Noninvasive Positive-Pressure Ventilation To Treat Hypercapnic Coma Secondary to Respiratory Failure

High-Flow Nasal Oxygen in Patients with Acute Hypercapnic Respiratory Failure: A Narrative Review of the Physiological Rationale and Clinical Evidence

Acute hypercapnic respiratory failure is a life-threatening condition caused by alveolar hypoventilation. It is mostly caused by an acute exacerbation of chronic obstructive pulmonary disease or conditions yielding muscle dysfunction. Noninvasive ventilation through a facemask is the cornerstone first-line strategy to support hypercapnic patients with acidemia, and current guidelines strongly recommend this intervention to improve survival and long-term clinical outcomes. Because of its benefits related to carbon dioxide washout from the upper airways and the enhanced comfort, high-flow nasal oxygen has been proposed as a respiratory support strategy in patients with hypercapnic respiratory failure, both as an alternative to and in combination with noninvasive ventilation. When compared to noninvasive ventilation as a first-line intervention, high-flow nasal oxygen shows a higher rate of failure. Hence, if not contraindicated, the use of noninvasive ventilation should be preferred. After the resolution of acidemia with noninvasive ventilation, high-flow nasal oxygen showed promising physiological effects compared to conventional oxygen. During weaning from mechanical ventilation in patients with or at risk of developing hypercapnia, high-flow nasal oxygen showed encouraging results, especially when applied alternating with sessions of noninvasive ventilation. Optimal settings of high-flow nasal oxygen in hypercapnic patients include the use of a smaller-size cannula, flows ranging between 30 and 40 L/min, and FiO2 adjusted to obtain SpO2 between 88% and 92%. Specific interfaces, such as asymmetric cannulas, may further enhance the benefits of a high flow in terms of carbon dioxide clearance. In this narrative review, we provide an updated overview of the physiological rationale and clinical evidence concerning the use of high-flow nasal oxygen in patients with acute hypercapnic respiratory failure.

[Non-invasive Mechanical Ventilation in Acute Respiratory Failure. Clinical Practice Guidelines - on behalf of the German Society of Pneumology and Ventilatory Medicine]

The guideline update outlines the advantages as well as the limitations of NIV in the treatment of acute respiratory failure in daily clinical practice and in different indications.Non-invasive ventilation (NIV) has a high value in therapy of hypercapnic acute respiratory failure, as it significantly reduces the length of ICU stay and hospitalization as well as mortality.Patients with cardiopulmonary edema and acute respiratory failure should be treated with continuous positive airway pressure (CPAP) and oxygen in addition to necessary cardiological interventions. This should be done already prehospital and in the emergency department.In case of other forms of acute hypoxaemic respiratory failure with only mild or moderately disturbed gas exchange (PaO2/FiO2 > 150 mmHg) there is no significant advantage or disadvantage compared to high flow nasal oxygen (HFNO). In severe forms of ARDS NIV is associated with high rates of treatment failure and mortality, especially in cases with NIV-failure and delayed intubation.NIV should be used for preoxygenation before intubation. In patients at risk, NIV is recommended to reduce extubation failure. In the weaning process from invasive ventilation NIV essentially reduces the risk of reintubation in hypercapnic patients. NIV is regarded useful within palliative care for reduction of dyspnea and improving quality of life, but here in concurrence to HFNO, which is regarded as more comfortable. Meanwhile NIV is also recommended in prehospital setting, especially in hypercapnic respiratory failure and pulmonary edema.With appropriate monitoring in an intensive care unit NIV can also be successfully applied in pediatric patients with acute respiratory insufficiency.

Effectiveness and safety of non-invasive ventilation in the management of cardiogenic shock

INTRODUCTION AND OBJECTIVES

Cardiogenic shock (CS) has long been considered a contraindication for the use of non-invasive ventilation (NIV). The main objective of this study was to analyze the effectiveness, measured as NIV success, in patients with respiratory failure due to CS. As secondary objective, we studied risk factors for NIV failure and compared the outcome of patients treated with NIV versus invasive mechanical ventilation (IMV).

METHODS

Retrospective study on a prospective database, over a period of 25 years, of all consecutively patients admitted to an intensive care unit, with a diagnosis of CS and treated with NIV. A comparison was made between patients on NIV and patients on IMV using propensity score matching analysis.

RESULTS

Three hundred patients were included, mean age 73.8 years, mean SAPS II 49. The main cause of CS was acute myocardial infarction (AMI): 164 (54.7%). NIV failure occurred in 153 (51%) cases. Independent factors for NIV failure included D/E stages of CS, AMI, NIV related complications, and being transferred from the ward. In the propensity analysis, hospital mortality (OR 1.69, 95% CI 1.09-2.63) and 1 year mortality (OR 1.61, 95% CI 1.04-2.51) was higher in IMV. Mortality was lower with NIV (vs. EIT-IMV) in C stage (10.1% vs. 32.9%; p<0.001) but did not differ in D stage or E stage.

CONCLUSIONS

NIV seems to be relatively effective and safe in the treatment of early-stage CS.

Acute dyspnea in the emergency department: a clinical review

Acute dyspnea represents one of the most frequent symptoms leading to emergency room evaluation. Its significant prognostic value warrants a careful evaluation. The differential diagnosis of dyspnea is complex due to the lack of specificity and the loose association between its intensity and the severity of the underlying pathological condition. The initial assessment of dyspnea calls for prompt diagnostic evaluation and identification of optimal monitoring strategy and provides information useful to allocate the patient to the most appropriate setting of care. In recent years, accumulating evidence indicated that lung ultrasound, along with echocardiography, represents the first rapid and non-invasive line of assessment that accurately differentiates heart, lung or extra-pulmonary involvement in patients with dyspnea. Moreover, non-invasive respiratory support modalities such as high-flow nasal oxygen and continuous positive airway pressure have aroused major clinical interest, in light of their efficacy and practicality to treat patients with dyspnea requiring ventilatory support, without using invasive mechanical ventilation. This clinical review is focused on the pathophysiology of acute dyspnea, on its clinical presentation and evaluation, including ultrasound-based diagnostic workup, and on available non-invasive modalities of respiratory support that may be required in patients with acute dyspnea secondary or associated with respiratory failure.

Advantages and drawbacks of helmet noninvasive support in acute respiratory failure

INTRODUCTION

Non-invasive ventilation (NIV) represents an effective strategy for managing acute respiratory failure. Facemask NIV is strongly recommended in acute exacerbation of chronic obstructive pulmonary disease (AECOPD) with hypercapnia and acute cardiogenic pulmonary edema (ACPE). Its role in managing acute hypoxemic respiratory failure (AHRF) remains a debated issue. NIV and continuous positive airway pressure (CPAP) delivered through the helmet are recently receiving growing interest for AHRF management.

AREAS COVERED

In this narrative review, we discuss the clinical applications of helmet support compared to the other available noninvasive strategies in the different phenotypes of acute respiratory failure.

EXPERT OPINION

Helmets enable the use of high positive end-expiratory pressure, which may protect from self-inflicted lung injury: in AHRF, the possible superiority of helmet support over other noninvasive strategies in terms of clinical outcome has been hypothesized in a network metanalysis and a randomized trial, but has not been confirmed by other investigations and warrants confirmation. In AECOPD patients, helmet efficacy may be inferior to that of face masks, and its use prompts caution due to the risk of CO₂ rebreathing. Helmet support can be safely applied in hypoxemic patients with ACPE, with no advantages over facemasks.

