The role of high-frequency oscillatory ventilation in the treatment of acute respiratory failure in adults

Oscillatory ventilation redux: alternative perspectives on ventilator-induced lung injury in the acute respiratory distress syndrome

For patients with the acute respiratory distress syndrome (ARDS), ventilation strategies that limit end-expiratory derecruitment and end-inspiratory overdistension are the only interventions to have significantly reduced the morbidity and mortality. For this reason, the use of high-frequency oscillatory ventilation (HFOV) was considered to be an ideal protective strategy, given its reliance on very low tidal volumes cycled at very high rates. However, results from clinical trials in adults with ARDS have demonstrated that HFOV does not improve clinical outcomes. Recent experimental and computational studies have shown that oscillation of a mechanically heterogeneous lung with multiple simultaneous frequencies can reduce parenchymal strain, improve gas exchange, and maintain lung recruitment at lower distending pressures compared to traditional ‘single-frequency’ HFOV. This review will discuss the theoretical rationale for the use of multiple oscillatory frequencies in ARDS, as well as the mechanisms by which it may reduce the risk for ventilator-induced lung injury.

Successful rescue combination of extracorporeal membrane oxygenation, high-frequency oscillatory ventilation and prone positioning for the management of severe methicillin-resistant Staphylococcus aureus pneumonia complicated by pneumothorax: a case report and literature review

BACKGROUND

To describe the experience of combination therapy with extracorporeal membrane oxygenation(ECMO), high-frequency oscillatory ventilation(HFOV) and prone positioning in treating severe respiratory failure caused by community acquired methicillin resistant Staphylococcus aureus(CA-MRSA).

CASE PRESENTATION

A 30-year-old female presented with fever and dyspnea for 3 days. She was diagnosed CA-MRSA pneumonia complicated by severe respiratory failure, pneumothorax and neutropenia. Venovenous ECMO was applied within 8 h of the pneumothorax diagnosis. For amelioration of ventilator-induced lung injury, HFOV and prone positioning were combined with ECMO. The patient's condition improved considerably. ECMO was weaned on day 19, and she was discharged on day 48 with good lung recovery.

CONCLUSIONS

To the best of our knowledge, this was the first case in which ECMO was combined with HFOV and prone positioning to treat severe necrotic CA-MRSA pneumonia complicated with pneumothorax. This combination therapy may provide safe respiratory support, may minimize the risk of barotrauma, and provide better drainage of secretions in patients with necrotizing pneumonia.

Different ventilation modes combined with ambroxol in the treatment of respiratory distress syndrome in premature infants

The aim of the present study was to compare the effectiveness of different modes of mechanical ventilation in combination with secretolytic therapy with ambroxol in premature infants with respiratory distress syndrome. Seventy-three premature infants with hyaline membrane disease (HMD) (stage III–IV), also known as respiratory distress syndrome, who were supported by mechanical ventilation in the neonatal intensive care unit (NICU) of Xuzhou Central Hospital, were involved in the present study, between January 2013 and February 2015. Forty cases were randomly selected and treated with high frequency oscillatory ventilation (HFOV), forming the HFOV group, whereas 33 cases were selected and treated with conventional mechanical ventilation (CMV), forming the CMV group. Patients in the two groups were administered ambroxol intravenously at a dosage rate of 30 mg/kg body weight at the beginning of the study. The present study involved monitoring the blood gas index as well as changes in the respiratory function index in the two groups. Additionally, the incidence of complications in the premature infants in the two groups was observed prior to and following the ventilation. Pulmonary arterial oxygen tension (PaO₂), the PaO₂/fraction of inspired oxygen (FiO₂) ratio, the oxygenation index [OI = 100 × mean airway pressure (MAP) × FiO₂/PaO₂], as well as the arterial/alveolar oxygen partial pressure ratio (a/APO₂) = PaO₂/(713 × FiO₂ partial pressure of carbon dioxide (PaCO₂)/0.8) of the patients in the HFOV group after 1, 12 and 24 h of treatment were significantly improved as compared to the patients of the CMV group. However, there was no significant difference between patients in the two groups with regard to the number of mortalities, complications such as pneumothorax, bronchopulmonary dysplasia (BPD), retinopathy of prematurity (ROP), intraventricular hemorrhage (IVH), periventricular leukomalacia (PVL), and the time of ventilation. In conclusion, combining HFOV with ambroxol secretolytic therapy is a more viable option, as the combined treatment resulted in significant improvements in arterial blood gas levels, oxygenation and the respiratory function of lungs in preterm infants.

