The Effect of PEEP on Pulmonary Vascular Resistance Depends on Lung Recruitability in ARDS Patients.

Rationale. A U-shape relationship should exist between lung volume and pulmonary vascular resistance (PVR), with minimal PVR at functional residual capacity. Thus, positive end-expiratory pressure (PEEP) in patients with acute respiratory distress syndrome (ARDS) should increase PVR if it induces significant lung distension compared to recruitment. However, this has never been proven in patients. Objectives. To study the effects of PEEP on PVR according to lung recruitability, evaluated by the recruitment-to-inflation (R/I) ratio. Methods. In patients with ARDS, we measured hemodynamic (pulmonary artery catheter), echocardiographic and ventilatory variables (including esophageal pressure), at both low PEEP and higher PEEP by 10 cmH2O. Preload responsiveness was assessed by the passive leg raising test at high PEEP. Measurements and Main Results. We enrolled 23 patients, including 10 low recruiters (R/I <0.5) and 13 high recruiters (R/I ≥0.5). Raising PEEP from 4 (2-5) to 14 (12-15) cmH2O increased PVR in low recruiters (from 160 (120-297) to 243 (166-380) dyn.s/cm5, p<0.01), while PVR was unchanged in high recruiters (from 224 (185-289) to 235 (168-300) dyn.s/cm5, p=0.55). Right-to-left ventricular end-diastolic areas ratio simultaneously increased in low recruiters (from 0.54 (0.50-0.59) to 0.64 (0.56-0.70), p<0.01), while remaining stable in high recruiters (from 0.70 (0.65-0.79) to 0.68 (0.58-0.80), p=0.48). Raising PEEP decreased cardiac index only in preload responsive patients. Conclusions. PEEP increases PVR only when it induces significant lung distension compared to recruitment according to the recruitment-to-inflation ratio. Tailoring PEEP on this recruitability index should mitigate its hemodynamic effects.

Occurrence of secondary insults during endovascular treatment of acute ischemic stroke and impact on outcome: the SIR-STROKE prospective observational study.

BACKGROUND: Neurological outcome after endovascular treatment (EVT) of acute ischemic stroke (AIS) may depend on both patient-specific and procedural factors. We hypothesized that altered systemic homeostasis might be frequent and affect outcome in these patients. The aim of this study was to analyze secondary insults during EVT of AIS and its association with outcome and anesthesiologic regimen. METHODS: This was a single-center prospective observational study on patients undergoing EVT for AIS under local anesthesia (LA), conscious sedation (CS), or general anesthesia (GA). Altered systemic parameters were recorded and quantified as secondary insults. The primary endpoint was to evaluate number, duration, and severity of secondary insults during EVT. Secondary endpoints were to analyze association of insults with modified Rankin Scale at 90 days and anesthesiologic regimen. RESULTS AND CONCLUSIONS: One hundred twenty patients were enrolled. Overall, 78% of patients experienced at least one episode of hypotension, 21% hypertension, 54% hypoxemia, 16% bradycardia, and 13% tachycardia. In patients monitored with capnometry, 70% experienced hypocapnia and 21% hypercapnia. LA was selected in 24 patients, CS in 84, and GA in 12. Hypotension insult was more frequent during GA than LA and CS (p = 0.0307), but intraprocedural blood pressure variation was higher during CS (p = 0.0357). Hypoxemia was more frequent during CS (p = 0.0087). Proportion of hypotension duration was higher in unfavorable outcome but secondary insults did not remain in the final model of multivariable analysis. Secondary insults occurred frequently during EVT for AIS but the main predictors of outcome were age, NIHSS at admission, and prompt and successful recanalization.

Awake prone position reduces work of breathing in patients with COVID-19 ARDS supported by CPAP.

BACKGROUND: The use of awake prone position concomitant to non-invasive mechanical ventilation in acute respiratory distress syndrome (ARDS) secondary to COVID-19 has shown to improve gas exchange, whereas its effect on the work of breathing remain unclear. The objective of this study was to evaluate the effects of awake prone position during helmet continuous positive airway pressure (CPAP) ventilation on inspiratory effort, gas exchange and comfort of breathing. METHODS: Forty consecutive patients presenting with ARDS due to COVID-19 were prospectively enrolled. Gas exchange, esophageal pressure swing (ΔPes), dynamic transpulmonary pressure (dTPP), modified pressure time product (mPTP), work of breathing (WOB) and comfort of breathing, were recorded on supine position and after 3 h on prone position. RESULTS: The median applied PEEP with helmet CPAP was 10 [8-10] cmH2O. The PaO2/FiO2 was higher in prone compared to supine position (Supine: 166 [136-224] mmHg, Prone: 314 [232-398] mmHg, p < 0.001). Respiratory rate and minute ventilation decreased from supine to prone position from 20 [17-24] to 17 [15-19] b/min (p < 0.001) and from 8.6 [7.3-10.6] to 7.7 [6.6-8.6] L/min (p < 0.001), respectively. Prone position did not reduce ΔPes (Supine: - 7 [- 9 to - 5] cmH2O, Prone: - 6 [- 9 to - 5] cmH2O, p = 0.31) and dTPP (Supine: 17 [14-19] cmH2O, Prone: 16 [14-18] cmH2O, p = 0.34). Conversely, mPTP and WOB decreased from 152 [104-197] to 118 [90-150] cmH2O/min (p < 0.001) and from 146 [120-185] to 114 [95-151] cmH2O L/min (p < 0.001), respectively. Twenty-six (65%) patients experienced a reduction in WOB of more than 10%. The overall sensation of dyspnea was lower in prone position (p = 0.005). CONCLUSIONS: Awake prone position with helmet CPAP enables a reduction in the work of breathing and an improvement in oxygenation in COVID-19-associated ARDS.