Effect of the prone position on patients with hydrostatic pulmonary edema compared with patients with acute respiratory distress syndrome and pulmonary fibrosis

Deep learning segmentation and registration-driven lung parenchymal volume and movement CT analysis in prone positioning

PURPOSE

To conduct a volumetric and movement analysis of lung parenchyma in prone positioning using deep neural networks (DNNs).

METHOD

We included patients with suspected interstitial lung abnormalities or disease who underwent full-inspiratory supine and prone chest CT at a single institution between June 2021 and March 2022. A thoracic radiologist visually assessed the fibrosis extent in the total lung (using units of 10%) on supine CT. After preprocessing the images into 192×192×192 resolution, a DNN automatically segmented the whole lung and pulmonary lobes in prone and supine CT images. Affine registration matched the patient's center and location, and the DNN deformably registered prone and supine CT images to calculate the x-, y-, z-axis, and 3D pixel movements.

RESULTS

In total, 108 CT pairs had successful registration. Prone positioning significantly increased the left lower (90.2±69.5 mL, P = 0.000) and right lower lobar volumes (52.5±74.2 mL, P = 0.000). During deformable registration, the average maximum whole-lung pixel movements between the two positions were 1.5, 1.9, 1.6, and 2.8 cm in each axis and 3D plane. Compared to patients with <30% fibrosis, those with ≥30% fibrosis had smaller volume changes (P<0.001) and smaller pixel movements in all axes between the positions (P = 0.000-0.007). Forced vital capacity (FVC) correlated with the left lower lobar volume increase (Spearman correlation coefficient, 0.238) and the maximum whole-lung pixel movements in all axes (coefficients, 0.311 to 0.357).

CONCLUSIONS

Prone positioning led to the preferential expansion of the lower lobes, correlated with FVC, and lung fibrosis limited lung expansion during prone positioning.

Use of Cardio-Pulmonary Ultrasound in the Neonatal Intensive Care Unit

Cardiopulmonary ultrasound (CPUS), the combination of lung ultrasound (LUS) and targeted neonatal echocardiography (TnECHO)AA, may offer a more appropriate approach to the challenging neonatal cardiovascular and respiratory disorders. This paper reviews the possible use of CPUS in the neonatal intensive care unit (NICU).

Chest wall loading in the ICU: pushes, weights, and positions

Clinicians monitor mechanical ventilatory support using airway pressures—primarily the plateau and driving pressure, which are considered by many to determine the safety of the applied tidal volume. These airway pressures are influenced not only by the ventilator prescription, but also by the mechanical properties of the respiratory system, which consists of the series-coupled lung and chest wall. Actively limiting chest wall expansion through external compression of the rib cage or abdomen is seldom performed in the ICU. Recent literature describing the respiratory mechanics of patients with late-stage, unresolving, ARDS, however, has raised awareness of the potential diagnostic (and perhaps therapeutic) value of this unfamiliar and somewhat counterintuitive practice. In these patients, interventions that reduce resting lung volume, such as loading the chest wall through application of external weights or manual pressure, or placing the torso in a more horizontal position, have unexpectedly improved tidal compliance of the lung and integrated respiratory system by reducing previously undetected end-tidal hyperinflation. In this interpretive review, we first describe underappreciated lung and chest wall interactions that are clinically relevant to both normal individuals and to the acutely ill who receive ventilatory support. We then apply these physiologic principles, in addition to published clinical observation, to illustrate the utility of chest wall modification for the purposes of detecting end-tidal hyperinflation in everyday practice.

The effect of prone positioning on pressure injury incidence in adult intensive care unit patients: A meta-review of systematic reviews

OBJECTIVE

Numerous systematic reviews have examined the impact of prone positioning on outcomes, including pressure injury (PI). The objective of this meta-review was to synthesise the evidence on the effect of prone positioning on the incidence and location of PIs in adult intensive care unit patients.

REVIEW METHOD

This is a meta-review of published systematic reviews. Five databases were searched; data were extracted by three authors and adjudicated by a fourth. The AMSTAR-2 tool was used to quality appraise the selected articles, which was completed by three authors with a fourth adjudicating.

RESULTS

Ten systematic reviews were synthesised. The cumulative incidence of PI in 15,979 adult patients ranged from 25.7% to 48.5%. One study did not report adult numbers. Only one review reported the secondary outcome of PI location. PIs were identified in 13 locations such as the face, chest, iliac crest, and knees. Using the AMSTAR-2, three reviews were assessed as high quality, six as moderate quality, and one as low quality.

CONCLUSION

The high incidence of PI in the prone position highlights the need for targeted preventative strategies. Care bundles may be one approach, given their beneficial effects for the prevention of PI in other populations. This review highlights the need for proactive approaches to limit unintended consequences of the use of the prone position, especially notable in the current COVID-19 pandemic.

