Prone ventilation reduces mortality in patients with acute respiratory failure and severe hypoxemia: systematic review and meta-analysis

Background

Prone position ventilation for acute hypoxemic respiratory failure (AHRF) improves oxygenation but not survival, except possibly when AHRF is severe.

Objective

To determine effects of prone versus supine ventilation in AHRF and severe hypoxemia [partial pressure of arterial oxygen (PaO₂)/inspired fraction of oxygen (FiO₂) <100 mmHg] compared with moderate hypoxemia (100 mmHg ≤ PaO₂/FiO₂ ≤ 300 mmHg).

Design

Systematic review and meta-analysis.

Data Sources

Electronic databases (to November 2009) and conference proceedings.

Methods

Two authors independently selected and extracted data from parallel-group randomized controlled trials comparing prone with supine ventilation in mechanically ventilated adults or children with AHRF. Trialists provided subgroup data. The primary outcome was hospital mortality in patients with AHRF and PaO₂/FiO₂ <100 mmHg. Meta-analyses used study-level random-effects models.

Results

Ten trials (N = 1,867 patients) met inclusion criteria; most patients had acute lung injury. Methodological quality was relatively high. Prone ventilation reduced mortality in patients with PaO₂/FiO₂ <100 mmHg [risk ratio (RR) 0.84, 95% confidence interval (CI) 0.74–0.96; p = 0.01; seven trials, N = 555] but not in patients with PaO₂/FiO₂ ≥100 mmHg (RR 1.07, 95% CI 0.93–1.22; p = 0.36; seven trials, N = 1,169). Risk ratios differed significantly between subgroups (interaction p = 0.012). Post hoc analysis demonstrated statistically significant improved mortality in the more hypoxemic subgroup and significant differences between subgroups using a range of PaO₂/FiO₂ thresholds up to approximately 140 mmHg. Prone ventilation improved oxygenation by 27–39% over the first 3 days of therapy but increased the risks of pressure ulcers (RR 1.29, 95% CI 1.16–1.44), endotracheal tube obstruction (RR 1.58, 95% CI 1.24–2.01), and chest tube dislodgement (RR 3.14, 95% CI 1.02–9.69). There was no statistical between-trial heterogeneity for most clinical outcomes.

Conclusions

Prone ventilation reduces mortality in patients with severe hypoxemia. Given associated risks, this approach should not be routine in all patients with AHRF, but may be considered for severely hypoxemic patients.     

Safety of performing fiberoptic bronchoscopy in critically ill hypoxemic patients with acute respiratory failure

Background

The safety of fiberoptic bronchoscopy (FOB) in nonintubated critically ill patients with acute respiratory failure has not been extensively evaluated. We aimed to measure the incidence of intubation and the need to increase ventilatory support following FOB and to identify predictive factors for this event.

Methods

A prospective multicenter observational study was carried out in eight French adult intensive care units. The study included 169 FOB performed in patients with a PaO₂/FiO₂ ratio ??300. The main end-point was intubation rate. The secondary end-point was rate of increased ventilatory support defined as an increase in oxygen requirement >50?%, the need to start noninvasive positive pressure ventilation (NI-PPV) or increase NI-PPV support.

Results

Within 24?h, an increase in ventilatory support was required following 59 bronchoscopies (35?%), of which 25 (15?%) led to endotracheal intubation. The existence of chronic obstructive pulmonary disease (COPD; OR 5.2, 95?% CI 1.6?C17.8; p?=?0.007) or immunosuppression (OR 5.4, 95?% CI 1.7?C17.2; p?=?0.004] were significantly associated with the need for intubation in the multivariable analysis. None of the baseline physiological parameters including the PaO₂/FiO₂ ratio was associated with intubation.

Conclusions

Bronchoscopy is often followed by an increase in ventilatory support in hypoxemic critically ill patients, but less frequently by the need for intubation. COPD and immunosuppression are associated with the need for invasive ventilation in the 24?h following bronchoscopy.     

