Terbutaline lessens protein fluxes across the alveolo-capillary barrier during high-volume ventilation

Objective

To evaluate whether a β₂-adrenergic agonist may reduce acute alveolo-capillary barrier alterations during high-volume ventilation.

Design

Experimental study.

Setting

Animal research laboratory.

Subjects

A total of 48 male Wistar rats.

Interventions

A zone of alveolar flooding was produced by liquid instillation in a distal airway. Proteins in the instilled solution were traced with ^99mTc-albumin. ¹¹¹In, which binds to transferrin, was injected into the systemic circulation. Terbutaline was administered in the instilled solution or intra-peritoneally. Conventional ventilation was applied for 30?min followed by different ventilation strategies for 90?min: conventional ventilation, high-volume ventilation with or without 6?cmH₂O PEEP.

Measurements and main results

Protein fluxes across the alveolar and microvascular barriers were evaluated by scintigraphy. High-volume ventilation resulted in immediate leakage of ^99mTc-albumin from alveolar spaces and increased pulmonary uptake of systemic ¹¹¹In-transferrin. Terbutaline in the instilled solution and PEEP lessened alveolar ^99mTc-albumin leakage and pulmonary ¹¹¹In-transferrin uptake due to high-volume ventilation, whereas terbutaline given intra-peritoneally only lessened ¹¹¹In-transferrin uptake. Terbutaline in the instilled solution also lessened the increase in lung wet-to-dry weight ratio due to high-volume ventilation.

Conclusions

Terbutaline reduces protein fluxes across the alveolar epithelial and pulmonary microvascular barriers during high-volume ventilation in vivo. The route of administration may be important.

     

Nasal continuous positive airway pressure decreases respiratory muscles overload in young infants with severe acute viral bronchiolitis

Objective

To determine the efficacy of nasal continuous positive airway pressure (nCPAP) on respiratory distress symptoms and respiratory effort in young infants with acute respiratory syncytial virus bronchiolitis.

Design

Prospective study.

Setting

The paediatric intensive care unit of a university hospital.

Patients

Twelve infants less than 3 months of age, with severe respiratory distress.

Interventions

Respiratory distress was quantified with a specific scoring system. Oesophageal pressure (Pes) was measured during spontaneous ventilation before and after nCPAP, delivered through an infant-adapted ventilator. Simultaneous recording of gastric pressure (Pgas) was performed in the five oldest patients.

Measurements and results

The respiratory distress score decreased after nCPAP, particularly accessory muscles’ use and expiratory wheezing. The breathing pattern was modified, with shorter inspiratory and longer expiratory time. Pes swings and PTPes_insp, two indices of inspiratory effort, were reduced by 54 (±4)% and 59 (±5)%. PTPgas_exp, an indicator of expiratory muscles activity, was completely abolished. A significant correlation was observed between the respiratory distress score and Pes swings at baseline and after nCPAP.

Conclusions

In young infants with severe acute respiratory syncytial virus bronchiolitis, nCPAP rapidly unloads respiratory muscles and improves respiratory distress symptoms.

     

Regional lung derecruitment after endotracheal suction during volume- or pressure-controlled ventilation: a study using electric impedance tomography

Objective

To assess lung volume and compliance changes during open- and closed-system suctioning using electric impedance tomography (EIT) during volume- or pressure-controlled ventilation.

Design and setting

Experimental study in a university research laboratory.

Subjects

Nine bronchoalveolar saline-lavaged pigs.

Interventions

Open and closed suctioning using a 14-F catheter in volume- or pressure-controlled ventilation at tidal volume 10?ml/kg, respiratory rate 20?breaths/min, and positive end-expiratory pressure 10?cmH₂O.

Measurements and results

Lung volume was monitored by EIT and a modified N₂ washout/-in technique. Airway pressure was measured via a pressure line in the endotracheal tube. In four ventral-to-dorsal regions of interest regional ventilation and compliance were calculated at baseline and 30?s and 1, 2, and 10?min after suctioning. Blood gases were followed. At disconnection functional residual capacity (FRC) decreased by 58?±?24% of baseline and by a further 22?±?10% during open suctioning. Arterial oxygen tension decreased to 59?±?14% of baseline value 1?min after open suctioning. Regional compliance deteriorated most in the dorsal parts of the lung. Restitution of lung volume and compliance was significantly slower during pressure-controlled than volume-controlled ventilation.