Determination of the Effect of the Fowler and Prone Position on Oxygen Saturation in Patients Diagnosed with COVID-19

Objective: This study was conducted to investigate the effect of the Fowler position and prone position on oxygen saturation in patients receiving treatment in clinics with the diagnosis of COVID-19 disease. Method: A total of 40 patients, admitted to the pandemic ward who met the inclusion criteria, were included in the quasi-experimental type study without any sampling. The patients were first given the Fowler position and then the prone position. There was a time interval of 15 minutes wait between the two positions. For each position, peripheral oxygen saturation, heart rate, respiratory and blood pressure values were obtained at initial position placement, after the 30th minute and every hour for the first four hours. Results: The mean age of the participants was 57.57±12.64 years. Respiratory distress, cough, fever, weakness, sweating and headache were the main symptoms. A total of 22.5% of them had a diagnosis of hypertension and Diabetes Mellitus. The requirement for the positioning was found to be 95% in the first five days after admittance. After treatment, 85% of them were discharged home. The mean oxygen saturation values of the patients for every hour in the Prone position were 93.15±1.718 (p=0.035), 93.60±1.809 (p=0.019), 93.93±1.774 (p=0.006) and 94.15±1.718 (p=0.002), respectively in the first four hours. These findings were statistically significant compared to the Fowler position. Respiratory values in the prone position were 17.30±1.159 (p=0.005), 17.20±1.344 (p=0.010), 17.20±1.181 (p=0.005), and 17.05±1.280 (p=0.001), respectively in the first four hours, which were statistically lower than in the Fowler position. There was no significant difference in the mean heart rate and blood pressure in both positions (p>0.05). Conclusion: The prone position was found to have a positive effect on oxygen saturation levels when Fowler and Prone positions were applied in patients receiving treatment with the diagnosis of COVID-19 in hospital wards. Therefore, it is recommended that patients admitted with the diagnosis of COVID-19 be placed in the prone position at regular intervals.

Early physiological effects of prone positioning in COVID-19 Acute Respiratory Distress Syndrome

BACKGROUND.

The mechanisms underlying oxygenation improvement after prone positioning in COVID-19 ARDS have not been fully elucidated yet. We hypothesized that the oxygenation increase with prone positioning is secondary to the improvement of ventilation-perfusion matching.

METHODS.

In a series of consecutive intubated COVID-19 ARDS patients receiving volume-controlled ventilation, we prospectively assessed the percent variation of ventilation-perfusion matching by electrical impedance tomography (EIT) before and 90 minutes after the first cycle of prone positioning (primary endpoint). We also assessed changes in the distribution and homogeneity of lung ventilation and perfusion, lung overdistention and collapse, respiratory system compliance, driving pressure, optimal positive end-expiratory pressure (PEEP), as assessed by EIT, and the ratio of partial pressure to fractional inspired oxygen (PaO2/FiO2) (secondary endpoints). Data are reported as medians [25th - 75th] or percentages.

RESULTS.

We enrolled 30 consecutive patients, all analyzed without missing data. Compared to supine position, prone positioning overall improved ventilation-perfusion matching from 58 [43-69] % to 68 [56-75] % (p=0.042), with a median difference of 8.0% (95% Confidence Interval 0.1 to 16.0%) . Dorsal ventilation increased from 39 [31-43] % to 52 [44-62] % (p<0.001), while dorsal perfusion did not significantly vary. Prone positioning also reduced lung overdistension from 9 [4-11] % to 4 [2-6] % (p=0.025), while it did not significantly affect ventilation and perfusion homogeneity, lung collapse, static respiratory system compliance, driving pressure, and optimal PEEP. PaO2/FiO2 overall improved from 141 [104-182] mmHg to 235 [164-267] mmHg (p=0.019). However, 9 (30%) patients were non-responders, experiencing an increase in PaO2/FiO2 <20% with respect to baseline.

CONCLUSIONS.

In COVID-19 ARDS patients, prone positioning overall produced an early increase in ventilation-perfusion matching and dorsal ventilation. These effects were, however, heterogeneous among patients.

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.

Acute exacerbation of interstitial lung disease in the intensive care unit

Acute exacerbations of interstitial lung disease (AE-ILD) represent an acute, frequent and often highly morbid event in the disease course of ILD patients. Admission in the intensive care unit (ICU) is very common and the need for mechanical ventilation arises early. While non-invasive ventilation has shown promise in staving off intubation in selected patients, it is unclear whether mechanical ventilation can alter the exacerbation course unless it is a bridge to lung transplantation. Risk stratification using clinical and radiographic findings, and early palliative care involvement, are important in ICU care. In this review, we discuss many of the pathophysiological aspects of AE-ILD and raise the hypothesis that ventilation strategies used in acute respiratory distress syndrome might be implemented in AE-ILD. We present possible decision-making and management algorithms that can be used by the intensivist when caring for these patients.