Fiberoptic bronchoscopy under noninvasive ventilation and propofol target-controlled infusion in hypoxemic patients

Purpose

In critically ill patients with acute respiratory failure (ARF), fiberoptic bronchoscopy and bronchoalveolar lavage (FOB-BAL) are important tools in diagnostic strategies. In nonintubated patients, the patient??s agitation may lead to desaturation and compromise the realization of FOB. The aim of this study was to assess the feasibility and safety of target-controlled (TCI) propofol sedation during FOB-BAL in nonintubated hypoxemic patients.

Methods

The first end point in our prospective investigation within an intensive care unit (ICU) was the avoidance of endotracheal intubation within 24?h. Secondary end points were changes in the PaO₂/FiO₂ ratio, hemodynamic stability, patient comfort, occurrence of adverse effects, and quality of FOB. Patients self-evaluated their comfort after FOB.

Results

Twenty-four FOBs were performed in 23 patients with ARF. PaO₂/FiO₂ before FOB was 181?±?50 (range 85?C286). All patients tolerated FOB with BAL. None was intubated during the 2?h after FOB. Loss of consciousness was obtained with an effect site concentration of propofol of 1.49?±?0.46???g/mL (range 2.6?C0.6). No significant adverse events occurred. TCI propofol allowed us to obtain amnesia, patient comfort, and it did not impair airway protection. Any hemodynamic changes observed were modest and transient.

Conclusions

FOB-BAL, under NIV and TCI with propofol, is feasible and safe in nonintubated patients with ARF. The TCI of propofol during FOB-BAL reduces patient discomfort with no significant adverse effects.     

Safety of research bronchoscopy in critically ill patients

Objective

Bronchoscopy and bronchoalveolar lavage (BAL) are common procedures in intensive care units; however, no contemporaneous safety and outcomes data have been reported, particularly for critically ill patients.

Design

This is a retrospective analysis of prospectively collected data from teaching hospital adult intensive care units.

Interventions

One hundred mechanically ventilated patients with severe sepsis, septic shock, acute lung injury (ALI), and/or acute respiratory distress syndrome underwent bronchoscopy with unilateral BAL. Data collected included demographics, presence of sepsis or ALI, Pao₂ to Fio₂ ratio, positive end-expiratory pressure, Acute Physiology and Chronic Health Evaluation score, Sequential Organ Failure Assessment score, and peri- or postprocedural complications.

Results

Men comprised 51% of the patients; 81% of the patients were black, and 15% were white. The mean age was 52 (SD, ± 16) years. The mean Acute Physiology and Chronic Health Evaluation score was 22 (± 7.5), whereas the median Sequential Organ Failure Assessment score was 9 (interquartile range, 5-12). Ten patients (10%) had complications during or immediately after the procedure. Hypoxemia during or immediately after the BAL was the most common complication. Ninety percent of the complications were related to transient hypoxemia, whereas bradycardia and hypotension each occurred in 1 patient. Age, female sex, and higher positive end-expiratory pressure were associated with complications.

Conclusions

Bronchoscopy with BAL in critically ill patients with sepsis and ALI is well tolerated with low risk of complications, primarily related to manageable hypoxemia.     

Three different mask physiotherapy regimens for prevention of post-operative pulmonary complications after heart and pulmonary surgery

Objective

An investigation into the incidence of post-operative complications after thoracic surgery with 3 different physiotherapy masks.

Design

A prospective, consecutive, randomized comparison.

Setting

Department of Thoracic and Heart Surgery at a University Hospital. The treatments were performed by experienced and specially trained physiotherapists.

Patients

160 patients were evaluated. 60 patients undergoing heart surgery, 59 patients having pulmonary resection, and 41 patients with exploratory thoractomy.

Interventions

In each operative category the patients were treated with one of three face mask systems used in addition to routine chest physiotherapy. These were either continuous positive airway pressure (CPAP), positive expiratory pressure (PEP), or inspiratory resistance — positive expiratory pressure (IR-PEP).

Measurements and results

Post-operative pulmonary complications were assessed by forced vital capacity (FVC), arterial oxygen tension (PaO₂), and chest X-ray examination, all measured pre-operatively and on the fourth and ninth post-operative day. The patients filled in a questionnaire expressing their opinion about their mask treatment. There was an equal decrease in FVC, FVC%, and PaO₂, and equal frequency of atelectasis in the 3 mask treatments. More patients with the PEP mask favoured their system than did those with the other 2 systems.

