A prospective survey of early 12-h prone positioning effects in patients with the acute respiratory distress syndrome

Enteral feeding tolerance during pharmacologic neuromuscular blockade

A common misperception is that critically ill patients who receive paralytic therapy will not tolerate enteral nutrition. As a result, some clinicians empirically withhold enteral feedings for critically ill patients who receive neuromuscular blocker pharmacotherapy (NMB). The intent of this review is to examine the evidence regarding enteral feeding tolerance for critically ill patients given NMB. Studies evaluating enteral feeding during paralytic therapy are provided and critiqued. Evidence examining enteral feeding tolerance during NMB is limited. Enteral feeding intolerance is more likely attributable to the underlying illnesses and concurrent opioid analgesia, sedation, and vasopressor therapies. Most critically ill patients can be successfully fed during NMB. Prokinetic pharmacotherapy may be warranted in some patients.

Extended prone positioning for intubated ARDS: a review

During the COVID-19 pandemic, several centers had independently reported extending prone positioning beyond 24 h. Most of these centers reported maintaining patients in prone position until significant clinical improvement was achieved. One center reported extending prone positioning for organizational reasons relying on a predetermined fixed duration. A recent study argued that a clinically driven extension of prone positioning beyond 24 h could be associated with reduced mortality. On a patient level, the main benefit of extending prone positioning beyond 24 h is to maintain a more homogenous distribution of the gas-tissue ratio, thus delaying the increase in overdistention observed when patients are returned to the supine position. On an organizational level, extending prone positioning reduces the workload for both doctors and nurses, which might significantly enhance the quality of care in an epidemic. It might also reduce the incidence of accidental catheter and tracheal tube removal, thereby convincing intensive care units with low incidence of ARDS to prone patients more systematically. The main risk associated with extended prone positioning is an increased incidence of pressure injuries. Up until now, retrospective studies are reassuring, but prospective evaluation is needed.

Enteral Nutrition Safety and Outcomes of Patients with COVID-19 on Continuous Infusion of Neuromuscular Blockers: A Retrospective Study

Background

Intravenous infusions of neuromuscular blocking agents (NMBAs) and prone positioning are recommended for acute respiratory distress syndrome (ARDS) due to COVID-19. The safety of enteral nutrition (EN) during these treatments is unclear. This study assessed EN tolerance and safety during NMBA infusion in proned and nonproned patients with ARDS due to COVID-19.

Methods

This retrospective study evaluated patients who were admitted to a tertiary-care ICU between March and December 2020, had ARDS due to COVID-19, and received NMBA infusion. We assessed their EN data, gastrointestinal events, and clinical outcomes. The primary outcome was gastrointestinal intolerance, defined as a gastric residual volume (GRV) ≥500 ml or 200-500 ml with vomiting. We compared proned and nonproned patients.

Results

We studied 181 patients (mean age 61.2 ± 13.7 years, males 71.1%, and median body mass index 31.4 kg/m2). Most (63.5%) patients were proned, and 94.3% received EN in the first 48 hours of NMBA infusion at a median dose <10 kcal/kg/day. GRV was mostly below 100 ml. Gastrointestinal intolerance occurred in 6.1% of patients during NMBA infusion and 10.5% after NMBA discontinuation (similar rates in proned and nonproned patients). Patients who had gastrointestinal intolerance during NMBA infusion had a higher hospital mortality (90.9% versus 60.0%; p=0.05) and longer mechanical ventilation duration and ICU and hospital stays compared with those who did not.

Conclusion

In COVID-19 patients on NMBA infusion for ARDS, EN was provided early at low doses for most patients, and gastrointestinal intolerance was uncommon in proned and nonproned patients, occurred at a higher rate after discontinuing NMBAs and was associated with worse outcomes. Our study suggests that EN was tolerated and safe in this patient population.

Feeding intolerance during prolonged prone position in overweight and obese patients with severe COVID-19

OBJECTIVE

the aim of this study was to compare the incidence rate of feeding intolerance (FI) during supine (SP) or prone positioning (PP) in critically ill COVID-19 patients.

