Effectiveness and safety of a new helmet CPAP configuration allowing tidal volume monitoring in patients with COVID-19

BACKGROUND

High generated tidal volumes (Vt) have been correlated with higher risk of self-induced lung injury and worse clinical outcome. This study aimed to evaluate the effectiveness and safety of a new helmet continuous positive airway pressure delivered (h-CPAP) configuration allowing Vt monitoring in patients affected by COVID-19.

METHODS

This prospective observational study was performed in the respiratory intermediate care unit of University Hospital in Turin, Italy, between March 24th, and June 15th, 2020. Included patients were treated with CPAP via a single-limb intentional leak configuration by a turbine-driven ventilator, provided with a dedicated patch. Effectiveness and safety of the configuration and healthcare workers safety were the outcomes of the study.

MAIN FINDINGS

Thirty-five patients were included in this study. Median age was 67 years (IQR 57-76 years), and 30 patients (85.7%) were men. Median value of overall leaks (intentional plus unintentional) was 68 L/min (IQR 63-75). Reliability of Vt measurements was 100%. An out of scale of Vt (above 50% compared to the previous values) was never recorded. Six patients (17.1%) needed more than two helmet replacements, due to leak test >10 l/min. Arm oedema and skin breakdowns were reported in sixteen (45.7%) and seven (20%) patients respectively. Among the 63 healthcare workers involved in the care of COVID-19 patients during the study only one was positive at RT-PCR nasopharyngeal swab testing.

CONCLUSIONS

The use of h-CPAP for treating COVID-19 in this configuration allowed for reliable Vt monitoring. Further studies evaluating this configuration in larger patients' cohorts are needed.

Performance of helmet CPAP using different configurations: Turbine-driven ventilators vs Venturi devices

BACKGROUND

Traditionally, Venturi-based flow generators have been preferred over mechanical ventilators to provide continuous positive airway pressure (CPAP) through the helmet (h-CPAP). Recently, modern turbine-driven ventilators (TDVs) showed to be safe and effective in delivering h-CPAP. We aimed to compare the pressure stability during h-CPAP delivered by Venturi devices and TDVs and assess the impact of High Efficiency Particulate Air (HEPA) filters on their performance.

METHODS

We performed a bench study using an artificial lung simulator set in a restrictive respiratory condition, simulating two different levels of patient effort (high and low) with and without the interposition of the HEPA filter. We calculated the average of minimal (Pmin), maximal (Pmax) and mean (Pmean) airway pressure and the time product measured on the airway pressure curve (PTPinsp). We defined the pressure swing (Pswing) as Pmax - Pmin and pressure drop (Pdrop) as End Expiratory Pressure - Pmin.

RESULTS

Pswing across CPAP levels varied widely among all the tested devices. During "low effort", no difference in Pswing and Pdrop was found between Venturi devices and TDVs; during high effort, Pswing (p<0.001) and Pdrop (p<0.001) were significantly higher in TDVs compared to Venturi devices, but the PTPinsp was lower (1.50 SD 0.54 vs 1.67 SD 0.55, p<0.001). HEPA filter addition almost doubled Pswing and PTPinsp (p<0.001) but left unaltered the differences among Venturi and TDVs systems in favor of the latter (p<0.001).

CONCLUSIONS

TDVs performed better than Venturi systems in delivering a stable positive pressure level during h-CPAP in a bench setting.

Use of Helmet CPAP in COVID-19 - A practical review

Helmet CPAP (H-CPAP) has been recommended in many guidelines as a noninvasive respiratory support during COVID-19 pandemic in many countries around the world. It has the least amount of particle dispersion and air contamination among all noninvasive devices and may mitigate the ICU bed shortage during a COVID surge as well as a decreased need for intubation/mechanical ventilation. It can be attached to many oxygen delivery sources. The MaxVenturi setup is preferred as it allows for natural humidification, low noise burden, and easy transition to HFNC during breaks and it is the recommended transport set-up. The patients can safely be proned with the helmet. It can also be used to wean the patients from invasive mechanical ventilation. Our article reviews in depth the pathophysiology of COVID-19 ARDS, provides rationale of using H-CPAP, suggests a respiratory failure algorithm, guides through its setup and discusses the issues and concerns around using it.

Rationale and evidence on the use of tocilizumab in COVID-19: a systematic review

BACKGROUND

Tocilizumab is an IL-6 receptor-blocking agent proposed for the treatment of severe COVID-19. The aim of this systematic review was to describe the rationale for the use of tocilizumab for the treatment of COVID-19 and to summarize the available evidence regarding its efficacy and safety.

METHODS

MEDLINE, PubMed, EMBASE, pre-print repositories (bioRxiv and medRxiv) and two trial Registries were searched for studies on the use of tocilizumab in COVID-19 or SARS-CoV-2 infection, viral pneumonia, and/or sepsis until 20th June 2020.

RESULTS

We identified 3 indirect pre-clinical studies and 28 clinical studies including 5776 patients with COVID-19 (13 with a comparison group, 15 single-arm). To date, no randomized trials have been published. We retrieved no studies at low risk of bias. Forty-five ongoing studies were retrieved from trial registries.

