Iron lung versus mask ventilation in acute exacerbation of COPD: a randomised crossover study

Diaphragm Neurostimulation Assisted Ventilation in Critically Ill Patients

Diaphragm neurostimulation consists of placing electrodes directly on or in proximity to the phrenic nerve(s) to elicit diaphragmatic contractions. Since its initial description in the 18th century, indications have shifted from cardiopulmonary resuscitation to long-term ventilatory support. Recently, the technical development of devices for temporary diaphragm neurostimulation has opened up the possibility of a new era for the management of mechanically ventilated patients. Combining positive pressure ventilation with diaphragm neurostimulation offers a potentially promising new approach to the delivery of mechanical ventilation which may benefit multiple organ systems. Maintaining diaphragm contractions during ventilation may attenuate diaphragm atrophy and accelerate weaning from mechanical ventilation. Preventing atelectasis and preserving lung volume can reduce lung stress and strain and improve homogeneity of ventilation, potentially mitigating ventilator-induced lung injury. Furthermore, restoring the thoracoabdominal pressure gradient generated by diaphragm contractions may attenuate the drop in cardiac output induced by positive pressure ventilation. Experimental evidence suggests diaphragm neurostimulation may prevent neuroinflammation associated with mechanical ventilation. This review describes the historical development and evolving approaches to diaphragm neurostimulation during mechanical ventilation and surveys the potential mechanisms of benefit. The review proposes a research agenda and offers perspectives for the future of diaphragm neurostimulation assisted mechanical ventilation for critically ill patients.

Causal association between iron deficiency anemia and chronic obstructive pulmonary disease: A bidirectional two-sample Mendelian randomization study

BACKGROUND

Observational studies have found an association between iron deficiency anemia (IDA) and chronic obstructive pulmonary disease (COPD) risk. However, whether IDA plays a role in COPD development remains unclear.

OBJECTIVES

This study was performed to explore the causal association between IDA and COPD.

METHODS

We obtained summary statistics for IDA from 6087 cases and 211,115 controls of European ancestry in an open genome-wide association study (GWAS) to select strongly associated single nucleotide polymorphisms that could serve as instrumental variables for IDA (P < 5 × 10-8). Additional summary statistics for COPD were obtained from 6915 COPD cases and 186,723 controls of European ancestry from a publicly available GWAS. A bidirectional Mendelian randomization analysis was performed using inverse variance weighting as the primary method of analysis. The reliability of the results was verified by heterogeneity and sensitivity analysis.

RESULTS

IDA increased the risk of COPD, with an odds ratio (OR) of 1.15 (95% confidence interval (CI: 1.04-1.25, p = 0.002). There was no evidence of a causal effect of COPD on IDA risk, with an OR of 0.99 (95% CI: 0.87-1.13, p = 0.91). The sensitivity analysis showed no evidence of heterogeneity or horizontal pleiotropy.

CONCLUSIONS

We found that IDA increases the risk of COPD. Additionally, there was no evidence that COPD increases the risk of IDA. Therefore, IDA should be considered in future COPD risk studies and reintroduced as a potential therapeutic target. The relationship between COPD and IDA risk requires further study using indirect mechanisms.

Assessing Treatment Success or Failure as an Outcome in Randomised Clinical Trials of COPD Exacerbations. A Meta-Epidemiological Study

A recently published ERS core outcome set recommends that all trials of COPD exacerbation management should assess the treatment success (or “cure” of the exacerbation), defined as a dichotomous measure of the overall outcome of an exacerbation. This methodological systematic review describes and compares the instruments that were used to assess treatment success or failure in 54 such RCTs, published between 2006–2020. Twenty-three RCTs used composite measures consisting of several undesirable outcomes of an exacerbation, together defining an overall unfavourable outcome, to define treatment failure. Thirty-four RCTs used descriptive instruments that used qualitative or semi-quantitative descriptions to define cure, marked improvement, improvement of the exacerbation, or treatment failure. Treatment success and failure rates among patients receiving guidelines-directed treatments at different settings and timepoints are described and could be used to inform power calculations in future trials. Descriptive instruments appeared more sensitive to treatment effects compared to composite instruments. Further methodological studies are needed to optimise the evaluation of treatment success/failure. In the meantime, based on the findings of this systematic review, the ERS core outcome set recommends that cure should be defined as sufficient improvement of the signs and symptoms of the exacerbation such that no additional systemic treatments are required.