Targeted management of evolving and established chronic lung disease of prematurity assisted by cardiopulmonary ultrasound: A case report of four patients

Bronchopulmonary dysplasia (BPD) is one of the most common complications of premature birth. The current definition of BPD is based on the duration of oxygen therapy and/or respiratory support. Among the pitfalls of all the diagnostic definitions, the lack of a proper pathophysiologic classification makes it difficult to choose an appropriate drug strategy for BPD. In this case report, we describe the clinical course of four premature infants, admitted to the neonatal intensive care unit, for whom the use of lung and cardiac ultrasound was an integral part of the diagnostic and therapeutic process. We describe, for the first time to our knowledge, four different cardiopulmonary ultrasound patterns of evolving and established chronic lung disease of prematurity and the consequent therapeutic choices. This approach, if confirmed in prospective studies, may guide the personalized management of infants suffering from evolving and established BPD, optimizing the chances of success of the therapies and at the same time reducing the risk of exposure to inadequate and potentially harmful drugs.

Early versus late awake prone positioning in non-intubated patients with COVID-19

BACKGROUND

Awake prone positioning (APP) is widely used in the management of patients with coronavirus disease (COVID-19). The primary objective of this study was to compare the outcome of COVID-19 patients who received early versus late APP.

METHODS

Post hoc analysis of data collected for a randomized controlled trial (ClinicalTrials.gov NCT04325906). Adult patients with acute hypoxemic respiratory failure secondary to COVID-19 who received APP for at least one hour were included. Early prone positioning was defined as APP initiated within 24 h of high-flow nasal cannula (HFNC) start. Primary outcomes were 28-day mortality and intubation rate.

RESULTS

We included 125 patients (79 male) with a mean age of 62 years. Of them, 92 (73.6%) received early APP and 33 (26.4%) received late APP. Median time from HFNC initiation to APP was 2.25 (0.8-12.82) vs 36.35 (30.2-75.23) hours in the early and late APP group (p < 0.0001), respectively. Average APP duration was 5.07 (2.0-9.05) and 3.0 (1.09-5.64) hours per day in early and late APP group (p < 0.0001), respectively. The early APP group had lower mortality compared to the late APP group (26% vs 45%, p = 0.039), but no difference was found in intubation rate. Advanced age (OR 1.12 [95% CI 1.0-1.95], p = 0.001), intubation (OR 10.65 [95% CI 2.77-40.91], p = 0.001), longer time to initiate APP (OR 1.02 [95% CI 1.0-1.04], p = 0.047) and hydrocortisone use (OR 6.2 [95% CI 1.23-31.1], p = 0.027) were associated with increased mortality.

CONCLUSIONS

Early initiation (< 24 h of HFNC use) of APP in acute hypoxemic respiratory failure secondary to COVID-19 improves 28-day survival. Trial registration ClinicalTrials.gov NCT04325906.

A Quick Review on the Multisystem Effects of Prone Position in Acute Respiratory Distress Syndrome (ARDS) Including COVID-19

Objective:

The purpose of this review is to highlight the multisystem effects of prone position in ARDS patients with a focus on current findings regarding its use in COVID-19 patients.

Methods:

Two reviewers comprehensively searched PubMed database for literature regarding pathophysiology and efficacy of prone position in ARDS patients as well as specific data regarding this approach in COVID-19 patients.

Conclusion:

Prone positioning is well-documented to improve oxygenation and cardiac function in ARDS patients and might confer increased survival, with benefits that outweigh risks such as facial edema, endotracheal tube displacement, and intraabdominal organ dysfunction in obese patients. Severe COVID-19 pneumonia, while meeting ARDS criteria, differs from typical ARDS in several ways. Data would suggest that advantages of prone position would become limited after significant disease progression and fibrosis. The use of this technique in COVID-19 requires prolonged sessions that are unprecedented in the treatment of ARDS patients. New data regarding COVID-19 pathophysiology and patients continues to evolve daily. More frequently, patients are proned while maintaining spontaneous breathing—the results of this intervention are an area for future studies. There is more to learn about the appropriate use of prone position in COVID-19 patients. The multisystem risks and benefits require clinicians to adopt a patient centered decision-making algorithm when employing this technique in COVID-19 patients.

Level of evidence:

NA

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.

Characteristics and evaluation of acute exacerbations in chronic interstitial lung diseases

Acute exacerbations of fibrosing interstitial lung disease (ILD) occur in both idiopathic pulmonary fibrosis (IPF) as well as non-IPF ILDs. An expert consensus definition has allowed for more frequent reporting of IPF exacerbations. The same is lacking for non-IPF ILD exacerbations. The incidence of non-IPF ILD exacerbations is likely less than in IPF, but the two entities share similar risk factors, such as increased frequency as physiologic derangements advance. The radiologic and histopathologic spectrum of acute ILD exacerbations extends from organizing pneumonia (OP) to the more treatment-refractory diffuse alveolar damage (DAD) pattern. Indeed, responsiveness to various therapies may depend on the relative components of these entities, favoring OP over DAD. There are no proven therapies for acute ILD exacerbations. Corticosteroids are a mainstay in any regimen although clear evidence of benefit does not exist. A variety of immunosuppressant agents have purported success in historical cohort studies - cyclophosphamide, cyclosporine A, and tacrolimus most commonly. Only one randomized controlled trial has been published, studying recombinant thrombomodulin for IPF exacerbation, but the primary outcome of survivor proportion at 90 days was not met. Other novel therapies for ILD exacerbations are still under investigation. The short and long-term prognosis of acute exacerbations of ILD is poor, especially in patients with IPF. Transplant referral should be considered early for both IPF as well as fibrosing non-IPF ILDs, given the unpredictability of the exacerbation event.