Conclusion

There was no statistically significant difference between the treatments: continuous positive airway pressure (CPAP), positive expiratory pressure (PEP), and inspiratory resistance — positive expiratory pressure (IR-PEP) on post-operative complications. Any of the three treatments may be used as supplement to standard chest physiotherapy.     

Prevalence of undiagnosed hypoxemia in adults and children in an under-resourced district hospital in Zambia

Background

In adequately resourced clinical environments, diagnosis of hypoxemia via pulse oximetry is routine. Unfortunately, pulse oximetry is rarely utilized in under-resourced hospitals in developing countries.

Aim

The prevalence of undiagnosed hypoxemia among adults and children with illnesses other than pneumonia in these environments remains poorly described.

Methods

This cross-sectional analysis of the prevalence of hypoxemia was conducted in Kapiri Mposhi, Zambia, at the 60-bed District Hospital, which serves a population of 320,000. The resting room air oxygen saturations of two consecutive samples of all adult and pediatric inpatients were measured in December 2008 and March 2009 using handheld pulse oximetry. Hypoxemia was defined as resting room air SpO₂ less than 90%.

Results

A total of 192 patients were enrolled: 68 young children (<5 years old), 15 older children (5–17 years old), and 109 adults (≥18 years old). Five young children (7%), 0 older children (0%), and 10 adults (9%) were hypoxemic. No hypoxemic patients were receiving oxygen therapy at the time of diagnosis. Pneumonia, tuberculosis, and malnutrition were the most common conditions among those with hypoxemia. Oximetry data changed clinical management in all observed cases of hypoxemia and several cases of normoxemia, leading to application of supplemental oxygen, initiation of further diagnostic testing, prolongation of inpatient stay, or expedited discharge home.

Conclusions

Undiagnosed hypoxemia is present among inpatients at this district hospital in rural Zambia with high prevalence in both adults and young children. These results support routine screening for hypoxemia in similar facilities in both age groups. Further investigation is warranted into the clinical impact and cost-effectiveness of pulse oximetry, provision of oxygen concentrators, and training on their use in developing countries.     

The standard of care of patients with ARDS: ventilatory settings and rescue therapies for refractory hypoxemia

Purpose

Severe ARDS is often associated with refractory hypoxemia, and early identification and treatment of hypoxemia is mandatory. For the management of severe ARDS ventilator settings, positioning therapy, infection control, and supportive measures are essential to improve survival.

Methods and results

A precise definition of life-threating hypoxemia is not identified. Typical clinical determinations are: arterial partial pressure of oxygen < 60 mmHg and/or arterial oxygenation < 88 % and/or the ratio of PaO₂/FIO₂ < 100. For mechanical ventilation specific settings are recommended: limitation of tidal volume (6 ml/kg predicted body weight), adequate high PEEP (>12 cmH₂O), a recruitment manoeuvre in special situations, and a ‘balanced’ respiratory rate (20-30/min). Individual bedside methods to guide PEEP/recruitment (e.g., transpulmonary pressure) are not (yet) available. Prone positioning [early (≤ 48 hrs after onset of severe ARDS) and prolonged (repetition of 16-hr-sessions)] improves survival. An advanced infection management/control includes early diagnosis of bacterial, atypical, viral and fungal specimen (blood culture, bronchoalveolar lavage), and of infection sources by CT scan, followed by administration of broad-spectrum anti-infectives. Neuromuscular blockage (Cisatracurium ≤ 48 hrs after onset of ARDS), as well as an adequate sedation strategy (score guided) is an important supportive therapy. A negative fluid balance is associated with improved lung function and the use of hemofiltration might be indicated for specific indications.

Conclusions

A specific standard of care is required for the management of severe ARDS with refractory hypoxemia.

     

Intrapulmonary percussive ventilation in acute exacerbations of COPD patients with mild respiratory acidosis: a randomized controlled trial [ISRCTN17802078]

Introduction

We hypothesized that the use of intrapulmonary percussive ventilation (IPV), a technique designed to improve mucus clearance, could prove effective in avoiding further deterioration in patients with acute exacerbations of chronic obstructive pulmonary disease (COPD) with mild respiratory acidosis.

