Cardiopulmonary effects of non-invasive positive pressure ventilation (NPPV)--a controlled, prospective study

Immediate changes in hemodynamics and gas exchange after initiation of noninvasive ventilation in cardiac surgical patients

Introduction

Cardiac surgery is associated with pulmonary dysfunction and complications such as prolonged intubation and reintubation. Bilevel positive airway pressure (BiPAP) machine has been used in the clinical settings to improve oxygenation, reduce work of breathing, and avoid reintubation. The effect of BiPAP on cardiovascular parameters is not well established, and very few studies have targeted hemodynamic changes. The aim of the study was to assess the immediate effect of BiPAP on respiratory and hemodynamic parameters in post-cardiac surgery patients.

Materials and Methods

This quasi-experimental study was done on 33 adult cardiac surgery patients. Ethical review committee approval was sought and consent was taken. All patients who were in respiratory distress with respiratory rate of >30/min and/or PaO₂:FiO₂ ratio of <200 were included. Hemodynamic and respiratory parameters were recorded just before and 15 min after BiPAP application. Sample size was determined on the basis of BiPAP effect on one of the variables, PaO₂:FiO₂ ratio.

Results

A total of 33 patients were included in the study. The average age of the patients was 60.97 ± 10.8, of which 23 (69.7%) were males and 10 (30.7%) females. BiPAP application leads to statistically significant improvement in ventilator parameters including SaO₂ 29 (87.7%), PaO₂ 29 (87.8%), PaCO₂ 21 (63.6%), and PaO₂:FiO₂ ratio in 27 (81.8%).

Conclusion

Ventilatory parameters were significantly improved after BiPAP application in this study, but hemodynamic parameters showed no statistically significant change. BiPAP application was also able to decrease the need for reintubation in post-cardiac surgery patients.

Effects of non-invasive ventilation in patients with acute respiratory failure excluding post-extubation respiratory failure, cardiogenic pulmonary edema and exacerbation of COPD: a systematic review and meta-analysis

BACKGROUND

This meta-analysis compared the effects of non-invasive ventilation (NIV) with invasive mechanical ventilation (InMV) and standard oxygen (O₂) therapy on mortality and rate of tracheal intubation in patients presenting acute respiratory failure (ARF).

METHODS

We searched the MEDLINE, EMBASE and Cochrane Central Register of clinical trials databases between 1949 and May 2015 to identify randomized trials of NIV for ARF. We excluded the ARF caused by extubation, cardiogenic pulmonary edema, and COPD.

RESULTS

The meta-analysis included 21 studies and 1691 patients, of whom 846 were assigned to NIV and 845 to control (InMV or standard O₂ therapy). One hundred ninety-one patients (22.6%) in the NIV group and 261 patients (30.9%) in the control group died before discharge from hospital. The pooled odds ratio (OR) for short-term mortality (in-hospital mortality) was 0.56 (95% CI 0.40-0.78). When comparing NIV with standard O₂ therapy, the short-term mortality was 155 (27.4%) versus 204 (36.0%), respectively. For this comparison, the pooled OR of short-term mortality was 0.56 (95% CI 0.36-0.85). When comparing NIV with InMV, the short-term mortality was 36 (12.9%) versus 57 (20.5%) patients, respectively. For this comparison, the pooled OR of short-term mortality was 0.56 (95% CI 0.34-0.90). Tracheal intubation was performed in 106 patients (22.7%) in the NIV and in 183 patients (39.4%) in the standard O₂ group, representing a pooled OR of 0.37 (95% CI 0.25-0.55). There were publication biases and the quality of the evidence was graded as low.

CONCLUSION

Compared with standard O₂ therapy or InMV, NIV lowered both the short-term mortality and the rate of tracheal intubation in patients presenting with ARF.

Noninvasive ventilation for acute lung injury a meta-analysis of randomized controlled trials

PURPOSE

To compare the effect of noninvasive ventilation (NIV) and standard oxygen therapy on treating acute lung injury (ALI).

METHODS

A search on PubMed, Embase, Springer, Cochrane Central Register of Controlled Trials and Clinical Trials was carried out up to Nov 2015 for randomized controlled trials (RCTs) with NIV as cases and standard oxygen therapy as controls. Risk ratios and weight mean difference were used for estimation.