CONCLUSIONS

There is insufficient evidence regarding the clinical efficacy and safety of tocilizumab in patients with COVID-19. Its use should be considered experimental, requiring ethical approval and clinical trial oversight.

Effect of Intraoperative High Positive End-Expiratory Pressure (PEEP) With Recruitment Maneuvers vs Low PEEP on Postoperative Pulmonary Complications in Obese Patients: A Randomized Clinical Trial

IMPORTANCE

An intraoperative higher level of positive end-expiratory positive pressure (PEEP) with alveolar recruitment maneuvers improves respiratory function in obese patients undergoing surgery, but the effect on clinical outcomes is uncertain.

OBJECTIVE

To determine whether a higher level of PEEP with alveolar recruitment maneuvers decreases postoperative pulmonary complications in obese patients undergoing surgery compared with a lower level of PEEP.

DESIGN, SETTING, AND PARTICIPANTS

Randomized clinical trial of 2013 adults with body mass indices of 35 or greater and substantial risk for postoperative pulmonary complications who were undergoing noncardiac, nonneurological surgery under general anesthesia. The trial was conducted at 77 sites in 23 countries from July 2014-February 2018; final follow-up: May 2018.

INTERVENTIONS

Patients were randomized to the high level of PEEP group (n = 989), consisting of a PEEP level of 12 cm H2O with alveolar recruitment maneuvers (a stepwise increase of tidal volume and eventually PEEP) or to the low level of PEEP group (n = 987), consisting of a PEEP level of 4 cm H2O. All patients received volume-controlled ventilation with a tidal volume of 7 mL/kg of predicted body weight.

MAIN OUTCOMES AND MEASURES

The primary outcome was a composite of pulmonary complications within the first 5 postoperative days, including respiratory failure, acute respiratory distress syndrome, bronchospasm, new pulmonary infiltrates, pulmonary infection, aspiration pneumonitis, pleural effusion, atelectasis, cardiopulmonary edema, and pneumothorax. Among the 9 prespecified secondary outcomes, 3 were intraoperative complications, including hypoxemia (oxygen desaturation with Spo2 ≤92% for >1 minute).

RESULTS

Among 2013 adults who were randomized, 1976 (98.2%) completed the trial (mean age, 48.8 years; 1381 [69.9%] women; 1778 [90.1%] underwent abdominal operations). In the intention-to-treat analysis, the primary outcome occurred in 211 of 989 patients (21.3%) in the high level of PEEP group compared with 233 of 987 patients (23.6%) in the low level of PEEP group (difference, -2.3% [95% CI, -5.9% to 1.4%]; risk ratio, 0.93 [95% CI, 0.83 to 1.04]; P = .23). Among the 9 prespecified secondary outcomes, 6 were not significantly different between the high and low level of PEEP groups, and 3 were significantly different, including fewer patients with hypoxemia (5.0% in the high level of PEEP group vs 13.6% in the low level of PEEP group; difference, -8.6% [95% CI, -11.1% to 6.1%]; P < .001).

CONCLUSIONS AND RELEVANCE

Among obese patients undergoing surgery under general anesthesia, an intraoperative mechanical ventilation strategy with a higher level of PEEP and alveolar recruitment maneuvers, compared with a strategy with a lower level of PEEP, did not reduce postoperative pulmonary complications.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02148692.

Protective ventilation with high versus low positive end-expiratory pressure during one-lung ventilation for thoracic surgery (PROTHOR): study protocol for a randomized controlled trial

BACKGROUND

Postoperative pulmonary complications (PPC) may result in longer duration of in-hospital stay and even mortality. Both thoracic surgery and intraoperative mechanical ventilation settings add considerably to the risk of PPC. It is unclear if one-lung ventilation (OLV) for thoracic surgery with a strategy of intraoperative high positive end-expiratory pressure (PEEP) and recruitment maneuvers (RM) reduces PPC, compared to low PEEP without RM.

METHODS

PROTHOR is an international, multicenter, randomized, controlled, assessor-blinded, two-arm trial initiated by investigators of the PROtective VEntilation NETwork. In total, 2378 patients will be randomly assigned to one of two different intraoperative mechanical ventilation strategies. Investigators screen patients aged 18 years or older, scheduled for open thoracic or video-assisted thoracoscopic surgery under general anesthesia requiring OLV, with a maximal body mass index of 35 kg/m2, and a planned duration of surgery of more than 60 min. Further, the expected duration of OLV shall be longer than two-lung ventilation, and lung separation is planned with a double lumen tube. Patients will be randomly assigned to PEEP of 10 cmH2O with lung RM, or PEEP of 5 cmH2O without RM. During two-lung ventilation tidal volume is set at 7 mL/kg predicted body weight and, during OLV, it will be decreased to 5 mL/kg. The occurrence of PPC will be recorded as a collapsed composite of single adverse pulmonary events and represents the primary endpoint.

DISCUSSION

PROTHOR is the first randomized controlled trial in patients undergoing thoracic surgery with OLV that is adequately powered to compare the effects of intraoperative high PEEP with RM versus low PEEP without RM on PPC. The results of the PROTHOR trial will support anesthesiologists in their decision to set intraoperative PEEP during protective ventilation for OLV in thoracic surgery.

TRIAL REGISTRATION

The trial was registered in clinicaltrials.gov ( NCT02963025 ) on 15 November 2016.