Methods

The study was performed in a medical intensive care unit of a university hospital. Thirty-three patients with exacerbations of COPD with a respiratory frequency ≥ 25/min, a PaCO₂ > 45 Torr and 7.35 ≤ pH ≤ 7.38 were included in the study. Patients were randomly assigned to receive either standard treatment (control group) or standard treatment plus IPV (IPV group). The IPV group underwent two daily sessions of 30 minutes performed by a chest physiotherapist through a full face mask. The therapy was considered successful when both worsening of the exacerbation and a decrease in pH to under 7.35, which would have required non-invasive ventilation, were avoided.

Results

Thirty minutes of IPV led to a significant decrease in respiratory rate, an increase in PaO₂ and a decrease in PaCO₂ (p < 0.05). Exacerbation worsened in 6 out of 17 patients in the control group versus 0 out of 16 in the IPV group (p < 0.05). The hospital stay was significantly shorter in the IPV group than in the control group (6.8 ± 1.0 vs. 7.9 ± 1.3 days, p < 0.05).

Conclusion

IPV is a safe technique and may prevent further deterioration in patients with acute exacerbations of COPD with mild respiratory acidosis.     

Associations between ventilator settings during extracorporeal membrane oxygenation for refractory hypoxemia and outcome in patients with acute respiratory distress syndrome: a pooled individual patient data analysis

Purpose

Extracorporeal membrane oxygenation (ECMO) is a rescue therapy for patients with acute respiratory distress syndrome (ARDS). The aim of this study was to evaluate associations between ventilatory settings during ECMO for refractory hypoxemia and outcome in ARDS patients.

Methods

In this individual patient data meta-analysis of observational studies in adult ARDS patients receiving ECMO for refractory hypoxemia, a time-dependent frailty model was used to determine which ventilator settings in the first 3 days of ECMO had an independent association with in-hospital mortality.

Results

Nine studies including 545 patients were included. Initiation of ECMO was accompanied by significant decreases in tidal volume size, positive end-expiratory pressure (PEEP), plateau pressure, and driving pressure (plateau pressure ? PEEP) levels, and respiratory rate and minute ventilation, and resulted in higher PaO₂/FiO₂, higher arterial pH and lower PaCO₂ levels. Higher age, male gender and lower body mass index were independently associated with mortality. Driving pressure was the only ventilatory parameter during ECMO that showed an independent association with in-hospital mortality [adjusted HR, 1.06 (95 % CI, 1.03–1.10)].

Conclusion

In this series of ARDS patients receiving ECMO for refractory hypoxemia, driving pressure during ECMO was the only ventilator setting that showed an independent association with in-hospital mortality.

     

Pulmonary-derived phosphoinositide 3-kinase gamma (PI3Kγ) contributes to ventilator-induced lung injury and edema

Background

Ventilator-induced lung injury (VILI) occurs in part by increased vascular permeability and impaired alveolar fluid clearance. Phosphoinositide 3-kinase gamma (PI3Kγ) is activated by mechanical stress, induces nitric oxide (NO) production, and participates in cyclic adenosine monophosphate (cAMP) hydrolysis, each of which contributes to alveolar edema. We hypothesized that lungs lacking PI3Kγ or treated with PI3Kγ inhibitors would be protected from ventilation-induced alveolar edema and lung injury.

Methods

Using an isolated and perfused lung model, wild-type (WT) and PI3Kγ-knockout (KO) mice underwent negative-pressure cycled ventilation at either ?25 cmH₂O and 0 cmH₂O positive end-expiratory pressure (PEEP) (HIGH STRESS) or ?10 cmH₂O and ?3 cmH₂O PEEP (LOW STRESS).