Outcome of patients with acute heart failure secondary to acute myocardial infarction treated with noninvasive mechanical ventilation

INTRODUCTION AND OBJECTIVES

Noninvasive ventilation (NIV) has been shown to reduce the rate of endotracheal intubation and mortality in patients with acute heart failure (AHF). However, patients with AHF secondary to acute coronary syndrome/acute myocardial infarction (ACS-AMI) have been excluded from many clinical trials. The purpose of this study was to compare the effectiveness of NIV between patients with AHF triggered by ACS-AMI and by other etiologies.

METHODS

Prospective cohort study of all patients with AHF treated with NIV admitted to the intensive care unit for a period of 20 years. Patients were divided according to whether they had ACS-AMI as the cause of the AHF episode. NIV failure was defined as the need for endotracheal intubation or death.

RESULTS

A total of 1009 patients were analyzed, 403 (40%) showed ACS-AMI and 606 (60%) other etiologies. NIV failure occurred in 61 (15.1%) in the ACS-AMI group and in 64 (10.6%) in the other group (P=.031), without differences in in-hospital mortality (16.6% and 14.9%, respectively; P=.478).

CONCLUSIONS

The presence of ACS-AMI as the triggering cause of AHF did not influence patients with acute respiratory failure requiring noninvasive respiratory support.

Validity of a clinical scale in predicting the failure of non-invasive ventilation in hypoxemic patients

INTRODUCTION

The HACOR scale is a clinical score that can predict early failure of NIV in hypoxemic acute respiratory failure (ARF) The aim of this study is to analyze the validity of the HACOR scale.

METHODS

A retrospective study of a cohort of over 2749 episodes on 2711 consecutive patients requiring NIV for hypoxemic ARF in a polyvalent intensive care unit. The scale was measured before starting NIV and at 1, 6, 12, 24 and 48 h after the initiation of NIV.

RESULTS

NIV failure occurred in 963 patients (35%). The value of the HACOR scale before NIV did not differ between success and failure. However, at 1, 6, 12, 24 and 48 h of NIV, the scale values clearly differed between the two groups. The HACOR scale at NIV initiation accurately predicts NIV failure in the first hour, with an optimal cut-off value of 8 points. The AUC for predicting NIV failure with HACOR at 1 h is greater than 0.9 in patients with pneumonia and adult respiratory distress syndrome (ARDS).

CONCLUSIONS

The HACOR scale measured at 1 h after NIV initiation accurately predicts NIV failure, especially in pneumonia and ARDS.

Noninvasive Ventilation and High-Flow Nasal Therapy Administration in Chronic Obstructive Pulmonary Disease Exacerbations

Noninvasive ventilation (NIV) is considered to be the standard of care for the management of acute hypercapnic respiratory failure in patients with chronic obstructive pulmonary disease exacerbation. It can be delivered safely in any dedicated setting, from emergency rooms to high dependency or intensive care units and wards. NIV helps improving dyspnea and gas exchange, reduces the need for endotracheal intubation, and morbidity and mortality rates. It is therefore recognized as the gold standard in this condition. High-flow nasal therapy helps improving ventilatory efficiency and reducing the work of breathing in patients with severe chronic obstructive pulmonary disease. Early studies indicate that some patients with acute hypercapnic respiratory failure can be managed with high-flow nasal therapy, but more information is needed before specific recommendations for this therapy can be made. Therefore, high-flow nasal therapy use should be individualized in each particular situation and institution, taking into account resources, and local and personal experience with all respiratory support therapies.

Prehospital reversal of profound respiratory acidosis and hypercapnic coma by non-invasive ventilation: a report of two cases

BACKGROUND

In chronic obstructive pulmonary disease (COPD) patients with acute respiratory failure (ARF), non-invasive ventilation (NIV) is generally recommended and has proven its benefits by reducing endotracheal intubation (ETI) rates, intensive care unit (ICU) admissions, complications, and mortality. Choosing between immediate ETI or NIV trial is often difficult when such patients present with an altered mental status. Some guidelines recommend avoiding NIV when consciousness is impaired given the risk of aspiration, and some authors suggest that a pH < 7.25 is highly predictive of NIV failure. Though clinical response to a well-adjusted NIV treatment can be both swift and spectacular, these contraindications probably encourage physicians to proceed to immediate ETI. Some studies indeed report that NIV was not even considered in as many as 60% of patients who might have benefited from this therapy, though ETI related complications might have been avoided had NIV been successfully applied.

CASE PRESENTATION

We report two cases of ARF in COPD patients who were successfully treated by NIV in prehospital setting and avoided ETI despite contraindications (altered mental status with a Glasgow Coma Scale < 8) and failure risk factors (severe respiratory acidosis with pH < 7.25).

CONCLUSION

In COPD patients presenting ARF, NIV trial could be considered even when relative contraindications such as an altered level of consciousness or a severe respiratory acidosis are present.

Indications for Non-Invasive Ventilation in Respiratory Failure

BACKGROUND

Non-invasive ventilation (NIV) is increasingly being used to treat episodes of acute respiratory failure not only in critical care and respiratory wards, but also in emergency departments.

AIM

Aim of this review is to summarize the current indications for the management of NIV for respiratory failure.

METHODS

Current literature about the topic was reviewed and critically reported to describe the rationale and physiologic advantages of NIV in various situations of respiratory failure.

RESULTS

Early NIV use is commonly associated with the significant decrease in endotracheal intubation rate, the incidence of infective complications (especially ventilatory associated pneumonia), Intensive Care Units and the length of hospital stay and, in selected conditions, also in mortality rates. Severe acute exacerbation of chronic obstructive pulmonary disease (pH<7.35 and relative hypercarbia) and acute cardiogenic pulmonary oedema are the most common NIV indications; in these conditions NIV advantages are clearly documented. Not so evident are the NIV benefits in hypoxaemic respiratory failure occurring without prior chronic respiratory disease (De novo respiratory failure). One recent randomized control trial reported in hypoxaemic respiratory failure a survival benefit of high-flow nasal cannulae over standard oxygen therapy and bilevel NIV. Evidence suggests the advantages of NIV also in respiratory failure in immunocompromised patients or chest trauma patients. Use during a pandemic event has been assessed in several observational studies but remains controversial; there also is not sufficient evidence to support the use of NIV treatment in acute asthma exacerbation.

CONCLUSION

NIV eliminates morbidity related to the endotracheal tube (loss of airway defense mechanism with increased risk of pneumonia) and in selected conditions (COPD exacerbation, acute cardiogenic pulmonary edema, immunosuppressed patients with pulmonary infiltrates and hypoxia) is clearly associated with a better outcome in comparison to conventional invasive ventilation. However, NIV is associated with complications, especially minor complications related to interface. Major complications like aspiration pneumonia, barotrauma and hypotension are infrequent.

