Prone position in mechanically ventilated patients with severe acute respiratory failure

Respiratory effects of prone position in COVID-19 acute respiratory distress syndrome differ according to the recruitment-to-inflation ratio: a prospective observational study

BACKGROUND

Improvements in oxygenation and lung mechanics with prone position (PP) in patients with acute respiratory distress syndrome (ARDS) are inconstant. The objectives of the study were (i) to identify baseline variables, including the recruitment-to-inflation ratio (R/I), associated with a positive response to PP in terms of oxygenation (improvement of the ratio of arterial oxygen partial pressure over the inspired oxygen fraction (PaO2/FiO2) ≥ 20 mmHg) and lung mechanics; (ii) to evaluate whether the response to the previous PP session is associated with the response to the next session.

METHODS

In this prospective, observational, single-center study in patients who underwent PP for ARDS due to COVID-19, respiratory variables were assessed just before PP and at the end of the session. Respiratory variables included mechanical ventilation settings and respiratory mechanics variables, including R/I, an estimate of the potential for lung recruitment compared to lung overinflation.

RESULTS

In 50 patients, 201 PP sessions lasting 19 ± 3 h were evaluated. Neuromuscular blockades were used in 116 (58%) sessions. The PaO2/FiO2 ratio increased from 109 ± 31 mmHg to 165 ± 65 mmHg, with an increase ≥ 20 mmHg in 142 (71%) sessions. In a mixed effect logistic regression, only pre-PP PaO2/FiO2 (OR 1.12 (95% CI [1.01-1.24])/every decrease of 10 mmHg, p = 0.034) in a first model and improvement in oxygenation at the previous PP session (OR 3.69 (95% CI [1.27-10.72]), p = 0.017) in a second model were associated with an improvement in oxygenation with PP. The R/I ratio (n = 156 sessions) was 0.53 (0.30-0.76), separating lower- and higher-recruiters. Whereas PaO2/FiO2 improved to the same level in both subgroups, driving pressure and respiratory system compliance improved only in higher-recruiters (from 14 ± 4 to 12 ± 4 cmH2O, p = 0.027, and from 34 ± 11 to 38 ± 13 mL/cmH2O, respectively, p = 0.014).

CONCLUSIONS

A lower PaO2/FiO2 at baseline and a positive O2-response at the previous PP session are associated with a PP-induced improvement in oxygenation. In higher-recruiters, lung mechanics improved along with oxygenation. Benefits of PP could thus be greater in these patients.

Feasibility of Prone Positioning for Brain-injured Patients with Severe Acute Respiratory Distress Syndrome: A Systematic Review and Pilot Study (ProBrain)

BACKGROUND

Prone position is a key component to treat hypoxemia in patients with severe acute respiratory distress syndrome. However, most studies evaluating it exclude patients with brain injuries without any medical evidence.

METHODS

This study includes a systematic review to determine whether brain-injured patients were excluded in studies evaluating prone position on acute respiratory distress syndrome; a prospective study including consecutive brain-injured patients needing prone position. The primary endpoint was the evaluation of cerebral blood flow using transcranial Doppler after prone positioning. Secondary outcomes were intracranial pressure, cerebral perfusion pressure, and tissue oxygen pressure.

RESULTS

From 8,183 citations retrieved, 120 studies were included in the systematic review. Among them, 90 studies excluded brain-injured patients (75%) without any justification, 16 included brain-injured patients (4 randomized, 7 nonrandomized studies, 5 retrospective), and 14 did not retrieve brain-injured data. Eleven patients were included in the authors' pilot study. No reduction of cerebral blood flow surrogates was observed during prone positioning, with diastolic speed values (mean ± SD) ranging from 37.7 ± 16.2 cm/s to 45.2 ± 19.3 cm/s for the right side (P = 0.897) and 39.6 ± 18.2 cm/s to 46.5 ± 21.3 cm/s for the left side (P = 0.569), and pulsatility index ranging from 1.14 ± 0.31 to 1.0 ± 0.32 for the right side (P = 0.145) and 1.14 ± 0.31 to 1.02 ± 0.2 for the left side (P = 0.564) before and during prone position.

CONCLUSIONS

Brain-injured patients are largely excluded from studies evaluating prone position in acute respiratory distress syndrome. However, cerebral blood flow seems not to be altered considering increasing of mean arterial pressure during the session. Systematic exclusion of brain-injured patients appears to be unfounded, and prone position, while at risk in brain-injured patients, should be evaluated on these patients to review recommendations, considering close monitoring of neurologic and hemodynamic parameters.

EDITOR’S PERSPECTIVE

Prone positioning during CPAP therapy in SARS-CoV-2 pneumonia: a concise clinical review

During the COVID-19 pandemic, the number of patients with hypoxemic acute respiratory failure (ARF) due to SARS-CoV-2 pneumonia threatened to overwhelm intensive care units. To reduce the need for invasive mechanical ventilation (IMV), clinicians tried noninvasive strategies to manage ARF, including the use of awake prone positioning (PP) with continuous positive airway pressure (CPAP). In this article, we review the patho-physiologic rationale, clinical effectiveness and practical issues of the use of PP during CPAP in non-intubated, spontaneously breathing patients affected by SARS-CoV-2 pneumonia with ARF. Use of PP during CPAP appears to be safe and feasible and may have a lower rate of adverse events compared to IMV. A better response to PP is observed among patients in early phases of acute respiratory distress syndrome. While PP during CPAP may improve oxygenation, the impact on the need for intubation and mortality remains unclear. It is possible to speculate on the role of PP during CPAP in terms of improvement of ventilation mechanics and reduction of strain stress.

Effect of Chest Physiotherapy Technique on Bilateral Bronchial Pneumonia Secondary to Acute Respiratory Distress Syndrome: A Case Report

This case report investigates the impact of a specific chest physiotherapy technique on a patient with bilateral bronchial pneumonia secondary to acute respiratory distress syndrome (ARDS). ARDS is a life-threatening condition characterized by severe respiratory failure, and bronchial pneumonia can further complicate the clinical course. The chosen chest physiotherapy technique aims to improve respiratory function and alleviate symptoms in the context of this challenging scenario. ARDS can develop in individuals who are seriously injured or have other severe conditions. ARDS is characterized by insensitive cyanosis, declining lung compliance, and high morbidity in intensive care units. It is a complicated and accumulating condition that develops from acute damage to the lungs. The case involves a detailed examination of a patient diagnosed with bilateral bronchial pneumonia as a complication of ARDS. The application of a targeted chest physiotherapy technique is described, emphasizing its methodology and the rationale behind its selection. Through this case report, we aim to contribute valuable insights into the potential efficacy of the specific chest physiotherapy technique for managing respiratory complications associated with ARDS-induced bilateral bronchial pneumonia. The findings may have implications for clinical practice, guiding healthcare professionals in tailoring interventions for similar cases and optimizing patient care in critical respiratory conditions. Additionally, the report underscores the importance of individualized approaches in the management of complex respiratory disorders, highlighting the need for further research to validate and refine such therapeutic strategies. The report delves into the patient's response to the intervention, documenting any observable improvements in respiratory parameters, lung function, and overall clinical outcomes. There were numerous etiologists, and it frequently ended in intense respiratory failure; after that death, the majority of care is supportive and concentrates on treating the underlying cause as well as providing ventilation. Physical therapy should begin as soon as the ARDS is treated. In this case, we discuss and conclude the various aspects of physiotherapy interventions for bilateral bronchial pneumonia secondary to ARDS. Chest physiotherapy plays an important role in respiratory conditions for breathing effectiveness and to reduce airway resistance.

Lung ultrasound to predict gas-exchange response to prone positioning in COVID-19 patients: A prospective study in pilot and confirmation cohorts

PURPOSE

To examine whether lung ultrasound prior to prone positioning can predict the resulting gas-exchange response.

MATERIALS AND METHODS

This is a prospective observational study on critically-ill COVID-19 patients with a pilot and confirmation cohort. Lung ultrasound examinations were performed before prone positioning and gas-exchange parameters were recorded before and after position change.

RESULTS

A total of 79 patients, 36 in the pilot cohort and 43 in the confirmation cohort, were included. In the pilot cohort, a moderate correlation between pre-turn lung ultrasound score index (LUSI) and change in PaO2/FiO2 after prone positioning was found. These findings were corroborated and extended upon in the confirmation cohort. The confirmation cohort found that anterior LUSI had the strongest correlation with follow-up time-points 1, 6, 12, and 24 h after prone positioning, with strength of correlation gradually increasing up to 24 h. In a multivariate model anterior aeration loss (odds ratio 0.035; 95%CI 0.003-0.319 for anterior LUSI >50%) and higher pre-turn PaCO₂ (odds ratio 0.479 95% CI 0.235-0.979) were negatively predictive of a PaO2/FiO2 increase ≥20 mmHg.