Results

Compared with WT, PI3Kγ-knockout mice lungs were partially protected from VILI-induced derangement of respiratory mechanics (lung elastance) and edema formation [bronchoalveolar lavage (BAL) protein concentration, wet/dry ratio, and lung histology]. In PI3Kγ-knockout mice, VILI induced significantly less phosphorylation of protein kinase B (Akt), endothelial nitric oxide synthase (eNOS), production of nitrate and nitrotyrosine, as well as hydrolysis of cAMP, compared with wild-type animals. PI3Kγ wild-type lungs treated with AS605240, an inhibitor of PI3Kγ kinase activity, in combination with enoximone, an inhibitor of phosphodiesterase-3 (PDE3)-induced cAMP hydrolysis, were protected from VILI at levels comparable to knockout lungs.

Conclusions

Phosphoinositide 3-kinase gamma in resident lung cells mediates part of the alveolar edema induced by high-stress ventilation. This injury is mediated via altered Akt, eNOS, NO, and/or cAMP signaling. Anti-PI3Kγ therapy aimed at resident lung cells represents a potential pharmacologic target to mitigate VILI.     

Use of high flow nasal cannula in critically ill infants, children, and adults: a critical review of the literature

Background

High flow nasal cannula (HFNC) systems utilize higher gas flow rates than standard nasal cannulae. The use of HFNC as a respiratory support modality is increasing in the infant, pediatric, and adult populations as an alternative to non-invasive positive pressure ventilation.

Objectives

This critical review aims to: (1) appraise available evidence with regard to the utility of HFNC in neonatal, pediatric, and adult patients; (2) review the physiology of HFNC; (3) describe available HFNC systems (online supplement); and (4) review ongoing and planned trials studying the utility of HFNC in various clinical settings.

Results

Clinical neonatal studies are limited to premature infants. Only a few pediatric studies have examined the use of HFNC, with most focusing on this modality for viral bronchiolitis. In critically ill adults, most studies have focused on acute respiratory parameters and short-term physiologic outcomes with limited investigations focusing on clinical outcomes such as duration of therapy and need for escalation of ventilatory support. Current evidence demonstrates that HFNC generates positive airway pressure in most circumstances; however, the predominant mechanism of action in relieving respiratory distress is not well established.

Conclusion

Current evidence suggests that HFNC is well tolerated and may be feasible in a subset of patients who require ventilatory support with non-invasive ventilation. However, HFNC has not been demonstrated to be equivalent or superior to non-invasive positive pressure ventilation, and further studies are needed to identify clinical indications for HFNC in patients with moderate to severe respiratory distress.     

Noninvasive ventilation after early extubation in patients recovering from hypoxemic acute respiratory failure: a single-centre feasibility study

Purpose

The use of noninvasive ventilation (NIV) to facilitate discontinuation of mechanical ventilation in patients with acute hypoxemic respiratory failure (hypoxemic ARF) has never been explored. This pilot study aims to assess the feasibility of early extubation followed by immediate NIV, compared conventional weaning, in patients with resolving hypoxemic ARF.

Methods

Twenty consecutive hypoxemic patients were randomly assigned to receive either conventional weaning or NIV. The changes in arterial blood gases and respiratory rate were compared between the two groups at 1, 12, 24 and 48?h. Differences in the rate of extubation failure, ICU and hospital mortality, number of invasive-ventilation-free-days at day 28, septic complications, number of tracheotomies, days and rates of continuous intravenous sedation, and ICU length of stay were also determined.

Results

No patient interrupted the study protocol. Arterial blood gases were similar during invasive mechanical ventilation, 1?h after NIV application following extubation, and after 12, 24 and 48?h. Respiratory rate was higher after 1?h in the NIV group, but no different after 12, 24 and 48?h. The number of invasive-ventilation-free-days at day 28 was 20?±?8 (min?=?0, max?=?25) days in the treatment group and 10?±?9 (min?=?0, max?=?25) days in the control group (p?=?0.014). The rate of extubation failure, ICU and hospital mortality, tracheotomies, septic complications, days and rates of continuous sedation, and ICU length of stay were not significantly different between the two groups.

Conclusions

In a highly experienced centre NIV may be used to facilitate discontinuation of mechanical ventilation in selected patients with resolving hypoxemic ARF.     