One-year resource utilisation, costs and quality of life in patients with acute respiratory distress syndrome (ARDS): secondary analysis of a randomised controlled trial

Background

The long-term economic and quality-of-life outcomes of patients admitted to intensive care unit (ICU) with acute respiratory distress syndrome are not well understood. In this study, we investigate 1-year costs, survival and quality of life following ICU admission in patients who required mechanical ventilation for acute respiratory distress syndrome.

Methods

Economic analysis of data collected alongside a UK-based multi-centre randomised, controlled trial, aimed at comparing high-frequency oscillatory ventilation with conventional mechanical ventilation. The study included 795 critically ill patients admitted to ICU. Hospital costs were assessed using daily data. Post-hospital healthcare costs, patient out-of-pocket expenses, lost earnings of survivors and their carers and health-related quality of life were assessed using follow-up surveys.

Results

The mean cost of initial ICU stay was £26,857 (95 % CI £25,222–£28,491), and the average daily cost in ICU was £1738 (CI £1667–£1810). Following hospital discharge, the average 1-year cost among survivors was £7523 (CI £5692–£9354). The mean societal cost at 1 year was £44,077 (£41,168–£46,985), and the total societal cost divided by the number of 1-year survivors was £90,206. Survivors reported significantly lower health-related quality of life than the age- and sex-matched reference population, and this difference was more marked in younger patients.

Conclusions

Given the high costs and low health-related quality of life identified, there is significant scope for further research aimed at improving care in this in-need patient group.

Trial registration

ISRCTN10416500

Approaches to ventilation in intensive care

BACKGROUND

Mechanical ventilation is a common and often life-saving intervention in intensive care medicine. About 35% of all patients in intensive care are mechanically ventilated; about 15% of these patients develop a ventilation-associated pneumonia. The goal of ventilation therapy is to lessen the work of respiration and pulmonary gas exchange and thereby maintain or restore an adequate oxygen supply to the body's tissues. Mechanical ventilation can be carried out in many different modes; the avoidance of ventilation-induced lung damage through protective ventilation strategies is currently a major focus of clinical interest.

METHOD

This review is based on pertinent articles retrieved by a selective literature search.

RESULTS

Compared to conventional lung-protecting modes of mechanical ventilation, the modern modes of ventilation presented here are further developments that optimize lung protection while improving pulmonary function and the synchrony of the patient with the ventilator. In high-frequency ventilation, tidal volumes of 1-2 mL/kgBW (body weight) are given, at a respiratory rate of up to 12 Hz. Assisted forms of spontaneous respiration are also in use, such as proportional assist ventilation (PAV), neurally adjusted ventilatory assist (NAVA), and variable pressure-support ventilation. Computer-guided closed-loop ventilation systems enable automated ventilation; according to a recent meta-analysis, they shorten weaning times by 32% .

CONCLUSION

The currently available scientific evidence with respect to clinically relevant endpoints is inadequate for all of these newer modes of ventilation. It appears, however, that they can lower both the invasiveness and the duration of mechanical ventilation, and thus improve the care of patients who need ventilation. Randomized trials with clinically relevant endpoints must be carried out before any final judgments can be made.

High-frequency oscillation ventilation for hypercapnic failure of conventional ventilation in pulmonary acute respiratory distress syndrome

Introduction

High-frequency oscillation ventilation (HFOV) is regarded as particularly lung protective. Recently, HFOV has been shown to be not beneficial for acute respiratory distress syndrome (ARDS) patients in general. Due to its special physical effects, it could be beneficial, however, in inhomogeneous ARDS. This study evaluates the effect of HFOV on PaCO₂ removal in hypercapnic patients with ARDS of pulmonary origin.

Methods

Between October 2010 and June 2014 patients with ARDS of pulmonary origin with PaO₂/FiO₂ ratio >60 mmHg, but respiratory acidosis (pH <7.26) under optimized protective ventilation were switched to HFOV, using moderate airway pressure (adopting the mean airway pressure of the prior ventilation). Data from these patients were analyzed retrospectively; PaCO₂ and pH before, 1 h and 24 h after the start of HFOV were compared.

Results

Twenty-six patients with PaO₂/FiO₂ ratio 139 ± 49 and respiratory acidosis (PaCO₂ 68 ± 12 mmHg) were put on HFOV after 17 ± 22 h of conventional ventilation. Mean airway pressure was 19 cm H₂O (15 to 28). PaCO₂ decreased significantly: after 1 hour the mean difference was −14 ± 10 mmHg; P <0.01 and after 24 hours −17 ± 12 mmHg; P <0.01; n = 24. CO₂ clearance improved in all but two patients; in those, extracorporeal lung support was initiated. Oxygenation remained unchanged after 1 h and slightly increased after 24 h. No complications related to HFOV were observed. Twenty-two patients improved and could be weaned from HFOV. Twenty patients (77%) were alive on day 30.