CONCLUSIONS

Anterior LUSI, in addition to other clinical parameters, may be used to aid COVID-19 respiratory strategy and a clinician's decision to prone.

Impact of prone positioning duration on the outcome of patients receiving venovenous extracorporeal membrane oxygenation for acute respiratory distress syndrome: A meta-analysis

Purpose

Research has shown that prone positioning (PP) improves the survival of patients receiving venovenous extracorporeal membrane oxygenation (V-V ECMO) for acute respiratory distress syndrome (ARDS). However, the reported impact of PP duration on the outcome of V-V ECMO patients with ARDS varies across studies.

Methods

A meta-analysis approach was used to identify studies that investigated the impact of PP duration on the outcome of ARDS patients who were treated with V-V ECMO; the following databases were used: MEDLINE, Embase, Wanfang, and the China National Knowledge Infrastructure. The primary outcome was cumulative survival. Secondary outcomes were length of stay in an intensive care unit, exchange of arterial blood gases, and adverse events.

Results

A total of 8 studies were included in the final meta-analysis. Patients with longer duration of PP (≥12 h) had a longer survival period (risk ratio: 1.24; 95% confidence interval: 1.00, 1.54]) than those with PP < 12 h. There was no evidence of publication bias across the studies.

Conclusion

Our results imply that a longer duration of PP ≥ 12 h might improve the outcome of patients with ARDS who receive V-V ECMO therapy.

Prognostic value of computed tomographic findings in acute respiratory distress syndrome and the response to prone positioning

Background

Prone positioning enables the redistribution of lung weight, leading to the improvement of gas exchange and respiratory mechanics. We aimed to evaluate whether the initial findings of acute respiratory distress syndrome (ARDS) on computed tomography (CT) are associated with the subsequent response to prone positioning in terms of oxygenation and 60-day mortality.

Methods

We retrospectively included patients who underwent prone positioning for moderate to severe ARDS from October 2014 to November 2020 at a medical center in Taiwan. A semiquantitative CT rating scale was used to quantify the extent of consolidation and ground-glass opacification (GGO) in the sternal, central and vertebral regions at three levels (apex, hilum and base) of the lungs. A prone responder was identified by a 20% increase in the ratio of arterial oxygen pressure (PaO₂) to the fraction of oxygen (FiO₂) or a 20 mmHg increase in PaO₂.

Results

Ninety-six patients were included, of whom 68 (70.8%) were responders. Compared with nonresponders, responders had a significantly greater median dorsal–ventral difference in CT-consolidation scores (10 vs. 7, p = 0.046) but not in CT-GGO scores (− 1 vs. − 1, p = 0.974). Although dorsal–ventral differences in neither CT-consolidation scores nor CT-GGO scores were associated with 60-day mortality, high total CT-GGO scores (≥ 15) were an independent factor associated with 60-day mortality (odds ratio = 4.07, 95% confidence interval, 1.39–11.89, p = 0.010).

Conclusions

In patients with moderate to severe ARDS, a greater difference in the extent of consolidation along the dependent-independent axis on CT scan is associated with subsequent prone positioning oxygenation response, but not clinical outcome regarding survival. High total CT-GGO scores were independently associated with 60-day mortality.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-01864-9.

Implementation and Assessment of a Proning Protocol for Nonintubated Patients With COVID-19

INTRODUCTION

The COVID-19 pandemic has caused over 1,250,000 deaths worldwide. With limited therapeutic options, proning nonintubated patients emerged as a safe and affordable intervention to manage hypoxemia.

METHODS

A proning protocol to identify and prone eligible patients was implemented. Patients were encouraged to self-prone for 2-3 hours, 3 times daily. Investigators created educational materials for nurses and patients and developed a COVID-19-specific proning order within the electronic health record (EHR). Investigators completed an 800-person retrospective chart review to study the implementation of this protocol.

RESULTS

From March 22, 2020, to June 5, 2020, 586 patients were admitted to the COVID-19 floor. Of these patients, 42.8% were eligible for proning. Common contraindications were lack of hypoxia, altered mental status, and fall risk. The proning protocol led to a significant improvement in provider awareness of patients appropriate for proning, increasing from 12% to 83%, as measured by placement of a proning order into the EHR. There was a significant improvement in all appropriate patients documented as proned, increasing from 18% to 45% of eligible patients.

CONCLUSIONS

The creation of an effective hospital-wide proning protocol to address the exigencies of the COVID-19 pandemic is possible and may be accomplished in a short period of time.

Efficiency of Prolonged Prone Positioning for Mechanically Ventilated Patients Infected with COVID-19

Hypoxemia of the acute respiratory distress syndrome can be reduced by turning patients prone. Prone positioning (PP) is labor intensive, risks unplanned tracheal extubation, and can result in facial tissue injury. We retrospectively examined prolonged, repeated, and early versus later PP for 20 patients with COVID-19 respiratory failure. Blood gases and ventilator settings were collected before PP, at 1, 7, 12, 24, 32, and 39 h after PP, and 7 h after completion of PP. Analysis of variance was used for comparisons with baseline values at supine positions before turning prone. PP for >39 h maintained PaO₂/FiO₂ (P/F) ratios when turned supine; the P/F decrease at 7 h was not significant from the initial values when turned supine. Patients turned prone a second time, when again turned supine at 7 h, had significant decreased P/F. When PP started for an initial P/F ≤ 150 versus P/F > 150, the P/F increased throughout the PP and upon return to supine. Our results show that a single turn prone for >39 h is efficacious and saves the burden of multiple prone turns, and there is no significant advantage to initiating PP when P/F > 150 compared to P/F ≤ 150.

Facial Pressure Injuries from Prone Positioning in the COVID-19 Era

OBJECTIVE/HYPOTHESIS

This study aimed to determine the incidence of facial pressure injuries associated with prone positioning for COVID-19 patients as well as to characterize the location of injuries and treatments provided.

METHODS

This was a retrospective chart review of 263 COVID-19 positive patients requiring intubation in the intensive care units at MedStar Georgetown University Hospital and MedStar Washington Hospital Center between March 1st and July 26th, 2020. Information regarding proning status, duration of proning, presence, or absence of facial pressure injuries and interventions were collected. Paired two-tailed t-test was used to evaluate differences between proned patients who developed pressure injuries with those who did not.

RESULTS

Overall, 143 COVID-19 positive patients required proning while intubated with the average duration of proning being 5.15 days. Of those proned, 68 (47.6%) developed a facial pressure injury. The most common site involved was the cheek with a total of 57 (84%) followed by ears (50%). The average duration of proning for patients who developed a pressure injury was significantly longer when compared to those who did not develop pressure injuries (6.79 days vs. 3.64 days, P < .001).

CONCLUSIONS

Facial pressure injuries occur with high incidence in patients with COVID-19 who undergo prone positioning. Longer duration of proning appears to confer greater risk for developing these pressure injuries. Hence, improved preventative measures and early interventions are needed.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E2139-E2142, 2021.

Prone ventilation as treatment of acute respiratory distress syndrome related to COVID-19

Prone ventilation refers to the delivery of mechanical ventilation with the patient lying in the prone position. The improvement of oxygenation during prone ventilation is multifactorial, but occurs mainly by reducing lung compression and improving lung perfusion. CT imaging modeling data demonstrated that the asymmetry of lung shape leads to a greater induced pleural pressure gravity gradient when supine as compared to prone positioning. Although proning is indicated in patients with severe ARDS who are not responding to other ventilator modalities, this technique has moved away from a salvage therapy for refractory hypoxemia to an upfront lung-protective strategy intended to improve survival in severe ARDS, especially due to the current COVID-19 pandemic. In view of different roles, we surgeons had to take during the COVID-19 pandemic, it is of importance to learn how to implement this therapeutic measure, especially in a surgical critical care unit setting. As such, this article aims to review the physiological principles and effects of the prone ventilation, positioning, as well as its contraindications and complications.

Quantitative Dual-Energy Computed Tomography Predicts Regional Perfusion Heterogeneity in a Model of Acute Lung Injury

Objective

The aims of this study were to investigate the ability of contrast-enhanced dual-energy computed tomography (DECT) for assessing regional perfusion in a model of acute lung injury, using dynamic first-pass perfusion CT (DynCT) as the criterion standard and to evaluate if changes in lung perfusion caused by prone ventilation are similarly demonstrated by DECT and DynCT.