ISCCM Guidelines for the Use of Non-invasive Ventilation in Acute Respiratory Failure in Adult ICUs

A. ACUTE HYPERCAPNIC RESPIRATORY FAILURE A1. Acute Exacerbation of COPD: Recommendations: NIV should be used in management of acute exacerbation of COPD in patients with acute or acute-on-chronic respiratory acidosis (pH = 7.25-7.35). (1A) NIV should be attempted in patients with acute exacerbation of COPD (pH <7.25 & PaCO2 ≥ 45) before initiating invasive mechanical ventilation (IMV) except in patients requiring immediate intubation. (2A). Lower the pH higher the chance of failure of NIV. (2B) NIV should not to be used routinely in normo- or mildly hyper-capneic patients with acute exacerbation of COPD, without acidosis (pH > 7.35). (2B) A2. NIV in ARF due to Chest wall deformities/Neuromuscular diseases: Recommendations: NIV may be used in patients of ARF due to chest wall deformity/Neuromuscular diseases. (PaCO2 ≥ 45) (UPP) A3. NIV in ARF due to Obesity hypoventilation syndrome (OHS): Recommendations: NIV may be used in AHRF in OHS patients when they present with acute hypercapnic or acute on chronic respiratory failure (pH 45). (3B) NIV/CPAP may be used in obese, hypercapnic patients with OHS and/or right heart failure in the absence of acidosis. (UPP) B.

NIV IN ACUTE HYPOXEMIC RESPIRATORY FAILURE

B1. NIV in Acute Cardiogenic Pulmonary Oedema: Recommendations: NIV is recommended in hospital patients with ARF, due to Cardiogenic pulmonary edema. (1A). NIV should be used in patients with acute heart failure/ cardiogenic pulmonary edema, right from emergency department itself. (1B) Both CPAP and BiPAP modes are safe and effective in patients with cardiogenic pulmonary edema. (1A). However, BPAP (NIV-PS) should be preferred in cardiogenic pulmonary edema with hypercapnia. (3A) B2. NIV in acute hypoxemic respiratory failure: Recommendations: NIV may be used over conventional oxygen therapy in mild early acute hypoxemic respiratory failure (P/F ratio <300 and >200 mmHg), under close supervision. (2B) We strongly recommend against a trial of NIV in patients with acute hypoxemic failure with P/F ratio <150. (2A) B3. NIV in ARF due to Chest Trauma: Recommendations: NIV may be used in traumatic flail chest along with adequate pain relief. (3B) B4. NIV in Immunocompromised Host: Recommendations: In Immunocompromised patients with early ARF, we may consider NIV over conventional oxygen. (2B). B5. NIV in Palliative Care: Recommendations: We strongly recommend use of NIV for reducing dyspnea in palliative care setting. (2A) B6. NIV in post-operative cases: Recommendations: NIV should be used in patients with post-operative acute respiratory failure. (2A) B6a. NIV in abdominal surgery: Recommendations: NIV may be used in patients with ARF following abdominal surgeries. (2A) B6b. NIV in bariatric surgery: Recommendations: NIV may be used in post-bariatric surgery patients with pre-existent OSA or OHS. (3A) B6c. NIV in Thoracic surgery: Recommendations: In cardiothoracic surgeries, use of NIV is recommended post operatively for acute respiratory failure to improve oxygenation and reduce chance of reintubation. (2A) NIV should not be used in patients undergoing esophageal surgery. (UPP) B6d. NIV in post lung transplant: Recommendations: NIV may be used for shortening weaning time and to avoid re-intubation following lung transplantation. (2B) B7. NIV during Procedures (ETI/Bronchoscopy/TEE/Endoscopy): Recommendations: NIV may be used for pre-oxygenation before intubation. (2B) NIV with appropriate interface may be used in patients of ARF during Bronchoscopy/Endoscopy to improve oxygenation. (3B) B8. NIV in Viral Pneumonitis ARDS: Recommendations: NIV cannot be considered as a treatment of choice for patients with acute respiratory failure with H1N1 pneumonia. However, it may be reasonable to use NIV in selected patients with single organ involvement, in a strictly controlled environment with close monitoring. (2B) B9. NIV and Acute exacerbation of Pulmonary Tuberculosis: Recommendations: Careful use of NIV in patients with acute Tuberculosis may be considered, with effective infection control precautions to prevent air-borne transmission. (3B) B10. NIV after planned extubation in high risk patients: Recommendation: We recommend that NIV may be used to wean high risk patients from invasive mechanical ventilation as it reduces re-intubation rate. (2B) B11. NIV for respiratory distress post extubation: Recommendations: We recommend that NIV therapy should not be used to manage respiratory distress post-extubation in high risk patients. (2B) C.

APPLICATION OF NIV

Recommendation: Choice of mode should be mainly decided by factors like disease etiology and severity, the breathing effort by the patient and the operator familiarity and experience. (UPP) We suggest using flow trigger over pressure triggering in assisted modes, as it provides better patient ventilator synchrony. Especially in COPD patients, flow triggering has been found to benefit auto PEEP. (3B) D.

MANAGEMENT OF PATIENT ON NIV

D1. Sedation: Recommendations: A non-pharmacological approach to calm the patient (Reassuring the patient, proper environment) should always be tried before administrating sedatives. (UPP) In patients on NIV, sedation may be used with extremely close monitoring and only in an ICU setting with lookout for signs of NIV failure. (UPP) E.

EQUIPMENT

Recommendations: We recommend that portable bilevel ventilators or specifically designed ICU ventilators with non-invasive mode should be used for delivering Non-invasive ventilation in critically ill patients. (UPP) Both critical care ventilators with leak compensation and bi-level ventilators have been equally effective in decreasing the WOB, RR, and PaCO2. (3B) Currently, Oronasal mask is the most preferred interface for non-invasive ventilation for acute respiratory failure. (3B) F.

WEANING

Recommendations: We recommend that weaning from NIV may be done by a standardized protocol driven approach of the unit. (2B) How to cite this article: Chawla R, Dixit SB, Zirpe KG, Chaudhry D, Khilnani GC, Mehta Y, et al. ISCCM Guidelines for the Use of Non-invasive Ventilation in Acute Respiratory Failure in Adult ICUs. Indian J Crit Care Med 2020;24(Suppl 1):S61-S81.

Noninvasive Ventilation in Patients With Do-Not-Intubate and Comfort-Measures-Only Orders: A Systematic Review and Meta-Analysis

OBJECTIVES

To assess the effectiveness of noninvasive ventilation in patients with acute respiratory failure and do-not-intubate or comfort-measures-only orders.

DATA SOURCES

MEDLINE, EMBASE, CINAHL, Scopus, and Web of Science from inception to January 1, 2017.

STUDY SELECTION

Studies of all design types that enrolled patients in the ICU or hospital ward who received noninvasive ventilation and had preset do-not-intubate or comfort-measures-only orders.

DATA EXTRACTION

Data abstraction followed Meta-analysis of Observational Studies in Epidemiology guidelines. Data quality was assessed using a modified Newcastle-Ottawa Scale.

DATA SYNTHESIS

Twenty-seven studies evaluating 2,020 patients with do-not-intubate orders and three studies evaluating 200 patients with comfort-measures-only orders were included. In patients with do-not-intubate orders, the pooled survival was 56% (95% CI, 49-64%) at hospital discharge and 32% (95% CI, 21-45%) at 1 year. Hospital survival was 68% for chronic obstructive pulmonary disease, 68% for pulmonary edema, 41% for pneumonia, and 37% for patients with malignancy. Survival was comparable for patients treated in a hospital ward versus an ICU. Quality of life of survivors was not reduced compared with baseline, although few studies evaluated this. No studies evaluated quality of dying in nonsurvivors. In patients with comfort-measures-only orders, a single study showed that noninvasive ventilation was associated with mild reductions in dyspnea and opioid requirements.