METHODS

this was a retrospective cohort study of critically ill patients with overweight or obesity who received enteral nutrition (EN) in prone or supine positioning continuously during the first five days of mechanical ventilation. Nutritional risk, anthropometric measurements and body composition were assessed at the first 24 hours upon Intensive Care Unit (ICU) admission. Biochemical and clinical variables (Sequential Organ Failure Assessment [SOFA], Acute Physiology and Chronic Health Evaluation II [APACHE II], Acute Kidney Injury [AKI] or comorbidities diagnosis) were collected. Pharmacotherapy (prokinetics, sedatives or neuromuscular blocking agents) and FI incidence (gastric residual volume [GRV] ≥ 200 ml or ≥ 500 ml, vomiting or diarrhea) were daily recorded. Constipation was defined as the absence of evacuation for five consecutive days.

RESULTS

eighty-two patients were included. Higher rate of prophylactic prokinetic prescription was observed in PP (42.8 vs 12.5 %, p = 0.002). GRV ≥ 200 in supine position was not different when compared to PP (p = 0.47). Vomiting episodes in supine compared to PP showed no difference between groups (15 % vs 24 %, p = 0.31). No differences in diarrhea events were detected (10 % vs 4.7 %, p = 0.36). Constipation was common in both groups (95 % vs 82 %, p = 0.06).

CONCLUSION

FI during prone position was not different in comparison to supine position. Routinely use of prokinetics in continuous prone position may help to prevent FI incidence. Algorithm development is necessary for FI prevention and treatment so to avoid EN interruptions and adverse clinical outcomes.

Long-term complications of prone position ventilation with relevance for acute and postacute rehabilitation: a systematic review of the literature

INTRODUCTION

Prone positioning ventilation (PPV) is an effective treatment for patients with moderate to severe acute respiratory distress syndrome (ARDS). Despite the benefits of PPV, different kinds of short and long-term consequences have been noted. This review summarizes long-term complications of PPV that impact treatment strategies and outcomes in acute and postacute rehabilitation.

EVIDENCE ACQUISITION

PubMed/Medline, Cochrane Library, Cochrane COVID-19 Study Register databases and the Google Scholar search engine were systematically searched for studies investigating long-term complications of PPV. The final search date for all sources/databases was January 31, 2022. For our methodological appraisal, we conducted a systematic review of articles without any restrictions on types of articles or publication dates. Only articles published in English and available as full texts were eligible for inclusion. After the screening process, data of interest were extracted from eligible sources: PPV sequelae and conclusions (i.e. possible effects on the course of rehabilitation and therapy strategies).

EVIDENCE SYNTHESIS

A total of 59 studies are included in this review. Long-term consequences are mainly pressure ulcers and nerve lesions that exist after discharge from the Intensive Care Unit (ICU). Publications rarely recommend treatment strategies for long-term complications after PPV. Due to the quality of the included studies, no robust conclusions as to effective strategies can be drawn.

CONCLUSIONS

Further high-quality research is required, considering the different long-term complications after PPV and their impact on rehabilitation in order to draw conclusions about viable physical therapies. Crucially, however, prone positioning (PP) sequelae pose new challenges to physicians and therapists in acute and postacute rehabilitation medicine as well as follow-up care.

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.

Caloric Intake with High Ratio of Enteral Nutrition Associated with Lower Hospital Mortality for Patients with Acute Respiratory Distress Syndrome Using Prone Position Therapy