Spontaneous Breathing and Evolving Phenotypes of Lung Damage in Patients with COVID-19: Review of Current Evidence and Forecast of a New Scenario

The mechanisms of acute respiratory failure other than inflammation and complicating the SARS-CoV-2 infection are still far from being fully understood, thus challenging the management of COVID-19 patients in the critical care setting. In this unforeseen scenario, the role of an individual’s excessive spontaneous breathing may acquire critical importance, being one potential and important driver of lung injury and disease progression. The consequences of this acute lung damage may impair lung structure, forecasting the model of a fragile respiratory system. This perspective article aims to analyze the progression of injured lung phenotypes across the SARS-CoV-2 induced respiratory failure, pointing out the role of spontaneous breathing and also tackling the specific respiratory/ventilatory strategy required by the fragile lung type.

Prevention of pressure ulcers among individuals cared for in the prone position: lessons for the COVID-19 emergency

OBJECTIVE

Pressure ulcers (PUs) involve the destruction of skin and underlying tissue due to prolonged pressure and shear forces. These ulcers are painful and significantly reduce a person's quality of life. PUs are also expensive to manage and impact negatively on the achievement of cost-effective, efficient care delivery.

METHOD

Prone positioning is a postural therapy that aims to enhance respiratory function through increasing oxygenation levels. In contemporary clinical practice, ventilation in the prone position is indicated for patients with severe acute respiratory distress syndrome. However, despite its advantages in terms of respiratory function, several studies have examined complications of prone position ventilation and have identified PUs (facial PUs as well as PUs on other weight-bearing areas of the body) as a frequent complication in patients who are already in a precarious medical situation. International data suggest that up to 57% of patients nursed in the prone position develop a PU. The aim of this clinical review is to identify and review evidence-based recommendations developed to facilitate the selection and application of preventive interventions aimed at reducing PU development in patients ventilated in the prone position. Given the current COVID-19 crisis, this review is timely as intensive care unit (ICU) patients with COVID-19 require ventilation in the prone position at a level that is disproportionate to the general intensive care population. Up to 28% of patients admitted to the ICU with confirmed infection due to severe COVID-19 are cared for in the prone position. The scope of this review is limited to adult individuals only.

RESULTS

The skin assessment should be undertaken before proning and following positioning the patient back into the supine position. Although it is essential to keep the skin clean and moisturised, using pH-balanced cleansers, there is inconsistency in terms of the evidence to support the type of moisturiser. Use of positioning devices in addition to repositioning is recommended to offload pressure points on the face and body. Further, using dressings such as hydrocolloids, transparent film and silicone may be of benefit in decreasing facial skin breakdown.

CONCLUSION

Given the importance of PU prevention in this cohort of patients, adopting a focused prevention strategy, including skin assessment and care, offloading and pressure redistribution, and dressings for prevention may contribute to a reduction in the incidence and prevalence of these largely preventable wounds.

Donor prone positioning protects lungs from injury during warm ischemia

A large proportion of controlled donation after circulatory death (cDCD) donor lungs are declined because cardiac arrest does not occur within a suitable time after the withdrawal of life-sustaining therapy. Improved strategies to preserve lungs after asystole may allow the recovery team to arrive after death actually occurs and enable the recovery of lungs from more cDCD donors. The aim of this study was to determine the effect of donor positioning on the quality of lung preservation after cardiac arrest in a cDCD model. Cardiac arrest was induced by withdrawal of ventilation under anesthesia in pigs. After asystole, animals were divided into 2 groups based on body positioning (supine or prone). All animals were subjected to 3 hours of warm ischemia. After the observation period, donor lungs were explanted and preserved at 4°C for 6 hours, followed by 6 hours of physiologic and biological lung assessment under normothermic ex vivo lung perfusion. Donor lungs from the prone group displayed significantly greater quality as reflected by better function during ex vivo lung perfusion, less edema formation, less cell death, and decreased inflammation compared with the supine group. A simple maneuver of donor prone positioning after cardiac arrest significantly improves lung graft preservation and function.

Respiratory mechanics in patients with acute respiratory distress syndrome

Despite the recognition of its iatrogenic potential, mechanical ventilation remains the mainstay of respiratory support for patients with acute respiratory distress syndrome (ARDS). The low volume ventilation has been recognized as the only method to reduce mortality of ARDS patients and plateau pressure as the lighthouse for delivering safe ventilation. Recent investigations suggest that a ventilation based on lung mechanics (tidal ventilation tailored to the available lung volume able to receive it, i.e., driving pressure) is a successful approach to improve outcome. However, currently available bedside mechanical variables do not consider regional mechanical properties of ARDS affected lungs, which include the role of local stress risers at the boundaries of areas with different aeration. A unifying approach considers lung-related causes and ventilation-related causes of lung injury. These last may be incorporated in the mechanical power (i.e., amount of mechanical energy transferred per unit of time). Ventilation-induced lung injury (which includes the self-inflicted lung injury of a spontaneously breathing patient) can therefore be prevented by the adoption of measures promoting an increase of ventilable lung and its homogeneity and by delivering lower levels of mechanical power. Prone position promotes lung homogeneity without increasing the delivered mechanical power. This review describes the recent developments on respiratory mechanics in ARDS patients, providing both bedside and research insights from the most updated evidence.