CONCLUSIONS

A large proportion of patients with do-not-intubate orders who received noninvasive ventilation survived to hospital discharge and at 1 year, with limited data showing no decrease in quality of life in survivors. Provision of noninvasive ventilation in a well-equipped hospital ward may be a viable alternative to the ICU for selected patients. Crucial questions regarding quality of life in survivors, quality of death in nonsurvivors, and the impact of noninvasive ventilation in patients with comfort-measures-only orders remain largely unanswered.

Outcome of Frail Do-Not-Intubate Subjects With End-Stage Chronic Respiratory Failure and Their Opinion of Noninvasive Ventilation to Reverse Hypercapnic Coma

BACKGROUND

The use of noninvasive ventilation (NIV) in the emergency setting to reverse hypercapnic coma in frail patients with end-stage chronic respiratory failure and do-not-intubate orders remains a questionable issue given the poor outcome of this vulnerable population. We aimed to answer this issue by assessing not only subjects' outcome with NIV but also subjects' point of view regarding NIV for this indication.

METHODS

A prospective observational case-control study was conducted in 3 French tertiary care hospitals during a 2-y period. Forty-three individuals who were comatose (with pH < 7.25 and PaCO2 > 100 mm Hg at admission) were compared with 43 subjects who were not comatose and who were treated with NIV for acute hypercapnic respiratory failure. NIV was applied by using the same protocol in both groups. They all had a do-not-intubate order and were considered vulnerable individuals with end-stage chronic respiratory failure according to well-validated scores.

RESULTS

NIV yielded similar outcomes in the 2 groups regarding in-hospital mortality (n = 12 [28%] vs n = 12 [28%] in the noncomatose controls, P > .99) and 6-month survival (n = 28 [65%] vs n = 22 [51%] in the noncomatose controls, P = .31). Despite poor quality of life scores (21.5 ± 10 vs 31 ± 6 in the awakened controls, P = .056) as assessed by using the VQ11 questionnaire 6 months to 1 y after hospital discharge, a large majority of the survivors (n = 23 [85%]) would be willing to receive NIV again if a new episode of acute hypercapnic respiratory failure occurs.

CONCLUSIONS

In the frailest subjects with supposed end-stage chronic respiratory failure that justifies treatment limitation decisions, it is worth trying NIV when acute hypercapnic respiratory failure occurs, even in the case of extreme respiratory acidosis with hypercapnic coma at admission.

Acute non-invasive ventilation - getting it right on the acute medical take

Non-invasive ventilation (NIV) given to the right patient, in the right setting, in the right way and at the right time improves outcomes. However, national audits reveal poor practice in patient selection, clinical judgement, treatment initiation and availability of trained staff. NIV is indicated for persistent acute hypercapnic respiratory failure (AHRF) with acidosis after usual medical management in chronic obstructive pulmonary disease (COPD) exacerbation and even without acidosis in neuromuscular disorders or other restrictive conditions eg obesity hypoventilation or kyphoscoliosis. Having trained staff in a suitable environment with adequate equipment are keys to its success, along with close monitoring. A plan should be put in place at the time of initiating NIV about the ceiling of care, eg escalation to intubation or palliation, if the patient is not improving with NIV. Early NIV failure is most likely due to technical issues, such as inadequate pressures or mask leak, while late failure is usually the consequence of advanced disease. Any presentation with AHRF is a poor prognostic indicator and outpatient respiratory follow-up is indicated following discharge. For selected patients with COPD who remain hypercapnic 2 weeks after an exacerbation, domiciliary NIV can reduce admissions and improve survival. For patients with neuromuscular disorders or kyphoscoliosis a presentation with AHRF almost always indicates the need for domiciliary NIV.

Ventilação não invasiva na unidade de terapia intensiva de um hospital universitário: características relacionadas ao sucesso e insucesso

RESUMO O objetivo deste estudo foi descrever características de sucesso e insucesso do uso da ventilação não invasiva (VNI) na unidade de terapia intensiva (UTI) de um hospital universitário. Trata-se de um estudo observacional prospectivo no qual foram incluídos 75 pacientes, com idade média de 58,3±18,8 anos. Desses, doze necessitaram do uso da VNI por mais de uma vez, totalizando 92 utilizações. Evidenciou-se que, delas, a taxa de sucesso foi de 60,9% (56). O grupo insucesso apresentou mais indivíduos do sexo masculino (p=0,006) e número maior de pacientes com diagnóstico de infecção extrapulmonar (p=0,012). Não foram encontradas diferenças entre os grupos de sucesso e insucesso nos quesitos de modo, modelo, máscara, tempo total de permanência e razões para a instalação da VNI. No grupo insucesso, a pressão positiva inspiratória nas vias aéreas (Ipap) e o volume corrente (VC) foram superiores (p=0,029 e p=0,011, respectivamente). A saturação periférica de oxigênio (p=0,047), o pH (p=0,004), base excess (p=0,006) e o bicarbonato (p=0,013) apresentaram valores inferiores. Concluiu-se que os indivíduos do sexo masculino com diagnóstico de infecção extrapulmonar e que evoluíram com acidose metabólica evoluíram com mais insucesso na utilização da VNI. Esses, necessitaram de parâmetros elevados de Ipap e VC.

NIV for acute respiratory failure in COPD: high in-hospital mortality is determined by patient selection

Introduction: Hospital mortality among chronic obstructive pulmonary disease (COPD) patients receiving NIV for acute respiratory failure has shown to be significantly higher in clinical settings than in the randomized trials (RCTs) which clinical guidelines are based on. This may be due to the quality of care of NIV or patient selection. In daily clinical practice, we include patients with terminal pulmonary disease with a do-not-intubate (DNI) or a do-not-resuscitate (DNR) order with a high mortality risk compared to highly selected patients in RCTs. The aim of this study was to determine the role of patient selection for in-hospital mortality among patients receiving NIV for acute respiratory failure of COPD.

Methods: We conducted a retrospective study including all patients receiving acute NIV due to acute respiratory failure at the respiratory wards in 2012–2013 at two hospitals in Greater Copenhagen.

Results: Overall in-hospital mortality rate was 30%. In patients with a DNI/DNR order, mortality was 59% and in patients with no limitations in treatment 2%. Patients who fulfilled the exclusion criteria of the RCT by Plant et al. had a mortality of 41% compared to 25% in the remaining population.

Conclusions: High overall in-hospital mortality reflects that patient selection in clinical practice is very different from RCT. Quality of acute NIV treatment seems acceptable in clinical practice for patients with less severe COPD and no limitations in treatment. Higher mortality in patients with DNI/DNR order may be due to inefficient NIV treatment for these patients with more severe COPD.

