1975; accepted: April 12, 1975.
I slam
105
Theory (a) The V/y diagram provides maximum expiratory flow (VEmax) and forced vital capacity (FVC). The FVC and VEmax are highly related to each other. With smaller compliance and resistance, the system may empty quicker, i.e. requires shorter time. Whereas increased resistance and compli ance may produce slow emptying. Therefore, it may be said that the same VC can produce greater VEmax, when Ci and Raw are smaller but reverse in increased Ci and Raw. The relation of VC and VEmax of healthy subjects as well as patients are worked out as given below: VEmix ml/sec = {1,310 + 0.148 x VC ml)}
From the above analogy we can expect that the computed VEmax will be greater than the measured one in patients with obstruction (greater Raw), smaller in patients with restrictive disorder (smaller Q). (b) V/^ diagram is really the expression of emptying rate or, in other words, it has the dimension of time (t). It can be derived as follows:
V = volume, V = (low, t = time
Resistance (R) x compliance (C), also providing the factor with a dimension of time, can be derived as follows: R C R •C
P •t ~ V P P-t-V V •P
= t
Therefore, R • C and V/$ have the same dimension and can be written as: R • C = V/v or: V = -/R V V V
= v'p _ V ~ P Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/14/2018 4:06:46 AM
C
106
I slam
Table I. Subjects categorized into four groups according to airway resistance and lung compliance Group II
III
IV
3.00
>0.160 22
0.160 13
