Behavior of oxygenation parameters in patients with early and late pneumonia following resuscitated cardiac arrest

Pneumonia is the most common infectious complication following a recovered cardiac arrest (CA), with worsening in oxygenation being one of its diagnostic criteria. However, there are currently no data regarding the prognosis that the severity of respiratory failure (RF) generates. The objective of this analysis is to describe and compare the oxygenation parameters between patients with recovered CA with and without pneumonia (both early (EP) and late pneumonia (LP)).

A retrospective observational study was conducted using a prospective registry of patients admitted for recovered CA to the Acute Cardiovascular Care Unit at a tertiary hospital between September 2006 and April 2022. The severity of deterioration in oxygenation was classified according to Berlin criteria for acute respiratory distress, using the PaFI (partial arterial oxygen pressure/inspired oxygen concentration). If arterial blood gases were not available, the modified Kigali criteria were employed, using SaFI (oxygen saturation/inspired oxygen concentration).

A total of 575 patients were included, with an incidence of pneumonia of 41% (235), of which 28% (161) were EP and 13% (74) were LP. At the time of admission, all patients presented with moderate to severe RF. In patients with EP, improvement in PaFI values was significantly lower compared to patients without pneumonia in the first 24-48 hours. In the LP group, after an initial improvement (first 24 hours), there was a progressive deterioration with statistically significant differences compared to patients without pneumonia at 48, 72, 96, and 120 hours. Regarding the behavior of the SaFI, the improvement in EP was significantly lower at 24 and 48 hours. When comparing LP versus no pneumonia, after the initial improvement, there was a significantly greater progressive deterioration in those with LP at 72, 96, and 120 hours.

Patients with CA are exposed to various factors such as resuscitation maneuvers, emergency intubation, and bronchial aspiration, which promote the initial development of moderate to severe RF. This situation improves in the first 24 hours, likely due to post-CA care, especially if pneumonia does not develop. The behavior of the PaFI and SaFI values helps determine the degree of RF. In cases where blood gas analyses are not available, the SaFI can be reliable