Prone Position Session Research Articles

Effects of positive end-expiratory pressure strategy in supine and prone position on lung and chest wall mechanics in acute respiratory distress syndrome

BackgroundIn acute respiratory distress syndrome (ARDS) patients, it has recently been proposed to set positive end-expiratory pressure (PEEP) by targeting end-expiratory transpulmonary pressure. This approach, which relies on the measurement of absolute esophageal pressure (Pes), has been used in supine position (SP) and has not been investigated in prone position (PP). Our purposes were to assess Pes-guided strategy to set PEEP in SP and in PP as compared with a PEEP/FIO2 table and to explore the early (1 h) and late (16 h) effects of PP on lung and chest wall mechanics.ResultsWe performed a prospective, physiologic study in two ICUs in university hospitals on ARDS patients with PaO2/FIO2 < 150 mmHg. End-expiratory Pes (Pes,ee) was measured in static (zero flow) condition. Patients received PEEP set according to a PEEP/FIO2 table then according to the Pes-guided strategy targeting a positive (3 ± 2 cmH2O) static end-expiratory transpulmonary pressure in SP. Then, patients were turned to PP and received same amount of PEEP from PEEP/FIO2 table then Pes-guided strategy. Respiratory mechanics, oxygenation and end-expiratory lung volume (EELV) were measured after 1 h of each PEEP in each position. For the rest of the 16-h PP session, patients were randomly allocated to either PEEP strategy with measurements done at the end. Thirty-eight ARDS patients (27 male), mean ± SD age 63 ± 13 years, were included. There were 33 primary ARDS and 26 moderate ARDS. PaO2/FIO2 ratio was 120 ± 23 mmHg. At same PEEP/FIO2 table-related PEEP, Pes,ee averaged 9 ± 4 cmH2O in both SP and PP (P = 0.88). With PEEP/FIO2 table and Pes-guided strategy, PEEP was 10 ± 2 versus 12 ± 4 cmH2O in SP and 10 ± 2 versus 12 ± 5 cmH2O in PP (PEEP strategy effect P = 0.05, position effect P = 0.96, interaction P = 0.96). With the Pes-guided strategy, chest wall elastance increased regardless of position. Lung elastance and transpulmonary driving pressure decreased in PP, with no effect of PEEP strategy. Both PP and Pes-guided strategy improved oxygenation without interaction. EELV did not change with PEEP strategy. At the end of PP session, respiratory mechanics did not vary but EELV and PaO2/FIO2 increased while PaCO2 decreased.ConclusionsThere was no impact of PP on Pes measurements. PP had an immediate improvement effect on lung mechanics and a late lung recruitment effect independent of PEEP strategy.

Prone positioning in acute respiratory distress syndrome after abdominal surgery: a multicenter retrospective study

Background The recent demonstration of prone position’s strong benefit on patient survival has rendered proning a major therapeutic intervention in severe ARDS. Uncertainties remain as to whether or not ARDS patients in the postoperative period of abdominal surgery should be turned prone because of the risk of abdominal complications. Our aim was to investigate the prevalence of surgical complications between patients with and without prone position after abdominal surgery.MethodsThis study was a multicenter retrospective cohort of patients with ARDS in a context of recent abdominal surgery. Primary outcome was the number of patients who had at least one surgical complication that could be induced or worsened by prone position. Secondary outcomes included effects of prone position on oxygenation. Data from the prone group were compared with those from the supine group (not having undergone at least a prone position session).Results Among 98 patients included, 36 (37%) had at least one prone position session. The rate of surgical complications induced or worsened by prone position did not differ between prone and supine groups [respectively, 14 (39%) vs 27 (44%); p = 0.65]. After propensity score application, there was no significant difference between the two groups (OR 0.72 [0.26–2.02], p = 0.54). Revision surgery did not differ between the groups. The first prone session significantly increased PaO2/FiO2 ratio from 95 ± 47 to 189 ± 92 mmHg, p < 0.0001.Conclusion Prone position of ARDS patients after abdominal surgery was not associated with an increased rate of surgical complication. Intensivists should not refrain from proning these patients.