Association between night-time surgery and occurrence of intraoperative adverse events and postoperative pulmonary complications

BACKGROUND

The aim of this post hoc analysis of a large cohort study was to evaluate the association between night-time surgery and the occurrence of intraoperative adverse events (AEs) and postoperative pulmonary complications (PPCs).

METHODS

LAS VEGAS (Local Assessment of Ventilatory Management During General Anesthesia for Surgery) was a prospective international 1-week study that enrolled adult patients undergoing surgical procedures with general anaesthesia and mechanical ventilation in 146 hospitals across 29 countries. Surgeries were defined as occurring during 'daytime' when induction of anaesthesia was between 8:00 AM and 7:59 PM, and as 'night-time' when induction was between 8:00 PM and 7:59 AM.

RESULTS

Of 9861 included patients, 555 (5.6%) underwent surgery during night-time. The proportion of patients who developed intraoperative AEs was higher during night-time surgery in unmatched (43.6% vs 34.1%; P<0.001) and propensity-matched analyses (43.7% vs 36.8%; P=0.029). PPCs also occurred more often in patients who underwent night-time surgery (14% vs 10%; P=0.004) in an unmatched cohort analysis, although not in a propensity-matched analysis (13.8% vs 11.8%; P=0.39). In a multivariable regression model, including patient characteristics and types of surgery and anaesthesia, night-time surgery was independently associated with a higher incidence of intraoperative AEs (odds ratio: 1.44; 95% confidence interval: 1.09-1.90; P=0.01), but not with a higher incidence of PPCs (odds ratio: 1.32; 95% confidence interval: 0.89-1.90; P=0.15).

CONCLUSIONS

Intraoperative adverse events and postoperative pulmonary complications occurred more often in patients undergoing night-time surgery. Imbalances in patients' clinical characteristics, types of surgery, and intraoperative management at night-time partially explained the higher incidence of postoperative pulmonary complications, but not the higher incidence of adverse events.

CLINICAL TRIAL REGISTRATION

NCT01601223.

Ten important articles on noninvasive ventilation in critically ill patients and insights for the future: A report of expert opinions

Background

Noninvasive ventilation is used worldwide in many settings. Its effectiveness has been proven for common clinical conditions in critical care such as cardiogenic pulmonary edema and chronic obstructive pulmonary disease exacerbations.

Since the first pioneering studies of noninvasive ventilation in critical care in the late 1980s, thousands of studies and articles have been published on this topic. Interestingly, some aspects remain controversial (e.g. its use in de-novo hypoxemic respiratory failure, role of sedation, self-induced lung injury). Moreover, the role of NIV has recently been questioned and reconsidered in light of the recent reports of new techniques such as high-flow oxygen nasal therapy.

Methods

We conducted a survey among leading experts on NIV aiming to 1) identify a selection of 10 important articles on NIV in the critical care setting 2) summarize the reasons for the selection of each study 3) offer insights on the future for both clinical application and research on NIV.

Results

The experts selected articles over a span of 26 years, more clustered in the last 15 years. The most voted article studied the role of NIV in acute exacerbation chronic pulmonary disease. Concerning the future of clinical applications for and research on NIV, most of the experts forecast the development of innovative new interfaces more adaptable to patients characteristics, the need for good well-designed large randomized controlled trials of NIV in acute “de novo” hypoxemic respiratory failure (including its comparison with high-flow oxygen nasal therapy) and the development of software-based NIV settings to enhance patient-ventilator synchrony.

Conclusions

The selection made by the experts suggests that some applications of NIV in critical care are supported by solid data (e.g. COPD exacerbation) while others are still waiting for confirmation. Moreover, the identified insights for the future would lead to improved clinical effectiveness, new comparisons and evaluation of its role in still “lack of full evidence” clinical settings.

Electronic supplementary material

The online version of this article (10.1186/s12871-017-0409-0) contains supplementary material, which is available to authorized users.

Noninvasive ventilation in chest trauma: systematic review and meta-analysis

PURPOSE

Single studies of Noninvasive Ventilation (NIV) in the management of acute respiratory failure in chest trauma patients have produced controversial findings. The aim of this study is to critically review the literature to investigate whether NIV reduces mortality, intubation rate, length of stay and complications in patients with chest trauma, compared to standard therapy.

METHODS

We performed a systematic review and meta-analysis of randomized controlled trials, prospective and retrospective observational studies, by searching PubMed, EMBASE and bibliographies of articles retrieved. We screened for relevance studies that enrolled adults with chest trauma who developed mild to severe acute respiratory failure and were treated with NIV. We included studies reporting at least one clinical outcome of interest to perform a meta-analysis.

RESULTS

Ten studies (368 patients) met the inclusion criteria and were included for the meta-analysis. Five studies (219 patients) reported mortality and results were quite homogeneous across studies, with a summary relative risk for patients treated with NIV compared with standard care (oxygen therapy and invasive mechanical ventilation) of 0.26 (95 % confidence interval 0.09-0.71, p = 0.003). There was no advantage in mortality of continuous positive airway pressure over noninvasive pressure support ventilation. NIV significantly increased arterial oxygenation and was associated with a significant reduction in intubation rate, in the incidence of overall complications and infections.