Acute exacerbation of idiopathic pulmonary fibrosis: lessons learned from acute respiratory distress syndrome?

Idiopathic pulmonary fibrosis (IPF) is a fibrotic lung disease characterized by progressive loss of lung function and poor prognosis. The so-called acute exacerbation of IPF (AE-IPF) may lead to severe hypoxemia requiring mechanical ventilation in the intensive care unit (ICU). AE-IPF shares several pathophysiological features with acute respiratory distress syndrome (ARDS), a very severe condition commonly treated in this setting.A review of the literature has been conducted to underline similarities and differences in the management of patients with AE-IPF and ARDS.During AE-IPF, diffuse alveolar damage and massive loss of aeration occurs, similar to what is observed in patients with ARDS. Differently from ARDS, no studies have yet concluded on the optimal ventilatory strategy and management in AE-IPF patients admitted to the ICU. Notwithstanding, a protective ventilation strategy with low tidal volume and low driving pressure could be recommended similarly to ARDS. The beneficial effect of high levels of positive end-expiratory pressure and prone positioning has still to be elucidated in AE-IPF patients, as well as the precise role of other types of respiratory assistance (e.g., extracorporeal membrane oxygenation) or innovative therapies (e.g., polymyxin-B direct hemoperfusion). The use of systemic drugs such as steroids or immunosuppressive agents in AE-IPF is controversial and potentially associated with an increased risk of serious adverse reactions.Common pathophysiological abnormalities and similar clinical needs suggest translating to AE-IPF the lessons learned from the management of ARDS patients. Studies focused on specific therapeutic strategies during AE-IPF are warranted.

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.

Prone position ventilation support for acute exacerbation of interstitial lung disease?

INTRODUCTION

Prone position ventilation (PPV) has been shown to improve oxygenation and decrease pulmonary vascular resistance and mortality in patients with severe acute respiratory distress syndrome (ARDS). Whether these benefits of PPV occur similarly in acute exacerbations of interstitial lung disease (ILD) is not clear. We retrospectively explored the use of PPV in acute exacerbation with ILD versus those with severe acute respiratory distress syndrome (severe ARDS).

METHODS

Retrospective study of the application of PPV in 17 patients with acute exacerbations of ILD and in 19 patients with severe ARDS. Pre- and post-PPV hemodynamic parameters, respiratory mechanics, prognostic indicators, complications and mortality rates at 28, 60 and 90 days were compared.

RESULTS

There was no difference in baseline characteristics between the two groups except for higher driving pressure and more diastolic dysfunction in ILD group than severe ARDS group Compared with pre-PPV, cardiac index and driving pressure remained unchanged post-PPV in both groups. PPV increased PaO₂ /FiO₂ [118.7 (92.0, 147.8) pre-PPV vs 132.0 (93.5, 172.0) post-PPV; P < 0.05] and central venous oxygenation in patients with ILD. In patients with severe ARDS, PPV significantly increased PaO₂ /FiO₂ [109.23 (89,135) pre- PPV vs 126.13 (100.93, 170) post-PPV; P < 0.05] and intrathorax blood volume index. However, mortality rates at 28, 60 and 90 days remained high in both groups (76.4%, 88.2% and 88.2% vs 36.8%, 57.9% and 57.9% in ILD and severe ARDS, respectively; P < 0.05).

CONCLUSION

Our findings suggest that PPV may improve oxygenation and partially improve hemodynamic parameters during acute exacerbations of ILD.

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.

Outcome of Patients with Interstitial Lung Disease Treated with Extracorporeal Membrane Oxygenation for Acute Respiratory Failure

RATIONALE

Patients with interstitial lung disease and acute respiratory failure have a poor prognosis especially if mechanical ventilation is required.

OBJECTIVES

To investigate the outcome of patients with acute respiratory failure in interstitial lung disease undergoing extracorporeal membrane oxygenation (ECMO) as a bridge to recovery or transplantation.

METHODS

This was a retrospective analysis of all patients with interstitial lung disease and acute respiratory failure treated with or without ECMO from March 2012 to August 2015.