Methods

This was an institutional review board–approved study, compliant with guidelines for humane care of laboratory animals. A ventilator-induced lung injury protocol was applied to 6 landrace pigs. Perfused blood volume (PBV) and pulmonary blood flow (PBF) were respectively quantified by DECT and DynCT, in supine and prone positions. The lungs were segmented in equally sized regions of interest, namely, dorsal, middle, and ventral. Perfused blood volume and PBF values were normalized by lung density. Regional air fraction (AF) was assessed by triple-material decomposition DECT. Per-animal correlation between PBV and PBF was assessed with Pearson R. Regional differences in PBV, PBF, and AF were evaluated with 1-way analysis of variance and post hoc linear trend analysis (α = 5%).

Results

Mean correlation coefficient between PBV and PBF was 0.70 (range, 0.55–0.98). Higher PBV and PBF values were observed in dorsal versus ventral regions. Dorsal-to-ventral linear trend slopes were −10.24 mL/100 g per zone for PBV (P < 0.001) and −223.0 mL/100 g per minute per zone for PBF (P < 0.001). Prone ventilation also revealed higher PBV and PBF in dorsal versus ventral regions. Dorsal-to-ventral linear trend slopes were −16.16 mL/100 g per zone for PBV (P < 0.001) and −108.2 mL/100 g per minute per zone for PBF (P < 0.001). By contrast, AF was lower in dorsal versus ventral regions in supine position, with dorsal-to-ventral linear trend slope of +5.77%/zone (P < 0.05). Prone ventilation was associated with homogenization of AF distribution among different regions (P = 0.74).

Conclusions

Dual-energy computed tomography PBV is correlated with DynCT-PBF in a model of acute lung injury, and able to demonstrate regional differences in pulmonary perfusion. Perfusion was higher in the dorsal regions, irrespectively to decubitus, with more homogeneous lung aeration in prone position.

Optimal duration of prone positioning in patients with acute respiratory distress syndrome: a protocol for a systematic review and meta-regression analysis

INTRODUCTION

Several systematic reviews and meta-analyses have demonstrated that prolonged (≥16 hours) prone positioning can reduce the mortality associated with acute respiratory distress syndrome (ARDS). However, the effectiveness and optimal duration of prone positioning was not fully evaluated. To fill these gaps, we will first investigate the effectiveness of prone positioning compared with the conventional management of patients with ARDS, regarding outcomes using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system. Second, if statistical heterogeneity in effectiveness with regard to short-term mortality (intensive care unit death or ≤30-day mortality) is shown, we will conduct a meta-regression analysis to explore the association between duration and effectiveness, and determine the optimal duration of prone positioning.

METHOD AND ANALYSIS

Relevant studies are collected using PubMed/MEDLINE, Embase, Cochrane Central Register of Controlled Trials and the WHO International Clinical Trials Platform Search Portal. Randomised controlled trials comparing prone and supine positioning in adults with ARDS will be included in the meta-analysis. Two independent investigators will screen trials obtained by search eligibility and extract data from selected studies to standardised data recording forms. For each selected trial, the risk of bias and quality of evidence will be evaluated using the GRADE system. Meta-regression analyses will be performed to identify the most important factors associated with short-term mortality, and subgroup analysis will be used to analyse the following: duration of mechanical ventilation in the prone position per day, patient severity, tidal volume and cause of ARDS. If heterogeneity or inconsistency among the studies is detected, subgroup analysis will be conducted on factors that may cause heterogeneity.

ETHICS AND DISSEMINATION

This study requires no ethical approval. The results obtained from this systematic review and meta-analysis will be disseminated through international conference presentations and publication in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42017078340.

Transport of a Prone Position Acute Respiratory Distress Syndrome Patient

We report the case of a non-physician based critical care transport team (registered nurse and paramedic) that successfully initiated prone positioning of a severe acute respiratory distress patient prior to transport to an extracorporeal membrane oxygenation capable teaching hospital. With the increasing use of advanced treatments such as extracorporeal membrane oxygenation, prone positioning, and continuous renal replacement therapy for severe acute respiratory distress syndrome (ARDS), the necessity to transport these patients to specialized hospitals will correspondingly increase. Emergency Health Services Life Flight, the primary critical care transport program in Eastern Canada, developed a prone position protocol to meet this clinical need. Since the implementation of the protocol, we have successfully initiated prone positioning of 2 patients with ARDS before transport to an extracorporeal membrane oxygenation- and continuous renal replacement therapy-capable teaching hospital. This represents the first report of a nonphysician (registered nurse and paramedic) critical care team initiating prone positioning before transport. Consent for publication was only obtained in the second case, which we present here.

Lung volumes and lung volume recruitment in ARDS: a comparison between supine and prone position

Background

The use of positive end-expiratory pressure (PEEP) and prone position (PP) is common in the management of severe acute respiratory distress syndrome patients (ARDS). We conducted this study to analyze the variation in lung volumes and PEEP-induced lung volume recruitment with the change from supine position (SP) to PP in ARDS patients.

Methods

The investigation was conducted in a multidisciplinary intensive care unit. Patients who met the clinical criteria of the Berlin definition for ARDS were included. The responsible physician set basal PEEP. To avoid hypoxemia, FiO₂ was increased to 0.8 1 h before starting the protocol. End-expiratory lung volume (EELV) and functional residual capacity (FRC) were measured using the nitrogen washout/washin technique. After the procedures in SP, the patients were turned to PP and 1 h later the same procedures were made in PP.

Results

Twenty-three patients were included in the study, and twenty were analyzed. The change from SP to PP significantly increased FRC (from 965 ± 397 to 1140 ± 490 ml, p = 0.008) and EELV (from 1566 ± 476 to 1832 ± 719 ml, p = 0.008), but PEEP-induced lung volume recruitment did not significantly change (269 ± 186 ml in SP to 324 ± 188 ml in PP, p = 0.263). Dynamic strain at PEEP decreased with the change from SP to PP (0.38 ± 0.14 to 0.33 ± 0.13, p = 0.040).

Conclusions

As compared to supine, prone position increases resting lung volumes and decreases dynamic lung strain.

Electronic supplementary material

The online version of this article (10.1186/s13613-018-0371-0) contains supplementary material, which is available to authorized users.

Analysis of complications of prone position in acute respiratory distress syndrome: Quality standard, incidence and related factors

Introduction

The monitoring system based on standards of quality allows clinicians to evaluate and improve the patient's care. According to the quality indicators recommended by Sociedad Española de Medicina Intensiva Crítica y Unidades Coronarias, and due to the importance of prone position (PP) as a treatment in patients with acute respiratory distress syndrome, it is fundamental to keep accurate record of serious adverse events occurring during the prone position procedure and its posterior analysis.

Objectives

To establish fulfilment of the Sociedad Española de Medicina Intensiva Crítica y Unidades Coronarias standards of quality according to the register of serious complications.

To identify the incidence of serious complications registered as well as to identify possible factors related to these complications.

Method

Retrospective, cross-sectional descriptive study, polyvalent ICU (16 beds).

Study population

Patients with acute respiratory distress syndrome treated with PP (January 2012–December 2013).

Study variables

PP recording, accidental extubation, removal of catheters, decubitus ulcers (DU), ETT obstruction, urgency of the procedure, hours in PP, nutritional intake, type of feeding tube, food regurgitation/retention and use of prokinetics/muscle relaxant.

Results

The study sample comprised 38 cases, with an adequate record of complications in 92.1% of the cases.

DU were the only serious complication recorded, with a 25.7% incidence.

Possible factors related to DU: more hours in PP in patients developing DU (p = 0.067). Less incidence of DU in well-nourished patients (p = 0.577).

82.9% of patients were not appropriately nourished.

Conclusions

The percentage of records duly completed is very high. The presence of DU (grade 1–2 mostly) is to be noted. There is no statistical significance, although a trend is obsersed, between DU and hours in PP.

Analysis of complications of prone position in acute respiratory distress syndrome: quality standard, incidence and related factors

INTRODUCTION

The monitoring system based on standards of quality allows clinicians to evaluate and improve the patient's care. According to the quality indicators recommended by Sociedad Española de Medicina Intensiva Crítica y Unidades Coronarias, and due to the importance of prone position (PP) as a treatment in patients with acute respiratory distress syndrome, it is fundamental to keep accurate record of serious adverse events occurring during the prone position procedure and its posterior analysis.

OBJECTIVES

To establish fulfilment of the Sociedad Española de Medicina Intensiva Crítica y Unidades Coronarias standards of quality according to the register of serious complications. To identify the incidence of serious complications registered as well as to identify possible factors related to these complications.

METHOD

Retrospective, cross-sectionsl descriptive study, polyvalent ICU (16 beds). Study population Patients with acute respiratory distress syndrome treated with PP (January 2012-December 2013). Study variables PP recording, accidental extubation, removal of catheters, decubitus ulcers (DU), ETT obstruction, urgency of the procedure, hours in PP, nutritional intake, type of feeding tube, food regurgitation/retention and use of prokinetics/muscle relaxant.