A pilot study of short-term hemodynamic effects of negative pressure ventilation in chronic obstructive pulmonary disease assessed using electrical cardiometry

BACKGROUND

Pulmonary rehabilitation combined with negative pressure ventilation (NPV) demonstrated benefits in patients with chronic obstructive pulmonary disease (COPD). The effect of NPV remains unknown. This study aims to clarify the short-term response of the hemodynamic outcome of NPV in patients with COPD undergoing pulmonary rehabilitation program by electrical cardiometry.

METHODS

This is an observational retrospective study of COPD patients who had been treated in a pulmonary rehabilitation unit with NPV between January 2018 and December 2019 that were enrolled to analyze the hemodynamic outcomes.

RESULTS

Thirty patients with COPD that were undergoing a pulmonary rehabilitation program and were regularly receiving NPV were enrolled. Cardiac output (p < .001) and heart rate (p < .001) showed a significant decrease after NPV. Stroke volume did not demonstrate significant change (p = .15). There was a significant decrease in thoracic fluid content (p = .016) and a significant increase in stroke volume variation (p = .038) systemic vascular resistance (p < .001) and left ventricular ejection time (p < .001). Other hemodynamic parameters were all comparable before and after NPV.

CONCLUSIONS

Negative pressure ventilation demonstrated an impact on hemodynamics in patients with chronic obstructive pulmonary disease undergoing pulmonary rehabilitation. Electrical cardiometry is a feasible method of determining the hemodynamic effects of negative pressure ventilation. Thoracic fluid content significantly decreased immediately after the NPV.

Negative pressure ventilation as a bridge to lung transplant

Recent years have witnessed evolution of lung allocation strategies to prioritize sicker recipients. In the pre-transplant period, this has translated into increased utilization of invasive extracorporeal or mechanical ventilatory support as a bridge to lung transplantation. The morbidity associated with these strategies warrants consideration to less invasive respiratory support modalities. Herein, we present a case highlighting successful bridge to lung transplantation with a relatively non-invasive negative pressure ventilator.

Effects of extrathoracic mechanical ventilation on pulmonary hypertension secondary to lung disease

PURPOSE

Biphasic cuirass ventilation (BCV) is a form of non-invasive extrathoracic positive and negative pressure mechanical ventilation. The present study was conducted to quantify our positive experience using BCV to dramatically improve gas exchange and cardiac function in patients with acute exacerbation of chronic respiratory failure and secondary pulmonary hypertension (PH).

METHODS

BCV was applied for 2 weeks in 17 patients with PH caused by lung disease. Ventilation sessions were limited to 1 h per day to prevent exhaustion. To assess respiratory and circulatory effects, percutaneous arterial oxygen saturation (SpO2) was measured before and after each daily BCV session, and right heart catheter test [mean pulmonary artery pressure (mPAP), right atrium pressure (RAP), pulmonary artery occlusion pressure (PAOP) and cardiac index (CI)] and serum N-terminal pro-brain natriuretic peptide (NT-proBNP) were measured before and after a series of BCV sessions.

RESULTS

SpO2 transiently improved after each BCV session. After a series of BCV, mPAP decreased from 27.2 to 22.4 mmHg (p = 0.0007). PAOP, CI and serum NT-proBNP levels decreased compared with baseline. No patients were treated with epoprostenol, iloprost, bosentan or sildenafil for PH.

CONCLUSION

BCV may improve circulatory function in patients with PH caused by lung disease.

Pediatric Noninvasive Ventilation

Noninvasive ventilation has been available for many years for use in the pediatric population. Historically, continuous positive airway pressure and bilevel positive airway pressure modes were used for respiratory diseases, including neonatal apnea, bronchiolitis, asthma, and pneumonia. Newer studies suggest that noninvasive ventilation is also an effective and safe mode for support of children with acute respiratory distress syndrome and respiratory failure. The newest type of noninvasive respiratory support is high flow nasal cannula, which has gained popularity in the past few years and its use is being justified in the literature. Studies have shown that these therapies can decrease the need for intubation and ventilation, decrease length of intensive care days, and increase patient comfort. Additional research is needed to support optimal setting selection and recommendations for the use of noninvasive therapies for infants and children.