MEASUREMENTS AND MAIN RESULTS

Forty patients with interstitial lung disease referred to our intensive care unit for acute respiratory failure were included in the analysis. Twenty-one were treated with ECMO. Eight patients were transferred by air from other hospitals within a range of 320 km (linear distance) for extended intensive care including the option of lung transplant. In total, 13 patients were evaluated, and eight were finally found to be suitable for lung transplantation from an ECMO bridge. Four patients from external hospitals were de novo listed during acute respiratory failure. Six patients underwent lung transplant, and two died on the waiting list after 9 and 63 days on ECMO, respectively. A total of 14 of 15 patients who did not undergo lung transplantation (93.3%) died after 40.3 ± 27.8 days on ECMO. Five out of six patients (83.3%) receiving a lung transplant could be discharged from hospital.

CONCLUSIONS

ECMO is a lifesaving option for patients with interstitial lung disease and acute respiratory failure provided they are candidates for lung transplantation. ECMO is not able to reverse the poor prognosis in patients that do not qualify for lung transplantation.

Treatment of ARDS With Prone Positioning

Prone positioning was first proposed in the 1970s as a method to improve gas exchange in ARDS. Subsequent observations of dramatic improvement in oxygenation with simple patient rotation motivated the next several decades of research. This work elucidated the physiological mechanisms underlying changes in gas exchange and respiratory mechanics with prone ventilation. However, translating physiological improvements into a clinical benefit has proved challenging; several contemporary trials showed no major clinical benefits with prone positioning. By optimizing patient selection and treatment protocols, the recent Proning Severe ARDS Patients (PROSEVA) trial demonstrated a significant mortality benefit with prone ventilation. This trial, and subsequent meta-analyses, support the role of prone positioning as an effective therapy to reduce mortality in severe ARDS, particularly when applied early with other lung-protective strategies. This review discusses the physiological principles, clinical evidence, and practical application of prone ventilation in ARDS.

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.

Prone position

PURPOSE OF REVIEW

Prone position can prevent ventilator-induced lung injury in acute respiratory distress syndrome (ARDS) patients receiving conventional mechanical ventilation and, hence, may have the potential to improve survival from this basis. Even though no single randomized controlled trial has proven benefit on patient outcome until recently, two meta-analyses, one on grouped data and the other on individual data, have shown that patients with PaO2/FIO2 ratio less than 100 mmHg at the time of inclusion did benefit from prone position. As a fifth trial completed recently has shown a significant reduction in mortality in patients with severe and confirmed ARDS from using prone position, the purpose of this review is to revisit prone positioning in ARDS in the light of these new findings.

RECENT FINDINGS

In this trial done in patients with severe ARDS severity criteria (PaO2/FIO2 ratio less than 150 mmHg with positive end expiratory pressure of 5 cmH2O or more, FIO2 of 60% or more and tidal volume around 6 ml/kg predicted body weight) confirmed 12-24 h after the onset of ARDS, the day 28 mortality in the supine group (229 patients) was 32.8 versus 16% in the prone group (237 patients) (P < 0.001). Significant reduction in mortality was confirmed at day 90.

SUMMARY

From the combined results of the two meta-analyses and the last randomized controlled trial, there is a very strong signal to use prone position in patients with severe ARDS, as early as possible and for long sessions.

Mechanisms of the effects of prone positioning in acute respiratory distress syndrome

INTRODUCTION

Prone positioning has been used for many years in patients with acute respiratory distress syndrome (ARDS). The initial reason for prone positioning in ARDS patients was improvement in oxygenation. It was later shown that mechanical ventilation in the prone position can be less injurious to the lung and hence the primary reason to use prone positioning is prevention of ventilator-induced lung injury (VILI).

MATERIAL AND METHODS

A large body of physiologic benefits of prone positioning in ARDS patients accumulated but these failed to translate into clinical benefits. More recently, meta-analyses and randomized controlled trial in a specific subgroup of ARDS patients demonstrated that prone positioning can improve survival. This review covers the effects of prone positioning on oxygenation, respiratory mechanics, and VILI.

CONCLUSIONS

We conclude with the effects of prone positioning on patient outcome, in particular on survival.

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.

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.

Approach to acute exacerbation of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial pneumonia with a median survival of 3 years after diagnosis. Acute exacerbation of IPF (AE-IPF) is now identified as a life-threatening complication. It presents as worsening dyspnea with new ground glass opacities superimposed upon a radiographic usual interstitial pneumonia (UIP) pattern. It is a diagnosis of exclusion. The prognosis of AE-IPF is poor and treatment strategies lack standardization. In order to rule out any reversible etiology for an acute decompensation of a previously stable IPF patient diagnostic modalities include computerized tomographic angiogram (CTA) coupled with high-resolution computerized tomography (HRCT) imaging of the chest, bronchoalveolar lavage (BAL) and echocardiogram with bubble study. Avoiding risk factors, identifying underlying causes and supportive care are the mainstays of treatment. Anti-inflammatory and immunosuppressant medications have not shown to improve survival in AE-IPF. Most of the patients are managed in a critical care setting with mechanical ventilation. Lung transplantation is a promising option but most institutions are not equipped and not every patient is a candidate.

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.

