Tag Archives: NIV

High Flow Nasal Cannulae In Paediatric Retrieval

High Flow Nasal Cannulae (HFNC) oxygen therapy was introduced in paediatric interfacility retrievals undertaken by the Mater Children’s PICU Retrieval Team in Queensland, Australia. In 793 under 2 year olds, HFNC was associated with a reduction in infants receiving invasive or non-invasive ventilation. 77% of the patients had bronchiolitis.
The rationale for this treatment is explained as:

Owing to the inherent properties of the infant respiratory system with small airways and high chest compliance, the risk of developing atelectasis is high in bronchiolitis. HFNC therapy applied early in the disease process may prevent progression of the disease and maintain normal lung volumes, thereby preventing atelectasis. As a result, the functional residual capacity can be maintained and work of breathing reduced, which may stabilize the patient sufficiently to avoid the need for intubation. For this purpose we used flow rates of 2 L/kg/min which have been shown to result in a positive end-expiratory pressure of 4–5 cmH2O

Read more on high-flow nasal cannula oxygen therapy.
High-flow nasal cannula (HFNC) support in interhospital transport of critically ill children
Intensive Care Med. 2014 Feb 15. [Epub ahead of print]
[EXPAND Abstract]

BACKGROUND: Optimal respiratory support for interhospital transport of critically ill children is challenging and has been scarcely investigated. High-flow nasal cannula (HFNC) therapy has emerged as a promising support mode in the paediatric intensive care unit (PICU), but no data are available on HFNC used during interhospital transport. We aimed to assess the safety of HFNC during retrievals of critically ill children and its impact on the need for invasive ventilation (IV).
METHODS: This was a retrospective, single-centre study of children under 2 years old transported by a specialized paediatric retrieval team to PICU. We compared IV rates before (2005-2008) and after introduction of HFNC therapy (2009-2012).
RESULTS: A total of 793 infants were transported. The mean transport duration was 1.4 h (range 0.25-8), with a mean distance of 205 km (2-2,856). Before introduction of HFNC, 7 % (n = 23) were retrieved on non-invasive ventilation (NIV) and 49 % (n = 163) on IV. After introduction of HFNC, 33 % (n = 150) were retrieved on HFNC, 2 % (n = 10) on NIV, whereas IV decreased to 35 % (n = 162, p < 0.001). No patients retrieved on HFNC required intubation during retrieval, or developed pneumothorax or cardiac arrest. Using HFNC was associated with a significant reduction in IV initiated by the retrieval team (multivariate OR 0.51; 95 % CI 0.27-0.95; p = 0.032).
CONCLUSIONS: We report on a major change of practice in transport of critically ill children in our retrieval system. HFNC therapy was increasingly used and was not inferior to low-flow oxygen or NIV. Randomized trials are needed to assess whether HFNC can reduce the need for IV in interhospital transport of critically ill children.


High flow nasal cannula oxygen

Where I work high flow humidified nasal cannula oxygen (HFNC) is used for infants with bronchiolitis and our ICU also employs it for selected adult patients. This is a relatively recent addition to our choice of oxygen delivery systems, and many emergency physicians may still be unfamiliar with it.
A recent review outlines the (scant) evidence for its use in neonates, infants, and adults, and proposes some mechanisms for its effect.
It’s a bit like the traditional delivery of oxygen via nasal cannulae. However, it is recommended that flow rates above 6 l/min are heated and humidified, so the review referred to heated, humidified, high flow nasal cannulae (HFNC).
HFNC began as an alternative to nasal CPAP for premature infants. There are as yet no definitive studies showing its superiority over CPAP.
HFNC may decrease the need for intubation when compared to standard nasal cannula in infants with bronchiolitis.
No hard outcome data yet exist. It has mainly been used for hypoxemic respiratory failure rather than patients with hypercarbia such as COPD patients.
How it works
The following are proposed mechanisms for improvements in gas exchange / oxygenation:

1. A high FiO2 is maintained because flow rates are higher than spontaneous inspiratory demand, compared with standard facemasks and low flow nasal cannulae which entrain a significant amount of room air.

2. Nasopharyngeal dead space ‘washout’. The additional gas flow within the nasopharyngeal space may  reduce dead space: tidal volume ratio. There are some animal neonatal data to show improved CO2 clearance with flows up to 8 l/min.

3. Stenting of the upper airway by positive pressure may decrease upper airways resistance and reduce work of breathing.

4. Some positive pressure (akin to CPAP) may be generated, which can help recruit lung and decrease ventilation–perfusion mismatch; however this is not consistently present in all studies, and high flows are needed to generate even modest pressures. For example, in a study on postoperative cardiac surgery patients, HFNC at 35 l/min generated a nasopharyngeal pressure of only 2.7 ± 1 cmH2O.

Drawbacks and things to know

Studies suggest that if benefit is going to be seen in adult or paediatric patients, this should be evident in the first 30-60 minutes.

Any modest positive pressure generated will be reduced by an open mouth or when there is a significant leak between the cannulae and the nares.