RESULTS

This meta-analysis included seventeen RCTs. Results showed NIV significantly reduced the intubation rate, length of ICU stay and hospital mortality. The length of hospital stay and ICU mortality were not different. High heterogeneity was found across the studies of intubation rate. The types of acute respiratory failure might be a source of heterogeneity.

CONCLUSION

Our results suggest that NIV is effective for ALI in reducing the intubation rate, hospital mortality and length of ICU stay than the standard oxygen therapy.

Noninvasive Positive-Pressure Ventilation in Treatment of Hypoxemia After Extubation Following Type-A Aortic Dissection

OBJECTIVES

To assess the efficacy of noninvasive positive-pressure ventilation (NPPV) in improving hypoxemia after extubation for Stanford type-A aortic dissection and to compare NPPV using a mask or a helmet.

DESIGN

Prospective, interventional study.

SETTING

Department of Cardiac Surgery of the Beijing Anzhen Hospital, a tertiary university hospital.

PARTICIPANTS

Patients experiencing hypoxemia within 24 hours after extubation for Stanford type-A aortic dissection.

INTERVENTIONS

The patients were divided into the following 3 groups: high-flux inhalation of oxygen with a Venturi mask (control patients), NPPV with a mask (mask group), and NPPV with a helmet (helmet group) (n = 25/group).

MEASUREMENTS AND MAIN RESULTS

Data for blood gas analysis, vital signs, heart function, and complications were collected before the treatment, after 1 and 6 hours of treatment, and at the end of treatment. The oxygen partial pressure/fraction of inspired oxygenation index or PaO₂/FIO₂ ratio and the oxygen partial pressure were higher and carbon dioxide partial pressure was lower in the mask and helmet groups compared with that of control patients. Compared with control patients and the mask group, the helmet group showed a slower heart rate, lower average arterial pressure, and improved left ventricular ejection fraction, leading to a lower incidence of reintubation and a shorter hospital stay.

CONCLUSIONS

NPPV with a helmet may quickly improve oxygen partial pressure, decrease carbon dioxide partial pressure, decrease the reintubation rate, and effectively shorten the hospital stay after extubation for Stanford type-A aortic dissection.

[Cardiopulmonary interactions in the course of mechanical ventilation]

INTRODUCTION

The haemodynamic consequences of ventilation are multiple and complex and may affect all the determinants of cardiac performance such as heart rate, preload, contractility and afterload. These consequences affect both right and left ventricle and are also related to the biventricular interdependence.

STATE-OF-THE-ART

Ventilation modifies the lung volume and also the intrathoracic pressure. Variations in lung volume have consequences on the pulmonary vascular resistance, hypoxic pulmonary vasoconstriction and ventricular interdependence. Variations in intrathoracic pressure have a major impact and affect systemic venous return, right ventricular preload, left ventricular preload, right ventricular afterload, left ventricular afterload and myocardial contracility. The haemodynamic consequences of positive pressure ventilation depend on the underlying chronic cardiopulmonary pathologies leading to the acute respiratory failure that was the indication for ventilation.

CONCLUSION

In this review, we will focus on severe COPD exacerbation, acute left heart failure and weaning from ventilation.

Noninvasive ventilation for acute respiratory failure

PURPOSE OF REVIEW

This article reviews the use of noninvasive ventilation (NIV) in patients with acute respiratory failure (ARF), with a critical review of the most recent literature in this setting.

RECENT FINDINGS

The efficacy of NIV is variable depending on the cause of the episode of ARF. In community-acquired pneumonia, NIV is often associated with poor response, with better response in patients with preexisting cardiac or respiratory disease. In patients with pandemic influenza H1N1 and severe ARF, NIV has been associated with high failure rates but relatively favorable mortality. In acute respiratory distress syndrome, NIV should be used very cautiously and restricted to patients with mild-moderate acute respiratory distress syndrome without shock or metabolic acidosis due to the high failure rate observed in several reports. Despite limited evidence, NIV may improve the outcomes of patients with chest trauma and severe ARF. In postoperative ARF, both continuous positive airway pressure and NIV are effective to improve clinical outcomes, particularly in those with abdominal, cardiac, and thoracic surgery.