Benefits of non-invasive ventilation in acute hypercapnic respiratory failure

Non-invasive ventilation (NIV) with bilevel positive airway pressure is a non-invasive technique, which refers to the provision of ventilatory support through the patient's upper airway using a mask or similar device. This technique is successful in correcting hypoventilation. It has become widely accepted as the standard treatment for patients with hypercapnic respiratory failure (HRF). Since the 1980s, NIV has been used in intensive care units and, after initial anecdotal reports and larger series, a number of randomized trials have been conducted. Data from these trials have shown that NIV is a valuable treatment for HRF. This review aims to explore the principal areas in which NIV can be useful, focusing particularly on patients with acute HRF (AHRF). We will update the evidence base with the goal of supporting clinical practice. We provide a practical description of the main indications for NIV in AHRF and identify the group of patients with hypercapnic failure who will benefit most from the application of NIV.

Non-invasive ventilation or high-flow oxygen therapy: When to choose one over the other?

It has been found that high-flow oxygen therapy (HFOT) can reduce mortality of patients admitted to intensive care unit (ICU) for de novo acute respiratory failure (ARF) as compared to non-invasive ventilation (NIV). HFOT might therefore be considered as a first-line strategy of oxygenation in these patients. The beneficial effects of HFOT may be explained by its good tolerance and by physiological characteristics including delivery of high FiO₂ , positive end expiratory pressure (PEEP) effect and continuous dead space washout contributing to decreased work of breathing. In contrast, NIV should be used cautiously in patients with de novo ARF due to high tidal volumes promoted by pressure support and that may potentially worsen pre-existing lung injury. Although recent studies have reported no benefit and even deleterious effects of NIV in immunocompromised patients with ARF, the experts have recommended its use as a first-line strategy. In patients with acute-on-chronic respiratory failure and respiratory acidosis, it has been clearly shown that NIV is the best strategy of oxygenation. However, HFOT seems able to reverse respiratory acidosis and further studies are needed to evaluate whether HFOT could represent an alternative to standard oxygen. Although NIV is recommended to treat ARF in post-operative patients or to prevent post-extubation respiratory failure in ICU, recent large-scale randomized studies suggest that HFOT could be equivalent to NIV. While recent recommendations have been established from studies comparing NIV with standard oxygen, new studies are needed to compare NIV versus HFOT in order to better define the appropriate indications for both treatments.

Noninvasive Options

Noninvasive ventilation (NIV) has assumed a central role in the treatment of selected patients with acute respiratory failure due to exacerbated chronic obstructive pulmonary disease or acute cardiogenic pulmonary edema. Recent advances in the understanding of physiologic aspects of NIV application through different interfaces and ventilator settings have led to improved patient-machine interaction, enhancing favorable NIV outcome. In recent years, the growing role of NIV in the acute care setting has led to the development of technical innovations to overcome the problems related to gas leakage and dead space, improving the quality of the devices and optimizing ventilation modes.

Application of BiPAP through Endotracheal Tube in Comatose Patients with COPD Exacerbation

Objective

To evaluate the effectiveness and safety of using BiPAP through endotracheal tube in comatose Chronic Obstructive Pulmonary Disease (COPD) patients with hypercapnic respiratory failure.

Methods

This is a prospective study done at Department of Chest Medicine, Jinnah Postgraduate Medical Centre, Karachi, during March to June 2017. It included all comatose COPD patients with hypercapnic respiratory failure who had a poor functional status prior to the illness and who did not meet the criteria to be kept on mechanical ventilator. Patients with apnea and other causes of coma were excluded. These patients were applied BiPAP through endotracheal tube and its response on blood gases and neurological status was evaluated.

Results

The success rate of BiPAP through endotracheal tube was 70.5% (31/44). Improvement in Glasgow Coma Scale (GCS) score (p<0.01), pH (p<0.01), and PaCO₂ (<0.01) was observed among the responders following two hours and 24 hours of therapy. No significant difference was found in response with regards to gender, smoking status, prior use of noninvasive ventilation or duration of disease. No complications were observed during the therapy.

Conclusion

In resource poor settings, the use of BiPAP through endotracheal tube can be an effective and safe intervention for comatose COPD patients with hypercapnic respiratory failure.

Non-invasive ventilation in the ED: Whom, When, How?

As emergency physicians, we encounter patients suffering from either hypoxemic and/or hypercarbic respiratory problems on a daily basis. A stepwise approach to solving this problem seems logical from an emergency medicine perspective. Current literature supports the notion that NIV decreases endotracheal intubation rates and, mortality in select patient populations. The key to the success of NIV is patient cooperation and support for the care givers. In this narrative review, non-invasive ventilation (NIV) is discussed in terms of modes of delivery, interface and patient selection, as well as practical considerations.

The efficacy of initial ventilation strategy for adult immunocompromised patients with severe acute hypoxemic respiratory failure: study protocol for a multicentre randomized controlled trial (VENIM)

Background

Acute respiratory failure (ARF) is still one of the most severe complications in immunocompromised patients. Our previous systematic review showed noninvasive mechanical ventilation (NIV) reduced mortality, length of hospitalization and ICU stay in AIDS/hematological malignancy patients with relatively less severe ARF, compared to invasive mechanical ventilation (IMV). However, this systematic review was based on 13 observational studies and the quality of evidence was low to moderate. The efficacy of NIV in more severe ARF and in patients with other causes of immunodeficiency is still unclear. We aim to determine the efficacy of the initial ventilation strategy in managing ARF in immunocompromised patients stratified by different disease severity and causes of immunodeficiency, and explore predictors for failure of NIV.

Methods and analysis

The VENIM is a multicentre randomized controlled trial (RCT) comparing the effects of NIV compared with IMV in adult immunocompromised patients with severe hypoxemic ARF. Patients who meet the indications for both forms of ventilatory support will be included. Primary outcome will be 30-day all-cause mortality. Secondary outcomes will include in-hospital mortality, length of stay in hospital, improvement of oxygenation, nosocomial infections, seven-day organ failure, adverse events of intervention, et al. Subgroups with different disease severity and causes of immunodeficiency will also be analyzed.

Discussion

VENIM is the first randomized controlled trial aiming at assessing the efficacy of initial ventilation strategy in treating moderate and severe acute respiratory failure in immunocompromised patients. The result of this RCT may help doctors with their ventilation decisions.

Trial registration

ClinicalTrials.gov NCT02983851. Registered 2 September 2016.

Official ERS/ATS clinical practice guidelines: noninvasive ventilation for acute respiratory failure

Noninvasive mechanical ventilation (NIV) is widely used in the acute care setting for acute respiratory failure (ARF) across a variety of aetiologies. This document provides European Respiratory Society/American Thoracic Society recommendations for the clinical application of NIV based on the most current literature.The guideline committee was composed of clinicians, methodologists and experts in the field of NIV. The committee developed recommendations based on the GRADE (Grading, Recommendation, Assessment, Development and Evaluation) methodology for each actionable question. The GRADE Evidence to Decision framework in the guideline development tool was used to generate recommendations. A number of topics were addressed using technical summaries without recommendations and these are discussed in the supplementary material.This guideline committee developed recommendations for 11 actionable questions in a PICO (population-intervention-comparison-outcome) format, all addressing the use of NIV for various aetiologies of ARF. The specific conditions where recommendations were made include exacerbation of chronic obstructive pulmonary disease, cardiogenic pulmonary oedema, de novo hypoxaemic respiratory failure, immunocompromised patients, chest trauma, palliation, post-operative care, weaning and post-extubation.This document summarises the current state of knowledge regarding the role of NIV in ARF. Evidence-based recommendations provide guidance to relevant stakeholders.