Conclusions

HFOV could be a useful alternative in patients with ARDS of pulmonary origin with hypercapnic failure of lung-protective conventional ventilation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0935-4) contains supplementary material, which is available to authorized users.

Use of sedation and neuromuscular blockers in critically ill adults receiving high-frequency oscillatory ventilation

BACKGROUND

Nearly all patients receive sedation and neuromuscular blockers (NMBs) during high-frequency oscillatory ventilation (HFOV).

OBJECTIVE

To describe analgo-sedation and NMB use prior to and during HFOV in adults with acute respiratory distress syndrome.

METHODS

Retrospective single-center study of 131 consecutive adults whose care was managed with HFOV from 2002 to 2011.

RESULTS

During the first 4 days of HFOV, 89% and 95% of patients received sedation and opioids, respectively. Upon HFOV initiation, 119 (90.8%) patients received fentanyl doses higher than 200 µg/h; of these, 48 also received more than 20 mg/h of midazolam. Analgo-sedation doses increased significantly over time such that doses were double by day 3. Factors independently associated with fentanyl doses higher than 200 µg/h were NMB ever used (OR 4.43; 95% CI 1.26-15.65, p = 0.02), pH less than 7.15 (OR 2.08; 95% CI 1.22-3.5, p = 0.007), worsening partial pressure of oxygen/fraction of inspired oxygen (OR 1.05; 95% CI 1.00-1.10, p = 0.04), and Acute Physiology and Chronic Health Evaluation (APACHE) II score (OR 0.87; 95% CI 0.79-0.97, p = 0.009). Deep sedation was commonly administered when NMBs were not being used, with 99.2% of sedation-agitation scores of 1 or 2. Eighty-six patients (65.6%) received NMBs and use was greatest on day 1 (59.5%). Train-of-Four was measured every hour for 53.4% of patients; 29.2% of the measurements were 0 of 4. NMB use declined over the 10-year study period.

CONCLUSIONS

High analgo-sedation doses were associated with APACHE II scores, worsening gas exchange, and NMB use. Two thirds of patients received NMBs; use was highest on day 1 and subsequently declined. The percentage of patients who received NMB during HFOV in our study was lower than that previously reported. Future research should evaluate patient outcomes with and without use of NMBs, as well as the potential to manage patients with less sedation.

High-frequency oscillatory ventilation versus conventional ventilation: hemodynamic effects on lung and heart

Abstract High-frequency oscillatory ventilation (HFOV) may improve gas exchange in patients who are inadequately ventilated by conventional mechanical ventilation (CV); however, the hemodynamic consequences of switching to HFOV remain unclear. We compared the effects of CV and HFOV on pulmonary vascular conductance and left ventricular (LV) preload and performance at different airway and filling pressures. In anesthetized dogs, we measured LV dimensions, aortic and pulmonary artery (PA) flow, and mean airway ( AW) and pericardial pressures. Catheter-tip pressure manometers measured aortic, LV, left atrial, and PA pressures. The pericardium and chest were closed. At LV end-diastolic pressure (PLVED) = 5 mmHg and 12 mmHg, PEEP was varied (6 cm H2O, 12 cm H2O, and 18 cm H2O) during CV. Then, at airway pressures equal to those during CV, HFOV was applied at 4 Hz, 10 Hz, and 15 Hz. Increased AW decreased pulmonary vascular conductance. As cardiac output increased, conductance increased. At PLVED = 12 mmHg, conductance was greatest during HFOV at 4 Hz. LV preload (i.e., ALV, our index of end-diastolic volume) was similar during HFOV and CV for all conditions. At PLVED = 12 mmHg, SWLV was similar during CV and HFOV, but, at PLVED = 5 mmHg and AW 10 cm H2O, SWLV was lower during HFOV than CV. Compared to pulmonary vascular conductance at higher frequencies, at PLVED = 12 mmHg, conductance was greater at HFOV of 4 Hz. Effects of CV and HFOV on LV preload and performance were similar except for decreased SWLV at PLVED = 5 mmHg. These observations suggest the need for further studies to assess their potential clinical relevance.

Higher Frequency Ventilation Attenuates Lung Injury during High-frequency Oscillatory Ventilation in Sheep Models of Acute Respiratory Distress Syndrome

Background:

High-frequency oscillatory ventilation (HFOV) at higher frequencies minimizes the tidal volume. However, whether increased frequencies during HFOV can reduce ventilator-induced lung injury remains unknown.

Methods:

After the induction of acute respiratory distress syndrome in the model by repeated lavages, 24 adult sheep were randomly divided into four groups (n = 6): three HFOV groups (3, 6, and 9 Hz) and one conventional mechanical ventilation (CMV) group. Standard lung recruitments were performed in all groups until optimal alveolar recruitment was reached. After lung recruitment, the optimal mean airway pressure or positive end-expiratory pressure was determined with decremental pressure titration, 2 cm H2O every 10 min. Animals were ventilated for 4 h.