SUMMARY

Although patients with severe hypoxemic ARF are, in general, less likely to be intubated when NIV is used, the efficacy is different among these heterogeneous populations. Therefore, NIV is not routinely recommended in all patients with severe hypoxemic ARF.

Effects of Noninvasive Positive-Pressure Ventilation with Different Interfaces in Patients with Hypoxemia after Surgery for Stanford Type A Aortic Dissection

Background

Hypoxemia is a severe perioperative complication that can substantially increase intensive care unit and hospital stay and mortality. The aim of this study was to determine the effects of non-invasive positive-pressure ventilation (NIPPV) in patients with hypoxemia after surgery for Stanford type A aortic dissection, and to compare the effects of helmet and mask NIPPV.

Material/Methods

We recruited 40 patients who developed hypoxemia within 24 h after extubation after surgery for Stanford type A aortic dissection in the Beijing Anzhen Hospital. The patients were randomly divided into the helmet and mask NIPPV groups. The primary endpoints were blood oxygenation levels at 1 and 6 h after initiation and at the end of the treatment. The secondary endpoint was patient outcome, including mortality; incidence of pulmonary atelectasis, pneumonia, re-intubation, and sepsis; and length of ICU and hospital stays.

Results

NIPPV improved oxygenation in both groups. Compared with pretreatment levels, the oxygenation index (PaO₂/FiO₂), PaO₂, PaCO₂, and respiratory rate (RR) improved in the initial (0–1 h), maintenance (1–6 h), and end stages of the treatment (P<0.05). Compared with mask ventilation, helmet ventilation better improved pH, PaO₂, SpO₂, PaO₂/FiO_2, and decreased PaCO₂ in the 3 stages (P<0.05). The incidence of major complications, including flatulence, intolerance, and facial pressure sores, was significantly lower with helmet ventilation.

Conclusions

NIPPV effectively improved oxygenation and reduced PaCO₂ in patients who developed hypoxemia soon after extubation following surgery for Stanford type A aortic dissection. Compared with mask NIPPV, helmet NIPPV more rapidly increased PaO₂ and reduced PaCO₂, increased patient tolerance and comfort, and reduced complications.

Efficacy of cardiopulmonary rehabilitation with adaptive servo-ventilation in patients undergoing off-pump coronary artery bypass grafting

BACKGROUND

Postoperative complications after cardiac surgery increase mortality. This study aimed to evaluate the efficacy of cardiopulmonary rehabilitation with adaptive servo-ventilation (ASV) in patients undergoing off-pump coronary artery bypass grafting (OPCAB).

METHODS AND RESULTS

A total of 66 patients undergoing OPCAB were enrolled and divided into 2 groups according to the use of ASV (ASV group, 30 patients; non-ASV group, 36 patients). During the perioperative period, all patients undertook cardiopulmonary rehabilitation. ASV was used from postoperative day (POD) 1 to POD5. Hemodynamics showed a different pattern in the 2 groups. Blood pressure (BP) on POD6 in the ASV group was significantly lower than that in the non-ASV group (systolic BP, 112.9±12.6 vs. 126.2±15.8 mmHg, P=0.0006; diastolic BP, 62.3±9.1 vs. 67.6±9.3 mmHg, P=0.0277). The incidence of postoperative atrial fibrillation (POAF) was lower in the ASV group than in the non-ASV group (10% vs. 33%, P=0.0377). The duration of oxygen inhalation in the ASV group was significantly shorter than that in the non-ASV group (5.1±2.2 vs. 7.6±6.0 days, P=0.0238). The duration of postoperative hospitalization was significantly shorter in the ASV group than in the non-ASV group (23.5±6.6 vs. 29.0±13.1 days, P=0.0392).

CONCLUSIONS

Cardiopulmonary rehabilitation with ASV after OPCAB reduces both POAF occurrence and the duration of hospitalization.