Clinical review: idiopathic pulmonary fibrosis acute exacerbations--unravelling Ariadne's thread

Idiopathic pulmonary fibrosis (IPF) is a dreadful, chronic, and irreversibly progressive fibrosing disease leading to death in all patients affected, and IPF acute exacerbations constitute the most devastating complication during its clinical course. IPF exacerbations are subacute/acute, clinically significant deteriorations of unidentifiable cause that usually transform the slow and more or less steady disease decline to the unexpected appearance of acute lung injury/acute respiratory distress syndrome (ALI/ARDS) ending in death. The histological picture is that of diffuse alveolar damage (DAD), which is the tissue counterpart of ARDS, upon usual interstitial pneumonia, which is the tissue equivalent of IPF. ALI/ARDS and acute interstitial pneumonia share with IPF exacerbations the tissue damage pattern of DAD. 'Treatment' with high-dose corticosteroids with or without an immunosuppressant proved ineffective and represents the coup de grace for these patients. Provision of excellent supportive care and the search for and treatment of the 'underlying cause' remain the only options. IPF exacerbations require rapid decisions about when and whether to initiate mechanical support. Admission to an intensive care unit (ICU) is a particular clinical and ethical challenge because of the extremely poor outcome. Transplantation in the ICU setting often presents insurmountable difficulties.

Clinical meaning of early oxygenation improvement in severe acute respiratory distress syndrome under prolonged prone positioning

BACKGROUND/AIMS

Ventilating patients with acute respiratory distress syndrome (ARDS) in the prone position has been shown to improve arterial oxygenation, but prolonged prone positioning frequently requires continuous deep sedation, which may be harmful to patients. We evaluated the meaning of early gas exchange in patients with severe ARDS under prolonged (> or = 12 hours) prone positioning.

METHODS

We retrospectively studied 96 patients (mean age, 60.1 +/- 15.6 years; 75% men) with severe ARDS (PaO(2)/FiO2 < or = 150 mmHg) admitted to a medical intensive care unit (MICU). The terms "PaO2 response" and "PaCO2 response" represented responses that resulted in increases in the PaO2/FiO2 ratio of > or = 20 mmHg and decreases in PaCO2 of > or = 1 mmHg, respectively, 8 to 12 hours after first placement in the prone position.

RESULTS

The mean duration of prone positioning was 78.5 +/- 61.2 hours, and the 28-day mortality rate after MICU admission was 56.3%. No significant difference in clinical characteristics was observed between PaO2 and PaCO2 responders and non-responders. The PaO2 responders after prone positioning showed an improved 28-day outcome, compared with non-responders by Kaplan-Meier survival estimates (p < 0.05 by the log-rank test), but the PaCO12 responders did not.

CONCLUSIONS

Our results suggest that the early oxygenation improvement after prone positioning might be associated with an improved 28-day outcome and may be an indicator to maintain prolonged prone positioning in patients with severe ARDS.

Acute lung injury after thoracic surgery

In this review, the authors discussed criteria for diagnosing ALI; incidence, etiology, preoperative risk factors, intraoperative management, risk-reduction strategies, treatment, and prognosis. The anesthesiologist needs to maintain an index of suspicion for ALI in the perioperative period of thoracic surgery, particularly after lung resection on the right side. Acute hypoxemia, imaging analysis for diffuse infiltrates, and detecting a noncardiogenic origin for pulmonary edema are important hallmarks of acute lung injury. Conservative intraoperative fluid administration of neutral to slightly negative fluid balance over the postoperative first week can reduce the number of ventilator days. Fluid management may be optimized with the assistance of new imaging techniques, and the anesthesiologist should monitor for transfusion-related lung injuries. Small tidal volumes of 6 mL/kg and low plateau pressures of < or =30 cmH2O may reduce organ and systemic failure. PEEP may improve oxygenation and increases organ failure-free days but has not shown a mortality benefit. The optimal mode of ventilation has not been shown in perioperative studies. Permissive hypercapnia may be needed in order to reduce lung injury from positive-pressure ventilation. NO is not recommended as a treatment. Strategies such as bronchodilation, smoking cessation, steroids, and recruitment maneuvers are unproven to benefit mortality although symptomatically they often have been shown to help ALI patients. Further studies to isolate biomarkers active in the acute setting of lung injury and pharmacologic agents to inhibit inflammatory intermediates may help improve management of this complex disease.

Prone positioning in hypoxemic respiratory failure: meta-analysis of randomized controlled trials

PURPOSE

Prone positioning is used to improve oxygenation in patients with hypoxemic respiratory failure (HRF). However, its role in clinical practice is not yet clearly defined. The aim of this meta-analysis was to assess the effect of prone positioning on relevant clinical outcomes, such as intensive care unit (ICU) and hospital mortality, days of mechanical ventilation, length of stay, incidence of ventilator-associated pneumonia (VAP) and pneumothorax, and associated complications.

METHODS

We used literature search of MEDLINE, Current Contents, and Cochrane Central Register of Controlled Trials. We focused only on randomized controlled trials reporting clinical outcomes in adult patients with HRF. Four trials met our inclusion criteria, including 662 patients randomized to prone ventilation and 609 patients to supine ventilation.