HFNC maintain a fixed flow and generate variable pressures, and the pressures may be more inconsistent in patients with respiratory distress with high respiratory rates and mouth breathing. Compare this with non-invasive ventilation (CPAP and or BiPAP) in which variable flow is used to generate a fixed pressure.

The authors’ summary is helpful:

We postulate that the predominant benefit of HFNC is the ability to match the inspiratory demands of the distressed patient while washing out the nasopharyngeal dead space. Generation of positive airway pressure is dependent on the absence of significant leak around the nares and mouth and seems less likely to be a predominant factor in relieving respiratory distress for most patients.

NIV such as CPAP and bilevel positive airway pressure should still be considered first line therapy in moderately distressed patients in whom supplementation oxygen is insufficient and when a consistent positive pressure is indicated.

There are numerous ongoing trials which should hopefully clarify indications for HFNC and the mechanisms by which it may be beneficial.

An earlier summary of the evidence was written by my Scandinavian chums. And Reuben Strayer uses it to optimise oxygenation during RSI as a modification of the NODESAT technique.
Use of high flow nasal cannula in critically ill infants, children, and adults: a critical review of the literature
Intensive Care Med. 2013 Feb;39(2):247-57
[EXPAND Abstract]

BACKGROUND: High flow nasal cannula (HFNC) systems utilize higher gas flow rates than standard nasal cannulae. The use of HFNC as a respiratory support modality is increasing in the infant, pediatric, and adult populations as an alternative to non-invasive positive pressure ventilation.
OBJECTIVES: This critical review aims to: (1) appraise available evidence with regard to the utility of HFNC in neonatal, pediatric, and adult patients; (2) review the physiology of HFNC; (3) describe available HFNC systems (online supplement); and (4) review ongoing and planned trials studying the utility of HFNC in various clinical settings.
RESULTS: Clinical neonatal studies are limited to premature infants. Only a few pediatric studies have examined the use of HFNC, with most focusing on this modality for viral bronchiolitis. In critically ill adults, most studies have focused on acute respiratory parameters and short-term physiologic outcomes with limited investigations focusing on clinical outcomes such as duration of therapy and need for escalation of ventilatory support. Current evidence demonstrates that HFNC generates positive airway pressure in most circumstances; however, the predominant mechanism of action in relieving respiratory distress is not well established.
CONCLUSION: Current evidence suggests that HFNC is well tolerated and may be feasible in a subset of patients who require ventilatory support with non-invasive ventilation. However, HFNC has not been demonstrated to be equivalent or superior to non-invasive positive pressure ventilation, and further studies are needed to identify clinical indications for HFNC in patients with moderate to severe respiratory distress.


Pre-hospital CPAP for pulmonary oedema

The physician-staffed mobile intensive care units of SAMU (Service d’Aide Médicale Urgente) in France provided the location for this randomised controlled trial of CPAP for acute cardiogenic pulmonary oedema.

STUDY OBJECTIVE: The purpose of this randomized controlled trial was to determine the immediate and delayed effects of noninvasive ventilation for patients in acute cardiogenic pulmonary edema (ACPE) in addition to aggressive usual care in a medical prehospital setting.

METHODS: Out-of-hospital patients in severe ACPE were eligible for the study. Patients were randomized to receive either usual care, including conventional optimal treatment with furosemide, oxygen, and high-dose boluses of isosorbide dinitrate plus oxygen, or conventional medications plus out-of-hospital continuous positive airway pressure (CPAP). The primary outcome was the treatment success defined as all of respiratory rate less than 25 breaths per minute and oxygen saturation of greater than 90% at the end of 1-hour study. Secondary end points included death during 30 days after inclusion. Lengths of intensive care unit and hospital stays were also recorded.

RESULTS: In total, 124 patients were enrolled into the study. The 2 groups had similar baseline characteristics. For the primary outcome analysis, 22 (35.5%) of 62 patients were considered as experiencing a treatment success in the usual care group vs 19 (31.7%) of 60 in the CPAP group (P = .65). Seven patients died within 30 days in the usual care group vs 6 in the CPAP group (P = .52). There were no statistically significant differences between the treatment groups for length of stay either in hospital or in the intensive care unit.

CONCLUSION: In the prehospital setting, in spite of its potential advantages for patients in ACPE, CPAP may not be preferred to a strict optimal intravenous treatment.

Continuous positive airway pressure for cardiogenic pulmonary edema: a randomized study
Am J Emerg Med. 2011 Sep;29(7):775-81

Pre-hospital NIV

"The driver's dyspneic - pass the Boussignac valve!"

Pre-hospital non-invasive ventilation for patients with acute dyspnoea features in two journals this month. Researchers at the Ambulance Service New South Wales published an evidence-based review of pre-hospital NIV for acute cardiogenic pulmonary oedema, concluding that there are probable benefits.