Results:

After lung recruitment, sustained improvements in gas exchange and compliance were observed in all groups. Compared with the HFOV-3 Hz and CMV groups, the transpulmonary pressure and tidal volumes were statistically significantly lower in the HFOV-9 Hz group. The lung injury scores and wet/dry weight ratios were significantly reduced in the HFOV-9 Hz group compared with the HFOV-3 Hz and CMV groups. Expression of interleukin-1β and interleukin-6 in the lung tissue, decreased significantly in the HFOV-9 Hz group compared with the HFOV-3 Hz and CMV groups. Malondialdehyde expression and myeloperoxidase activity in lung tissues in the HFOV-9 Hz group decreased significantly, compared with the HFOV-3 Hz and CMV groups.

Conclusion:

The use of HFOV at 9 Hz minimizes lung stress and tidal volumes, resulting in less lung injury and reduced levels of inflammatory mediators compared with the HFOV-3 Hz and CMV conditions.

Balancing the risks and benefits of oxygen therapy in critically III adults

Oxygen therapy is an integral part of the treatment of critically ill patients. Maintenance of adequate oxygen delivery to vital organs often requires the administration of supplemental oxygen, sometimes at high concentrations. Although oxygen therapy is lifesaving, it may be associated with deleterious effects when administered for prolonged periods at high concentrations. Here, we review the recent advances in our understanding of the molecular responses to hypoxia and high levels of oxygen and review the current guidelines for oxygen therapy in critically ill patients.

Mechanical ventilation: past lessons and the near future

The ability to compensate for life-threatening failure of respiratory function is perhaps the signature technology of intensive care medicine. Unchanging needs for providing effective life-support with minimized risk and optimized comfort have been, are now, and will be the principal objectives of providing mechanical ventilation. Important lessons acquired over nearly half-a-century of ICU care have brought us closer to meeting them, as technological advances in instrumentation now effectively put this hard-won knowledge into action. Rising demand in the face of economic constraints is likely to drive future innovations focused on reducing the need for user input, automating multi-element protocols, and carefully monitoring the patient for progress and complications.

Intensive buffering can keep pH above 7.2 for over 4 h during apnea: an experimental porcine study

BACKGROUND

Ventilation with low tidal volumes reduces mortality in acute respiratory distress syndrome. A further reduction of tidal volumes might be beneficial, and it is known that apneic oxygenation (no tidal volumes) with arteriovenous CO(2) removal can keep acid-base balance and oxygenation normal for at least 7 h in an acute lung injury model. We hypothesized that adequate buffering might be another approach and tested whether tris-hydroxymethyl aminomethane (THAM) alone could keep pH at a physiological level during apneic oxygenation for 4 h.

METHODS

Six pigs were anesthetized, muscle relaxed, and normoventilated. The lungs were recruited, and apneic oxygenation as well as administration of THAM, 20 mmol/kg/h, was initiated. The experiment ended after 270 min, except one that was studied for 6 h.

RESULTS

Two animals died before the end of the experiment. Arterial pH and arterial carbon dioxide tension (PaCO(2) ) changed from 7.5 (7.5, 7.5) to 7.3 (7.2, 7.3) kPa, P < 0.001 at 270 min, and from 4.5 (4.3, 4.7) to 25 (22, 28) kPa, P < 0.001, respectively. Base excess increased from 5 (3, 6) to 54 (51, 57) mM, P < 0.001. Cardiac output and arterial pressure were well maintained. The pig, which was studied for 6 h, had pH 7.27 and PaCO(2) 27 kPa at that time.

CONCLUSION

With intensive buffering using THAM, pH can be kept in a physiologically acceptable range for 4 h during apnea.

Strategies to reduce ventilator-associated lung injury (VALI)

Optimal management of the acute respiratory distress syndrome (ARDS) requires prompt recognition, treatment of the underlying cause and the prevention of secondary injury. Ventilator-associated lung injury (VALI) is one of the several iatrogenic factors that can exacerbate lung injury and ARDS. Reduction of VALI by protective low tidal volume ventilation is one of the only interventions with a proven survival benefit in ARDS. There are, however, several factors inhibiting the widespread use of this technique in patients with established lung injury. Prevention of ARDS and VALI by detecting at-risk patients and implementing protective ventilation early is a feasible strategy. Detection of injurious ventilation itself is possible, and potential biological markers of VALI have been investigated. Finally, facilitation of protective ventilation, including techniques such as extracorporeal support, can mitigate VALI.