Heterogeneity of Ventilation/Perfusion Mismatch at Different Levels of PEEP and in Respiratory Mechanics Phenotypes of COVID-19 ARDS

Abstract

BACKGROUND: COVID-19-related ARDS is characterized by severe hypoxemia with initially preserved lung compliance and impaired ventilation/perfusion (V ˙/Q ˙) matching. PEEP can increase end-expiratory lung volume, but its effect on V ˙/Q ˙mismatch in COVID-19-related ARDS is not clear. METHODS: We enrolled intubated and mechanically ventilated subjects with COVID-19 ARDS and used the automatic lung parameter estimator (ALPE) to measure V ˙/Q ˙. Respiratory mechanics measurements, shunt, and V ˙/Q ˙mismatch (low V ˙/Q ˙and high V ˙/Q ˙) were collected at 3 PEEP levels (clinical PEEP 5 intermediate PEEP, low PEEP [clinical 2 50%], and high PEEP [clinical + 50%]). A mixed-effect model was used to evaluate the impact of PEEP on V ˙/Q ˙. We also investigated if PEEP might have a different effect on V ˙/Q ˙mismatch in 2 different respiratory mechanics phenotypes, that is, high elastance/low compliance (phenotype H) and low elastance/high compliance (phenotype L). RESULTS: Seventeen subjects with COVID-related ARDS age 66 [60-71] y with a P aO 2 /F IO 2 of 141 6 74 mm Hg were studied at low PEEP 5 5.6 6 2.2 cm H 2 O, intermediate PEEP 5 10.6 6 3.8 cm H 2 O, and high PEEP 5 15 6 5 cm H 2 O. Shunt, low V ˙/Q ˙, high V ˙/Q ˙, and alveolar dead space were not significantly influenced, on average, by PEEP. Respiratory system compliance decreased significantly when increasing PEEP without significant variation of P aO 2 /F IO 2 (P 5 .26). In the 2 phenotypes, PEEP had opposite effects on shunt, with a decrease in the phenotype L and an increase in phenotype H (P 5 .048). CONCLUSIONS: In subjects with COVID-related ARDS placed on invasive mechanical ventilation for > 48 h, PEEP had a heterogeneous effect on V ˙/Q ˙mismatch and, on average, higher levels were not able to reduce shunt. The subject's compliance could influence the effect of PEEP on V ˙/Q ˙mismatch since an increased shunt was observed in subjects with lower compliance, whereas the opposite occurred in those with higher compliance.

Mechanical Power in Prone Position Intubated Patients with COVID-19-Related ARDS: A Cohort Study

“…Tere has not been a uniform PEEP titration strategy during the prone maneuver, despite the fact that PEEP has variable responses in patients with COVID-19. In a previous study, the shunt fraction, alveolar dead space, and ventilation/perfusion matching were not afected by PEEP [22]. However, a potential impact of PEEP titration on MP cannot be assessed, as suggested in a previous study [9].…”

Decision support system to evaluate VENTilation in the Acute Respiratory Distress Syndrome

“…Secondary clinical outcome measures were. Secondary clinical outcome measures were: (1) daily average calculated delivered pressure over time, for periods of spontaneous breathing; (2) daily average calculated mechanical power over time; (3) daily average calculated oxygenation index over time; (4) daily average ventilatory ratio over time; (5) ventilator free days at 90 days; (5) time from control mode to support mode; (6) number of changes in ventilator settings per day; (7) percentage of time in control mode ventilation; (8) percentage of time in support mode ventilation; (9) total duration of mechanical ventilation; (10) tidal volume over time; (11) PEEP setting over time; (12) ventilation related complications e.g. pneumothorax and/or pneumomediastinum; (13) device malfunction event rate; (14) device related adverse event rate; and (15) number of times the advice from the Beacon system is followed through the duration of the study.…”

Incidence and Determinants of Acute Kidney Injury after Prone Positioning in Severe COVID-19 Acute Respiratory Distress Syndrome

“…The following supporting information can be downloaded at: www.mdpi.com/xxx/s1, Table S1: Multivariable regression analysis on predictors of ventilator-free days (VFDs), censored at 28 days; Table S2: Logistic regression analysis on predictors of ICU mortality. Prone positioning has extensively demonstrated a survival benefit in moderate-severe ARDS patients [5][6][7][8][9], despite the possible effect on intrabdominal pressure. In our study, we did not test if PP can increase the risk of AKI, as this is out of the scope of the current study.…”

“…Prone positioning (PP) has been extensively used in the management of severe COVID-19 ARDS (C-ARDS) [5] for its beneficial effects on V/Q mismatch, gas exchanges, and respiratory mechanics [6][7][8]. The rationale behind PP lies in improved regional ventilation homogeneity [9] and the enhancement of a lung-protective ventilation strategy [10,11]. Despite large trials highlighting the positive impacts of PP in patient outcomes, including mortality [12], PP is not free from potential adverse effects, like procedural risks, loss of venous access points, involuntary extubation, and potential hemodynamic instability [10,13].…”