[Measurement of dead space/tidal volume ratio during exercise in patients with heart failure].
Dead space (VD)/tidal volume (VT) ratio is an indirect index of ventilation/perfusion matching. Therefore, it is currently evaluated in patients with congestive heart failure to detect the organ system limiting the exercise tolerance. The VD/VT calculation requires measurement of arterial CO2 partial pressure (PaCO2). For practical reasons, the software of most metabolic carts substitutes the PaCO2 with the end-expiratory CO2 (PETCO2) or the PJCO2 (calculated as PJCO2 = 5.5 +/- 0.9 PETCO2-2.1 VT). Nonetheless, the applicability of these methods in congestive heart failure is unknown. We compared in 63 patients with congestive heart failure 326 measurements of PaCO2 versus PETCO2 and PJCO2 and VD/VT measured with PaCO2 versus VD/VT estimated with PETCO2 (estimation 1) or PJCO2 (estimation 2). Comparisons were made at rest (Phase 1), during submaximal exercise (Phase 2), and at peak exercise (Phase 3). We found a strong correlation, but not an identity, between PaCo2 and PETCO2 (PaCO2 = 7.25 +/- 0.80 PETCO2, r = 0.84; p < 0.0001); similarly for PaCO2 and PETCO2. Several observations were out of 95% confidence interval, and some measurements exceeded mean +/- 2 SD when the differences between PaCo2 and PETCO2 or PJCO2 were plotted against the averages from the two (Bland and Altman method). Measured VD/VTs also strongly correlated with the estimated ones (VD/VT measured = -0.03 +/- 1.11 VD/VT estimated 1 r = 0.90; p < 0.0001 e VD/VT measured = 0.03 +/- 0.92 VD/VT estimated 2 r = 0.90; p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)
Guazzi
M
M
Istituto di Cardiologia, Università degli Studi, IRCCS, Milano.
Agostoni
P G
PG
Marenzi
G C
GC
Cattadori
G
G
Perego
G B
GB
Lauri
G
G
Guazzi
M D
MD
D000293:Adolescent; D000328:Adult; D000368:Aged; D016001:Confidence Intervals; D015444:Exercise; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D012126:Respiratory Dead Space; D013990:Tidal Volume
Calcolo del rapporto spazio morto/volume corrente nello scompenso cardiaco durante esercizio.