Conclusions

EIT can be used to monitor rapid lung volume changes. The two dorsal regions of the lavaged lungs are most affected by disconnection and suctioning with marked decreases in compliance. Volume-controlled ventilation can be used to rapidly restitute lung aeration and oxygenation after lung collapse induced by open suctioning.

     

Distribution of lung ventilation in spontaneously breathing neonates lying in different body positions

Objective

The aim of our study was to determine the effect of the irregular spontaneous breathing pattern and posture on the spatial distribution of ventilation in neonates free from respiratory disease by the non-invasive imaging method of electrical impedance tomography (EIT). Scanning of spontaneously breathing neonates is the prerequisite for later routine application of EIT in babies with lung pathology undergoing ventilator therapy.

Design

Prospective study.

Setting

Neonatal intensive care unit at a university hospital.

Patients

Twelve pre-term and term neonates (mean age: 23 days; mean body weight: 2,465 g; mean gestational age: 34 weeks; mean birth weight: 2,040 g).

Interventions

Change in body position in the sequence: supine, right lateral, prone, supine.

Measurements and results

EIT measurements were performed using the Göttingen GoeMF I system. EIT scans of regional lung ventilation showing the distribution of respired air in the chest cross-section were generated during phases of rapid tidal breathing and deep breaths. During tidal breathing, 54.5±8.3%, 55.2±10.5%, 59.9±8.4% and 54.2±8.5% of inspired air (mean values ± SD) were directed into the right lung in the supine, right lateral, prone and repeated supine postures respectively. During deep inspirations, the right lung ventilation accounted for 52.6±7.9%, 68.5±8.5%, 55.4±8.2% and 50.5±6.6% of total ventilation respectively.

Conclusion

The study identified the significant effect of breathing pattern and posture on the spatial distribution of lung ventilation in spontaneously breathing neonates. The results demonstrate that changes in regional ventilation can easily be determined by EIT and bode well for the future use of this method in paediatric intensive care.

     

Olanzapine vs haloperidol: treating delirium in a critical care setting

Objective

To compare the safety and estimate the response profile of olanzapine, a second-generation antipsychotic, to haloperidol in the treatment of delirium in the critical care setting.

Design

Prospective randomized trial

Setting

Tertiary care university affiliated critical care unit.

Patients

All admissions to a medical and surgical intensive care unit with a diagnosis of delirium.

Interventions

Patients were randomized to receive either enteral olanzapine or haloperidol.

Measurements

Patient’s delirium severity and benzodiazepine use were monitored over 5 days after the diagnosis of delirium.

Main results

Delirium Index decreased over time in both groups, as did the administered dose of benzodiazepines. Clinical improvement was similar in both treatment arms. No side effects were noted in the olanzapine group, whereas the use of haloperidol was associated with extrapyramidal side effects.

Conclusions

Olanzapine is a safe alternative to haloperidol in delirious critical care patients, and may be of particular interest in patients in whom haloperidol is contraindicated.

     

Effects of sigh during pressure control and pressure support ventilation in pulmonary and extrapulmonary mild acute lung injury

Introduction

Sigh improves oxygenation and lung mechanics during pressure control ventilation (PCV) and pressure support ventilation (PSV) in patients with acute respiratory distress syndrome. However, so far, no study has evaluated the biological impact of sigh during PCV or PSV on the lung and distal organs in experimental pulmonary (p) and extrapulmonary (exp) mild acute lung injury (ALI).

Methods

In 48 Wistar rats, ALI was induced by Escherichia coli lipopolysaccharide either intratracheally (ALIp) or intraperitoneally (ALIexp). After 24 hours, animals were anesthetized and mechanically ventilated with PCV or PSV with a tidal volume of 6 mL/kg, FiO₂ = 0.4, and PEEP = 5 cmH₂O for 1 hour. Both ventilator strategies were then randomly assigned to receive periodic sighs (10 sighs/hour, Sigh) or not (non-Sigh, NS). Ventilatory and mechanical parameters, arterial blood gases, lung histology, interleukin (IL)-1β, IL-6, caspase-3, and type III procollagen (PCIII) mRNA expression in lung tissue, and number of apoptotic cells in lung, liver, and kidney specimens were analyzed.