Lung ultrasonography for assessment of oxygenation response to prone position ventilation in ARDS.

Prone position (PP) improves oxygenation and outcome of acute respiratory distress syndrome (ARDS) patients with a PaO2/FiO2 ratio <150mmHg. Regional changes in lung aeration can be assessed by lung ultrasound (LUS). Our aim was to predict the magnitude of oxygenation response after PP using bedside LUS. We conducted a prospective multicenter study that included adult patients with severe and moderate ARDS. LUS data were collected at four time points: 1h before (baseline) and 1h after turning the patient to PP, 1h before and 1h after turning the patient back to the supine position. Regional lung aeration changes and ultrasound reaeration scores were assessed at each time. Overdistension was not assessed. Fifty-one patients were included. Oxygenation response after PP was not correlated with a specific LUS pattern. The patients with focal and non-focal ARDS showed no difference in global reaeration score. With regard to the entire PP session, the patients with non-focal ARDS had an improved aeration gain in the anterior areas. Oxygenation response was not associated with aeration changes. No difference in PaCO2 change was found according to oxygenation response or lung morphology. In ARDS patients with a PaO2/FiO2 ratio ≤150mmHg, bedside LUS cannot predict oxygenation response after the first PP session. At the bedside, LUS enables monitoring of aeration changes during PP.

A Comprehensive Review of Prone Position in ARDS.

Prone position (PP) has been used since the 1970s to treat severe hypoxemia in patients with ARDS because of its effectiveness at improving gas exchange. Compared with the supine position (SP), placing patients in PP effects a more even tidal volume distribution, in part, by reversing the vertical pleural pressure gradient, which becomes more negative in the dorsal regions. PP also improves resting lung volume in the dorsocaudal regions by reducing the superimposed pressure of both the heart and the abdomen. In contrast, pulmonary perfusion remains preferentially distributed to the dorsal lung regions, thus improving overall alveolar ventilation/perfusion relationships. Moreover, the larger tissue mass suspended from a wider dorsal chest wall effects a more homogeneous distribution of pleural pressures throughout the lung that reduces abnormal strain and stress development. This is believed to ameliorate the severity or development of ventilator-induced lung injury and may partly explain why PP reduces mortality in severe ARDS. Over 40 years of clinical trials have consistently reported improved oxygenation in approximately 70% of subjects with ARDS. Early initiation of PP is more likely to improve oxygenation than initiation during the subacute phase. Maximal oxygenation improvement occurs over a wide time frame ranging from several hours to several days. Meta-analyses of randomized controlled trials suggest that PP provides a survival advantage only in patients with relatively severe ARDS (PaO2 /FIO2 < 150 mm Hg). Moreover, survival is enhanced when patients are managed with a smaller tidal volume (≤ 8 mL/kg), higher PEEP (10-13 cm H2O), and longer duration of PP sessions (> 10-12 h/session). Combining adjunctive therapies (high PEEP, recruitment maneuvers, and inhaled vasodilators) with PP has an additive effect in improving oxygenation and may be particularly helpful in stabilizing gas exchange in very severe ARDS.

Ultrasound-guided insertion of dialysis catheter in the prone position

A 66-year-old man was admitted to the intensive care unit for a septic shock with acute renal failure and acute respiratory distress syndrome (ARDS) with a PaO2/FiO2 ratio of 72 mmHg, an FiO2 of 90 %, a PEEP of 10 cmH2O, and a tidal volume of 6 ml/kg of predicted body weight ventilation. The patient was turned to the prone position (PP) on the first day of admission. During the PP period, he presented anuric renal failure. The first studies related to the potential use of PP in ARDS treatment were published in 2011. The Proning Severe ARDS Patients (PROSEVA) group demonstrated the beneficial effect of a prolonged PP session during mechanical ventilatory support in a recent study. Sepsis-associated acute kidney injury was associated with a poor prognosis, substantiated by mortality rates of up to 75 %. In this context, we decided to maintain the PP session and to insert the dialysis catheter under ultrasound guidance (Fig. 1) in the left jugular by the posterior approach (Supplemental Fig. 1). We controlled the catheter placement by chest X-ray in the PP (Supplemental Fig. 2), no complication was observed and haemodialysis was started during the PP session.

