Pulmonary Vascular Resistance in Emphysema: Results

Data are presented as mean ± SD. Significance of difference between sample means was determined by the two-tailed unpaired t test. Linear regression analysis was performed by the least squares method. Partial correlation analysis was performed in order to examine the relationship between two variables independent of their relationship with a third variable. A p value of less than 0.05 was considered significant.
Mean pulmonary function data for the 12 patients with emphysema (COPD-A) are shown in Table 1. Average FEV/FVC percent was 51 ± 8 percent. When divided according to the degree of airflow obstruction, as measured by the ratio of FEWl to FVC, two patients demonstrated mild obstruction (60 < FEV/FVC percent <70), eight had moderate obstruction (40 < FEV/ FVC percent <60), and two had severe obstruction (FEVj/FVC percent <40). Alternatively, test results were divided according to the ratio of RV to TLC, an index of air trapping in subjects with airways obstruction. Two patients had normal values of the ratio of RV to TLC (RV/TLC percent <40), eight had mild-moderate elevation (60<RV/TLC percent <40), and two had severe elevation (60 < RV/TLC percent). Average DcoSB percent predicted was 62 ± 29 percent, with a wide range of values (26 to 102 percent) More info canadian neighbor pharmacy. At FIo2 0.21, mean Pa02 was 72 ± 11 mm Hg (range, 59 to 97 mm Hg). No patients exhibited severe hypercarbia or respiratory acidemia.
For comparison, Table 1 also lists the data for 33 patients with ILD. These patients were younger than those in the COPD-A group, and they demonstrated a broad range of reduction in lung volumes without evidence of airflow obstruction. The DcoSB percent predicted was reduced in parallel to the reduction in lung volumes, especially the FVC. At FIo2 0.21, there was no evidence of significant hypoxemia or hypercarbia.
Hemodynamic observations in patients with COPDA and ILD are shown in Figure 1. In the COPD-A group, pulmonary arterial and pulmonary arterial wedge pressures were normal, yet the average PDG was 5 ± 3 mm Hg, indicating mildly elevated resistance to pulmonary blood flow. Cardiac output was 4.1 ± 1.0 U min (range, 2.4 to 5.6 L/min) and mean heart rate was 77 ± 9 beats/min (range, 60 to 90 beats/min). Subjects with ILD and FVC >50 percent predicted (mild-moderate ILD) demonstrated a similar pattern of normal pulmonary arterial pressures with mildly increased pulmonary vascular resistance (PDG = 4 ± 3 mm Hg). The PDG in patients with COPD-A did not differ significantly from that in subjects with ILD when FVC was greater than 50 percent predicted (p >0.1). Subjects with ILD and FVC less than 50 percent predicted (moderate-severe ILD) had pulmonary hypertension.

Table 1 — Comparison of Mean Pulmonary Function Data in Type A COPD (n = 12) and ILD (n = 33)

Sex, M/F 7/5 11/22
Age, yr 65±8(51-74) 43 ±9 (24-58)
FVC, % pred 80± 17 (60-112) 63 ±22 (25-97)
FEV,, % pred 59± 18 (41-93) 63±22(30-100)
FEV./FVC % 51 ±8 (41-63) 83 ±20 (70-100)
RV/TLC % 48± 11 (30-65) 32 ±12 (18-64)
TLC, % pred 103 ±15 (81-127) 62 ±20 (24-104)
DcoSB, % pred 62 ±29 (26-102) 54±25(19-100)
Pa02, mm Hg 72 ±12 (59-97) 81 ±14 (49-99)
P&C02, mm Hg 39 ±5 (29-48) 36±5(32-43)
pHa 7.42 ±0.04 (7.36-7.49) 7.43±0.04(7.35-7.50)


Figure 1. Hemodynamic data in patients with emphysema (type A COPD) and ILD. Resistance to pulmonary blood flow, assessed as the difference between PA diastolic and mean wedge pressures, and expressed as the pulmonary diastolic gradient (PDG, hatched area) was mildly increased in patients with emphysema. PDG in emphysema was less (p < 0.001) than that in ILD when VC < 50 percent predicted, but it did not differ from that observed when VC > 50 percent predicted.

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