CONCLUSIONS

These results suggest that NIV could be useful in the management of acute respiratory failure due to chest trauma.

Recommendations for anesthesia and perioperative management of patients with neuromuscular disorders

Patients with neuromuscular disorders are at high risk of intraoperative and postoperative complications. General anesthesia in these patients may exacerbate respiratory and cardiovascular failure due to a marked sensitivity to several anesthetic drugs. Moreover, succinylcholine and halogenated agents can trigger life-threatening reactions, such as malignant hyperthermia, rhabdomyolysis and severe hyperkalemia. Therefore, regional anesthesia should be used whenever possible. If general anesthesia is unavoidable, special precautions must be taken. In particular, for patients at increased risk of respiratory complications (i.e., postoperative atelectasis, acute respiratory failure, nosocomial infections), noninvasive ventilation associated with aggressive airway clearance techniques can successfully treat upper airway obstruction, hypoventilation and airway secretion retention, avoiding prolonged intubation and tracheotomy. Anesthesia and perioperative management of patients with neuromuscular disorders are described in this article. To grade the strength of recommendations and the quality of evidence we adopted the GRADE approach. In case of low-quality evidence, these recommendations represent the collective opinion of the expert panel.

Gaze-controlled, computer-assisted communication in Intensive Care Unit: "speaking through the eyes"

BACKGROUND

The aim of this study was to test the hypothesis that a gaze-controlled communication system (eye tracker, ET) can improve communication processes between completely dysarthric ICU patients and the hospital staff, in three main domains: 1) basic communication processes (i.e., fundamental needs, desire, and wishes); 2) the ability of the medical staff to understand the clinical condition of the patient; and 3) the level of frustration experienced by patient, nurses and physicians.

METHODS

Fifteen fully conscious medical and surgical patients, 8 physicians, and 15 nurses were included in the study. The experimental procedure was composed by three phases: in phase 1 all groups completed the preintervention questionnaire; in phase 2 the ET was introduced and tested as a communication device; in phase 3 all groups completed the postintervention questionnaire.

RESULTS

Patients preintervention questionnaires showed remarkable communication deficits, without any group effect. Answers of physicians and nurses were pretty much similar to the one of patients. Postintervention questionnaires showed in all groups a remarkable and statistically significant improvement in different communication domains, as well as a remarkable decrease of anxiety and disphoric thought. Improvement was also reported by physicians and nurses in their ability to understand patient's clinical conditions.

CONCLUSION

Our results show an improvement in the quality of the examined parameters. Better communication processes seem also to lead to improvements in several psychological parameters, namely anxiety and drop-out depression perceived by both patients and medical staff. Further controlled studies are needed to define the ET role in ICU.

Non-invasive ventilation in postoperative patients: a systematic review

BACKGROUND

Postoperative pulmonary complications, generally defined as any pulmonary abnormality occurring in the postoperative period, are still a significant issue in clinical practice increasing hospital length of stay, morbidity and mortality. Non-invasive ventilation (NIV), primarily applied in cardiogenic pulmonary edema, decompensated COPD and hypoxemic pulmonary failure, is nowadays also used in perioperative settings.

OBJECTIVE

Investigate the application and results of preventive and therapeutic NIV in postsurgical patients.

DESIGN

A systematic review.

DATA SOURCES

Medical literature databases were searched for articles about "clinical trials," "randomized controlled trials" and "meta-analyses." The keywords "cardiac surgery," "thoracic surgery," "lung surgery," "abdominal surgery," "solid organ transplantation," "thoraco-abdominal surgery" and "bariatric surgery" were combined with any of these: "non-invasive positive pressure ventilation," "continuous positive airway pressure," "bilevel ventilation," "postoperative complications," "postoperative care," "respiratory care," "acute respiratory failure," "acute lung injury" and "acute respiratory distress syndrome."

RESULTS

Twenty-nine articles (N=2,279 patients) met the inclusion criteria. Nine studies evaluated NIV in post-abdominal surgery, three in thoracic surgery, eight in cardiac surgery, three in thoraco-abdominal surgery, four in bariatric surgery and two in post solid organ transplantation used both for prophylactic and therapeutic purposes. NIV improved arterial blood gases in 15 of the 22 prophylactic and in 4 of the 7 therapeutic studies, respectively. NIV reduced the intubation rate in 11 of the 29 studies and improved outcome in only 1.

CONCLUSIONS

Despite these limited data and the necessity of new randomized trials, NIV could be considered as a prophylactic and therapeutic tool to improve gas exchange in postoperative patients.

Non-invasive ventilation in pediatric intensive care

The aims of this paper are: to examine the physiological rationale for noninvasive respiratory support (NRS) in children with acute respiratory failure (ARF); to review clinical available data and to give some practical recommendations to its safe application. NRS is the delivery of ventilatory support without the need of an invasive airway. Two types of NRS are commonly used in the pediatric population: non-invasive continuous positive airway pressure (nCPAP) and non-invasive positive pressure ventilation (nPPV). In general, the evidence to promote the use of NRS in children with ARF is scarce. However, two randomized studies have been recently published suggesting that nPPV ameliorates clinical signs and gas exchange while reducing the need for endotracheal intubation. Moreover, nCPAP and heliox may improve clinical scores and CO2 washout in infants with severe bronchiolitis, without major complications. Data from non controlled studies show that NRS unloads the respiratory muscles and that the helmet can be a valid alternative to facial and/or nasal mask when nCPAP is administered to children in the early stage of ARF.