Results

In both ALI etiologies: (1) PCV-Sigh and PSV-Sigh reduced transpulmonary pressure, and (2) PSV-Sigh reduced the respiratory drive compared to PSV-NS. In ALIp: (1) PCV-Sigh and PSV-Sigh decreased alveolar collapse as well as IL-1β, IL-6, caspase-3, and PCIII expressions in lung tissue, (2) PCV-Sigh increased alveolar-capillary membrane and endothelial cell damage, and (3) abnormal myofibril with Z-disk edema was greater in PCV-NS than PSV-NS. In ALIexp: (1) PSV-Sigh reduced alveolar collapse, but led to damage to alveolar-capillary membrane, as well as type II epithelial and endothelial cells, (2) PCV-Sigh and PSV-Sigh increased IL-1β, IL-6, caspase-3, and PCIII expressions, and (3) PCV-Sigh increased the number of apoptotic cells in the lung compared to PCV-NS.

Conclusions

In these models of mild ALIp and ALIexp, sigh reduced alveolar collapse and transpulmonary pressures during both PCV and PSV; however, improved lung protection only during PSV in ALIp.

     

Low dose quetiapine induced galactorrhoea: a case report

Background

Quetiapine causes less prolactin elevation and/or galactorrhoea than other atypical antipsychotics.

Case Presentation

Ms AB had galactorrhoea and raised prolactin levels at only 100 mg of quetiapine daily.

Conclusion

Low dose quetiapine can also cause galactorrhoea.

     

Explore the influence of BMI in the optimal time of weaning from sequential mechanical ventilation for severity chronic obstructive pulmonary disease

Objective

To study the clinical effect of body mass index (BMI) in the optimal time of weaning from sequential invasive-noninvasive mechanical ventilation (MV) by treating severity chronic obstructive pulmonary disease (COPD) patients.

Methods

94 patients with severity COPD were divided into the control group (BMI<21) and the study group (BMI>21). These two groups were treated by similar symptomatic therapies such as mechanical ventilation, antibacterial, antispasmodic, relieving asthma, antitussive, expectorant, correction of electrolyte imbalance and acid-base balance disorders, strengthen nutritional support, etc.

Results

Compared with the control group, the study group had shorter duration of invasive mechanical ventilation, non-invasive mechanical ventilation time, total mechanical ventilation time, total hospital stay (P<0.01). There are significant differences between these two groups in re-intubation rate, VAP occurred in the number of case, hospital mortality rate in 28 days (P<0.05).

Conclusions

It is difficult to wean successfully from sequential mechanical ventilation for severity COPD patients (BMI<21), so BMI as one of important reference index can be used to estimate the optimal time for weaning from sequential mechanical ventilation for severity COPD patients.

     

Automatic adjustment of pressure support by a computer-driven knowledge-based system during noninvasive ventilation: a feasibility study

Objective

To evaluate the feasibility of using a knowledge-based system designed to automatically titrate pressure support (PS) to maintain the patient in a “respiratory comfort zone” during noninvasive ventilation (NIV) in patients with acute respiratory failure.

Design and setting

Prospective crossover interventional study in an intensive care unit of a university hospital.

Patients

Twenty patients.

Interventions

After initial NIV setting and startup in conventional PS by the chest physiotherapist NIV was continued for 45?min with the automated PS activated.

Measurements and results

During automated PS minute-volume was maintained constant while respiratory rate decreased significantly from its pre-NIV value (20?±?3 vs. 25?±?3?bpm). There was a trend towards a progressive lowering of dyspnea. In hypercapnic patients PaCO₂ decreased significantly from 61?±?9 to 51?±?2?mmHg, and pH increased significantly from 7.31?±?0.05 to 7.35?±?0.03. Automated PS was well tolerated. Two system malfunctions occurred prompting physiotherapist intervention.