Background Non-invasive ventilation (NIV) is increasingly being implemented by many ambulance jurisdictions as a standard of care in the out-of-hospital management of acute cardiogenic pulmonary oedema (ACPO). This implementation appears to be based on the body of evidence from the emergency department (ED) setting, with the assumption that earlier administration by paramedics would give benefits with regard to inhospital mortality and the rate of endotracheal intubation beyond those seen when initiated in the ED. This paper sought to identify and review the current level of evidence supporting NIV in the prehospital setting.

Methods Electronic searches of Medline, EMBASE, CINAHL, Cochrane Database of Systematic Reviews and Cochrane Database of Controlled Trials were conducted and reference lists of relevant articles were hand searched.

Results The search identified 12 primary studies documenting the use of NIV, either continuous positive airway pressure or bi-level non-invasive ventilation, for ACPO in the out-of-hospital setting. Only three studies were randomised controlled trials, with none addressing inhospital mortality as a primary outcome measure. The majority of articles were non-comparative descriptive studies.

Conclusion Early prehospital NIV appears to be a safe and feasible therapy that results in faster improvement in physiological status and may decrease the need for intubation when compared with delayed administration in the ED. There is weak evidence that is may decrease mortality. The cost versus benefit equation of system-wide prehospital implementation of NIV is unclear and, based on the current evidence, should be considered with caution.

Prehospital non-invasive ventilation for acute cardiogenic pulmonary oedema: an evidence-based review.
Emerg Med J. 2011 Jul;28(7):609-12
At the same time, the National Association of EMS Physicians has published a position statement on noninvasive positive pressure ventilation, for the general indication of acute dyspnoea. It states:

The general indication for NIPPV is dyspnea accompanied by early respiratory failure in patients with intact protective airway reflexes and mental status. The majority of NIPPV studies have focused on patients with acute pulmonary edema.

However, NIPPV may prove useful with other reversible disease processes such as chronic obstructive pulmonary disease or asthma exacerbations. While utilized in in-hospital practice, the role of NIPPV for pneumonia-associated respiratory failure is less clear. While some clinicians advocate the use of NIPPV to augment oxygenation prior to ETI in the in- hospital setting, there are no studies evaluating this strategy in the prehospital setting.

Noninvasive positive pressure ventilation: resource document for the National Association of EMS Physicians position statement.
Prehosp Emerg Care. 2011 Jul-Sep;15(3):432-8
Full Text of Position Statement

CPAP in LVF again

Another stab at assessing noninvasive ventilation in cardiogenic pulmonary oedema has been made by Italian researchers who compared CPAP with noninvasive pressure support ventilation (nPSV – similar to BiPAP) in a randomised trial of  80 patients. The primary outcome was endotracheal intubation rates. There was no significant difference between the two modalities. This result is in keeping with the much larger 3CPO trial.

Continuous Positive Airway Pressure vs. Pressure Support Ventilation in Acute Cardiogenic Pulmonary Edema: A Randomized Trial
J Emerg Med. 2010 Nov;39(5):676-84

NIV in chest trauma

ICU patients with thoracic trauma who had no other indication for intubation than marked hypoxaemia (pO2/FiO2 < 200 mmHg) were randomised to intubation vs non-invasive ventilation (NIV). Analgesia was via epidural bupivacaine / fentanyl or iv remifentanil. Numbers are small (total 50 patients) - partly because the trial was stopped early due to large difference in the outcome of tracheal intubation between the two groups favouring NIV. Length of hospital stay was significantly shorter in the NIV group but there was no survival difference. Noninvasive ventilation reduces intubation in chest trauma-related hypoxemia: a randomized clinical trial
Chest. 2010 Jan;137(1):74-80

Heliox in COPD exacerbation

A 65:35 helium-oxygen mix was compared with 35% oxygen in air in patients with COPD exacerbations requiring non-invasive ventilation. In this RCT there was no difference in intubation rates between the heliox or air/oxygen groups.
A multicenter, randomized trial of noninvasive ventilation with helium-oxygen mixture in exacerbations of chronic obstructive lung disease
Crit Care Med. 2010 Jan;38(1):145-51

NIV for weaning

Use of non-invasive ventilation to wean critically ill adults off invasive ventilation: meta-analysis and systematic review
The growing evidence base in support of liberating patients from invasive mechanical ventilation by means of non-invasive weaning is summarised in this systematic review of 12 randomised trials. Non-invasive weaning was associated with decreased mortality, ventilator associated pneumonia, length of stay in intensive care and hospital, total duration of mechanical ventilation, and duration of invasive ventilation. It should be noted that most of the trials exclusively enrolled patients with exacerbation of chronic obstructive pulmonary disease; benefits in other types of ventilated patients remain to be firmly proven.
BMJ. 2009 May 21;338:b157

Nurse-delivered prehospital CPAP

A nurse-based pre-hospital care system in Holland describes its experience with pre-hospital CPAP for acute cardiogenic pulmonary oedema. It appears that the simple Boussignac apparatus is straightforward to apply in the ambulance environment. Arguments about lack of outcome studies aside, if it’s necessary to undertake an interhospital transfer of a patient established on CPAP then this might be a relatively straightforward means of doing so.