Does gas exchange response to prone position predict mortality in hypoxemic acute respiratory failure?

To determine whether gas exchange response to a first prone position session can predict patient outcome in hypoxemic acute respiratory failure. Data from a previous multicenter randomized controlled trial were retrospectively analyzed for relationship between PaO(2)/FIO(2) ratio and PaCO(2) changes during the first 8-h prone position session to day 28 mortality rate; 370 prone position sessions were analyzed. Arterial blood gas was measured in supine position before proning and in prone position at the end of the session. Gas exchange improvement was defined as increase in the PaO(2)/FIO(2) ratio of more than 20% (PaO(2)R) or decrease in PaCO(2) of more than 1 mmHg (PaCO(2)R). The 28-day mortality rate was 26.5% in PaO(2)R-PaCO(2)R, 31.7% in PaO(2)R-PaCO(2)NR, 38.9% in PaO(2)NR-PaCO(2)R, and 43% in PaO(2)NR-PaCO(2)NR (log-rank 14.02, p = 0.003). In a Cox proportional hazards model the gas exchange response was a significant predictor to patient outcome with a 82.5% increase in risk of death in the case of PaO(2)NR-PaCO(2)R or PaO(2)NR-PaCO(2)NR, relative to the gas exchange improvement response (odds ratio 1.825). However, after adjusting for the difference in oxygenation between day 2 and day 1 the gas exchange response does no longer reach significance. In patients with hypoxemic acute respiratory failure initial improvement in gas exchange in the first PP session was associated with a better outcome, but this association disappeared when the change in oxygenation from day 1 to day 2 was taken into account, suggesting that underlying illness was the most important predictor of mortality in this patient population.

Ventilation in the prone position in patients with acute lung injury/acute respiratory distress syndrome

To contrast the beneficial effects of the prone position on the lungs and the lack of proven clinical benefits on patient outcome. Recent human investigations in acute respiratory distress syndrome have shown that the prone position was able to abolish tidal expiratory flow limitation, to improve oxygenation in the case of localized infiltrates, to allow for reducing positive end-expiratory pressure level, and to reduce lung stress and strain. Experimental studies have confirmed that distribution of ventilation was more homogeneous in the prone position but showed that positive end-expiratory pressure affected ventilation distribution differently in the prone and in the supine position. Experimental work has also shown that proning reduced strains imposed on the lungs and made them more homogeneously distributed. Finally, one recent large randomized controlled trial of systematic proning in hypoxemic patients showed no reduction in mortality but less ventilator-associated pneumonia incidence in the prone position group. The prone position is not systematically used in hypoxemic patients. Patients who could benefit from prone position sessions are those with the most severe acute respiratory distress syndrome and those with dorsal lung infiltrates. Whether this can be translated into improvement in patient outcome has yet to be tested in clinical trials.

Le décubitus ventral dans le syndrome de détresse respiratoire aiguë

It is now well established that prone position (PP) sessions can improve arterial oxygenation in the majority of patients with acute hypoxemic respiratory failure. The underlying mechanism of this beneficial response is not completely understood but is likely due to the alveolar recruitment of the dependent lung units which are atelectatic in supine position and remain still perfused in prone position. Some animal studies suggest that PP could reduce the extent of lung damage resulting from high tidal volumes applied during mechanical ventilation, and can increase the efficiency of recruitment manoeuvres, like sustained inflation, at lower levels of positive-end expiratory pressure. Optimal prone positioning is relatively easy to perform without any specific additional equipment. It requires, however, trained and motivated medical and nursing staff and an available written procedure. The impressive complications observed in the early days, such as endotracheal tube or central venous lines removal while changing positions, no longer occur. The overpressure-induced skin lesions can be significantly reduced by following precise recommendations. Some questions are still not resolved in the clinical practice, such as: when should PP be started from the onset of mechanical ventilation? Probably as early as possible. What should be the optimal duration of the PP session? For how long should we continue PP in a responder patient? One important issue, namely the impact of PP on patient outcome, is being tested in randomized control trials, which are ongoing in three European countries.