RESULTS

The pooled odds ratio (OR) for the ICU mortality in the intention-to-treat analysis was 0.97 (95% confidence interval [CI], 0.77-1.22), for the comparison between prone and supine ventilated patients. Interestingly, the pooled OR for the ICU mortality in the selected group of the more severely ill patients favored prone positioning (OR, 0.34; 95% CI, 0.18-0.66). The duration of mechanical ventilation and the incidence of pneumothorax were not different between the 2 groups. The incidence of VAP was lower but not statistically significant in patients treated with prone positioning (OR, 0.81; 95% CI, 0.61-1.10). However, prone positioning was associated with a higher risk of pressure sores (OR, 1.49; 95% CI, 1.17-1.89) and a trend for more complications related to the endotracheal tube (OR, 1.30; 95% CI, 0.94-1.80).

CONCLUSIONS

Despite the inherent limitations of the meta-analytic approach, it seems that prone positioning has no discernible effect on mortality in patients with HRF. It may decrease the incidence of VAP at the expense of more pressure sores and complications related to the endotracheal tube. However, a subgroup of the most severely ill patients may benefit most from this intervention.

Efficacy of prone ventilation in adult patients with acute respiratory failure: a meta-analysis

PURPOSE

The use of prone ventilation in acute respiratory failure has been investigated by several randomized controlled trials in the recent past. To date, there has been no systematic review or meta-analysis of these trials.

MATERIAL AND METHODS

Systematic literature search was performed between 1966 and July 2006 to identify randomized trials evaluating prone ventilation. Outcome measures included mortality, changes in oxygenation, incidence of pneumonia, duration of mechanical ventilation, intensive care unit (ICU) and hospital stay, cost-effectiveness, and adverse effects including pressure sores, endotracheal tube, or intravascular catheter complications.

RESULTS

Prone ventilation was not associated with reduction in mortality, but improvement in oxygenation was statistically significant (mean difference, 21.2 mm Hg; P < .001). There was no significant difference in incidence of pneumonia, ICU stay, and endotracheal tube complications. There was a trend toward an increased incidence of pressure sores in prone ventilated patients (odds ratio = 1.95; 95% confidence interval, 0.09-4.15; P = .08). The data on other outcomes were not suitable for meta-analysis.

CONCLUSIONS

The use of prone ventilation is associated with improved oxygenation. It is not associated with a reduction in mortality, pneumonia, or ICU stay and may be associated with an increased incidence of pressure sores.

Acute lung injury and the acute respiratory distress syndrome: a clinical review

Acute respiratory distress syndrome and acute lung injury are well defined and readily recognised clinical disorders caused by many clinical insults to the lung or because of predispositions to lung injury. That this process is common in intensive care is well established. The mainstay of treatment for this disorder is provision of excellent supportive care since these patients are critically ill and frequently have coexisting conditions including sepsis and multiple organ failure. Refinements in ventilator and fluid management supported by data from prospective randomised trials have increased the methods available to effectively manage this disorder.

[The prone position in acute respiratory distress syndrome: a critical systematic review]

OBJECTIVE

To do a critical systematic review regarding effects of prone positioning (PP) in patients with acute respiratory distress syndrome (ARDS).

METHODS

A systematic review (Highwire, Medline, Cochrane Library from 1976 to 2004), using the keywords: prone position, acute respiratory distress syndrome, allowed us to include the human studies on PP in ARDS patients, independantly of their objectives or their type of protocol. To appreciate the studies validity, we scored the quality evidence of the studies in order to grade our conclusions.

RESULTS AND CONCLUSION

The qualitative analysis of the 58 included studies (1,500 patients returned prone, 4,000 episodes of PP) led to the following main conclusions: 1) the PP improves oxygenation in the majority of ARDS patients (level of evidence I); 2) the PP improves the pulmonary haemodynamics without altering the systemic haemodynamics (level of evidence III); 3) the PP enhances the recruitment maneuvers (level of evidence III); 4) because there are no formal predictive criteria for response to the PP, a "trial of PP" or better two PP trials are necessary to look for the responders; 5) the PP should be performed as early as possible in the course of severe ARDS; 6) the optimal duration of PP is 18 to 23 hours daily, and it should be continued until improvement of arterial oxygenation, or loss of the positive effect of PP on arterial oxygenation or evidently patient's death.

Adjunctive therapy to mechanical ventilation: surfactant therapy, liquid ventilation, and prone position

Acute lung injury and acute respiratory distress syndrome are associated with significant morbidity and mortality in critically ill patients. Although lung protective mechanical ventilation is the only therapy shown to reduce mortality and development of organ failure, several biologic pathways have been identified and provided an opportunity for therapeutic interventions. No pharmacologic or adjunctive treatments are available. Clinical studies demonstrated that prone position results in significant and clinically relevant improvement in oxygenation and ventilation, which persist when patients are returned to supine position; the beneficial response is not limited to patients turned early in disease course. Few complications are associated with prone ventilation. Clinical experience suggests that prone ventilation may protect the lung from potential detrimental effects of mechanical ventilation. Further studies are needed.