Experience of step-wise protocol using noninvasive positive pressure ventilation for treating cardiogenic pulmonary edema

Analysis of the effect of CPAP on hemodynamics using clinical data and a theoretical model: CPAP therapy decreases cardiac output mechanically but increases it via afterload reduction

BACKGROUND

Noninvasive positive pressure ventilation (NIPPV) has been established as an effective treatment for heart failure. Positive airway pressure such as continuous positive airway pressure (CPAP) increases cardiac output (CO) in some patients but decreases it in others. However, the mechanism behind such unpredictable responses remains undetermined.

METHODS AND RESULTS

We measured hemodynamic parameters of 38 cases using Swan-Ganz catheter before and after CPAP in chronic heart failure status. In those whose CO increased by CPAP, pulmonary vascular resistance (PVR) was significantly decreased and SpO2 significantly increased, but the other parameters were not changed. On the other hand, PVR was not changed, but systemic vascular resistance (SVR) was increased in those whose CO decreased by CPAP. To explain this phenomenon, we simulated the cardiovascular system using a cardiac model of time-varying elastance. In this model, it was indicated that CPAP decreases CO irrespective of cardiac function or filling status under constant PVR condition. However, when reduction of PVR by CPAP was taken into account, an increase in CO was expected especially in the hypervolemic and low right ventricle (RV) systolic function cases.

CONCLUSIONS

CPAP would increase CO only where PVR can be reduced by CPAP therapy, especially in the case with hypervolemia and/or low RV systolic function. Understanding the underlying mechanism should help identify the patients for whom NIPPV would be effective.

Predictors of Successful Weaning from Noninvasive Ventilation in Patients with Acute Exacerbation of Chronic Obstructive Pulmonary Disease: A Single-Center Retrospective Cohort Study

Purpose

Noninvasive ventilation (NIV) is often required for patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD), and it can significantly reduce the need for endotracheal intubation. Currently, there is no standard method for predicting successful weaning from NIV. Therefore, we aimed to evaluate whether a weaning index can predict NIV outcomes of patients with AECOPD.

Methods

This study was conducted at a single academic public hospital in northern Taiwan from February 2019 to January 2021. Patients with AECOPD admitted to the hospital with respiratory failure who were treated with NIV were included in the study. Univariate and multivariate logistic regression analyses were used to identify independent predictors of successful weaning from NIV. Receiver operating characteristic curve methodology was used to assess the predictive capacity.

Results

A total of 85 patients were enrolled, 65.9% of whom were successfully weaned from NIV. The patients had a mean age of 75.8 years and were mostly men (89.4%). The rapid shallow breathing index (RSBI) (P < 0.001), maximum inspiratory pressure (P = 0.014), and maximum expiratory pressure (P = 0.004) of the successful group were significant while preparing to wean. The area under the receiver operating characteristic curve for the RSBI was 0.804, which was considered excellent discrimination.

Conclusion

The RSBI predicted successful weaning from NIV in patients with AECOPD with hypercapnic respiratory failure. This index may be useful for selecting patients with AECOPD that are suitable for NIV weaning.

Protocolos para desmame da ventilação mecânica não invasiva: uma revisão sistemática

RESUMO O objetivo deste trabalho foi realizar revisão sistemática de estudos que investigaram protocolos de desmame da ventilação não invasiva (VNI) em indivíduos adultos ou idosos hospitalizados. Por meio dessa revisão, baseada no protocolo Prisma, foram selecionados estudos de oito bases de dados publicados em português, inglês ou espanhol. Os desfechos primários desta revisão foram taxa de sucesso de desmame da VNI, duração da VNI e duração da permanência na unidade de terapia intensiva (UTI) e no hospital, e como desfecho secundário foram considerados os efeitos adversos associados aos protocolos de desmame da VNI. A qualidade metodológica dos ensaios clínicos foi avaliada por meio da escala PEDro, e a escala de Downs e Black foi utilizada para a avaliação dos estudos observacionais. Das 18.476 referências iniciais, quatro atenderam aos critérios de inclusão e foram incluídas nesta revisão. Dois dos quatro artigos eram ensaios clínicos randomizados e os outros dois eram estudos observacionais. Os estudos envolveram pacientes idosos com insuficiência respiratória, principalmente por exacerbação da doença pulmonar obstrutiva crônica (DPOC) e edema agudo de pulmão cardiogênico. Foram observadas elevadas taxas de sucesso de desmame em três dos quatro estudos, e um destes demonstrou a superioridade da implementação de um protocolo de desmame imediato na redução da duração da VNI e da permanência na UTI. No entanto, devido à heterogeneidade e à baixa qualidade metodológica dos estudos, não foi possível fazer recomendação sobre a implementação dos protocolos de desmame nessa população.