Official ERS/ATS clinical practice guidelines: noninvasive ventilation for acute respiratory failure

Noninvasive mechanical ventilation (NIV) is widely used in the acute care setting for acute respiratory failure (ARF) across a variety of aetiologies. This document provides European Respiratory Society/American Thoracic Society recommendations for the clinical application of NIV based on the most current literature.The guideline committee was composed of clinicians, methodologists and experts in the field of NIV. The committee developed recommendations based on the GRADE (Grading, Recommendation, Assessment, Development and Evaluation) methodology for each actionable question. The GRADE Evidence to Decision framework in the guideline development tool was used to generate recommendations. A number of topics were addressed using technical summaries without recommendations and these are discussed in the supplementary material.This guideline committee developed recommendations for 11 actionable questions in a PICO (population-intervention-comparison-outcome) format, all addressing the use of NIV for various aetiologies of ARF. The specific conditions where recommendations were made include exacerbation of chronic obstructive pulmonary disease, cardiogenic pulmonary oedema, de novo hypoxaemic respiratory failure, immunocompromised patients, chest trauma, palliation, post-operative care, weaning and post-extubation.This document summarises the current state of knowledge regarding the role of NIV in ARF. Evidence-based recommendations provide guidance to relevant stakeholders.

Discontinuing noninvasive ventilation in severe chronic obstructive pulmonary disease exacerbations: a randomised controlled trial

We assessed whether prolongation of nocturnal noninvasive ventilation (NIV) after recovery from acute hypercapnic respiratory failure (AHRF) in chronic obstructive pulmonary disease (COPD) patients with NIV could prevent subsequent relapse of AHRF.A randomised controlled trial was performed in 120 COPD patients without previous domiciliary ventilation, admitted for AHRF and treated with NIV. When the episode was resolved and patients tolerated unassisted breathing for 4 h, they were randomly allocated to receive three additional nights of NIV (n=61) or direct NIV discontinuation (n=59). The primary outcome was relapse of AHRF within 8 days after NIV discontinuation.Except for a shorter median (interquartile range) intermediate respiratory care unit (IRCU) stay in the direct discontinuation group (4 (2-6) versus 5 (4-7) days, p=0.036), no differences were observed in relapse of AHRF after NIV discontinuation (10 (17%) versus 8 (13%) for the direct discontinuation and nocturnal NIV groups, respectively, p=0.56), long-term ventilator dependence, hospital stay, and 6-month hospital readmission or survival.Prolongation of nocturnal NIV after recovery from an AHRF episode does not prevent subsequent relapse of AHRF in COPD patients without previous domiciliary ventilation, and results in longer IRCU stay. Consequently, NIV can be directly discontinued when the episode is resolved and patients tolerate unassisted breathing.

Non invasive ventilation in patients with chronic obstructive pulmonary disease in a hospital and at home

Last two decades, active use of non-invasive ventilation (NIV) has provided a significant improvement in the management of chronic obstructive pulmonary disease (COPD), both in patients with acute exacerbation and in stable patients. Currently, NIV is the first-line treatment for patients with acute exacerbation of COPD and acute hypercapnic respiratory failure. This method of respiratory support is also effective after extubation, as it could facilitate weaning from the ventilator and affects positively prevention and treatment of postextubation respiratory failure. Also, NIV has been successfully used in co-morbidity of COPD and sleep apnea syndrome, COPD and pneumonia, and in early postoperative period after thoracic surgery. NIV can be used in COPD patients with chronic respiratory failure. Long-term NIV at home is more reasonable in patients with daytime hypercapnia. The most effective strategy of respiratory support in COPD is thought to be decrease in the partial pressure of carbon dioxide in the arterial blood, i.e. high-intensity NIV. Currently available portable non-invasive ventilators could improve significantly physical activity of patients with severe COPD.

Delayed but successful response to noninvasive ventilation in COPD patients with acute hypercapnic respiratory failure

BACKGROUND

We evaluated a new noninvasive ventilation (NIV) protocol that allows the pursuit of NIV in the case of persistent severe respiratory acidosis despite a first NIV challenge in COPD patients with acute hypercapnic respiratory failure (AHRF).

PATIENTS AND METHODS

A prospective observational multicentric pilot study was conducted in three tertiary hospitals over a 12-month study period. A total of 155 consecutive COPD patients who were admitted for AHRF and treated by NIV were enrolled. Delayed response to NIV was defined as a significant clinical improvement in the first 48 h following NIV initiation despite a persistent severe respiratory acidosis (pH <7.30) after the first 2 h of NIV trial.

RESULTS

NIV failed in only 10 patients (6.5%). Delayed responders to NIV (n=83, 53%) exhibited similar nutritional status, comorbidities, functional status, frailty score, dyspnea score, and severity score at admission, compared with early responders (n=62, 40%). Only age (66 vs 70 years in early responders; P=0.03) and encephalopathy score (3 [2-4] vs 3 [2-4] in early responders; P=0.015) were different among the responders. Inhospital mortality did not differ between responders to NIV (n=10, 12% for delayed responders vs n=10, 16% for early responders, P=0.49). A second episode of AHRF occurred in 20 responders (14%), equally distributed among early and delayed responders to NIV (n=9, 14.5% in early responders vs n=11, 13% in delayed responders; P=0.83), with a poor survival rate (n=1, 5%).

CONCLUSION

Most of the COPD patients with AHRF have a successful outcome when NIV is pursued despite a persistent severe respiratory acidosis after the first NIV trial. The outcome of delayed responders is similar to the one of the early responders. On the contrary, the second episode of AHRF during the hospital stay carries a poor prognosis.

Noninvasive Ventilation

Noninvasive ventilation (NIV) has assumed a prominent role in the treatment of patients with both hypoxemic and hypercapnic acute respiratory failure (ARF). The main theoretic advantages of NIV include avoiding side effects and complications associated with endotracheal intubation, improving patient comfort, and preserving airway defense mechanisms. Factors that affect the success of NIV in patients with ARF are clinicians' expertise, selection of patient, choice of interface, selection of ventilator setting, proper monitoring, and patient motivation. Advances in the understanding of the physiologic aspects of using NIV through different interfaces and ventilator modalities have improved patient-machine interaction, thus enhancing favorable NIV outcome.

Managing Respiratory Failure in Obstructive Lung Disease

Exacerbations of obstructive lung disease are common causes of acute respiratory failure. Short-acting bronchodilators and systemic glucocorticoids are the foundation of pharmacologic management. For patients requiring ventilator support, use of noninvasive ventilation reduces the risk of mortality and progression to invasive mechanical ventilation. Challenges associated with invasive ventilation include ventilator dyssynchrony, air trapping, and dynamic hyperinflation. Careful monitoring and adjustment of ventilatory support parameters helps to optimize the patient-ventilator interaction and minimizes the risk of associated morbidity. Extracorporeal life support is an emerging treatment for refractory hypercapnic respiratory failure associated with obstructive lung disease.