RESULTS

The study sample comprised 38 cases, with an adequate record of complications in 92.1% of the cases. DU were the only serious complication recorded, with a 25.7% incidence. Possible factors related to DU: more hours in PP in patients developing DU (p= .067). Less incidence of DU in well-nourished patients (p= .577). 82.9% of patients were not appropriately nourished.

CONCLUSIONS

The percentage of records duly completed is very high. The presence of DU (grade 1-2 mostly) is to be noted. There is no stastistical significance, although a trend is obversed, between DU and hours in PP.

Rapid Reduction of Oxygenation Index by Employment of a Recruitment Technique in Patients with Severe ARDS

Mechanical ventilation of patients with acute respiratory distress syndrome (ARDS) may contribute to pulmonary injury and systemic inflammation. The objective of this study was to examine the safety and efficacy of a recruitment maneuver that rapidly improves atelectasis and oxygenation, and in so doing may reduce the potential for ventilator-induced lung injury. Nineteen patients with severe ARDS (defined as PaO2: FiO2 ≤ 150) from diverse etiologies were turned prone and a positive pressure of 40 cmH2O was applied for a period of 90 seconds. This pressure was increased in 5 cmH2O increments in subsequent maneuvers to a maximum of 50 cmH2O if there was an inadequate initial response. Subsequently pressure-limited mechanical ventilation with a PEEP of 15 cmH2O was instituted to prevent derecruitment. Peak pressures were maintained at ≤35 cmH2O. Outcome measures were oxygenation index, PaO2: FiO2 ratio, and alveolar-arterial oxygen difference. The oxygenation index decreased from a median of 31 cmH2O/mmHg to 14 cmH2O/mmHg immediately after recruitment and to 11 cmH2O/mmHg (p < 0.0001) 24 hours later. The A-aDO2 improved from 454 mmHg to 128 mmHg (p < 0.0001) and the PaO2:FiO2 ratio from 75 to 218 (p < 0.0001) 24 hours later. Twenty-five percent of patients had PaO2:FiO2 ratios of more than 300 mmHg at 24 hours. Mean airway pressure increased by 3 cmH2O initially, from 23 cmH2O to 26 cmH2O as a consequence of the increase in PEEP, but this had decreased to 25 cmH2O after 24 hours. There were no significant complications. Rapid reductions in FiO2 can be achieved safely by the implementation of a relatively simple recruitment technique.

Prone position in patients with acute respiratory distress syndrome

Acute respiratory distress syndrome occupies a great deal of attention in intensive care units. Despite ample knowledge of the physiopathology of this syndrome, the focus in intensive care units consists mostly of life-supporting treatment and avoidance of the side effects of invasive treatments. Although great advances in mechanical ventilation have occurred in the past 20 years, with a significant impact on mortality, the incidence continues to be high. Patients with acute respiratory distress syndrome, especially the most severe cases, often present with refractory hypoxemia due to shunt, which can require additional treatments beyond mechanical ventilation, among which is mechanical ventilation in the prone position. This method, first recommended to improve oxygenation in 1974, can be easily implemented in any intensive care unit with trained personnel.

Prone position has extremely robust bibliographic support. Various randomized clinical studies have demonstrated the effect of prone decubitus on the oxygenation of patients with acute respiratory distress syndrome measured in terms of the PaO₂/FiO₂ ratio, including its effects on increasing patient survival.

The members of the Respiratory Therapists Committee of the Sociedad Argentina de Terapia Intensiva performed a narrative review with the objective of discovering the available evidence related to the implementation of prone position, changes produced in the respiratory system due to the application of this maneuver, and its impact on mortality. Finally, guidelines are suggested for decision-making.

Infant position in neonates receiving mechanical ventilation

BACKGROUND

In patients of various ages undergoing mechanical ventilation (MV), it has been observed that positions other than the standard supine position, such as the prone position, may improve respiratory parameters. The benefits of these positions have not been clearly defined for critically ill newborns receiving MV.This is an update of a review first published in 2005 and last updated in 2013.

OBJECTIVES

Primary objectiveTo assess the effects of different positioning of newborn infants receiving MV (supine vs prone, lateral decubitus or quarter turn from prone) in improving short-term respiratory outcomes. Secondary objectiveTo assess the effects of different positioning of newborn infants receiving MV on mortality and neuromotor and developmental outcomes over the long term, and on other complications of prematurity.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 8), MEDLINE via PubMed (1966 to 22 August 2016), Embase (1980 to 22 August 2016) and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to 22 August 2016). We also searched clinical trials databases, conference proceedings and reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

Randomised and quasi-randomised clinical trials comparing different positions in newborns receiving mechanical ventilation.

DATA COLLECTION AND ANALYSIS

Three unblinded review authors independently assessed trials for inclusion in the review and extracted study data. We used standard methodological procedures as expected by The Cochrane Collaboration and assessed the quality of the evidence using the GRADE approach. If the meta-analysis was not appropriate owing to substantial clinical heterogeneity between trials, we presented review findings in narrative format.

MAIN RESULTS

We included in this review 19 trials involving 516 participants. Seven of the included studies (N = 222) had not been evaluated in the previous review. Investigators compared several positions: prone versus supine, prone alternant versus supine, prone versus lateral right, lateral right versus supine, lateral left versus supine, lateral alternant versus supine, lateral right versus lateral left, quarter turn from prone versus supine, quarter turn from prone versus prone and good lung dependent versus good lung uppermost.Apart from two studies that compared lateral alternant versus supine, one comparing lateral right versus supine and two comparing prone or prone alternant versus the supine position, all included studies had a cross-over design. In five studies, infants were ventilated with continuous positive airway pressure (CPAP); in the other studies, infants were treated with conventional ventilation (CV).Risks of bias did not differ substantially for different comparisons and outcomes. This update detects a moderate to high grade of inconsistency, similar to previous versions. However, for the analysed outcomes, the direction of effect was the same in all studies. Therefore, we consider that this inconsistency had little effect on the conclusions of the meta-analysis. When comparing prone versus supine position, we observed an increase in arterial oxygen tension (PO₂) in the prone position (mean difference (MD) 5.49 mmHg, 95% confidence interval (CI) 2.92 to 8.05 mmHg; three trials; 116 participants; I²= 0). When percent haemoglobin oxygen saturation was measured with pulse oximetry (SpO₂), improvement in the prone position was between 1.13% and 3.24% (typical effect based on nine trials with 154 participants; I²= 89%). The subgroup ventilated with CPAP (three trials; 59 participants) showed a trend towards improving SpO2 in the prone position compared with the supine position, although the mean difference (1.91%) was not significant (95% CI -1.14 to 4.97) and heterogeneity was extreme (I²= 95%).Sensitivity analyses restricted to studies with low risk of selection bias showed homogeneous results and verified a small but significant effect (MD 0.64, 95% CI 0.26 to 1.02; four trials; 92 participants; I²= 0).We also noted a slight improvement in the number of episodes of desaturation; it was not possible to establish whether this effect continued once the intervention was stopped. Investigators studied few adverse effects from the interventions in sufficient detail. Two studies analysed tracheal cultures of neonates after five days on MV, reporting lower bacterial colonisation in the alternating lateral position than in the supine posture. Other effects - positive or negative - cannot be excluded in light of the relatively small numbers of neonates studied.

AUTHORS' CONCLUSIONS

This update of our last review in 2013 supports previous conclusions. Evidence of low to moderate quality favours the prone position for slightly improved oxygenation in neonates undergoing mechanical ventilation. However, we found no evidence to suggest that particular body positions during mechanical ventilation of the neonate are effective in producing sustained and clinically relevant improvement.

Pediatric Acute Hypoxemic Respiratory Failure: Management of Oxygenation

Acute hypoxemic respiratory failure (AHRF) is one of the hallmarks of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), which are caused by an inflammatory process initiated by any of a number of potential systemic and/or pulmonary insults that result in heterogeneous disruption of the capillary-pithelial interface. In these critically sick patients, optimizing the management of oxygenation is crucial. Physicians managing pediatric patients with ALI or ARDS are faced with a complex array of options influencing oxygenation. Certain treatment strategies can influence clinical outcomes, such as a lung protective ventilation strategy that specifies a low tidal volume (6 mL/kg) and a plateau pressure limit (30 cm H2O). Other strategies such as different levels of positive end expiratory pressure, altered inspiration to expiration time ratios, recruitment maneuvers, prone positioning, and extraneous gases or drugs may also affect clinical outcomes. This article reviews state-of-the-art strategies on the management of oxygenation in acute hypoxemic respiratory failure in children.

