Clinical determinants and prognostic significance of hypocapnia in acute heart failure.

Aim: The aim of this research was to examine the prevalence of hyperventilation (defined by pCO 2 value) among acute heart failure (AHF) patients and to link it with potential triggers and prognosis. Methods. AHF patients underwent multidirectional assessment including capillary blood gas examination on hospital admission and during hospitalization. Results. Out of 241 AHF patients, 57(24%) were assigned to low pCO 2 group (pCO 2  > 30mmHg) and 184 (76%) to normal pCO 2 group (pCO 2  > 30mmHg). Low pCO 2 group had significantly lower HCO 3 - (22.3 ± 3.4 mmol/L vs 24.7 ± 2.9 mmol/L p < 0.0001) and significantly higher lactate level (2.53 ± 1.6 vs 2.14 ± 0.97 p = 0.03). No differences between groups were observed in respect to the following potential triggers of hyperventilation: hypoxia (sO2 92.5 ± 5.2 vs 92 ± 5.6, p = 0.57), infection (CRP 10.5[4.9–26.4] vs 7.15[3.45–17.35], p = 0.47), dyspnea severity (7.8 ± 2.3 vs 8.0 ± 2.3, p = 0.59) and pulmonary congestion (82.5% vs 89.1%, p = 0.19), respectively. Low pCO 2 value was related to an increased one-year all-cause mortality hazard ratio (HR) (95%CI): 2.2 (1.3–3.6); p = 0.002 and risk of death and of rehospitalization for HF, HR (95%CI): 2.0 (1.3-3.0); p = 0.002. Conclusion. Hyperventilation is relatively frequent in AHF and is related to poor prognosis. Low pCO 2 was not contingent on expected potential triggers of dyspnea but rather on tissue hypoperfusion.