Noninvasive Ventilation for the Emergency Physician

Noninvasive ventilation (NIV) improves oxygenation and ventilation, prevents endotracheal intubation, and decreases the mortality rate in select patients with acute respiratory failure. Although NIV is used commonly for acute exacerbations of chronic obstructive pulmonary disease and acute cardiogenic pulmonary edema, there are emerging indications for its use in the emergency department. Emergency physicians must be knowledgeable regarding the indications and contraindications for NIV in emergency department patients with acute respiratory failure as well as the means of initiating it and monitoring patients who are receiving it.

[Hypercapnic respiratory failure. Pathophysiology, indications for mechanical ventilation and management]

BACKGROUND

Acute hypercapnic respiratory failure is mostly seen in patients with chronic obstructive pulmonary disease (COPD) and obesity hypoventilation syndrome (OHS). Depending on the underlying cause it may be associated with hypoxemic respiratory failure and places high demands on mechanical ventilation.

OBJECTIVE

Presentation of the current knowledge on indications and management of mechanical ventilation in patients with hypercapnic respiratory failure.

MATERIAL AND METHODS

Review of the literature.

RESULTS

Important by the selection of mechanical ventilation procedures is recognition of the predominant pathophysiological component. In hypercapnic respiratory failure with a pH < 7.35 non-invasive ventilation (NIV) is primarily indicated unless there are contraindications. In patients with severe respiratory acidosis NIV requires a skilled and experienced team and close monitoring in order to perceive a failure of NIV. In acute exacerbation of COPD ventilator settings need a long expiration and short inspiration time to avoid further hyperinflation and an increase in intrinsic positive end-expiratory pressure (PEEP). Ventilation must be adapted to the pathophysiological situation in patients with OHS or overlap syndrome. If severe respiratory acidosis and hypercapnia cannot be managed by mechanical ventilation therapy alone extracorporeal venous CO2 removal may be necessary. Reports on this approach in awake patients are available.

CONCLUSION

The use of NIV is the predominant treatment in patients with hypercapnic respiratory failure but close monitoring is necessary in order not to miss the indications for intubation and invasive ventilation. Methods of extracorporeal CO2 removal especially in awake patients need further evaluation.

Changing use of noninvasive ventilation in critically ill patients: trends over 15 years in francophone countries

PURPOSE

Over the last two decades, noninvasive ventilation (NIV) has been proposed in various causes of acute respiratory failure (ARF) but some indications are debated. Current trends in NIV use are unknown.

METHODS

Comparison of three multicenter prospective audits including all patients receiving mechanical ventilation and conducted in 1997, 2002, and 2011 in francophone countries.

RESULTS

Among the 4132 patients enrolled, 2094 (51%) required ventilatory support for ARF and 2038 (49 %) for non-respiratory conditions. Overall NIV use was markedly increased in 2010/11 compared to 1997 and 2002 (37% of mechanically ventilated patients vs. 16% and 28%, P < 0.05). In 2010/11, the use of first-line NIV for ARF had reached a plateau (24% vs. 16% and 23%, P < 0.05) whereas pre-ICU and post-extubation NIV had substantially increased (11% vs. 4% and 11% vs. 7%, respectively, P < 0.05). First-line NIV remained stable in acute-on-chronic RF, continued to increase in cardiogenic pulmonary edema, but decreased in de novo ARF (16% in 2010/11 vs. 23% in 2002, P < 0.05). The NIV success rate increased from 56% in 2002 to 70% in 2010/11 and remained the lowest in de novo ARF. NIV failure in de novo ARF was associated with increased mortality in 2002 but not in 2010/11. Mortality decreased over time, and overall, NIV use was associated with a lower mortality.

CONCLUSION

Increases in NIV use and success rate, an overall decrease in mortality, and a decrease of the adverse impact NIV failure has in de novo ARF suggest better patient selection and greater proficiency of staff in administering NIV.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier NCT01449331.

Effectiveness and predictors of failure of noninvasive mechanical ventilation in acute respiratory failure

OBJECTIVE

To assess the effectiveness and identify predictors of failure of noninvasive ventilation.

DESIGN

A retrospective, longitudinal descriptive study was made.

SETTING

Adult patients with acute respiratory failure.

PATIENTS

A total of 410 consecutive patients with noninvasive ventilation treated in an Intensive Care Unit of a tertiary university hospital from 2006 to 2011.

PROCEDURES

Noninvasive ventilation.

MAIN VARIABLES OF INTEREST

Demographic variables and clinical and laboratory test parameters at the start and two hours after the start of noninvasive ventilation. Evolution during admission to the Unit and until hospital discharge.

RESULTS

The failure rate was 50%, with an overall mortality rate of 33%. A total of 156 patients had hypoxemic respiratory failure, 87 postextubation respiratory failure, 78 exacerbation of chronic obstructive pulmonary disease, 61 hypercapnic respiratory failure without chronic obstructive pulmonary disease, and 28 had acute pulmonary edema. The failure rates were 74%, 54%, 27%, 31% and 21%, respectively. The etiology of respiratory failure, serum bilirubin at the start, APACHEII score, radiological findings, the need for sedation to tolerate noninvasive ventilation, changes in level of consciousness, PaO2/FIO2 ratio, respiratory rate and heart rate from the start and two hours after the start of noninvasive ventilation were independently associated to failure.

CONCLUSIONS

The effectiveness of noninvasive ventilation varies according to the etiology of respiratory failure. Its use in hypoxemic respiratory failure and postextubation respiratory failure should be assessed individually. Predictors of failure could be useful to prevent delayed intubation.

Early non-invasive ventilation treatment for respiratory failure due to severe community-acquired pneumonia

BACKGROUND AND AIMS

Severe community-acquired pneumonia (sCAP) have been as defined pneumonia requiring admission to the intensive care unit or carrying a high risk of death. Currently, the treatment of sCAP consists of antibiotic therapy and ventilator support. The use of invasive ventilation causes several complications as does admission to ICU. For this reason, non-invasive ventilation (NIV) has been used for acute respiratory failure to avoid endotracheal intubation. However, few studies have currently assessed the usefulness of NIV in sCAP.

METHODS

We prospectively assessed 127 patients with sCAP and severe acute respiratory failure [oxygen arterial pressure/oxygen inspiratory fraction ratio (PaO2/FiO2) <250]. We defined successful NIV as avoidance of intubation and the achievement of PaO2/FiO2 >250 with spontaneous breathing. We assessed predictors of NIV failure and hospital mortality using univariate and multivariate analyses.

RESULTS

NIV failed in 32 patients (25.1%). Higher chest X-ray score at admission, chest X-ray worsening, and a lower PaO2/FiO2 and higher alveolar-arteriolar gradient (A-aDO2) after 1 h of NIV all independently predicted NIV failure. Higher lactate dehydrogenase and confusion, elevated blood urea, respiratory rate, blood pressure plus age ≥65 years at admission, higher A-aDO2, respiratory rate and lower PaO2/FiO2 after 1 h of NIV and intubation rate were directly related to hospital mortality.

CONCLUSIONS

Successful treatment is strongly related to less severe illness as well as to a good initial and sustained response to medical therapy and NIV treatment. Constant monitoring of these patients is mandatory.

Noninvasive ventilation and lung volume reduction

As parenchymal lung disease in chronic obstructive pulmonary disease becomes increasingly severe there is a diminishing prospect of drug therapies conferring clinically useful benefit. Lung volume reduction surgery is effective in patients with heterogenous upper zone emphysema and reduced exercise tolerance, and is probably underused. Rapid progress is being made in nonsurgical approaches to lung volume reduction, but use outside specialized centers cannot be recommended presently. Noninvasive ventilation given to patients with acute hypercapnic exacerbation of chronic obstructive pulmonary disease reduces mortality and morbidity, but the place of chronic non-invasive ventilatory support remains more controversial.