Clonidine in perioperative medicine and intensive care unit: more than an anti-hypertensive drug

Clonidine is classified as an imidazoline and it is the prototypical alpha-2 receptor agonists. It has been used for several years to treat hypertension. It has also been used, "off label", for a variety of purposes, including opioid and anesthetic sparing effects, anxiolysis and sedation, drug withdrawal as well as stabilizing blood pressure and reducing stress response to surgery. Particularly in the case of patients with overt or underlying cardiac disease and in those at risk of perioperative ischemia the action of clonidine can be expected to reduce the risk of procedure-related cardiac events. In addition, clonidine used as a premedication drug before surgery or surgical procedure, has been shown to substantially reduce anaesthetic, benzodiazepine and opioids requirements. However, its "off label" use, the absence of an intravenous form of in the United States, possible inadvertent hypotension, bradycardia or post-operative sedation, and the variability of the haemodynamic response to different doses or rates of administration, have limited its use in clinical practice. This review discusses the potential role of clonidine and the supporting evidence for the use of this drug beyond its anti-hypertensive use in perioperative medicine and critical care in adults patients.

Understanding international differences in terminology for delirium and other types of acute brain dysfunction in critically ill patients

BACKGROUND

Delirium (acute brain dysfunction) is a potentially life threatening disturbance in brain function that frequently occurs in critically ill patients. While this area of brain dysfunction in critical care is rapidly advancing, striking limitations in use of terminology related to delirium internationally are hindering cross-talk and collaborative research. In the English literature, synonyms of delirium such as the Intensive Care Unit syndrome, acute brain dysfunction, acute brain failure, psychosis, confusion, and encephalopathy are widely used. This often leads to scientific "confusion" regarding published data and methodology within studies, which is further exacerbated by organizational, cultural and language barriers.

OBJECTIVE

We undertook this multinational effort to identify conflicts in terminology and phenomenology of delirium to facilitate communication across medical disciplines and languages.

METHODS

The evaluation of the terminology used for acute brain dysfunction was determined conducting communications with 24 authors from academic communities throughout countries/regions that speak the 13 variants of the Romanic languages included into this manuscript.

RESULTS

In the 13 languages utilizing Romanic characters, included in this report, we identified the following terms used to define major types of acute brain dysfunction: coma, delirium, delirio, delirium tremens, délire, confusion mentale, delir, delier, Durchgangs-Syndrom, acute verwardheid, intensiv-psykose, IVA-psykos, IVA-syndrom, akutt konfusion/forvirring. Interestingly two terms are very consistent: 100 % of the selected languages use the term coma or koma to describe patients unresponsive to verbal and/or physical stimuli, and 100% use delirium tremens to define delirium due to alcohol withdrawal. Conversely, only 54% use the term delirium to indicate the disorder as defined by the DSM-IV as an acute change in mental status, inattention, disorganized thinking and altered level of consciousness.

CONCLUSIONS

Attempts towards standardization in terminology, or at least awareness of differences across languages and specialties, will help cross-talk among clinicians and researchers.

A chart of failure risk for noninvasive ventilation in patients with COPD exacerbation

Knowing the likelihood of failure of noninvasive positive pressure ventilation (NPPV) in patients with exacerbation of chronic obstructive pulmonary disease (COPD) could indicate the best choice between NPPV and endotracheal intubation instituted earlier. For this purpose, two risk charts were designed (at admission and after 2 h of NPPV) that included all relevant measurable clinical prognostic indicators derived from a population representing the patients seen routinely in clinical practice. Risk stratification of NPPV failure was assessed in 1,033 consecutive patients admitted to experienced hospital units, including two intensive care units, six respiratory intermediate care units, and five general wards. NPPV was successful in 797 patients. Patients with a Glasgow Coma Score <11, acute physiology and chronic health evaluation (APACHE) II > or =29, respiratory rate > or =30 breaths x min(-1) and pH at admission <7.25 have a predicted risk of failure >70%. A pH <7.25 after 2 h greatly increases the risk (>90%). The risk charts were validated on an independent group of 145 consecutive COPD patients treated with NPPV due to an acute ventilatory failure episode. To identify patients with a probability of failure >50%, the sensitivity and specificity were 33% and 96.7% on admission and 52.9% and 94.1% after 2 h of NPPV, respectively. The prediction chart, based on data from the current study, can function as a simple tool to predict the risk of failure of noninvasive positive pressure ventilation and thus improve clinical management of patients tailoring medical intervention.

Translaryngeal open ventilation to treat acute respiratory failure in acute exacerbation of chronic obstructive pulmonary disease. A preliminary report

PURPOSE

To describe a minimally invasive alternative to conventional mechanical ventilation, using a small size uncuffed nasotracheal tube (translaryngeal open ventilation) paired with pressure control ventilation, in acute respiratory failure complicating chronic obstructive pulmonary disease (COPD).