A pilot study of a new test to predict extubation failure

Introduction

In acute lung injury, repair of the damaged alveolar-capillary barrier is an essential part of recovery. Endostatin is a 20 to 28 kDa proteolytic fragment of the basement membrane collagen XVIII, which has been shown to inhibit angiogenesis via action on endothelial cells. We hypothesised that endostatin may have a role in inhibiting lung repair in patients with lung injury. The aims of the study were to determine if endostatin is elevated in the plasma/bronchoalveolar lavage fluid of patients with acute lung injury and ascertain whether the levels reflect the severity of injury and alveolar inflammation, and to assess if endostatin changes occur early after the injurious lung stimuli of one lung ventilation and lipopolysaccharide (LPS) challenge.

Methods

Endostatin was measured by ELISA and western blotting.

Results

Endostatin is elevated within the plasma and bronchoalveolar lavage fluid of patients with acute lung injury. Lavage endostatin reflected the degree of alveolar neutrophilia and the extent of the loss of protein selectivity of the alveolar-capillary barrier. Plasma levels of endostatin correlated with the severity of physiological derangement. Western blotting confirmed elevated type XVIII collagen precursor levels in the plasma and lavage and multiple endostatin-like fragments in the lavage of patients. One lung ventilation and LPS challenge rapidly induce increases in lung endostatin levels.

Conclusions

Endostatin may adversely affect both alveolar barrier endothelial and epithelial cells, so its presence within both the circulation and the lung may have a pathophysiological role in acute lung injury that warrants further evaluation.     

Helmet CPAP vs. oxygen therapy in severe hypoxemic respiratory failure due to pneumonia

Purpose

The efficacy of noninvasive continuous positive airway pressure (CPAP) to improve outcomes in severe hypoxemic acute respiratory failure (hARF) due to pneumonia has not been clearly established. The aim of this study was to compare CPAP vs. oxygen therapy to reduce the risk of meeting criteria for endotracheal intubation (ETI).

Methods

In a multicenter randomized controlled trial conducted in four Italian centers patients with severe hARF due to pneumonia were randomized to receive helmet CPAP (CPAP group) or oxygen delivered with a Venturi mask (control group). The primary endpoint was the percentage of patients meeting criteria for ETI, including either one or more major criteria (respiratory arrest, respiratory pauses with unconsciousness, severe hemodynamic instability, intolerance) or at least two minor criteria (reduction of at least 30 % of basal PaO₂/FiO₂ ratio, increase of 20 % of PaCO₂, worsening of alertness, respiratory distress, SpO₂ less than 90 %, exhaustion).

Results

Between February 2010 and 2013, 40 patients were randomized to CPAP and 41 to Venturi mask. The proportion of patients meeting ETI criteria in the CPAP group was significantly lower compared to those in the control group (6/40 = 15 % vs. 26/41 = 63 %, respectively, p < 0.001; relative risk 0.24, 95 % CI 0.11–0.51; number needed to treat, 2) two patients were intubated in the CPAP group and one in the control group. The CPAP group showed a faster and greater improvement in oxygenation in comparison to controls (p < 0.001). In either study group, no relevant adverse events were detected.

Conclusions

Helmet CPAP reduces the risk of meeting ETI criteria compared to oxygen therapy in patients with severe hARF due to pneumonia.     

Protective effect of resin adsorption on septic plasma-induced tubular injury

Introduction

Recent cohort studies have identified the use of large tidal volumes as a major risk factor for development of lung injury in mechanically ventilated patients without acute lung injury (ALI). We compared the effect of conventional with lower tidal volumes on pulmonary inflammation and development of lung injury in critically ill patients without ALI at the onset of mechanical ventilation.

Methods

We performed a randomized controlled nonblinded preventive trial comparing mechanical ventilation with tidal volumes of 10 ml versus 6 ml per kilogram of predicted body weight in critically ill patients without ALI at the onset of mechanical ventilation. The primary end point was cytokine levels in bronchoalveolar lavage fluid and plasma during mechanical ventilation. The secondary end point was the development of lung injury, as determined by consensus criteria for ALI, duration of mechanical ventilation, and mortality.