Positioning patients in the prone position leads to reduced hospital mortality rates for those with severe acute respiratory distress syndrome (ARDS). What constitutes the optimal feeding strategy for prone patients with ARDS is controversial. We conducted a retrospective study that enrolled 110 prone patients with ARDS in two medical intensive care units (ICUs) from September 2015 to November 2018. Inclusion criteria were as follows: age ≥20 years, diagnosis of respiratory failure requiring mechanical ventilation, diagnosis of ARDS within 72 h of ICU admission, placement in a prone position within the first 7 days of ICU admission, and ICU stay of more than 7 days. Exclusion criteria were as follows: nil per os orders because of gastrointestinal bleeding or hemodynamic instability, and ventilator dependency because of chronic respiratory failure. The consecutive daily enteral nutrition(EN)/EN + parenteral nutrition(PN) ratio could predict hospital mortality rates within the first 7 days of admission when using generalized estimating equations (p = 0.013). A higher average EN/EN + PN ratio within the first 7 days predicted (hazard ratio: 0.97, confidence interval: 0.96-0.99) lower hospital mortality rates. To reduce hospital mortality rates, caloric intake with a higher EN ratio may be considered for patients in prone positions with ARDS.

Enteral Nutrition Safety With Advanced Treatments: Extracorporeal Membrane Oxygenation, Prone Positioning, and Infusion of Neuromuscular Blockers

This review aims at assessing the safety and efficacy of enteral nutrition in critically ill patients receiving extracorporeal membrane oxygenation, prone positioning, and infusion of neuromuscular blockers. Existing data from randomized controlled trials demonstrate the survival benefit of early enteral nutrition in critically ill patients. Observational data have demonstrated that enteral nutrition in patients receiving extracorporeal membrane oxygenation, prone positioning, and infusion of neuromuscular blockers is generally safe. However, these patients are at increased risk for gastrointestinal complications from enteral nutrition because of critical illness-induced gastrointestinal dysfunction; associated shock; the concomitant use of vasopressor agents, sedatives, and narcotics; possibly mesenteric circulatory compromise; and regurgitation associated with prone positioning. Therefore, early enteral nutrition is generally recommended in these patients in the absence of severe gastrointestinal dysfunction or shock. To reduce the complications, early nutrition should be advanced gradually (trophic feeding or permissive underfeeding), the bed should be tilted to a maximum of 30°, and concentrated nutritional formulae and the use of prokinetics may be considered to treat enteral feeding intolerance. Physicians should be vigilant about monitoring for early signs of acute mesenteric ischemia, which should lead to holding enteral feeding. Parenteral nutrition may be utilized in patients who cannot receive enteral nutrition or are unable to reach their nutrition goals by the end of the first week.

Administration of enteral nutrition in the prone position, gastric residual volume and other clinical outcomes in critically ill patients: a systematic review

This systematic review of longitudinal studies aimed to evaluate the effect of enteral feeding of critically ill adult and pediatric patients in the prone position on gastric residual volume and other clinical outcomes. A literature search was conducted in the databases PubMed, Scopus and Embase using terms related to population and intervention. Two independent reviewers analyzed the titles and abstracts, and data collection was performed using a standardized form. Discrepancies were resolved by a third reviewer. The methodological quality of the studies was evaluated considering the potential for systematic errors, and the data were qualitatively analyzed. Four studies with adult patients and one with preterm patients were included. The gastric residual volume was evaluated as the main outcome: three studies did not show differences in the gastric residual volume between the prone and supine positions (p > 0.05), while one study showed a higher gastric residual volume during enteral feeding in the prone position (27.6mL versus 10.6mL; p < 0.05), and another group observed a greater gastric residual volume in the supine position (reduction of the gastric residual volume by 23.3% in the supine position versus 43.9% in the prone position; p < 0.01). Two studies evaluated the frequency of vomiting; one study found that it was higher in the prone position (30 versus 26 episodes; p < 0.001), while the other study found no significant difference (p > 0.05). The incidence of aspiration pneumonia and death were evaluated in one study, with no difference between groups (p > 0.05). The literature on the administration of enteral feeding in the prone position in critically ill patients is sparse and of limited quality, and the results regarding gastric residual volume are contradictory. Observational studies with appropriate sample sizes should be conducted to support conclusions on the subject.

Lung ultrasound: Predictor of acute respiratory distress syndrome in intensive care unit patients

PURPOSE

The purpose of the study was to review and summarize current literature concerning the validation and application of lung ultrasound (LUS) in critically ill patients with acute respiratory distress syndrome (ARDS).