CLINICAL FEATURES

Two cooperative COPD patients, who failed noninvasive mechanical ventilation, were intubated nasotracheally. Mechanical ventilation was initiated in pressure control mode via an uncuffed 6 mm tube.

RESULTS

Respiratory rate improved after 1 hour (from 44 to 28 breaths*min(-1) in case 1 and from 32 to 25 breaths*min(-1) in case 2); PaC0(2) decreased (from 120 to 62 mmHg in case 1 and from 69 to 51 mmHg in case 2); with pressure control mode levels of 45 cm H(2)O and 55 cm H(2)O respectively. PaO(2) increased from 40 mmHg (with FIO(2) 0.3) to 55 mmHg (with FIO(2) 0.3) in the first patient and from 55 mmHg (with FIO(2) 0.4) to 60 mmHg (with FIO(2) 0.4 ) in the second patient; pH improved from 7.18 to 7.31 in case 1 and from 7.22 to 7.39 in case 2. Patients were able to trigger the ventilator, speak, swallow and to clear secretions spontaneously. Both patients were ventilated for three days in this manner without any adverse effects. Both survived and were discharged home after 20 and 18 days in hospital respectively.

CONCLUSION

This very preliminary report suggests that, in carefully selected patients who fail mask ventilation, mechanical support with translaryngeal open ventilation can improve gas exchange, breathing pattern and tachypnea, without hindering glottic function.

Predictors of failure of noninvasive positive pressure ventilation in patients with acute hypoxemic respiratory failure: a multi-center study

CONTEXT

In patients with hypoxemic acute respiratory failure (ARF), randomized studies have shown noninvasive positive pressure ventilation (NPPV) to be associated with lower rates of endotracheal intubation. In these patients, predictors of NPPV failure are not well characterized.

OBJECTIVE

To investigate variables predictive of NPPV failure in patients with hypoxemic ARF.

DESIGN

Prospective, multicenter cohort study.

SETTING

Eight Intensive Care Units (ICU) in Europe and USA.

PATIENTS

Of 5,847 patients admitted between October 1996 and December 1998, 2,770 met criteria for hypoxemic ARF. Of these, 2,416 were already intubated and 354 were eligible for the study.

RESULTS

NPPV failed in 30% (108/354) of patients. The highest intubation rate was observed in patients with ARDS (51%) or community-acquired pneumonia (50%). The lowest intubation rate was observed in patients with cardiogenic pulmonary edema (10%) and pulmonary contusion (18%). Multivariate analysis identified age > 40 years (OR 1.72, 95% CI 0.92-3.23), a simplified acute physiologic score (SAPS II) > or = 35 (OR 1.81, 95% CI 1.07-3.06), the presence of ARDS or community-acquired pneumonia (OR 3.75, 95% CI 2.25-6.24), and a PaO2:FiO2 < or = 146 after 1 h of NPPV (OR 2.51, 95% CI 1.45-4.35) as factors independently associated with failure of NPPV. Patients requiring intubation had a longer duration of ICU stay ( P < 0.001), higher rates of ventilator-associated pneumonia and septic complications ( P < 0.001), and a higher ICU mortality ( P < 0.001).

CONCLUSIONS

In hypoxemic ARF, NPPV can be successful in selected populations. When patients have a higher severity score, an older age, ARDS or pneumonia, or fail to improve after 1 h of treatment, the risk of failure is higher.

Physiologic evaluation of noninvasive mechanical ventilation delivered with three types of masks in patients with chronic hypercapnic respiratory failure

OBJECTIVE

The efficacy of noninvasive mechanical ventilation (NIMV) in improving breathing pattern and arterial blood gases (ABG) in hypercapnic patients has been well documented; however, little attention has been given to the choice of the interface and the ventilatory mode. We evaluated the effects of three types of masks and two modes of ventilation on patients' ABG, breathing pattern, and tolerance to ventilation.

DESIGN

Prospective randomized study.

SETTING

Two respiratory weaning centers.

PATIENTS

A total of 26 stable hypercapnic patients (pH, 7.38 +/- 0.04; PaCO2, 59.2. +/- 10.9 torr) had not received NIMV and were affected by restrictive thoracic disease or obstructive pulmonary disease.

INTERVENTIONS

Three 30-min runs of NIMV, delivered using volume-assisted (n = 13) or pressure-assisted modes of partial mechanical support (n = 13), were performed in random order with a full-face mask, a nasal mask, and nasal plugs.

MEASUREMENTS

ABG, breathing pattern, and patients' tolerance to ventilation.

MAIN RESULTS

Compared with spontaneous breathing, the application of NIMV significantly improved ABG and minute ventilation, irrespective of the ventilatory mode, the underlying pathology or the type of mask. Overall, a nasal mask was better tolerated than the other two interfaces (p < .005 vs. nasal plugs and full-face mask). PaCO2 was significantly lower (p < .01) with a full-face mask or nasal plugs than with a nasal mask (49.5 +/- 9.4 torr, 49.7 +/- 8 torr, and 52.4 +/- 11 torr, respectively). Minute ventilation was significantly higher with a full-face mask than with a nasal mask because of an increase in tidal volume. No differences were observed in tolerance to ventilation, ABG, or breathing pattern, using assist control or pressure-assisted modes.