Results

One hundred fifty patients (74 conventional versus 76 lower tidal volume) were enrolled and analyzed. No differences were observed in lavage fluid cytokine levels at baseline between the randomization groups. Plasma interleukin-6 (IL-6) levels decreased significantly more strongly in the lower-tidal-volume group ((from 51 (20 to 182) ng/ml to 11 (5 to 20) ng/ml versus 50 (21 to 122) ng/ml to 21 (20 to 77) ng/ml; P = 0.01)). The trial was stopped prematurely for safety reasons because the development of lung injury was higher in the conventional tidal-volume group as compared with the lower tidal-volume group (13.5% versus 2.6%; P = 0.01). Univariate analysis showed statistical relations between baseline lung-injury score, randomization group, level of positive end-expiratory pressure (PEEP), the number of transfused blood products, the presence of a risk factor for ALI, and baseline IL-6 lavage fluid levels and the development of lung injury. Multivariate analysis revealed the randomization group and the level of PEEP as independent predictors of the development of lung injury.

Conclusions

Mechanical ventilation with conventional tidal volumes is associated with sustained cytokine production, as measured in plasma. Our data suggest that mechanical ventilation with conventional tidal volumes contributes to the development of lung injury in patients without ALI at the onset of mechanical ventilation.

Trial registration

ISRCTN82533884     

High-flow nasal cannula oxygen versus non-invasive ventilation in patients with acute hypoxaemic respiratory failure undergoing flexible bronchoscopy - a prospective randomised trial

Introduction

Critically ill patients with respiratory failure undergoing bronchoscopy have an increased risk of hypoxaemia-related complications. Previous studies have shown that in awake, hypoxaemic patients non-invasive ventilation (NIV) is helpful in preventing gas exchange deterioration during bronchoscopy. An alternative and increasingly used means of oxygen delivery is its application via high-flow nasal cannula (HFNC). This study was conducted to compare HFNC with NIV in patients with acute hypoxaemic respiratory failure undergoing flexible bronchoscopy.

Methods

Prospective randomised trial randomising 40 critically ill patients with hypoxaemic respiratory failure to receive either NIV or HFNC during bronchoscopy in the intensive care unit.

Results

After the initiation of NIV and HFNC, oxygen levels were significantly higher in the NIV group compared to the HFNC group. Two patients were unable to proceed to bronchoscopy after the institution of HFNC due to progressive hypoxaemia. During bronchoscopy, one patient on HFNC deteriorated due to intravenous sedation requiring non-invasive ventilatory support. Bronchoscopy was well tolerated in all other patients. There were no significant differences between the two groups regarding heart rate, mean arterial pressure and respiratory rate. Three patients in the NIV group and one patient in the HFNC group were intubated within 24 hours after the end of bronchoscopy (P = 0.29).

Conclusions

The application of NIV was superior to HFNC with regard to oxygenation before, during and after bronchoscopy in patients with moderate to severe hypoxaemia. In patients with stable oxygenation under HFNC, subsequent bronchoscopy was well tolerated.

Trial registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT01870765","term_id":"NCT01870765"}}NCT01870765. Registered 30 May 2013.     

Bedside assessment of the effects of positive end-expiratory pressure on lung inflation and recruitment by the helium dilution technique and electrical impedance tomography

Purpose

Higher positive end-expiratory pressure might induce lung inflation and recruitment, yielding enhanced regional lung protection. We measured positive end-expiratory pressure-related lung volume changes by electrical impedance tomography and by the helium dilution technique. We also used electrical impedance tomography to assess the effects of positive end-expiratory pressure on regional determinants of ventilator-induced lung injury.

Methods

A prospective randomized crossover study was performed on 20 intubated adult patients: 12 with acute hypoxemic respiratory failure and 8 with acute respiratory distress syndrome. Each patient underwent protective controlled ventilation at lower (7 [7, 8] cmH₂O) and higher (12 [12, 13] cmH₂O) positive end-expiratory pressures. At the end of each phase, we collected ventilation, helium dilution, and electrical impedance tomography data.