Conclusions

The results of this feasibility study suggest that the system can be used during NIV in patients with acute respiratory failure. Further studies should now determine whether it can improve patient-ventilator interaction and reduce caregiver workload.

     

Automatic segmentation of airway tree based on local intensity filter and machine learning technique in 3D chest CT volume

Purpose

Airway segmentation plays an important role in analyzing chest computed tomography (CT) volumes for computerized lung cancer detection, emphysema diagnosis and pre- and intra-operative bronchoscope navigation. However, obtaining a complete 3D airway tree structure from a CT volume is quite a challenging task. Several researchers have proposed automated airway segmentation algorithms basically based on region growing and machine learning techniques. However, these methods fail to detect the peripheral bronchial branches, which results in a large amount of leakage. This paper presents a novel approach for more accurate extraction of the complex airway tree.

Methods

This proposed segmentation method is composed of three steps. First, Hessian analysis is utilized to enhance the tube-like structure in CT volumes; then, an adaptive multiscale cavity enhancement filter is employed to detect the cavity-like structure with different radii. In the second step, support vector machine learning will be utilized to remove the false positive (FP) regions from the result obtained in the previous step. Finally, the graph-cut algorithm is used to refine the candidate voxels to form an integrated airway tree.

Results

A test dataset including 50 standard-dose chest CT volumes was used for evaluating our proposed method. The average extraction rate was about 79.1 % with the significantly decreased FP rate.

Conclusion

A new method of airway segmentation based on local intensity structure and machine learning technique was developed. The method was shown to be feasible for airway segmentation in a computer-aided diagnosis system for a lung and bronchoscope guidance system.

     

Severe hypercapnia and outcome of mechanically ventilated patients with moderate or severe acute respiratory distress syndrome

Purpose

To analyze the relationship between hypercapnia developing within the first 48 h after the start of mechanical ventilation and outcome in patients with acute respiratory distress syndrome (ARDS).

Patients and methods

We performed a secondary analysis of three prospective non-interventional cohort studies focusing on ARDS patients from 927 intensive care units (ICUs) in 40 countries. These patients received mechanical ventilation for more than 12 h during 1-month periods in 1998, 2004, and 2010. We used multivariable logistic regression and a propensity score analysis to examine the association between hypercapnia and ICU mortality.

Main outcomes

We included 1899 patients with ARDS in this study. The relationship between maximum PaCO₂ in the first 48 h and mortality suggests higher mortality at or above PaCO₂ of ≥50 mmHg. Patients with severe hypercapnia (PaCO₂ ≥50 mmHg) had higher complication rates, more organ failures, and worse outcomes. After adjusting for age, SAPS II score, respiratory rate, positive end-expiratory pressure, PaO₂/FiO₂ ratio, driving pressure, pressure/volume limitation strategy (PLS), corrected minute ventilation, and presence of acidosis, severe hypercapnia was associated with increased risk of ICU mortality [odds ratio (OR) 1.93, 95% confidence interval (CI) 1.32 to 2.81; p = 0.001]. In patients with severe hypercapnia matched for all other variables, ventilation with PLS was associated with higher ICU mortality (OR 1.58, CI 95% 1.04–2.41; p = 0.032).

Conclusions

Severe hypercapnia appears to be independently associated with higher ICU mortality in patients with ARDS.

Trial registration

Clinicaltrials.gov identifier, NCT01093482.

     

Context region discovery for automatic motion compensation in fluoroscopy

Purpose

Image-based tracking for motion compensation is an important topic in image-guided interventions, as it enables physicians to operate in a less complex space. In this paper, we propose an automatic motion compensation scheme to boost image guidence power in transcatheter aortic valve implantation (TAVI).

Methods

The proposed tracking algorithm automatically discovers reliable regions that correlate strongly with the target. These discovered regions can assist to estimate target motion under severe occlusion, even if target tracker fails.

Results

We evaluate the proposed method for pigtail tracking during TAVI. We obtain significant improvement (12 %) over the baseline in a clinical dataset. Calcification regions are automatically discovered during tracking, which would aid TAVI processes.