Ventilator-Associated Pneumonia: A Review

Ventilator-associated pneumonia is the most frequent intensive care unit (ICU)-related infection in patients requiring mechanical ventilation. In contrast to other ICU-related infections, which have a low mortality rate, the mortality rate for ventilator-associated pneumonia ranges from 20% to 50%. These clinically significant infections prolong duration of mechanical ventilation and ICU length of stay, underscoring the financial burden these infections impose on the health care system. The causes of ventilator-associated pneumonia are varied and differ across different patient populations and different types of ICUs. This varied presentation underscores the need for the intensivist treating the patient with ventilator-associated pneumonia to have a clear knowledge of the ambient microbiologic flora in their ICU. Prevention of this disease process is of paramount importance and requires a multifaceted approach. Once a diagnosis of ventilator-associated pneumonia is suspected, early broad-spectrum antibiotic administration decreases morbidity and mortality and should be based on knowledge of the sensitivities of common infecting organisms in the ICU. De-escalation of therapy, once final culture results are available, is necessary to minimize development of resistant pathogens. Duration of therapy should be based on the patient’s clinical response, and every effort should be made to minimize duration of therapy, thus further minimizing the risk of resistance.

Efficacy of prone position in acute respiratory distress syndrome patients: A pathophysiology-based review

Acute respiratory distress syndrome (ARDS) is a syndrome with heterogeneous underlying pathological processes. It represents a common clinical problem in intensive care unit patients and it is characterized by high mortality. The mainstay of treatment for ARDS is lung protective ventilation with low tidal volumes and positive end-expiratory pressure sufficient for alveolar recruitment. Prone positioning is a supplementary strategy available in managing patients with ARDS. It was first described 40 years ago and it proves to be in alignment with two major ARDS pathophysiological lung models; the "sponge lung" - and the "shape matching" -model. Current evidence strongly supports that prone positioning has beneficial effects on gas exchange, respiratory mechanics, lung protection and hemodynamics as it redistributes transpulmonary pressure, stress and strain throughout the lung and unloads the right ventricle. The factors that individually influence the time course of alveolar recruitment and the improvement in oxygenation during prone positioning have not been well characterized. Although patients' response to prone positioning is quite variable and hard to predict, large randomized trials and recent meta-analyses show that prone position in conjunction with a lung-protective strategy, when performed early and in sufficient duration, may improve survival in patients with ARDS. This pathophysiology-based review and recent clinical evidence strongly support the use of prone positioning in the early management of severe ARDS systematically and not as a rescue maneuver or a last-ditch effort.

S2e guideline: positioning and early mobilisation in prophylaxis or therapy of pulmonary disorders : Revision 2015: S2e guideline of the German Society of Anaesthesiology and Intensive Care Medicine (DGAI)

The German Society of Anesthesiology and Intensive Care Medicine (DGAI) commissioneda revision of the S2 guidelines on "positioning therapy for prophylaxis or therapy of pulmonary function disorders" from 2008. Because of the increasing clinical and scientificrelevance the guidelines were extended to include the issue of "early mobilization"and the following main topics are therefore included: use of positioning therapy and earlymobilization for prophylaxis and therapy of pulmonary function disorders, undesired effects and complications of positioning therapy and early mobilization as well as practical aspects of the use of positioning therapy and early mobilization. These guidelines are the result of a systematic literature search and the subsequent critical evaluation of the evidence with scientific methods. The methodological approach for the process of development of the guidelines followed the requirements of evidence-based medicine, as defined as the standard by the Association of the Scientific Medical Societies in Germany. Recently published articles after 2005 were examined with respect to positioning therapy and the recently accepted aspect of early mobilization incorporates all literature published up to June 2014.

Prone position for acute respiratory failure in adults

BACKGROUND

Acute hypoxaemia de novo or on a background of chronic hypoxaemia is a common reason for admission to intensive care and for provision of mechanical ventilation. Various refinements of mechanical ventilation or adjuncts are employed to improve patient outcomes. Mortality from acute respiratory distress syndrome, one of the main contributors to the need for mechanical ventilation for hypoxaemia, remains approximately 40%. Ventilation in the prone position may improve lung mechanics and gas exchange and could improve outcomes.

OBJECTIVES

The objectives of this review are (1) to ascertain whether prone ventilation offers a mortality advantage when compared with traditional supine or semi recumbent ventilation in patients with severe acute respiratory failure requiring conventional invasive artificial ventilation, and (2) to supplement previous systematic reviews on prone ventilation for hypoxaemic respiratory failure in an adult population.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2014, Issue 1), Ovid MEDLINE (1950 to 31 January 2014), EMBASE (1980 to 31 January 2014), the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (1982 to 31 January 2014) and Latin American Caribbean Health Sciences Literature (LILACS) (1992 to 31 January 2014) in Ovid MEDLINE for eligible randomized controlled trials. We also searched for studies by handsearching reference lists of relevant articles, by contacting colleagues and by handsearching published proceedings of relevant journals. We applied no language constraints, and we reran the searches in CENTRAL, MEDLINE, EMBASE, CINAHL and LILACS in June 2015. We added five new studies of potential interest to the list of "Studies awaiting classification" and will incorporate them into formal review findings during the review update.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that examined the effects of prone position versus supine/semi recumbent position during conventional mechanical ventilation in adult participants with acute hypoxaemia.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed all trials identified by the search and assessed them for suitability, methods and quality. Two review authors extracted data, and three review authors reviewed the data extracted. We analysed data using Review Manager software and pooled included studies to determine the risk ratio (RR) for mortality and the risk ratio or mean difference (MD) for secondary outcomes; we also performed subgroup analyses and sensitivity analyses.

MAIN RESULTS

We identified nine relevant RCTs, which enrolled a total of 2165 participants (10 publications). All recruited participants suffered from disorders of lung function causing moderate to severe hypoxaemia and requiring mechanical ventilation, so they were fairly comparable, given the heterogeneity of specific disease diagnoses in intensive care. Risk of bias, although acceptable in the view of the review authors, was inevitable: Blinding of participants and carers to treatment allocation was not possible (face-up vs face-down).Primary analyses of short- and longer-term mortality pooled from six trials demonstrated an RR of 0.84 to 0.86 in favour of the prone position (PP), but findings were not statistically significant: In the short term, mortality for those ventilated prone was 33.4% (363/1086) and supine 38.3% (395/1031). This resulted in an RR of 0.84 (95% confidence interval (CI) 0.69 to 1.02) marginally in favour of PP. For longer-term mortality, results showed 41.7% (462/1107) for prone and 47.1% (490/1041) for supine positions, with an RR of 0.86 (95% CI 0.72 to 1.03). The quality of the evidence for both outcomes was rated as low as a result of important potential bias and serious inconsistency.Subgroup analyses for mortality identified three groups consistently favouring PP: those recruited within 48 hours of meeting entry criteria (five trials; 1024 participants showed an RR of 0.75 (95% CI 0.59 to 94)); those treated in the PP for 16 or more hours per day (five trials; 1005 participants showed an RR of 0.77 (95% CI 0.61 to 0.99)); and participants with more severe hypoxaemia at trial entry (six trials; 1108 participants showed an RR of 0.77 (95% CI 0.65 to 0.92)). The quality of the evidence for these outcomes was rated as moderate as a result of potentially important bias.Prone positioning appeared to influence adverse effects: Pressure sores (three trials; 366 participants) with an RR of 1.37 (95% CI 1.05 to 1.79) and tracheal tube obstruction with an RR of 1.78 (95% CI 1.22 to 2.60) were increased with prone ventilation. Reporting of arrhythmias was reduced with PP, with an RR of 0.64 (95% CI 0.47 to 0.87).

AUTHORS' CONCLUSIONS

We found no convincing evidence of benefit nor harm from universal application of PP in adults with hypoxaemia mechanically ventilated in intensive care units (ICUs). Three subgroups (early implementation of PP, prolonged adoption of PP and severe hypoxaemia at study entry) suggested that prone positioning may confer a statistically significant mortality advantage. Additional adequately powered studies would be required to confirm or refute these possibilities of subgroup benefit but are unlikely, given results of the most recent study and recommendations derived from several published subgroup analyses. Meta-analysis of individual patient data could be useful for further data exploration in this regard. Complications such as tracheal obstruction are increased with use of prone ventilation. Long-term mortality data (12 months and beyond), as well as functional, neuro-psychological and quality of life data, are required if future studies are to better inform the role of PP in the management of hypoxaemic respiratory failure in the ICU.

The efficacy and safety of prone positioning in adults patients with acute respiratory distress syndrome: a meta-analysis of randomized controlled trials

BACKGROUND

Prone positioning for acute respiratory distress syndrome (ARDS) has no impact on mortality despite significant improvements in oxygenation. However, a recent trial demonstrated reduced mortality rates in the prone position for severe ARDS. We evaluated effects of prone position duration and protective lung strategies on mortality rates in ARDS.

METHODS

We extensively searched MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials to identify randomized controlled trials (RCTs) reporting on prone positioning during acute respiratory failure in adults for inclusion in our meta-analysis.