Mechanical Ventilation in the Pediatric Cardiac Intensive Care Unit

Ventilating a child or newborn in the postoperative course after repair of congenital heart disease requires a solid basic understanding of respiratory system mechanics (pressure–volume relationship of the respiratory system and the concept of its time constants) and cardiopulmonary physiology. Furthermore, careful attention has to be paid to avoid damaging the lungs by potentially injurious mechanical ventilation. Optimizing ventilator settings during controlled and assisted ventilation, allowing as early as possible for spontaneous ventilation by still assisting mechanically the patient’s respiratory efforts are important features for lung protection, for minimizing potential hemodynamic side effects of positive pressure ventilation, and for early weaning from mechanical ventilation. In the search for being less invasive, the use of noninvasive ventilation in the cardiac intensive care setting is rapidly increasing despite still lacking evidence of its theoretical superiority and requires good knowledge of specific techniques and equipment available for this approach in this setting. This review will address many of these aspects and highlight the essentials to be known when ventilating a child in the Cardiac Intensive Care Unit (CICU).

[Non-invasive ventilation as treatment for acute respiratory insufficiency. Essentials from the new S3 guidelines]

BACKGROUND

Scientific evidence is accumulating that non-invasive ventilation (NIV) may be beneficial for different patient groups with acute respiratory insufficiency (ARI). The aim of the new S3 guidelines is to propagate evidence-based knowledge about the indications and limitations of NIV in clinical practice.

METHODS

A total of 28 experts from 12 German medical societies were involved in the process of development of the present guidelines. These experts systematically analyzed approximately 2,900 publications. Finally, the recommendations were discussed and approved in two consensus conferences.

RESULTS

In hypercapnic ARI, NIV reduces the length of stay and mortality during intensive care treatment [grade A recommendation (A)]. Patients with cardiopulmonary edema should be treated with continuous positive airway pressure (CPAP) or NIV (A). For immunocompromized patients with ARI, NIV reduces the mortality (A). In patients with postextubation respiratory failure and during weaning from mechanical ventilation, NIV reduces the risk of reintubation (A). For patients who decline to be ventilated invasively, NIV may be an acceptable alternative (B). Non-invasive ventilation can also successfully be used in pediatric patients with ARI caused by different reasons (C). In acute respiratory distress syndrome (ARDS) NIV cannot generally be recommended because the failure rate is relatively high.

CONCLUSION

Non-invasive ventilation is still not as widely implemented in clinical medicine as would be expected on the basis of the scientific literature. The aim of the present guidelines is to further propagate NIV for the treatment of ARI.

Clinical practice guideline: non-invasive mechanical ventilation as treatment of acute respiratory failure

INTRODUCTION

Non-invasive mechanical ventilation (NIV) has been used to treat acute respiratory failure (ARF) for approximately 20 years. This guideline addresses the indications for, and limitations of, NIV as treatment for ARF according to evidence-based criteria.

METHODS

A panel of experts from 12 scientific medical societies reviewed circa 2900 publications. The panel judged the clinical relevance of these studies and assessed the evidence presented in each, then held two interdisciplinary consensus conferences to formulate guideline recommendations and algorithms.

RESULTS

Whenever possible, NIV should be preferred to invasive mechanical ventilation, in order to avoid the risk of ventilator and tube-associated complications such as nosocomial pneumonia (grade of recommendation A). Particularly in patients with hypercapnic ARF, NIV reduces the rate of hospital-acquired pneumonia, the length of hospital stay and mortality in the intensive care unit and in the hospital (grade of recommendation A). NIV (or continuous positive airway pressure) is also recommended in cardiogenic pulmonary edema (grade of recommendation A), as treatment for ARF in immunocompromised patients (grade of recommendation A), to prevent postextubation failure, to facilitate weaning in patients with hypercapnic ARF (grade of recommendation A), and to improve dyspnea in palliative care (grade of recommendation C). NIV is not generally recommended in patients with hypoxic ARF because of its high failure rate of 30% to over 50% in such patients.

DISCUSSION

Although evidence indicates that NIV can be used as the treatment of first choice for several indications, it is still underutilized in the acute setting. These guidelines provide evidence-based information about the indications for, and limitations of, NIV in the treatment of ARF.