Conclusion

In this work, we open a new paradigm to provide dynamic real-time guidance for TAVI without user interventions, specially in case of severe occlusion where conventional tracking methods are challenged.

     

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.

     

Prone equals prone? Impact of positioning techniques on respiratory function in anesthetized and paralyzed healthy children

Objectives

Although the prone position is effectively used to improve oxygenation, its impact on functional residual capacity is controversial. Different techniques of body positioning might be an important confounding factor. The aim of this study was to determine the impact of two different prone positioning techniques on functional residual capacity and ventilation distribution in anesthetized, preschool-aged children.

Design

Functional residual capacity and lung clearance index, a measure of ventilation homogeneity, were calculated using a sulfur-hexafluoride multibreath washout technique. After intubation, measurements were taken in the supine position and, in random order, in the flat prone position and the augmented prone position (gel pads supporting the pelvis and the upper thorax).

Setting

Pediatric anesthesia unit of university hospital.

Patients and participants

Thirty preschool children without cardiopulmonary disease undergoing elective surgery.

Measurements and results

Mean (range) age was 48.5 (24–80) months, weight 17.2 (10.5–26.9)?kg, functional residual capacity (mean ±?SD) 22.9?±?6.2?ml.kg ^?1 in the supine position and 23.3?±?5.6?ml.kg ^?1 in the flat prone position, while lung clearance indices were 8.1?±?2.3 vs. 7.9?±?2.3, respectively. In contrast, functional residual capacity increased to 27.6 ± 6.5 ml.kg ^?1 (pp

Conclusions

Functional residual capacity and ventilation distribution were similar in the supine and flat prone positions, while these parameters improved significantly in the augmented prone position, suggesting that the technique of prone positioning has major implications for pulmonary function.

     

Adverse drug reactions and deliberate self-poisoning as cause of admission to the intensive care unit: a 1-year prospective observational cohort study

Objective

The aim of the present study was (1) to determine the prevalence of intensive care unit (ICU) admissions due to an adverse drug reaction (ADR), and (2) to compare affected patients with patients admitted to the ICU for the treatment of deliberate self-poisoning using medical drugs.

Design

Prospective observational cohort study.

Setting

Fourteen bed medical ICU including an integrated intermediate care (IMC) section at a tertiary referral center.

Patients

A total of 1,554 patients admitted on 1 January 2003 to 31 December 2003.

Results

Ninety-nine patients were admitted to the ICU with a diagnosis of ADR (6.4% of all admissions), 269 admissions (17.3%) were caused by deliberate self-poisoning. Patients admitted for treatment of ADR had a significantly higher age, a longer treatment duration in the ICU, a higher SAPS II score, and a higher 6-month mortality than those with deliberate self-poisoning. Most patients (71.7%) suffering from ADR required advanced supportive care in the ICU while the majority of patients (90.7%) with deliberate self-poisoning could be sufficiently treated in the IMC area. All diagnostic and therapeutic procedures in the ICU except mechanical ventilation were significantly more often performed in patients with ADR.

Conclusions

This study provides further evidence that ADR is a frequent cause of admission to medical ICUs resulting in a considerable use of ICU capacities. In the present setting patients with ADR required longer and more intense medical treatment in the ICU than those with deliberate self-poisoning.

     

Effect of synbiotic therapy on the incidence of ventilator associated pneumonia in critically ill patients: a randomised,double-blind,placebo-controlled trial

Objective

To investigate the effect of enteral Synbiotic 2000 FORTE^® (a mixture of lactic acid bacteria and fibre) on the incidence of ventilator associated pneumonia (VAP) in critically ill patients.

Design

Prospective, randomised, double blind, placebo controlled trial.

Setting

Tertiary referral centre, general Adult Intensive Care Unit (ICU).

Patients and participants

259 enterally fed patients requiring mechanical ventilation for 48 h or more were enrolled.

Intervention

All patients were enterally fed as per a standard protocol and randomly assigned to receive either synbiotic 2000 FORTE^® (twice a day) or a cellulose-based placebo for a maximum of 28 days.

