Paper: Goren NZ et al. Comparison of BPAP S/T and Average Volume-Assured Pressure Support Modes for Hypercapnic Respiratory Failure in the Emergency Department: A Randomized Controlled Trial. Balkan Med J 2021. PMID: 34462252
Clinical Question: Does AVAPS NIPPV in patients with hypercapnic respiratory failure improve PaCO2 and pH values better than traditional BiPAP NIPPV?
What They Did:
- Single-center, single blind, prospective, randomized clinical trial
- Patients with hypercapnic respiratory failure presenting to ED
- Patients randomized to:
- Average volume-assured pressure support (AVAPS)
- Target TV: 6 – 8mL/kg
- EPAP: 6cm H20
- IPAPmin: 12cmH20
- IPAPmax: 26cmH20
- Bilevel positive airway pressure spontaneous/timed (BPAP S/T)
- EPAP 6cmH20
- IPAP 12cmH20
- IPAP increased by 2cm H2O according to patients’ blood gas and clinical findings, under the physician’s decision on patients’ needs
- Average volume-assured pressure support (AVAPS)
Outcomes:
- Primary: Improvement in PaCO2 and pH values
- Secondary:
- Change in mode (Transition to the second mode) due to treatment failure or patient’s non-compliance
- Need for intubation
- ED outcomes
Inclusion:
- Shortness of breath
- PaCO2 >45mmHg on ABG
- Indications for NIPPV in the ED
- SpO2 <90% (on room air)
- SpO2 <93% (Despite 6LPM)
- Use of accessory respiratory muscles
- Inability to speak in whole sentences due to respiratory distress
- RR > 24
- Change in mental status
Exclusion:
- Urgent need for intubation
- Patient’s inability to maintain airway continuity
- Presence of pneumothorax
- Trauma
- Cardiac arrhythmias or suspected MI
- Patients with tracheostomy
Results:
- 148 patients presented to the ED with hypercapnic respiratory failure during the trial period
- 8 patients refused to participate in the study and 60 patients were excluded
- 80 patients with hypercapnic respiratory failure requiring NIPPV
- BPAP S/T: 33pts
- AVAPS: 47pts
- COPD most common comorbid disease: 63pts (78.8%)
- GCS Range: 9 to 15
- pH Change in 1st Hour
- BPAP S/T: 0.03
- AVAPS: 0.07
- P = 0.015
- PaCO2 Excretion in 1st Hour
- BPAP S/T: 4.75
- AVAPS: 10.20
- P = 0.033
- Secondary Outcomes
Strengths:
- Randomized clinical trial
- Age, comorbid diseases, vital signs, and baseline blood gas parameters similar between groups
- Important study which compares BPAP S/T vs AVAPS NIPPV
Limitations:
- Study was underpowered
- Unable to collect information on patients’ level of comfort with the different NIPPV modes
- 13 patients were transferred to ICUs of other hospitals which limited the ability to obtain further clinical information on these patients
- Study too small to make any conclusions on safety
- As clinicians knew what type of NIPPV each patient was receiving this could impact treatment decisions (i.e. need for intubation)
- Unclear what other treatments were given to patients
- Randomization scheme is weak (envelopes) and this could be why the split of patients (33 vs 47) was odd
- Primary outcome non-patient centered and may have influenced clinical decisions on treatment and intubation
- Baseline demographic information is rather limited
Discussion:
- Study needed a minimum sample size of 94 patients achieve a power of 95% which they did not achieve (Only recruited 80 patients)
- Of note patients with hypercapnic respiratory failure had comparatively similar improvements in blood gas parameters, but with faster rates in the AVAPS mode than in the BPAP S/T. Authors feel this is due to patients’ comfort and compliance, but this was not evaluated in this trial
Author Conclusion: “In this study, improvements in blood gas parameters in the AVAPS groups were faster compared to the S/T group; However, we did not find any significant difference between the groups in terms of clinical parameters. The AVAPS mode is as effective and safe as BPAP S/T in treating patients with hypercapnic respiratory failure in the ED.”
Clinical Take Home Point: In patients presenting to the ED with hypercapnic respiratory failure, AVAPS did lead to a faster improvement in pH and PaCO2 levels compared to BPAP S/T. Unfortunately, this RCT is too small with poor methodology which makes it difficult to draw any absolute conclusions. AVAPS may be useful, but we still need a well conducted RCT to find out if it is (i.e which patients and which conditions).
References:
- Goren NZ et al. Comparison of BPAP S/T and Average Volume-Assured Pressure Support Modes for Hypercapnic Respiratory Failure in the Emergency Department: A Randomized Controlled Trial. Balkan Med J 2021. PMID: 34462252
- Abubacker AP et al. Non-Invasive Positive Pressure Ventilation for Acute Cardiogenic Pulmonary Edema and Chronic Obstructive Pulmonary Disease in Prehospital and Emergency Settings. Cureus 2021. PMID: 34277241
For More Thoughts on This Topic Checkout:
Post Peer Reviewed By: Anand Swaminathan, MD (Twitter/X: @EMSwami)