Adaptive servo-ventilation therapy reduces hospitalization rate in patients with severe heart failure

INTRODUCTION

Adaptive servo-ventilation (ASV) therapy is a recently developed non-pharmacological therapy that has been reported to improve cardiac function and survival in patients with severe congestive heart failure (CHF). However, a recent large randomized study suggested that ASV does not improve survival in patients with reduced ejection fraction. It remains unclear whether ASV treatment can reduce the hospitalization rate of CHF patients. We thus examined the frequency of hospital admission before and after initiation of ASV therapy in patients with CHF.

METHODS AND RESULTS

Hospitalization frequencies during the 12months before and 12months after initiation of ASV therapy (24 consecutive months) were retrospectively compared in 44 consecutive patients with severe CHF. The admission frequency decreased from 1.9±1.4 admissions in the 12months before ASV to 1.1±1.6 admissions in the 12months after ASV initiation (P<0.001). The decrease tended to be greater in those patients with more frequent hospitalizations before ASV initiation.

CONCLUSION

ASV therapy reduces hospital admissions in patients with severe CHF who are receiving maximum medical treatment.

Noninvasive ventilation for acute respiratory failure: a review of the literature and current guidelines

Noninvasive ventilation, both continuous positive airway pressure and noninvasive positive pressure ventilation, has been used increasingly for acute respiratory failure over the past several years. Noninvasive ventilation has been proven to be beneficial for some causes of acute respiratory failure, most clearly for acute exacerbations of chronic obstructive pulmonary disease, while its use in other forms of acute respiratory failure remains more controversial. In this article, the evidence for the use of noninvasive ventilation in various kinds of acute respiratory failure will be examined. Particular attention will be paid to the clinical situations commonly encountered by emergency medicine and general internal medicine clinicians. The potential dangers of noninvasive ventilation as well as some guidelines for clinical decision making when treating patients with this mode of ventilator support will also be discussed.

Enhancement of cardiac performance by bilevel positive airway pressure ventilation in heart failure

BACKGROUND

Recent studies have reported the clinical usefulness of positive airway pressure ventilation therapy with various kinds of pressure support compared with simple continuous positive airway pressure (CPAP) for heart failure patients. However, the mechanism of the favorable effect of CPAP with pressure support can not be explained simply from the mechanical aspect and remains to be elucidated.

METHODS AND RESULTS

In 18 stable chronic heart failure patients, we performed stepwise CPAP (4, 8, 12 cm H(2)O) while the cardiac output and intracardiac pressures were continuously monitored, and we compared the effects of 4 cm H(2)O CPAP with those of 4 cm H(2)O CPAP plus 5 cm H(2)O pressure support. Stepwise CPAP decreased cardiac index significantly in patients with pulmonary arterial wedge pressure (PAWP) <12 mm Hg (n = 10), but not in those with PAWP ≥12 mm Hg (n = 8). Ventilation with CPAP plus pressure support increased cardiac index slightly but significantly from 2.2 ± 0.7 to 2.3 ± 0.7 L min(-1) m(-2) (P = .001) compared with CPAP alone, regardless of basal filling condition or cardiac index.

CONCLUSIONS

Our results suggest that CPAP plus pressure support is more effective than simple CPAP in heart failure patients and that the enhancement might be induced by neural changes and not simply by alteration of the preload level.