Measurements and results

Treatment group (n = 130) was well matched with placebo group (n = 129) for age (mean 49.5 and 50 years, respectively) and APACHE II score (median 17 for both). Oropharyngeal microbial flora and colonisation rates were unaffected by synbiotics. The overall incidence of VAP was lower than anticipated (11.2%) and no statistical difference was demonstrated between groups receiving synbiotic and placebo in the incidence of VAP (9 and 13%, P = 0.42), VAP rate per 1,000 ventilator days (13 and 14.6, P = 0.91) or hospital mortality (27 and 33%, P = 0.39), respectively.

Conclusions

Enteral administration of Synbiotic 2000 FORTE^® has no statistically significant impact on the incidence of VAP in critically ill patients.

     

Esophageal and transpulmonary pressure in the clinical setting: meaning,usefulness and perspectives

Purpose

Esophageal pressure (Pes) is a minimally invasive advanced respiratory monitoring method with the potential to guide management of ventilation support and enhance specific diagnoses in acute respiratory failure patients. To date, the use of Pes in the clinical setting is limited, and it is often seen as a research tool only.

Methods

This is a review of the relevant technical, physiological and clinical details that support the clinical utility of Pes.

Results

After appropriately positioning of the esophageal balloon, Pes monitoring allows titration of controlled and assisted mechanical ventilation to achieve personalized protective settings and the desired level of patient effort from the acute phase through to weaning. Moreover, Pes monitoring permits accurate measurement of transmural vascular pressure and intrinsic positive end-expiratory pressure and facilitates detection of patient–ventilator asynchrony, thereby supporting specific diagnoses and interventions. Finally, some Pes-derived measures may also be obtained by monitoring electrical activity of the diaphragm.

Conclusions

Pes monitoring provides unique bedside measures for a better understanding of the pathophysiology of acute respiratory failure patients. Including Pes monitoring in the intensivist’s clinical armamentarium may enhance treatment to improve clinical outcomes.

     

Diagnostic Accuracy of Bronchodilator Response for Asthma in a Population of South China

Introduction

A significant bronchodilator response is commonly defined as a 12% or greater and 200 ml or greater change in FEV₁ from baseline according to the 2005 American Thoracic Society (ATS)/European Respiratory Society (ERS) criterion. A number of studies have shown that the ATS/ERS criterion has limitations in asthma diagnosis, and some experts have argued for correcting the criteria. The aim of this study is to investigate the diagnostic value of acute bronchodilator response for asthma in a Southern Chinese population.

Methods

We prospectively evaluated 805 patients with obstructive lung disease (309 for asthma, 496 for non-asthma). Spirometry was performed according to the ATS/ERS guidelines. Data were analyzed by SPSS 18.0. The receiver-operating characteristic (ROC) curve was drawn to assess the diagnostic accuracy of the ATS/ERS criterion based on FEV₁. Linear regression was used to analyze the factors of FEV₁ change.

Results

The sensitivity and specificity of the acute bronchodilator test when judged by the ATS/ERS criteria (200 ml or higher and 12% improvement) were 68.6% and 78.2%, respectively. For the ATS/ERS criteria, the Youden Index, which comprehensively reflects the authenticity of a diagnostic test, was 46.8%. The absolute change of FEV₁ positively correlated with baseline FEV₁ and weight and negatively with age, while the percentage change of FEV₁ was negatively correlated with baseline FEV₁, age and height and positively with weight. Compared with the different diagnostic values, when ?FEV₁ was 195 ml and ?FEV_1i% was 14%, the Youden Index was the largest (48.2%) and the diagnostic capability of the test the biggest.

Conclusions

The ATS/ERS criterion for acute bronchodilator response might not be completely suitable for asthma in the Chinese population.

Trial Registration

Chinese Clinical Trial Registry (Registry ID: ChiCTR-DDT-14004976).

Funding

This work was supported by the National Natural Science Foundation of China (grant nos. 81670027, 81270080).