RESULTS

Eight trials met our inclusion criteria, Totals of 1,099 and 1,042 patients were randomized to the prone and supine ventilation positions. The mortality rates associated with the prone and supine positions were 41% and 47% [risk ratio (RR), 0.90; 95% confidence interval (CI), 0.82-0.98, P=0.02], but the heterogeneity was moderate (P=0.01, I(2)=61%). In a subgroup analysis, the mortality rates for lung protective ventilation (RR 0.73, 95% CI, 0.62-0.86, P=0.0002) and duration of prone positioning >12 h (RR 0.75, 95% CI, 0.65-0.87, P<0.0001) were reduced in the prone position. Prone positioning was not associated with an increased incidence of cardiac events (RR 1.01, 95% CI, 0.87-1.17) or ventilator associated pneumonia (RR 0.88, 95% CI, 0.71-1.09), but it was associated with an increased incidence of pressure sores (RR 1.23, 95% CI, 1.07-1.41) and endotracheal dislocation (RR 1.33, 95% CI, 1.02-1.74).

CONCLUSIONS

Prone positioning tends to reduce the mortality rates in ARDS patients, especially when used in conjunction with a lung protective strategy and longer prone position durations. Prone positioning for ARDS patients should be prioritized over other invasive procedures because related life-threatening complications are rare. However, further additional randomized controlled design to study are required for confirm benefit of prone position in ARDS.

Advantages of the prone position for minimally invasive esophagectomy in comparison to the left decubitus position: better oxygenation after minimally invasive esophagectomy

PURPOSE

The aim of this retrospective study was to evaluate whether minimally invasive esophagectomy (MIE) in the prone position has advantages over the left decubitus position.

METHOD

A total of 110 consecutive patients with esophageal cancer who had undergone MIE were included in the analysis. The clinical outcomes were compared between 51 patients treated in the prone position (prone group) and 59 patients treated in the left decubitus position (LD group). The main outcome was postoperative respiratory complications and postoperative oxygenation [arterial oxygen pressure/fraction of inspired oxygen (P/F ratio)]. The secondary outcomes included the length of the operation, blood loss, number of dissected lymph nodes, postoperative morbidities and mortality.

RESULTS

The P/F ratio after the operation was significantly higher in the prone group (0 h: P = 0.01, 12 h: P < 0.001). No significant differences were observed in the frequency of respiratory complications (P = 0.89). The blood loss in the prone group was significantly lower (P < 0.001), and the number of dissected intrathoracic lymph nodes was significantly higher (P = 0.03) than in the LD group. No significant differences were observed in the frequencies of overall postoperative complications.

CONCLUSION

MIE in the prone position preserves better oxygenation of patients during the early recovery period, and is associated with less blood loss and a larger number of dissected lymph nodes.

Does prone positioning improve oxygenation and reduce mortality in patients with acute respiratory distress syndrome?

The emergence of computed tomography imaging more than 25 years ago led to characterization of acute respiratory distress syndrome (ARDS) as areas of relatively normal lung parenchyma juxtaposed with areas of dense consolidation and atelectasis. Given that this heterogeneity is often dorsally distributed, investigators questioned whether care for ARDS patients in the prone position would lead to improved mortality outcomes. This clinical review discusses the physiological rationale and clinical evidence supporting prone positioning in treating ARDS, in addition to its complications and contraindications.

Prone position in acute respiratory distress syndrome. Rationale, indications, and limits

In the prone position, computed tomography scan densities redistribute from dorsal to ventral as the dorsal region tends to reexpand while the ventral zone tends to collapse. Although gravitational influence is similar in both positions, dorsal recruitment usually prevails over ventral derecruitment, because of the need for the lung and its confining chest wall to conform to the same volume. The final result of proning is that the overall lung inflation is more homogeneous from dorsal to ventral than in the supine position, with more homogeneously distributed stress and strain. As the distribution of perfusion remains nearly constant in both postures, proning usually improves oxygenation. Animal experiments clearly show that prone positioning delays or prevents ventilation-induced lung injury, likely due in large part to more homogeneously distributed stress and strain. Over the last 15 years, five major trials have been conducted to compare the prone and supine positions in acute respiratory distress syndrome, regarding survival advantage. The sequence of trials enrolled patients who were progressively more hypoxemic; exposure to the prone position was extended from 8 to 17 hours/day, and lung-protective ventilation was more rigorously applied. Single-patient and meta-analyses drawing from the four major trials showed significant survival benefit in patients with PaO2/FiO2 lower than 100. The latest PROSEVA (Proning Severe ARDS Patients) trial confirmed these benefits in a formal randomized study. The bulk of data indicates that in severe acute respiratory distress syndrome, carefully performed prone positioning offers an absolute survival advantage of 10-17%, making this intervention highly recommended in this specific population subset.

Beneficial hemodynamic effects of prone positioning in patients with acute respiratory distress syndrome

RATIONALE

The effects of prone positioning during acute respiratory distress syndrome on all the components of cardiac function have not been investigated under protective ventilation and maximal alveolar recruitment.

OBJECTIVES

To investigate the hemodynamic effects of prone positioning.

METHODS

We included 18 patients with acute respiratory distress syndrome ventilated with protective ventilation and an end-expiratory positive pressure titrated to a plateau pressure of 28-30 cm H2O. Before and within 20 minutes of starting prone positioning, hemodynamic, respiratory, intraabdominal pressure, and echocardiographic data were collected. Before prone positioning, preload reserve was assessed by a passive leg raising test.

MEASUREMENTS AND MAIN RESULTS

In all patients, prone positioning increased the ratio of arterial oxygen partial pressure over inspired oxygen fraction, the intraabdominal pressure, and the right and left cardiac preload. The pulmonary vascular resistance decreased along with the ratio of the right/left ventricular end-diastolic areas suggesting a decrease of the right ventricular afterload. In the nine patients with preload reserve, prone positioning significantly increased cardiac index (3.0 [2.3-3.5] to 3.6 [3.2-4.4] L/min/m(2)). In the remaining patients, cardiac index did not change despite a significant decrease in the pulmonary vascular resistance.

CONCLUSIONS

In patients with acute respiratory distress syndrome under protective ventilation and maximal alveolar recruitment, prone positioning increased the cardiac index only in patients with preload reserve, emphasizing the important role of preload in the hemodynamic effects of prone positioning.

Gas exchange in the respiratory distress syndromes

This article describes the gas exchange abnormalities occurring in the acute respiratory distress syndrome seen in adults and children and in the respiratory distress syndrome that occurs in neonates. Evidence is presented indicating that the major gas exchange abnormality accounting for the hypoxemia in both conditions is shunt, and that approximately 50% of patients also have lungs regions in which low ventilation-to-perfusion ratios contribute to the venous admixture. The various mechanisms by which hypercarbia may develop and by which positive end-expiratory pressure improves gas exchange are reviewed, as are the effects of vascular tone and airway narrowing. The mechanisms by which surfactant abnormalities occur in the two conditions are described, as are the histological findings that have been associated with shunt and low ventilation-to-perfusion.

Effect of prone positioning on cannula function and impaired oxygenation during extracorporeal circulation

Prone ventilation is an effective method for improving oxygenation in patients with acute respiratory failure. However, in extracorporeal circulation, there is a risk of cannula-related complications when changing the position. In this study, we investigated cannula-related complications when changing position for prone ventilation and the effect of prone ventilation on impaired oxygenation in patients who underwent extracorporeal membrane oxygenation (ECMO). The study subjects were patients who underwent prone ventilation during ECMO in the period from 2004 to 2011. Indication for prone ventilation was the presence of dorsal infiltration shown by lung computed tomography. Factors investigated were cannula insertion site, dislodgement or obstruction of the cannula, malfunction of vascular access and unplanned dislodgement of the catheters when changing position. Mean arterial pressure, PaO2/FiO2, PEEP level, blood flow and rotation speed of the pump were also determined before and after position change. Five patients were selected as study subjects. The mean duration of prone positioning was 15.3 ± 0.5 h. Strict management during position changes prevented cannula-related complications in the patients who underwent extracorporeal circulation. There were no significant changes in mean arterial pressure, PEEP level, blood flow and rotation speed of the pump when changing position. Low PaO2/FiO2 prior to prone ventilation was significantly increased after supine to prone and then prone to supine position. Prone positioning to improve impaired oxygenation is a safe procedure and not a contraindication in patients receiving extracorporeal circulation.