Negative Pressure Noninvasive Ventilation (NPNIV): History, Rationale, and Application

Man has recognized the vital role of breathing since antiquity, beginning with archeological findings depicting inhalation therapy using herbs, oils, and other substances since 6000 BC. Man has taken the automaticity of breathing for granted, expecting its adequacy for all activities whether awake or asleep. Dickinson W. Richards, MD, Nobel Laureate, said in 1962: “Breathing is that essential physiologic function that is straddled between the conscious & the unconscious and subject to both.” The understanding of the components of this critical physiologic function that starts at birth, and must be continuous and widely adaptable to support all levels of physical, metabolic, and functional needs, has evolved slowly over the millennia by many brilliant scientists from a combination of keen observation, imagination, daring experimentation, trial and error, and necessity, while overcoming dogma, religious inhibitions, and politics. It is this gradual chronologic process, still evolving, which guides what we do for patients today.

Negative- versus positive-pressure ventilation in intubated patients with acute respiratory distress syndrome

Introduction

Recent experimental data suggest that continuous external negative-pressure ventilation (CENPV) results in better oxygenation and less lung injury than continuous positive-pressure ventilation (CPPV). The effects of CENPV on patients with acute respiratory distress syndrome (ARDS) remain unknown.

Methods

We compared 2 h CENPV in a tankrespirator ("iron lung") with 2 h CPPV. The six intubated patients developed ARDS after pulmonary thrombectomy (n = 1), aspiration (n = 3), sepsis (n = 1) or both (n = 1). We used a tidal volume of 6 ml/kg predicted body weight and matched lung volumes at end expiration. Haemodynamics were assessed using the pulse contour cardiac output (PiCCO) system, and pressure measurements were referenced to atmospheric pressure.

Results

CENPV resulted in better oxygenation compared to CPPV (median ratio of arterial oxygen pressure to fraction of inspired oxygen of 345 mmHg (minimum-maximum 183 to 438 mmHg) vs 256 mmHg (minimum-maximum 123 to 419 mmHg) (P < 0.05). Tank pressures were -32.5 cmH₂O (minimum-maximum -30 to -43) at end inspiration and -15 cmH₂O (minimum-maximum -15 to -19 cmH₂O) at end expiration. NO Inspiratory transpulmonary pressures decreased (P = 0.04) and airway pressures were considerably lower at inspiration (-1.5 cmH₂O (minimum-maximum -3 to 0 cmH₂O) vs 34.5 cmH₂O (minimum-maximum 30 to 47 cmH₂O), P = 0.03) and expiration (4.5 cmH₂O (minimum-maximum 2 to 5) vs 16 cmH₂O (minimum-maximum 16 to 23), P =0.03). During CENPV, intraabdominal pressures decreased from 20.5 mmHg (12 to 30 mmHg) to 1 mmHg (minimum-maximum -7 to 5 mmHg) (P = 0.03). Arterial pressures decreased by approximately 10 mmHg and central venous pressures by 18 mmHg. Intrathoracic blood volume indices and cardiac indices increased at the initiation of CENPV by 15% and 20% (P < 0.05), respectively. Heart rate and extravascular lung water indices remained unchanged.

Conclusions

CENPV with a tank respirator improved gas exchange in patients with ARDS at lower transpulmonary, airway and intraabdominal pressures and, at least initially improving haemodynamics. Our observations encourage the consideration of further studies on the physiological effects and the clinical effectiveness of CENPV in patients with ARDS.

Respiratory High-Dependency Care Units for the burden of acute respiratory failure

The burden of acute respiratory failure (ARF) has become one of the greatest epidemiological challenges for the modern health systems. Consistently, the imbalance between the increasing prevalence of acutely de-compensated respiratory diseases and the shortage of high-daily cost ICU beds has stimulated new health cost-effective solutions. Respiratory High-Dependency Care Units (RHDCU) provide a specialised environment for patients who require an "intermediate" level of care between the ICU and the ward, where non-invasive monitoring and assisted ventilation techniques are preferentially applied. Since they are dedicated to the management of "mono-organ" decompensations, treatment of ARF patients in RHDCU avoids the dangerous "under-assistance" in the ward and unnecessary "over-assistance" in ICU. RHDCUs provide a specialised quality of care for ARF with health resources optimisation and their spread throughout health systems has been driven by their high-level of expertise in non-invasive ventilation (NIV), weaning from invasive ventilation, tracheostomy care, and discharging planning for ventilator-dependent patients.