     

Hypoxia and hypotension in patients intubated by physician staffed helicopter emergency medical services - a prospective observational multi-centre study

Background

The effective treatment of airway compromise in trauma and non-trauma patients is important. Hypoxia and hypotension are predictors of negative patient outcomes and increased mortality, and may be important quality indicators of care provided by emergency medical services. Excluding cardiac arrests, critical trauma and non-trauma patients remain the two major groups to which helicopter emergency medical services (HEMS) are dispatched. Several studies describe the impact of pre-hospital hypoxia or hypotension on trauma patients, but few studies compare this in trauma and non-trauma patients. The primary aim was to describe the incidence of pre-hospital hypoxia and hypotension in the two groups receiving pre-hospital tracheal intubation (TI) by physician-staffed HEMS.

Methods

Data were collected prospectively over a 12-month period, using a uniform Utstein-style airway template. Twenty-one physician-staffed HEMS in Europe and Australia participated. We compared peripheral oxygen saturation and systolic blood pressure before and after definitive airway management. Data were analysed using Cochran–Mantel–Haenszel methods and mixed-effects models.

Results

Eight hundred forty three trauma patients and 422 non-trauma patients receiving pre-hospital TI were included. Non-trauma patients had significantly lower predicted mean pre-intervention SpO₂ compared to trauma patients. Post-intervention and admission SpO₂ for the two groups were comparable. However, 3% in both groups were still hypoxic at admission. For hypotension, the differences between the groups were less prominent. However, 9% of trauma and 10% of non-trauma patients were still hypotensive at admission. There was no difference in short-term survival between trauma (97%) and non-trauma patients (95%). Decreased level of consciousness was the most frequent indication for TI, and was associated with increased survival to hospital (cOR 2.8; 95% CI: 1.4–5.4).

Conclusions

Our results showed that non-trauma patients had a higher incidence of hypoxia before TI than trauma patients, but few were hypoxic at admission. The difference for hypotension was less prominent, but one in ten patients were still hypotensive at admission. Further investigations are needed to identify reversible causes that may be corrected to improve haemodynamics in the pre-hospital setting. We found high survival rates to hospital in both groups, suggesting that physician-staffed HEMS provide high-quality emergency airway management in trauma and non-trauma patients.

Trial registration

Clinicaltrials.gov Identifier: NCT01502111. Registered 22 Desember 2011.

     

Determination of functional residual capacity by oxygen washin-washout: a validation study

Objective

To validate a new system for functional residual capacity (FRC) measurements using oxygen washin/washout in spontaneously breathing humans. The system (LUFU, Drägerwerk AG, Lübeck, Germany) consists of an unmodified EVITA 4 ventilator, a side-stream paramagnetic oxygen sensor and a dedicated software.

Design

Laboratory study and measurements in spontaneously breathing volunteers.

Setting

Pulmonary function laboratory of a university hospital.

Participants

20 healthy and 15 lung diseased volunteers.

Interventions

FRC was measured by LUFU (LUFU-FRC) and by helium dilution (He-FRC); intra-thoracic gas volume (ITGV) was determined by body plethysmography. Each measurement cycle consisted of four independent LUFU-FRC determinations (step change of FiO₂ from 0.21 to 0.5 and back and from 0.21 to 1.0 and back), two helium-dilution runs and two body box measurements. Repeatability and agreement between methods were determined by comparing different measurements of one technique and by comparing different techniques among each other.

Measurements and results

Repeatability of LUFU-FRC was estimated by comparing washin to washout and the different FiO₂steps. The difference of the means was 3.7% at the most. Agreement between methods resulted in the following differences (mean?±?standard deviation of differences) for healthy and lung-diseased volunteers, respectively: LUFU-FRC vs. He-FRC –0.40?±?0.50?L (0.02?±?0.95?L), LUFU-FRC vs. ITGV –0.43?±?0.54?L (–0.18?±?0.61?L) and He-FRC vs. ITGV –0.03?±?0.43?L (–0.20?±?0.98?L).

Conclusions

LUFU is a non-invasive method for the determination of FRC that requires only minor additional equipment and no modification to the ventilator. It can be used in difficult conditions such as breathing patterns with variations from breath to breath. The results of this study show that LUFU is sufficiently reliable and repeatable to warrant its clinical application.