CONCLUSIONS

In this physiologic study, we have shown that in patients with hypercapnic respiratory failure, irrespective of the underlying pathology, the type of interface affects the NIMV outcome more than the ventilatory mode.

Effects of predeposit and intentional perioperative haemodilution on blood saving program in major orthopaedic surgery

In this study we evaluated the effects of predeposit and intentional perioperative haemodilution on a blood saving program in major orthopaedic surgery. We demonstrated that autologous blood phlebotomy and maintenance of optimal levels of perioperative haemodilution by delaying blood transfusion, even autologous, are efficient techniques in reducing homologous, red blood cell (HRBC) transfusion. Patients who received autologous red blood cell (ARBC) or HRBC more than one day after surgery, while having Hb values <8 g/dl, are less at risk of needing the first or additional HRBCs. In conclusion, predeposit and intentional haemodilution obtained by delaying blood transfusions, even autotransfusional, is a correct way of conducting a blood saving program (BSP) in major orthopaedic surgery. These techniques are clinically effective in avoiding or reducing HRBC transfusion.

Patient-ventilator asynchrony during noninvasive ventilation: the role of expiratory trigger

OBJECTIVE

Air leaks around the mask are very likely to occur during noninvasive ventilation, in particular when prolonged ventilatory treatment is required. It has been suggested that leaks from the mask may impair the expiratory trigger cycling mechanism when inspiratory pressure support ventilation (PSV) is used. The aim of this study was to compare the short-term effect of two different expiratory cycling mechanisms (time-cycled vs flow-cycled) during noninvasive inspiratory pressure support ventilation (NIPSV) on patient-ventilator synchronisation in severe hypoxemic respiratory failure.

STUDY POPULATION

Six patients with acute lung injury (ALI) due to acquired immunodeficiency syndrome (AIDS)-related opportunistic pneumonia were enrolled in the protocol.

INTERVENTION

Each subject was first studied during spontaneous breathing with a Venturi oxygen mask (SB) and successively submitted to a randomly assigned 20' conventional flow-cycling (NIPSVfc) or time-cycling inspiratory pressure support ventilation (NIPSVtc). The pre-set parameters were: inspiratory pressure of 10 cm H2O, PEEP of 5 cm H2O for the same inspired oxygen fraction as during SB. A tight fit of the mask was avoided in order to facilitate air leaks around the mask. The esophageal pressure time product (PTPes) and tidal swings (delta Pes) were measured to evaluate the patient's respiratory effort. A subjective "comfort score" and the difference between patient and machine respiratory rate [delta RR(p-v)], calculated on esophageal and airway pressure curves, were used as indices of patient-machine interaction.

RESULTS

Air leaks through the mask occurred in five out of six patients. The values of PEEPi (< 1.9 cm H2O) excluded significant expiratory muscle activity. NIPSVtc significantly reduced PTPes, delta Pes, and delta RR(p-v) when compared to NIPS-Vfc [230 +/- 41 (SE) vs 376 +/- 72 cm H2O.s.min-1; 8 +/- 2 vs 13 +/- 2 cm H2O; 1 +/- 1 vs 9 +/- 2 br.min-1; respectively] with a concomitant significant improvement of the "comfort score".

CONCLUSIONS

In the presence of air leaks a time-cycled expiratory trigger provides a better patient-machine interaction than a flow-cycled expiratory trigger during NIPSV.

Noninvasive positive pressure ventilation in trauma patients with acute respiratory failure

The effectiveness of noninvasive pressure support ventilation (NIPSV) in treating trauma patients with acute respiratory failure (ARF) was evaluated in a retrospective clinical study. Forty-six conscious patients with ARF admitted to the general intensive care units (ICUs) of three hospitals between July 1988 and July 1991 were surveyed. Patients received NIPSV after a period of spontaneous breathing with supplemental oxygen. Blood gas levels and respiratory parameters were measured before the application of the mask and after 1, 6 and 12 h of NIPSV. Thirty-three (72%) patients were successfully weaned to spontaneous breathing (success group). Nine patients with hypercapnia and four with hypoxaemic respiratory failure failed to respond to prolonged mask ventilation and were intubated (failure group). Of the 13 patients who failed NIPSV, nine died after switching to invasive ventilation after a mean time of 10 +/- 3 days. No deaths occurred during NIPSV. A mean pressure support ventilation (PSV) of 11.7 +/- 4.2 cmH2O and positive end-expiratory pressure (PEEP) of 4.5 +/- 2.7 cmH2O were required to significantly increase arterial oxygen tension (Pa,O2)/inspiratory oxygen fraction (Fi,O2) from 152.4 +/- 41.7 (spontaneous breathing) to 277.9 +/- 108.7 (NIPSV) (p < 0.01) within the first hour. The expiratory tidal volume (VT) increased from 356.1 +/- 103.7 (spontaneous breathing) to 648.1 +/- 77.1 mL (NIPSV) (p < 0.01) with a concomitant reduction in the respiratory frequency (fR) from 31.4 +/- 5.2 (spontaneous breathing) to 20.4 +/- 4.3 (NIPSV) without significant differences between the success and failure group. In the 22 patients who were hypercapnic at the point of entering the study, the arterial carbon dioxide tension (Pa,CO2) decreased from 73.0 +/- 1.0 kPa (52.5 +/- 7.8 mmHg) (spontaneous breathing) to 5.5 +/- 1.0 kPa (41.5 +/- 7.5 mmHg) (NIPSV) (p < 0.01) and pH increased from 7.29 +/- 0.05 to 7.33 +/- 0.04 (p < 0.05). The median length of time of use of NIPSV was 55.5 h (range 6-144). In conclusion, noninvasive pressure support ventilation might effectively be used in a selected group of trauma patients as a means of treating respiratory failure.

