Competition for Intrathoracic Space Reduces Lung Capacity in Patients With Chronic Heart Failure: Statistical Analysis
Statistical analysis and graphic presentation were accomplished using statistical software (Prism version 4.0; Graphpad; San Diego, CA). One-way analysis of variance was used to test for differences in means among the groups, and unpaired t test was used to compare the means of the participant characteristics and radiographic variables between the control and chronic heart failure groups and between chronic heart failure groups. Pearson correlation coefficients were calculated between radiographic measures and measures of heart failure severity. Fisher Exact Test was used to examine the difference in medication usage and other categorical variables between groups. Statistical significance was set at p < 0.05 for all analyses. Data are presented as mean ± SD or number and percentage of the group, as appropriate.
The clinical characteristics of each study group and the medications in use by the patients at the time of the study are reported in Tables 1, 2, respectively. Notable differences between the groups include a significantly lower BMI for the control group compared to group A and group B (p < 0.05). These differences were due to a nonsignificant trend in the difference in body weight (p = 0.06) as opposed to differences in height. Also, the control group demonstrated significantly greater exercise habits as compared to either group A (p < 0.05) or group B (p < 0.05), with no significant differences between the chronic heart failure groups.
The results of the radiographic volumetric measurements are reported in Table 3. For absolute volumetric measurements, the groups differed significantly in diaphragmatic, cardiac, and blood and parenchymal tissue volumes (p < 0.05 for all) with a trend toward significance in lung volumes (p = 0.06) and no difference in total thoracic volume. Importantly, when examining these measurements as a percentage of the TTC, there were significant differences between the groups for all measurements (p < 0.05) except for the percent of the TTC volume that was blood and parenchymal tissue. The relationship between the NYHA class and absolute cardiac volume and percentage of the TTCV that is taken up by the heart is shown in Figure 2, top, A, and bottom, B, respectively. read more
Table 2—Heart Failure Patient Medications Separated by Group
Variables | Group A | Group B | p Value |
Angiotensin-converting enzyme inhibitors | 16(61.5) | 15 (83.3) | NS |
Angiotensin II receptor blockers | 4(15.4) | 2 (11.1) | NS |
p-Blockers | 14 (53.8) | 13 (72.2) | NS |
Digitalis | 16(61.5) | 12 (66.7) | NS |
Diuretics | 16(61.5) | 13 (72.2) | NS |
Table 3—Differences Between Groups in the Radiographic Volumetric Estimations
Variables | Control | Group A | Group B | p Value |
TTCV, cm | 8,288.2 ± 1,516.4 | 8,070 ± 1,716.6 | 8,594 ± 1,567.3 | NS |
Diaphragm volume, cm | 920.3 ± 293.0 | 936.3 ± 330.4t | 1,188.2 ± 552.5t | 0.03 |
Diaphragm, % | 11.0 ± 2.6 | 11.8 ± 4.0 | 13.8 ± 5.6t | 0.04 |
Cardiac volume, cm | 634.2 ± 178.1 | 978.7 ± 350.7t |
Ъ61
3 ± 5 4 ,3 |
0.001 |
Cardiac, % | 7.8 ± 2.2 | 12.3 ± 4.4t |
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± cr cc |
0.001 |
Blood and tissue volume, cm | 938.1 ± 129.8 | 997.5 ± 160.9 | 1,030 ± 118.4t | 0.04 |
Blood and tissue, % | 11.6 ± 2.0 | 12.8 ± 3.4 | 12.4 ± 2.8 | NS |
Lung volume, cm | 5,795.5 ± 1,229.5 | 5,158 ± 1,422.4 | 5,030.2 ± 1,463.7 | 0.06 |
Lung, % | 69.7 ± 3.9 | 63.1 ± 9.5t | 57.6 ± 7.7 | 0.001 |
Figure 2. Top, A: Absolute cardiac volume measurement separated by groups. Bottom, B: Percentage of the total TTCV taken up by the heart separated by groups. *p < 0.05 vs control (CTL) group; tp < 0.05 vs group A.