Gas exchange under altered gravitational stress

Efficient gas exchange in the lung depends on the matching of ventilation and perfusion. However, the human lung is a readily deformable structure and as a result gravitational stresses generate gradients in both ventilation and perfusion. Nevertheless, the lung is capable of withstanding considerable change in the applied gravitational load before pulmonary gas exchange becomes impaired. The postural changes that are part of the everyday existence for most bipedal species are well tolerated, as is the removal of gravity (weightlessness). Increases in the applied gravitational load result only in a large impairment in pulmonary gas exchange above approximately three times that on the ground, at which point the matching of ventilation to perfusion is so impaired that efficient gas exchange is no longer possible. Much of the tolerance of the lung to alterations in gravitation stress comes from the fact that ventilation and perfusion are inextricably coupled. Deformations in the lung that alter ventilation necessarily alter perfusion, thus maintaining a degree of matching and minimizing the disruption in ventilation to perfusion ratio and thus gas exchange.

Prone position during ECMO is safe and improves oxygenation

PURPOSE

Combination of prone positioning (PrP) and extracorporeal membrane oxygenation (ECMO) might be beneficial in severe acute respiratory distress syndrome (ARDS), because both approaches are recommended. However, PrP during ECMO might be associated with complications such as dislocation of ECMO cannulae. We investigated complications and change of oxygenation effects of PrP during ECMO to identify "responders" and discuss our results considering different definitions of response in the literature.


METHODS

Retrospective analysis of complications, gas exchange, and invasiveness of mechanical ventilation during first and second PrP on ECMO at specified time points (before, during, and after PrP). We used multivariate nonparametric analysis of longitudinal data (MANOVA) to compare changes of mechanical ventilation and hemodynamics associated with the first and second procedures.


RESULTS

In 12 ECMO patients, 74 PrPs were performed (median ECMO duration: 10 days (IQR: 6.3-
15.5 days)). No dislocations of intravascular catheters/cannulae, endotracheal tubes or chest tubes were observed. Two PrPs had to be interrupted (endotracheal tube obstruction, acute pulmonary embolism). PaO2/FiO2-ratio increased associated with the first and second PrP (p = 0.002) and lasted after PrP in 58% of these turning procedures ("responders") without changes in ECMO blood flow, respiratory pressures, minute ventilation, portion of spontaneously triggered breathing, and compliance. Hemodynamics did not change with exception of increased mean pulmonary arterial pressure during PrP and decrease after PrP (p<0.001), while norepinephrine dosage decreased (p = 0.03) (MANOVA).


CONCLUSIONS

Prone position during ECMO is safe and improves oxygenation even after repositioning. This might ameliorate hypoxemia and reduce the harm from mechanical ventilation.

Body position changes redistribute lung computed-tomographic density in patients with acute respiratory failure: impact and clinical fallout through the following 20 years

In patients with acute respiratory distress syndrome (ARDS), in supine position, there is a decrease of inflation along the sternum vertebral axis, up to lung collapse. In 1991 we published a report showing that, in ARDS patients, shifting from supine to prone position led immediately to the inversion of the inflation gradient and to a redistribution of densities from dorsal to ventral lung regions. This led to a "sponge model" as a wet sponge, similar to a heavy edematous lung, squeezes out the gas in the most dependent regions, due to the weight-related increase of the compressive forces. The sponge model accounts for density distribution in prone position, for which the unloaded dorsal regions are recruited, while the loaded ventral region, collapses. In addition, the sponge model accounts for the mechanism through which the positive end-expiratory pressure acts as counterforce to oppose the collapsing, compressing forces. The final result of proning was that the inversion of gravitational forces, together with other factors such as lung-chest wall shape-matching and the heart weight led to a more homogeneous distribution of inflation throughout the lung parenchyma. This is associated with oxygenation improvement as the dorsal recruitment, for anatomical reasons, prevails on the ventral de-recruitment. The more homogeneous distribution of inflation (i.e. of stress and strain) decreases/prevents the ventilator-induced lung injury, as consistently shown in animal experiments. Finally, and a series of clinical trials led to the conclusion that in patients with severe ARDS, the prone position provides a significant survival advantage.

Feasibility and effectiveness of prone position in morbidly obese patients with ARDS: a case-control clinical study

BACKGROUND

Obese patients are at risk for developing atelectasis and ARDS. Prone position (PP) may reduce atelectasis, and it improves oxygenation and outcome in severe hypoxemic patients with ARDS, but little is known about its effect in obese patients with ARDS.

METHODS

Morbidly obese patients (BMI ≥ 35 kg/m²) with ARDS (Pao₂/FIo₂ ratio ≤ 200 mm Hg) were matched to nonobese (BMI < 30 kg/m²) patients with ARDS in a case-control clinical study. The primary end points were safety and complications of PP; the secondary end points were the effect on oxygenation (Pao₂/FIo₂ ratio at the end of PP), length of mechanical ventilation and ICU stay, nosocomial infections, and mortality.

RESULTS

Between January 2005 and December 2009, 149 patients were admitted for ARDS. Thirty-three obese patients were matched with 33 nonobese patients. Median (25th-75th percentile) PP duration was 9 h (6-11 h) in obese patients and 8 h (7-12 h) in nonobese patients (P = .28). We collected 51 complications: 25 in obese and 26 in nonobese patients. The number of patients with at least one complication was similar across groups (n = 10, 30%). Pao₂/FIo₂ ratio increased significantly more in obese patients (from 118 ± 43 mm Hg to 222 ± 84 mm Hg) than in nonobese patients (from 113 ± 43 mm Hg to 174 ± 80 mm Hg; P = .03). Length of mechanical ventilation, ICU stay, and nosocomial infections did not differ significantly, but mortality at 90 days was significantly lower in obese patients (27% vs 48%, P < .05).

CONCLUSIONS

PP seems safe in obese patients and may improve oxygenation more than in nonobese patients. Obese patients could be a subgroup of patients with ARDS who may benefit the most of PP.

Infant position in neonates receiving mechanical ventilation

BACKGROUND

A variety of body positions other than the standard supine position have been used in patients undergoing intensive care with hopes of reducing the incidence of pressure ulcers of the skin, contractures or ankylosis and improving the patients' well being. In patients from different age groups undergoing mechanical ventilation (MV) it has been observed that particular positions, such as the prone position, may improve some respiratory parameters. Benefits from these positions have not been clearly defined in critically ill newborns who may require mechanical ventilation for extended periods of time.

OBJECTIVES

To assess the effects of different positioning of newborn infants receiving MV on short-term respiratory outcomes and complications of prematurity.

SEARCH METHODS

Databases searched (up to December 2012) were the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 3), Oxford Database of Perinatal Trials, MEDLINE, CINAHL and EMBASE. Handsearches of proceedings of the Society for Pediatric Research from 1990 to July 2011 were used to identify unpublished studies. Clinicaltrials.gov was searched for any ongoing studies.

SELECTION CRITERIA

Randomised or quasi-randomised clinical trials comparing different positions in newborns receiving mechanical ventilation.

DATA COLLECTION AND ANALYSIS

Three independent and unblinded review authors assessed the trials for inclusion in the review and extracted the data. Data were double-checked and entered into the Review Manager software (RevMan). Risks of bias of the included studies were assessed using methods of randomisation and allocation concealment, completeness of follow-up and blinding of outcome measurements.

MAIN RESULTS

Twelve trials involving 285 participants were included in this review. One of the included studies (N = 79) was not evaluated in the previous review. Several positions were compared: prone versus supine, prone versus lateral right, lateral right versus supine, lateral left versus supine, lateral alternant versus supine, lateral right versus lateral left, and good lung dependent versus good lung uppermost. Apart from one of the two studies that compared lateral right versus lateral left positions, one comparing lateral alternant versus supine, and one comparing prone versus the supine position, all the included studies had a crossover design. Comparing prone versus supine position, an increase in arterial oxygen tension (PO2) in the prone position of between 2.75 and 9.72 mm Hg (95% confidence interval (CI)) was observed (one trial). When % haemoglobin oxygen saturation was measured with pulse oximetry, the improvement in the prone position was from 1.18% to 4.36% (typical effect based on four trials). In addition, there was a slight improvement in the number of episodes of desaturation. It was not possible to establish whether this effect remained once the intervention was stopped. Negative effects from the interventions were not described, although these were not studied in sufficient detail. Effects of position on other outcomes were barely investigated. Only one study analysed tracheal cultures of neonates after five days of mechanical ventilation, finding lower bacterial colonization in the alternating l ateral position than in those neonates kept in the supine posture. Other effects, either positive or negative, cannot be excluded considering the small numbers of neonates that were studied.

AUTHORS' CONCLUSIONS

The prone position was found to slightly improve the oxygenation in neonates undergoing mechanical ventilation. However, we found no evidence concerning whether particular body positions during the mechanical ventilation of the neonate are effective in producing sustained and clinically relevant improvements.