Results

Positive end-expiratory pressure-induced changes in lung inflation and recruitment measured by electrical impedance tomography and helium dilution showed close correlations (R ² = 0.78, p < 0.001 and R ² = 0.68, p < 0.001, respectively) but with relatively variable limits of agreement. At higher positive end-expiratory pressure, recruitment was evident in all lung regions (p < 0.01) and heterogeneity of tidal ventilation distribution was reduced by increased tidal volume distending the dependent lung (p < 0.001); in the non-dependent lung, on the other hand, compliance decreased (p < 0.001) and tidal hyperinflation significantly increased (p < 0.001). In the subgroup of ARDS patients (but not in the whole study population) tidal hyperinflation in the dependent lung regions decreased at higher positive end-expiratory pressure (p = 0.05), probably indicating higher potential for recruitment.

Conclusions

Close correlations exist between bedside assessment of positive end-expiratory pressure-induced changes in lung inflation and recruitment by the helium dilution and electrical impedance tomography techniques. Higher positive end-expiratory pressure exerts mixed effects on the regional determinants of ventilator-induced lung injury; these merit close monitoring.

     

ECMO criteria for influenza A (H1N1)-associated ARDS: role of transpulmonary pressure

Purpose

To assess whether partitioning the elastance of the respiratory system (E _RS) between lung (E _L) and chest wall (E _CW) elastance in order to target values of end-inspiratory transpulmonary pressure (PPLAT_L) close to its upper physiological limit (25?cmH₂O) may optimize oxygenation allowing conventional treatment in patients with influenza A (H1N1)-associated ARDS referred for extracorporeal membrane oxygenation (ECMO).

Methods

Prospective data collection of patients with influenza A (H1N1)-associated ARDS referred for ECMO (October 2009?CJanuary 2010). Esophageal pressure was used to (a) partition respiratory mechanics between lung and chest wall, (b) titrate positive end-expiratory pressure (PEEP) to target the upper physiological limit of PPLAT_L (25?cmH₂O).

Results

Fourteen patients were referred for ECMO. In seven patients PPLAT_L was 27.2?±?1.2?cmH₂O; all these patients underwent ECMO. In the other seven patients, PPLAT_L was 16.6?±?2.9?cmH₂O. Raising PEEP (from 17.9?±?1.2 to 22.3?±?1.4?cmH₂O, P?=?0.0001) to approach the upper physiological limit of transpulmonary pressure (PPLAT_L?=?25.3?±?1.7?cm H₂O) improved oxygenation index (from 37.4?±?3.7 to 16.5?±?1.4, P?=?0.0001) allowing patients to be treated with conventional ventilation.

Conclusions

Abnormalities of chest wall mechanics may be present in some patients with influenza A (H1N1)-associated ARDS. These abnormalities may not be inferred from measurements of end-inspiratory plateau pressure of the respiratory system (PPLAT_RS). In these patients, titrating PEEP to PPLAT_RS may overestimate the incidence of hypoxemia refractory to conventional ventilation leading to inappropriate use of ECMO.     

Chest compressions versus ventilation plus chest compressions in a pediatric asphyxial cardiac arrest animal model

Objective

To compare the ventilation achieved with chest compressions (CC) or ventilation plus compressions (VC) in a pediatric animal model of cardiac arrest.

Design

Randomized experimental study.

Setting

Experimental department of a University Hospital.

Methods

Twelve infant pigs with asphyxial cardiac arrest. Sequential 3-min periods of VC and CC were performed for a total duration of 9 min. Tidal volume (TV), end-tidal CO₂ (EtCO₂), mean arterial pressure (MAP), central venous pressure (CVP), mean pulmonary arterial pressure (mPAP), and peripheral, cerebral, and renal saturations were recorded and arterial and venous blood gases were analyzed.

Results

VC achieved a TV similar to the preset parameters on the ventilator, whilst the TV in CC was very low (P < 0.001). EtCO₂ with VC was significantly higher than with CC (14.0 vs. 3.9 mmHg, P < 0.05). Arterial pH was higher with VC than with CC (6.99 vs. 6.90 mmHg, P < 0.05). Arterial PCO₂ was lower with VC than with CC (62.1 vs. 97.0 mmHg, P < 0.05). There were no significant differences in the MAP; CVP; mPAP; peripheral, renal, and cerebral saturations; or lactate concentrations between the two techniques.

Conclusions

VC achieves better ventilation than CC during cardiopulmonary resuscitation and has no negative effect on the hemodynamic situation.