Distribution of Ventilation/Perfusion Ratios in Pulmonary Embolism: An Adjunct to the Interpretation of Ventilation/Perfusion Lung Scans

Article Figures & Data

Download figure
Open in new tab
Download powerpoint
FIGURE 1.
Examples of V/Q distribution in patient with normal scan (A) and in patient with confirmed PE (B). Histogram shapes characteristically demonstrate single peak in 0.8–1.2 range in patient with normal scan and bimodal distribution in low (<0.8) and high (>1.2) ranges in PE patient.
Download figure
Open in new tab
Download powerpoint
FIGURE 2.
Correlation between distribution histogram and arterial blood gases in patients with confirmed PE. (A) Inverse relationship exists between percentage of low V/Q ratios and PaO₂ (regression equation: y = −1.09x + 112.7). (B) Relationship is positive between percentage of low V/Q ratios and A-aDO₂ (regression equation: y = +1.17x − 11.2).

TABLE 1

Patient Characteristics

Characteristic	No. of patients (n = 99)
Mean age (y)	63 ± 18
Sex
Male	39
Female	60
History of cardiopulmonary disease	48
Including obstructive lung disease	14
Referring department
Cardiology	44
Emergency room/reanimation	22
Internal medicine	10
Surgery	8
Other medical departments	15

TABLE 4

Distribution Histograms of V/Q Ratios Depending on Scan Normality and Absence or Presence of PE

% V/Q	Normal scan (n = 16)	PE absent (n = 65)	PE present (n = 34)	Unpaired t test result (P)
% V/Q	Normal scan (n = 16)	PE absent (n = 65)	PE present (n = 34)			Comparison 1*	Comparison 2^†
<0.4	12.2 ± 1.3	13.2 ± 2.3	14.3 ± 2.8	0.01	0.04
<0.8	26.9 ± 7.5	29.9 ± 7.5	34.5 ± 8.2	0.003	0.008
0.8–1.2	63.3 ± 13.0	59.1 ± 13.8	50.0 ± 16.0	0.006	0.005
>1.2	9.8 ± 5.8	11.0 ± 7.4	15.5 ± 10.0	0.04	0.01
>1.6	0.8 ± 1.4	1.8 ± 4.5	4.6 ± 7.0	0.04	0.02
First moment	0.87 ± 0.02	0.87 ± 0.05	0.89 ± 0.10	NS	NS
Second moment	0.33 ± 0.04	0.36 ± 0.08	0.44 ± 0.18	0.02	0.002

TABLE 5

Distribution Histograms of V/Q Ratios Within the 4 PIOPED Categories

% V/Q	Normal (n = 16)	Low (n = 13)	Intermediate (n = 45)	High (n = 25)
<0.4	12.2 ± 1.3*^†	13.2 ± 1.2	13.8 ± 2.7^‡	14.1 ± 3.0^‡
<0.8	26.9 ± 7.5^†	29.1 ± 6.5^†	30.4 ± 6.1^†	37.5 ± 9.2*^‡^§
0.8–1.2	63.3 ± 13.0^†	62.2 ± 12.1^†	59.8 ± 9.3^†	41.3 ± 17.4*^‡^§
>1.2	9.8 ± 5.8^†	8.7 ± 5.9^†	9.8 ± 4.3^†	21.3 ± 11.0*^‡^§
>1.6	0.8 ± 1.4^†	1.0 ± 1.8^†	0.7 ± 1.1^†	8.5 ± 8.6*^‡^§
First moment	0.87 ± 0.02^†	0.85 ± 0.02^†	0.85 ± 0.02^†	0.93 ± 0.12*^‡^§
Second moment	0.33 ± 0.04^†	0.34 ± 0.04^†	0.35 ± 0.03^†	0.51 ± 0.20*^‡^§