Physiologic evaluation of non-invasive pressure support ventilation in trauma patients with acute respiratory failure

OBJECTIVE

To investigate the effectiveness of noninvasive (face mask) versus invasive (endotracheal tube) equal pressure values on blood gases and respiratory pattern and to evaluate the feasibility of using mask ventilation after the short term physiologic study.

DESIGN

Open, prospective, physiologic study and uncontrolled clinical study.

SETTING

Intensive care unit of a trauma center.

PATIENTS

22 intubated trauma patients were studied.

INTERVENTIONS

Patients were intubated and ventilated in a pressure support mode (IPSV) of 13.5 +/- 1.5 cmH2O and a post end-expiratory pressure (PEEP) of 5.8 +/- 2.57 cmH2O. After a T-piece trial to assess patient's ability to breath spontaneously, patients were switched over to noninvasive pressure support (NIPSV). The pressure levels were set as during IPSV. Blood gases and respiratory parameters were measured during IPSV, during the T-piece trial, and after 1 h of NIPSV. After the physiologic study, all patients were asked if they wished to continue on NIPSV. The patient's subjective compliance with IPSV and NIPSV was measured by means of an arbitrary score. A successful outcome was defined as no need for reintubation.

MEASUREMENTS AND RESULTS

IPSVand NIPSV showed no statistical differences for blood gas and respiratory parameters by using the same values of PSV (13 +/- 5 vs 12.8 +/- 1.7 cmH2O, NS) and PEEP (5.8 +/- 2.5 and 5.2 +/- 2.2 cmH2O NS). The median length of time on NIPSV was 47 h (range 6 to 144). All patients wished to continue on NIPSV, but 9 patients (40.9%) were reintubated after 54 +/- 54 h. Six of them died after 36 +/- 13 days while still on mechanical ventilation. There was no statistically significant difference in compliance score between IPSVand NIPSV.

CONCLUSIONS

NIPSV is comparable to IPSV in terms of blood gases and respiratory pattern. The clinical uncontrolled study indicates that NIPSV could be used in selected trauma patients.

Pressure control ventilation and minitracheotomy in treating severe flail chest trauma

OBJECTIVE

To evaluate pressure control ventilation (PCV) delivered through a minitracheotomy in treating severe flail chest trauma.

DESIGN

Case report.

SETTING

Intensive care unit of a trauma center.

PATIENT

A 34-year-old woman affected by flail chest trauma and acute respiratory failure, who was initially treated with tracheal intubation to obtain internal pneumatic stabilization. The patient failed extubation and noninvasive mask treatment (pressure support ventilation plus PEEP) due to poor chestwall mechanics.

INTERVENTIONS

Minitracheotomy was performed and ventilation was achieved with high levels of inspiratory pressure (PCV or assisted PCV) to overcome the resistance of the cannula (Mini-Trach II, Portex, ID 4 mm). Esophageal and carinal pressures were monitored. Ventilatory treatment was always performed with the full cooperation of the patient; the patient's glottic function was always intact. The patient was successfully treated with pressure control ventilation delivered through the Mini-Trach. After 7 days of PCV, the patient was switched to assisted PCV. On the 20th day after admission, she was weaned from mechanical ventilation.

CONCLUSIONS

We conclude that a suitable gas exchange and pneumatic stabilization in a flail chest condition can be achieved using minitracheostomic ventilation. At the same time, this treatment could reduce some side effects of traditional tracheal intubation.

Monitoring propofol serum levels by rapid and sensitive reversed-phase high-performance liquid chromatography during prolonged sedation in ICU patients

A quick and sensitive reversed-phase high-performance liquid chromatography (HPLC) method has been developed in order to determine the concentration of Propofol (2,6 diisopropylphenol) in human serum. Propofol can be isolated from serum by adding 0.5 mL precipitating solution. This consists of an acetonitrile and perchloric acid (67:33, v/v) mixture, which also contains dibutylphthalate (2 mg/100 mL) as internal standard. The sample is then mixed for 1 min on a vortex-mixer. The endogenous serum substances precipitated by acetonitrile and perchloric acid are further separated by centrifugation. The supernatant is directly injected into the HPLC system. A 250- x 4.6-mm column, packed with 10-microns Spherisorb reversed-phase octadecylsilane particles (C18), is used for chromatographic separation. The mobile phase consists of an acetonitrile-water mixture (67:33 ratio) with 0.4 mL acetic acid (pH 4). Propofol is monitored by a UV-visible detector at 270 nm and 0.1-0.002 absorbance units full scale (AUFS). The detection limit of Propofol (in human serum) is 0.1 mg/L for a 20-microL injection volume. The time of the assay is less than 20 min, including sample preparation.