Is hypocapnia a risk factor for non-invasive ventilation failure in cardiogenic acute pulmonary edema?

Partial arterial carbon dioxide and oxygen pressure in patients with cardiogenic shock

In patients with acute cardiovascular diseases, hypocapnia, hypoxia and hyperoxia are known to be associated with increased mortality. This monocentric prospective registry study included 238 consecutive patients with cardiogenic shock (CS). The study aimed to assess the prognostic impact of partial arterial carbon dioxide (PaCO2) and oxygen pressure (PaO2) on 30-day all-cause mortality. Statistical analyses included t-tests, Spearman´s correlation, Kaplan-Meier and Cox regression analyses. No difference was found between quartiles of PaCO2 (log-rank p = 0.416) and PaO2 (log-rank p = 0.946) in the entire cohort. In the subgroup of patients with ventilation on admission, patients with PaCO2 ≤ 33 mmHg showed the highest 30-day all-cause mortality compared to the other quartiles (82.6% vs. 46.9% vs. 54.0% vs. 59.6% log-rank p = 0.026). No differences were found between levels of PaO2, when stratified by quartiles (log-rank p = 0.895). After differentiation between patients with PaCO2 ≤ 33 mmHg and PaCO2 > 33 mmHg the association with 30-day all-cause mortality remained significant (82.6% vs. 54.5% log-rank p = 0.006) in ventilated patients, whereas still no difference could be seen in the entire cohort (log-rank p = 0.264). Even after multivariable adjustment PaCO2 ≤ 33 mmHg remained an independent risk factor for 30-day all-cause mortality (HR 1.936; 95% CI 1.131-3.316; p = 0.016) in ventilated CS-patients. In conclusion, no association was found between different levels of PaCO2 and PaO2 with 30-day all-cause mortality in patients with CS. However, in the subgroup of CS-patients requiring ventilation, PaCO2 ≤ 33 mmHg was associated with an increased 30-day all-cause mortality.

Prognostic value of respiratory parameters for COVID-19 patients in the emergency department: results from the EC-COVID study

While several studies have evaluated the prognostic weight of respiratory parameters in patients with COVID-19, few have focused on patients' clinical conditions at the first emergency department (ED) assessment. We analyzed a large cohort of ED patients recruited within the EC-COVID study over the year 2020, and assessed the association between key bedside respiratory parameters measured in room air (pO2, pCO2, pH, and respiratory rate [RR]) and hospital mortality, after adjusting for key confounding factors. Analyses were based on a multivariable logistic Generalized Additive Model (GAM). After excluding patients who did not perform a blood gas analysis (BGA) test in room air or with incomplete BGA results, a total of 2458 patients were considered in the analyses. Most patients were hospitalized on ED discharge (72.0%); hospital mortality was 14.3%. Strong, negative associations with hospital mortality emerged for pO2, pCO2 and pH (p-values: < 0.001, < 0.001 and 0.014), while a significant, positive association was observed for RR (p-value < 0.001). Associations were quantified with nonlinear functions, learned from the data. No cross-parameter interaction was significant (all p-values were larger than 0.10), suggesting a progressive, independent effect on the outcome as the value of each parameter departed from normality. Our results collide with the hypothesized existence of patterns of breathing parameters with specific prognostic weight in the early stages of the disease.

Hypocapnia is an independent predictor of in-hospital mortality in acute heart failure

AIMS

Acute heart failure (AHF) poses a major threat to hospitalized patients for its high mortality rate and serious complications. The aim of this study is to determine whether hypocapnia [defined as the partial pressure of arterial carbon dioxide (PaCO₂ ) below 35 mmHg] on admission could be associated with in-hospital all-cause mortality in AHF.

METHODS AND RESULTS

A total of 676 patients treated in the coronary care unit for AHF were retrospectively analysed, and the study endpoint was in-hospital all-cause mortality. The 1:1 propensity score matching (PSM) analysis, Kaplan-Meier curve, and Cox regression model were used to explore the association between hypocapnia and in-hospital all-cause mortality in AHF. Receiver operating characteristic (ROC) curve and Delong's test were used to assess the performance of hypocapnia in predicting in-hospital all-cause mortality in AHF. The study cohort included 464 (68.6%) males and 212 (31.4%) females, and the median age was 66 years (interquartile range 56-74 years). Ninety-eight (14.5%) patients died during hospitalization and presented more hypocapnia than survivors (76.5% vs. 45.5%, P < 0.001). A 1:1 PSM was performed between hypocapnic and non-hypocapnic patients, with 264 individuals in each of the two groups after matching. Compared with non-hypocapnic patients, in-hospital mortality was significantly higher in hypocapnic patients both before (22.2% vs. 6.8%, P < 0.001) and after (20.8% vs. 8.7%, P < 0.001) PSM. Kaplan-Meier curve showed a significantly higher probability of in-hospital death in patients with hypocapnia before and after PSM (both P < 0.001 for the log-rank test). Multivariate Cox regression analysis showed that hypocapnia was an independent predictor of AHF mortality both before [hazard ratio (HR) 2.22; 95% confidence interval (CI) 1.23-3.98; P = 0.008] and after (HR 2.19; 95% CI 1.18-4.07; P = 0.013) PSM. Delong's test showed that the area under the ROC curve was improved after adding hypocapnia into the model (0.872, 95% CI 0.839-0.901 vs. 0.855, 95% CI 0.820-0.886, P = 0.028). PaCO₂ was correlated with the estimated glomerular filtration rate (r = 0.20, P = 0.001), left ventricular ejection fraction (r = 0.13, P < 0.001), B-type natriuretic peptide (r = -0.28, P < 0.001), and lactate (r = -0.15, P < 0.001). Kaplan-Meier curve of PaCO₂ tertiles and multivariate Cox regression analysis showed that the lowest PaCO₂ tertile was associated with increased risk of in-hospital mortality in AHF (all P < 0.05).

CONCLUSIONS

Hypocapnia is an independent predictor of in-hospital mortality for AHF.