MATERIALS AND METHODS

An extensive literature search was conducted using PubMed, Cochrane Review, Google Scholar, and Ohio State University Link based on the question if LUS should be considered a reliable investigational technique for ARDS diagnosis, treatment, and prognosis in pediatric and adult population.

RESULTS

LUS has been successfully validated for facilitating early diagnosis and diagnosis of simultaneous lung conditions, predicting lung recruitment treatment effect, and evaluating the prognosis in ARDS patients. Whether lung US is a useful tool in the prediction of prone position and oxygenation response in patients with ARDS is conflicting.

CONCLUSIONS

LUS is a noninvasive, radiation-free, cheap, and easy to perform tool for critically ill patients with ARDS and might be a promising technique used in the Intensive Care Unit for ARDS management.

Can lung ultrasonography predict prone positioning response in acute respiratory distress syndrome patients?

PURPOSE

The purpose was to assess whether lung ultrasonography (L-US) is a useful tool in prediction of prone positioning (PP) oxygenation response in patients with acute respiratory distress syndrome (ARDS).

METHODS

In a prospective study, 19 ARDS patients were included for assessment of PP oxygenation response. The latter was assessed for at least 12 hours 6 different ultrasonography windows were performed on each hemithorax before prone (H0, H2, H12 before return to supine and at H14 (2 hours after return to supine). Patients were classified into 2 groups (responders / non responders) according their oxygenation response to PP. Ultrasonography videos were blindly evaluated by 3 expert clinicians to classify lung regions as "normal", "moderate loss of aeration," "severe loss of aeration," or "lung consolidation." Oxygenation parameters were collected at H0, H2, and H14.

RESULTS

Association of each lung region aspect to PP oxygenation response was compared between the 2 groups. The normal aspect of the anterobasal regions was significantly associated with the oxygenation response (P = .0436), with a positive predictive value equal to or near 100%.

DISCUSSION

Our results demonstrated that a simple and short L-US examination could be a useful tool in prediction of PP oxygenation response in ARDS patients. A normal L-US pattern of both anterobasal lung regions in supine position may predict a significant PaO2/FIO2 ratio improvement.

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.

A practical approach to the use of prone therapy in acute respiratory distress syndrome

In this article we propose a practical approach to the use of prone therapy for acute respiratory distress syndrome (ARDS). We have attempted to provide information to improve the understanding and implementation of prone therapy based on the literature available and our own experience. We review the basic physiology behind ARDS and the theoretical mechanism by which prone therapy can be of benefit. The findings of the most significant studies regarding prone therapy in ARDS as they pertain to its implementation are summarized. Also provided is a discussion of the nuances of utilizing prone therapy, including potential pitfalls, complications, and contraindications. The specific considerations of prone therapy in open abdomens and traumatic brain injuries are discussed as well. Finally, we supply suggested protocols for the implementation of prone therapy discussing criteria for initiation and cessation of therapy as well as addressing issues such as the use of neuromuscular blockade and nutritional supplementation.

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.

Using the prone position for ventilated patients with respiratory failure: a review

AIMS

this review explored the evidence relating to prone positioning in ventilated patients diagnosed with respiratory failure, including acute lung injury (ALI) or adult respiratory distress syndrome (ARDS).

BACKGROUND

mortality rates for ventilated patients with ALI or ARDS are high, and there is a growing body of evidence suggesting that the position these patients are nursed in may influence clinical outcomes. However, there are no guidelines to inform nursing practice in positioning these patients.

METHOD

Medline, Scopus, Cinahl and the Cochrane Library databases were searched for original research reports or systematic reviews of evidence between 2000 and 2009. Reference lists of retrieved papers were hand searched and included studies were analysed using the Critical Appraisal and Skills Programme framework. A narrative data synthesis considered the strengths and limitations of studies, and findings were collated and interpreted.

