Mohd saif khanPresenter

Introduction

• Benefits of face mask NIV are controversial in acute hypoxemic respiratory failure.

• A recent investigation by Frat et al showed that high-flow nasal cannula has mortality benefit over NIV.

NIV in ARDS

• High PEEP requirements• Increased risk of air leak around the mask• Patient intolerance

• Solution to this problem: helmet interface• Advantages

• Improved tolerability • Less air leak • Improved seal integrity at the neck.

Methodology

• Adult medical ICU• Single centre study• Inclusion criteria– Patients 18 years or older – Requiring face mask NIV for at least 8 hours for

the management of ARDS – Acute respiratory distress syndrome was defined

by the Berlin criteria.

• Exclusion criteria• Impending cardiopulmonary arrest, • GCS<8, • Absence of airway protective gag reflex,• Elevated ICP,• Tracheostomy, or upper airway obstruction• Pregnant • had refused endotracheal intubation

• Intervention

After 8 hours of NIV via face mask

consent

Randomly assigned in a 1:1 ratio

Continue with the face mask

(control)

Switch to a helmet interface

(intervention)

Randomization method:A computer-generated, permuted block

randomization scheme with varying block sizes ranging from 4 to 8

Ventilator settings:• To avoid carbon dioxide rebreathing, pressure support levels

were set to maintain a ventilator inspiratory flow rate of more than 100 L/min

• To minimize inspiratory effort and optimize patient-ventilator synchrony, the ventilator pressurization time was set to 50 milliseconds and cycling off delay set to 50% of maximal inspiratory flow

• PEEP was increased in increments of 2 to 3 cmH2O SpO2 >90% at FIO2< 60

• Inspiratory pressure was increased in increments of 2 to 3 cmH2Oto obtain a RR<25/min and disappearance of accessory muscle activity.

• Patients were intubated if:–neurologic deterioration, –Persistent or worsening respiratory failure

(eg, oxygen saturation <88%, respiratory rate >36/min), – intolerance of face mask or helmet,–airway bleeding, or –copious respiratory secretions.

Study Outcomes

• Primary outcome: • Proportion of patients who required endotracheal

intubation

• Secondary outcomes • 28-day invasive ventilator-free days (ie, days alive

without mechanical ventilation),• Duration of ICU and hospital length of stay, • Hospital and 90-day mortality, and • Adverse events

Statistical Analysis

• Sample size calculation– Assuming an intubation rate of 50% for patients

with hypoxemic respiratory failure requiring NIV, – a total of206 patients would provide 80% power

to detect a 20% absolute reduction of the primary outcome, with a 2-sided α level of 0.05.

– All analyses: Intention-to-treat analysis.– χ2 test or Fisher exact test: compare

categorical variables–Wilcoxon-Mann-Whitney 2-sample rank

sum test or t tests for continuous variables.– Time to event analysis (Kaplan-Meier): To

evaluate the effect of the intervention on 90-day survival

Safety Monitoring

• Independent data and safety monitoring board (DSMB)

• Interim analyses were planned at one-third and two-thirds of enrolment

• DSMB recommended that the study be stopped for both efficacy and safety after the enrollment of 83 patients.

• The board felt that it would be difficult to justify enrolling more patients in the face-mask arm of the trial, which exposed them to greater risks.

Results

Discussion

• Main findings of this study were:• Helmet is superior to face mask– significantly reduced the intubation rate– Improved ventilator free days– Significant decrease in ICU LOS and 90-day

mortality

• This trial enrolled only those patients who were at high illness acuity and substantial chance of requiring intubation, therefore 8-hour period of face mask NIV was chosen.

• Helmet eased effective delivery of higher levels of PEEP and higher airway pressures without substantial air leak.

• high ventilator fresh gas flow reduce the risk of CO2 rebreathing.

• failures of helmet NIV were rarely due to respiratory failure, but instead usually due to mental status changes and loss of the airway protective reflex.

• Cautions and limitations• large internal volume of the helmet and its high

compliance may lead to CO2 rebreathing17,34 and patient-ventilator dyssynchrony

• learning curve-training of all physicians and staff will be needed

• Unblinded• No external validity-single-center trial