Timing of noninvasive ventilation failure: causes, risk factors, and potential remedies

Background

Identifying the predictors of noninvasive ventilation (NIV) failure has attracted significant interest because of the strong link between failure and poor outcomes. However, very little attention has been paid to the timing of the failure. This narrative review focuses on the causes of NIV failure and risk factors and potential remedies for NIV failure, based on the timing factor.

Results

The possible causes of immediate failure (within minutes to <1 h) are a weak cough reflex, excessive secretions, hypercapnic encephalopathy, intolerance, agitation, and patient-ventilator asynchrony. The major potential interventions include chest physiotherapeutic techniques, early fiberoptic bronchoscopy, changing ventilator settings, and judicious sedation. The risk factors for early failure (within 1 to 48 h) may differ for hypercapnic and hypoxemic respiratory failure. However, most cases of early failure are due to poor arterial blood gas (ABGs) and an inability to promptly correct them, increased severity of illness, and the persistence of a high respiratory rate. Despite a satisfactory initial response, late failure (48 h after NIV) can occur and may be related to sleep disturbance.

Conclusions

Every clinician dealing with NIV should be aware of these risk factors and the predicted parameters of NIV failure that may change during the application of NIV. Close monitoring is required to detect early and late signs of deterioration, thereby preventing unavoidable delays in intubation.

[Ventilation strategies for chronic obstructive pulmonary disease]

Chronic obstructive pulmonary disease (COPD) is considered to be one of the most frequent pulmonary diseases in industrialized countries. Non-invasive ventilation (NIV) is the first choice therapy in acute exacerbations of chronic hypercapnic respiratory failure (AE-COPD). Effective delivery of NIV requires a specialized interdisciplinary team with sufficient monitoring. NIV is delivered as assisted positive pressure ventilation where high inspiratory flow and peak pressure are required. The external positive end expiratory pressure (PEEP) should be adjusted to the intrinsic PEEP. Criteria of success are improvement in the clinical, especially neurological condition as well as improvement of pH and PaCO(2). Patients with a pH between 7.25 and 7.35 have demonstrated most benefit from NIV. In cases of patients not responding to NIV endotracheal intubation should be initiated in a timely manner. Assisted ventilation modes are preferred over controlled ventilation modes in intubated COPD patients. Settings of respirators have to be aimed at a reduction of intrinsic PEEP and dynamic hyperinflation. This includes sufficient external PEEP, long expiration times and low respiratory frequencies even allowing for permissive hypercapnia.

Noninvasive mechanical ventilation: An 18-month experience of two tertiary care hospitals in north India

BACKGROUND

Noninvasive mechanical ventilation (NIMV) is the delivery of positive pressure ventilation through an interface to upper airways without using the invasive airway. Use of NIMV is becoming common with the increasing recognition of its benefits.

OBJECTIVES

This study was done to evaluate the feasibility and outcome of NIMV in tertiary care centres.

MATERIALS AND METHODS

An observational, retrospective study conducted over a period of 18 months in two tertiary level hospitals of north India on 184 consecutive patients who were treated by NIMV, regardless of the indication. NIMV was given in accordance with the arterial blood gas (ABG) parameters defining respiratory failure (Type 1/Type 2).

RESULTS

The most common indication of NIMV in our hospitals was acute exacerbation of chronic obstructive pulmonary disease (AE-COPD 80.43%), and 90.54% AE-COPD patients were improved by NIMV. Application of NIMV resulted in significant improvement of pH and blood gases in COPD patients, while non-COPD patients showed significant improvement in partial pressure of oxygen (PaO2) alone. The mean duration of NIMV was 8.35 ± 5.98 days, and patients of interstitial lung disease (ILD) were on NIMV for the maximum duration (17 ± 8.48 days). None of the patients of acute respiratory distress syndrome were cured by NIMV; 13.04% patients on NIMV required intubation and mechanical ventilation.

CONCLUSION

This study demonstrates and encourages the use of NIMV as the first-line ventilatory treatment in AE-COPD patients with respiratory failure. It also supports NIMV usage in other causes of respiratory failure as a promising step toward prevention of mechanical ventilation.

Noninvasive ventilation: practical advice

PURPOSE OF REVIEW

This critical review discusses the key points that would be of practical help for the clinician who applies noninvasive ventilation (NIV) for treatment of patients with acute respiratory failure (ARF).

RECENT FINDINGS

In recent years, the growing role of NIV in the acute care setting has led to the development of technical innovations to overcome the problems related to gas leakage and dead space. A considerable amount of research has been conducted to improve the quality of the devices as well as optimize ventilation modes used to administer NIV. As a result, also mechanical ventilators have been implemented with modalities aimed at delivering NIV.

SUMMARY

The success of NIV in patients with ARF depends on several factors, including the skills of the clinician, selection of patient, choice of interface, selection of ventilation mode and ventilator setting, monitoring, and the motivation of the patient. Recent advances in the understanding of the physiological aspects of using NIV through different interfaces and ventilator settings have led to improve patient-machine interaction, enhancing favorable NIV outcome.

Noninvasive mechanical ventilation with average volume assured pressure support (AVAPS) in patients with chronic obstructive pulmonary disease and hypercapnic encephalopathy

BACKGROUND

Non-invasive mechanical ventilation (NIV) in patients with acute respiratory failure has been traditionally determined based on clinical assessment and changes in blood gases, with NIV support pressures manually adjusted by an operator. Bilevel positive airway pressure-spontaneous/timed (BiPAP S/T) with average volume assured pressure support (AVAPS) uses a fixed tidal volume that automatically adjusts to a patient's needs. Our study assessed the use of BiPAP S/T with AVAPS in patients with chronic obstructive pulmonary disease (COPD) and hypercapnic encephalopathy as compared to BiPAP S/T alone, upon immediate arrival in the Emergency-ICU.

METHODS

We carried out a prospective interventional match-controlled study in Guayaquil, Ecuador. A total of 22 patients were analyzed. Eleven with COPD exacerbations and hypercapnic encephalopathy with a Glasgow Coma Scale (GCS) <10 and a pH of 7.25-7.35 were assigned to receive NIV via BiPAP S/T with AVAPS. Eleven patients were selected as paired controls for the initial group by physicians who were unfamiliar with our study, and these patients were administered BiPAP S/T. Arterial blood gases, GCS, vital signs, and ventilatory parameters were then measured and compared between the two groups.

RESULTS

We observed statistically significant differences in favor of the BiPAP S/T + AVAPS group in GCS (P = .00001), pCO(2) (P = .03) and maximum inspiratory positive airway pressure (IPAP) (P = .005), among others. However, no significant differences in terms of length of stay or days on NIV were observed.

CONCLUSIONS

BiPAP S/T with AVAPS facilitates rapid recovery of consciousness when compared to traditional BiPAP S/T in patients with chronic obstructive pulmonary disease and hypercapnic encephalopathy.

TRIAL REGISTRATION

Current Controlled Trials application ref is ISRCTN05135218.