RESULTS

Application of the search strategy identified a systematic review, currently underway, which has not yet reported and 14 relevant studies eligible for inclusion in this review. Analysis showed considerable variation in study design, but suggests that PaO(2) /FiO(2) ratio, incidence of VAP and mortality may be positively affected by prone positioning.

CONCLUSIONS

evidence of the clinical benefits associated with prone positioning is inconclusive and provides little guidance for nursing practice. There is a need for further research into the clinical outcomes of prone positioning, and greater understanding of the practicalities of prone positioning critically ill patients is required.

RELEVANCE TO CLINICAL PRACTICE

nurses have a central role to play in the continual assessment and management of this patient group, including the position they are nursed in, not only to ensure the best clinical outcomes but also to provide care and comfort to the patient and their family. It is therefore important that their nursing practice and interventions are informed by the best available evidence.

Effects of prone position on inflammatory markers in patients with ARDS due to community-acquired pneumonia

BACKGROUND/PURPOSE

Acute respiratory distress syndrome (ARDS) is a serious disorder of intensive care unit patients. We evaluated the safety of continuous prone position ventilation (PRONE) and its effects on oxygenation and plasma cytokine concentrations in patients with ARDS caused by severe community-acquired pneumonia (CAP).

METHODS

This was a prospective observational clinical study conducted in a respiratory intensive care unit of a 1200-bed medical center in central Taiwan. Twenty-two patients with severe CAP and ARDS were included. They were treated by traditional supine ventilation (SUPINE, n = 11) or PRONE (n = 11) if they met the criteria for ARDS. Patients in the PRONE group were ventilated in prone position continuously for at least 72 hours. Plasma cytokines were collected and analyzed at baseline, 24 hours and 72 hours after enrolment. Serial PaO2/FiO2 and complications were evaluated.

RESULTS

Complications associated with PRONE were minor and self-limited. PRONE had higher PaO2/FiO2 ratio than SUPINE did at 48 hours after enrolment. The levels of plasma IL-6 concentration declined significantly with time in the PRONE group (p = 0.011). The levels of plasma IL-6 concentration at enrolment, 24 hours and 72 hours after enrolment also predicted the 14th day mortality of all patients.

CONCLUSION

PRONE was a safe and effective maneuver for improving oxygenation in patients with severe CAP and ARDS. PRONE also influenced IL-6 expression in patients with severe CAP.

Pediatric acute lung injury

Among ventilated children, the incidence of acute lung injury (ALI) was 9%; of that latter group 80% developed the acute respiratory distress syndrome (ARDS). The population-based prevalence of pediatric ARDS was 5.5 cases/100.000 inhabitants. Underlying diseases in children were septic shock (34%), respiratory syncytial virus infections (16%), bacterial pneumonia (15%), near-drowning 9%, and others. Mortality ranged from 18% to 27% for ALI (including ALI-non ARDS and ARDS) and from 29% to 50% for ARDS. Mortality was only 3%-11% in children with ALI-non ARDS. As risk factors, oxygenation indices and multi-organ failure have been identified. New insights into the pathophysiology (for example the interplay between intraalveolar coagulation/fibrinolysis and inflammation and the genetic polymorphism for the angiotensin-converting enzyme) offer new therapeutic options. Lung protective mechanical ventilation with optimal lung recruitment is the mainstay of supportive therapy. New therapeutic modalities refer to corticosteroid and surfactant treatment. Well-designed follow up studies are needed.

Prone positioning can be safely performed in critically ill infants and children

OBJECTIVE

To describe the effects of prone positioning on airway management, mechanical ventilation, enteral nutrition, pain and sedation management, and staff utilization in infants and children with acute lung injury.

DESIGN

Secondary analysis of data collected in a multiple-center, randomized, controlled clinical trial of supine vs. prone positioning.

SETTING

Seven pediatric intensive care units located in the United States.

PATIENTS

One hundred and two pediatric patients (51 prone and 51 supine) with acute lung injury.