Positioning for acute respiratory distress in hospitalised infants and children

BACKGROUND

Because of the association of prone positioning with sudden infant death syndrome (SIDS) it is recommended that young infants be placed on their backs (supine). However, the prone position may be a non-invasive way of increasing oxygenation in participants with acute respiratory distress. Because of substantial differences in respiratory mechanics between adults and children and the risk of SIDS in young infants, a specific review of positioning for infants and young children with acute respiratory distress is warranted.

OBJECTIVES

To compare the effects of different body positions in hospitalised infants and children with acute respiratory distress.

SEARCH METHODS

We searched Cochrane Central Register of Controlled Trials (CENTRAL 2012, Issue 3), which contains the Acute Respiratory Infections Group's Specialised Register, MEDLINE (1966 to April week 1, 2012), EMBASE (2004 to April 2012) and CINAHL (2004 to April 2012).

SELECTION CRITERIA

Randomised controlled trials (RCTs) or pseudo-RCTs comparing two or more positions in the management of infants and children hospitalised with acute respiratory distress.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data from each study. We resolved differences by consensus or referral to a third review author. We analysed bivariate outcomes using an odds ratio and 95% confidence interval (CI). We analysed continuous outcomes using a mean difference and 95% CI. We used a fixed-effect model unless heterogeneity was significant, in which case we used a random-effects model.

MAIN RESULTS

We extracted data from 53 studies. We included 24 studies with a total of 581 participants. Three studies used a parallel-group, randomised design which compared prone and supine positions only. The remaining 21 studies used a randomised cross-over design. These studies compared prone, supine, lateral, elevated and flat positions.Prone positioning was significantly more beneficial than supine positioning in terms of oxygen saturation (mean difference (MD) 1.97%, 95% CI 1.18 to 2.77), arterial oxygen (MD 6.24 mm Hg, 95% confidence interval (CI) 2.20 to 10.28), episodes of hypoxaemia (MD -3.46, 95% CI -4.60 to -2.33) and thoracoabdominal synchrony (MD -30.76, 95% CI -41.39 to -20.14). No adverse effects were identified. There were no statistically significant differences between any other positions.As the majority of studies did not describe how possible biases were addressed, the potential for bias in these findings is unclear.

AUTHORS' CONCLUSIONS

The prone position was significantly superior to the supine position in terms of oxygenation. However, as most participants were ventilated preterm infants, the benefits of prone positioning may be most relevant to these infants. In addition, although placing infants and children in the prone position may improve respiratory function, the association of SIDS with prone positioning means that infants should only be placed in this position while under continuous cardiorespiratory monitoring.

Prone positioning: is it safe and effective?

Prone positioning has been used as a treatment option for patients with acute lung injury or acute respiratory distress syndrome (ARDS) since the early 1970s. Prone position and extended prone position ventilation have been shown to increase end-expiratory lung volume, alveolar recruitment, and oxygenation in patients with severe hypoxemic and acute respiratory failure. Prone positioning is not a benign procedure, and there are potential risks (complications) that can occur to both the patient and the health care worker. Notable complications that can arise include: unplanned extubation, lines pulled, tubes kinked, and back and other injuries to personnel. Prone positioning is a viable, inexpensive therapy for the treatment of severe ARDS. This maneuver consistently improves systemic oxygenation in 70% to 80% of patients with ARDS. With the utilization of a standardized protocol and a trained and dedicated critical care staff, prone positioning can be performed safely.

Thoracoscopic esophagectomy in the prone position

BACKGROUND

Minimally invasive esophageal surgery has arisen in an attempt to reduce the significant complications associated with esophagectomy. Despite proposed technical and physiological advantages, the prone position technique has not been widely adopted. This article reviews the current status of prone thoracoscopic esophagectomy.

METHODS

A systematic literature search was performed to identify all published clinical studies related to prone esophagectomy. Medline, EMBASE and Google Scholar were searched using the keywords "prone," "thoracoscopic," and "esophagectomy" to identify articles published between January 1994 and September 2010. A critical review of these studies is given, and where appropriate the technique is compared to the more traditional minimally invasive technique utilising the left lateral decubitus position.

RESULTS

Twelve articles reporting the outcomes following prone thoracoscopic oesophagectomy were tabulated. These studies were all non-randomised single-centre prospective or retrospective studies of which four compared the technique to traditional minimally invasive surgery. Although prone esophagectomy is demonstrated as being both feasible and safe, there is no convincing evidence that it is superior to other forms of esophageal surgery. Most authors comment that the prone position is associated with superior surgical ergonomics and theoretically offers a number of physiological benefits.

CONCLUSION

The ideal approach within minimally invasive esophageal surgery continues to be a subject of debate since no single method has produced outstanding results. Further clinical studies are required to see whether ergonomic advantages of the prone position can be translated into improved patient outcomes.

Prone positioning in acute respiratory distress syndrome (ARDS): when and how?

Acute respiratory distress syndrome (ARDS) is a severe form of respiratory failure. It remains one of the most devastating conditions in the intensive care unit. Mechanical ventilation with positive end-expiratory pressure is a cornerstone therapy for ARDS patients. One adjuvant alternative is to place the patient in a prone position. Since it was first described in 1976, prone positioning has been safely employed to improve oxygenation in many patients with ARDS. Prone positioning may also minimize secondary lung injury induced by mechanical ventilation, although this benefit has not been investigated as extensively, despite its potential. In spite of a strong physiological justification, prone positioning is still not widely accepted as an adjunct therapy in ARDS patients and it is only used regularly in only 10% of ICUs. This may be explained in part by the reluctance to change position, risks and unclear effects on relevant outcomes. In this paper, we review all aspects of prone positioning, from the pathophysiology to the clinical studies of patient outcome, and we also discuss the latest controversies surrounding this treatment.

PaCO2 and alveolar dead space are more relevant than PaO2/FiO2 ratio in monitoring the respiratory response to prone position in ARDS patients: a physiological study

INTRODUCTION

Our aims in this study were to report changes in the ratio of alveolar dead space to tidal volume (VDalv/VT) in the prone position (PP) and to test whether changes in partial pressure of arterial CO2 (PaCO2) may be more relevant than changes in the ratio of partial pressure of arterial O2 to fraction of inspired O2 (PaO2/FiO2) in defining the respiratory response to PP. We also aimed to validate a recently proposed method of estimation of the physiological dead space (VDphysiol/VT) without measurement of expired CO2.

METHODS

Thirteen patients with a PaO2/FiO2 ratio < 100 mmHg were included in the study. Plateau pressure (Pplat), positive end-expiratory pressure (PEEP), blood gas analysis and expiratory CO2 were recorded with patients in the supine position and after 3, 6, 9, 12 and 15 hours in the PP. Responders to PP were defined after 15 hours of PP either by an increase in PaO2/FiO2 ratio > 20 mmHg or by a decrease in PaCO2 > 2 mmHg. Estimated and measured VDphysiol/VT ratios were compared.

RESULTS

PP induced a decrease in Pplat, PaCO2 and VDalv/VT ratio and increases in PaO2/FiO2 ratios and compliance of the respiratory system (Crs). Maximal changes were observed after six to nine hours. Changes in VDalv/VT were correlated with changes in Crs, but not with changes in PaO2/FiO2 ratios. When the response was defined by PaO2/FiO2 ratio, no significant differences in Pplat, PaCO2 or VDalv/VT alterations between responders (n = 7) and nonresponders (n = 6) were observed. When the response was defined by PaCO2, four patients were differently classified, and responders (n = 7) had a greater decrease in VDalv/VT ratio and in Pplat and a greater increase in PaO2/FiO2 ratio and in Crs than nonresponders (n = 6). Estimated VDphysiol/VT ratios significantly underestimated measured VDphysiol/VT ratios (concordance correlation coefficient 0.19 (interquartile ranges 0.091 to 0.28)), whereas changes during PP were more reliable (concordance correlation coefficient 0.51 (0.32 to 0.66)).

CONCLUSIONS

PP induced a decrease in VDalv/VT ratio and an improvement in respiratory mechanics. The respiratory response to PP appeared more relevant when PaCO2 rather than the PaO2/FiO2 ratio was used. Estimated VDphysiol/VT ratios systematically underestimated measured VDphysiol/VT ratios.

Physiotherapy in critically ill patients

Prolonged stay in Intensive Care Unit (ICU) can cause muscle weakness, physical deconditioning, recurrent symptoms, mood alterations and poor quality of life. Physiotherapy is probably the only treatment likely to increase in the short- and long-term care of the patients admitted to these units. Recovery of physical and respiratory functions, coming off mechanical ventilation, prevention of the effects of bed-rest and improvement in the health status are the clinical objectives of a physiotherapy program in medical and surgical areas. To manage these patients, integrated programs dealing with both whole-body physical therapy and pulmonary care are needed. There is still limited scientific evidence to support such a comprehensive approach to all critically ill patients; therefore we need randomised studies with solid clinical short- and long-term outcome measures.