INTERVENTIONS

Patients randomized to the supine group remained supine. Patients randomized to the prone group were positioned prone per protocol during the acute phase of their illness for a maximum of 7 days. Both groups were managed using ventilator and sedation protocols and nutrition and skin care guidelines.

MEASUREMENTS AND MAIN RESULTS

Airway management and mechanical ventilatory variables before and after repositioning, enteral nutrition management, pain and sedation management, staff utilization, and adverse event data were collected for up to 28 days after enrollment. There were a total of 202 supine-prone-supine cycles. There were no differences in the incidence of endotracheal tube leak between the two groups (p = .30). Per protocol, 95% of patients remained connected to the ventilator during repositioning. The inadvertent extubation rate was 0.85 for the prone group and 1.03 for the supine group per 100 ventilator days (p = 1.00). There were no significant differences in the initiation of trophic (p = .24), advancing (p = .82), or full enteral feeds (p = .80) between the prone and supine groups; in the average pain (p = .81) and sedation (p = .18) scores during the acute phase; and in the amount of comfort medications received between the two groups (p = .91). There were no critical events during a turn procedure. While prone, two patients experienced an obstructed endotracheal tube. One patient, supported on high-frequency oscillatory ventilation, experienced persistent hypercapnea when prone and was withdrawn from the study. The occurrence of pressure ulcers was similar between the two groups (p = .71). Compared with the supine group, more staff (p </= .001) and more time were necessary to reposition patients in the prone group.

CONCLUSIONS

Our data show that prone positioning can be safely performed in critically ill pediatric patients and that these patients can be safely managed while in the prone position for prolonged periods of time.

Alveolar recruitment during prone position: time matters

Alveolar recruitment is one of the beneficial effects of prone positioning in patients with ARDS (acute respiratory distress syndrome). However, responses vary among patients and, therefore, we hypothesized that alveolar recruitment is an individual time-dependent process and its measurement might be helpful to 'dose' prone positioning individually. In 13 patients diagnosed with ARDS, EELV (end-expiratory lung volume) was measured in the supine position, immediately after turning to the prone position, at 1, 2, 4 and 8 h in the prone position and after returning to the supine position. Responders were defined based on a 30% increase in oxygenation. EELV increased in responders, whereas it remained constant in non-responders. The time course was different in individual patients. In some responders, a plateau was reached as early as 2-4 h, whereas, in others, 8 h of prone positioning was not sufficient to allow complete recruitment. The increase in lung volume was associated with both an increase in arterial oxygenation and a decrease in venous admixture. Furthermore, responders had significantly lower baseline EELVs than non-responders. In conclusion, alveolar recruitment during prone positioning has been characterized as an individual time-dependent process. Its measurement might be useful to apply prone positioning more individually and might also help to identify responders.

Posição prona

A posição prona é uma manobra utilizada para combater a hipoxemia nos pacientes com síndrome do desconforto respiratório agudo. Apesar de hoje ser considerada um modo eficaz de melhorar a oxigenação, os mecanismos fisiológicos que levam à melhora da função respiratória ainda não estão completamente esclarecidos. O objetivo principal desta revisão é discutir os aspectos fisiológicos e clínicos da posição prona na síndrome do desconforto respiratório agudo.

New aspects of ventilation in acute lung injury

Recent recognition that artificial ventilation may cause damage to the acutely injured lung has caused renewed interest in ventilation techniques that minimise this potential harm. Many ventilation techniques have proved beneficial in small trials of very specific patient groups, but most have subsequently failed to translate into improved patient outcome in larger trials. An exception to this is 'protective ventilation' using reduced tidal volumes (to lower airway pressure) and increased PEEP (to reduce pulmonary collapse). Results of trials of protective ventilation have been encouraging, and the technique should now be adopted more widely. High frequency ventilation, inverse ratio ventilation, prone positioning and inhaled nitric oxide are all techniques that may be considered when, in spite of optimal artificial ventilation, the patient's gas exchange remains dangerously poor. Under these circumstances, the choice of technique is dependent on their availability, local expertise and individual patient needs.