Pulmonology · Medical Literature
Prehospital Use of Non-Invasive Ventilation for Acute Respiratory Failure due to Acute Exacerbation of Chronic Obstructive Pulmonary Disease. A Randomised Trial.
Abstract
In-hospital use of non-invasive ventilation improves outcomes in patients with acute respiratory failure caused by acute exacerbation of chronic obstructive pulmonary disease. Prehospital use of non-invasive ventilation is uncommon due to diagnostic uncertainty and logistical constraints. We hypothesised that prehospital non-invasive ventilation guided by arterial blood gas analysis would improve early physiological outcomes compared with standard medical treatment alone. This investigator-initiated, multicentre trial randomised patients with suspected acute respiratory failure due to acute exacerbation of chronic obstructive pulmonary disease with respiratory acidosis defined as pH 6.0 kPa to standard medical treatment alone or standard medical treatment plus non-invasive ventilation. Patients were attended by prehospital physician-manned emergency care units and enrolled without prior consent under emergency trial approval. The primary outcome was the change in arterial pH from enrolment to hospital arrival. The trial was terminated early due to low recruitment. Out of 111 screened patients, 16 were randomised and 14 were included in the analysis. The median prehospital pH change was 0.09 (interquartile range 0.02-0.12) in the non-invasive ventilation + standard medical treatment group and 0.02 (0.01-0.03) in the standard medical treatment alone group. Median on-scene time was 32 min in the non-invasive ventilation + standard medical treatment group versus 28 min in the standard medical treatment alone group. Recruitment was limited by strict inclusion criteria, procedural complexity and challenges related to the implementation of prehospital arterial blood gas analysis and trial procedures. Missing data further limited the assessment of in-hospital outcomes. The clinical effect of prehospital non-invasive ventilation could not be determined due to early termination. This trial highlights important challenges relevant to future clinical trials in the prehospital setting, including patient selection, diagnostic requirements and implementation of complex interventions. NCT06211920.
Clinical relevance
In patients with acute respiratory failure due to acute exacerbation of COPD and confirmed respiratory acidosis (pH 6.0 kPa) encountered in the prehospital setting, does adding non-invasive ventilation (NIV) to standard medical treatment improve arterial pH at hospital arrival compared with standard medical treatment alone? __SNAPSHOT__ {"studyDesign":"Investigator-initiated, multicentre, open-label, randomised controlled trial (PRENIV trial); terminated early due to insufficient recruitment","setting":"Physician-manned mobile emergency care units (MECUs), Central Denmark Region, Denmark; December 2023 – September 2024","sampleSize":"n=14 in final descriptive analysis (16 randomised; 2 excluded post-randomisation for protocol violations); planned sample size not reported in abstract","population":"Adults ≥18 years with known COPD and suspected acute respiratory failure due to AECOPD, confirmed by prehospital ABG showing pH 6.0 kPa, respiratory rate >25 breaths/min, and hypoxia (PaO2 <7.0 kPa and/or SpO2 <88% on room air); patients were critically ill and unable to provide informed consent, enrolled under emergency ethics approval","intervention":"Prehospital NIV via oro-nasal facemask (IPAP 12 cmH2O, PEEP 5 cmH2O, oxygen titrated to SpO2 88–92%, with further titration at physician discretion) added to standard medical treatment (SMT: inhaled bronchodilators, intravenous corticosteroids, titrated oxygen)","comparator":"Standard medical treatment alone (inhaled bronchodilators, intravenous corticosteroids, titrated oxygen supplementation)","primaryOutcome":"Change in arterial pH from prehospital enrolment to hospital arrival","followUp":"From prehospital enrolment to hospital arrival (duration not reported in available abstract/excerpts)","fundingSource":"Non-profit/charitable (Karen Elise Jensens Foundation, Health Research Foundation of Central Denmark Region, Grosserer L.F. Foghts Foundation); no industry involvement reported"}
Key findings
The PRENIV trial was terminated prematurely after enrolling only 14 evaluable patients (10% of planned sample) over a 10-month period, rendering the primary outcome analysis — change in arterial pH from enrolment to hospital arrival — underpowered and uninterpretable for efficacy. Individual arm pH values, absolute and relative treatment effects, confidence intervals, and p-values for the primary or secondary outcomes are not reported in the available abstract. Of 111 patients screened, 95 were excluded before randomisation: the most frequent reasons were failure to meet ABG thresholds for respiratory acidosis (n=25), failure to meet respiratory rate or hypoxia criteria (n=13), and short transport distance rendering trial initiation clinically inappropriate (n=13). Additional non-clinical exclusions included clinical team error (n=10), procedural misunderstanding (n=7), immediate need for NIV precluding randomisation (n=5), and technical issues (n=5). After randomisation, two patients were excluded: one without confirmed COPD and one enrolled using a venous rather than arterial blood gas. One adverse event was recorded — mask leakage during prehospital NIV in one patient; no other complications were reported. No NNT or NNH can be calculated from available data. The trial authors explicitly state that no conclusion can be drawn regarding the benefits or harms of prehospital NIV in this population.
Practice implications
This trial established that a prehospital, ABG-guided, NIV randomisation protocol is operationally feasible when physician-manned MECUs are available, but is severely limited in recruitment due to strict ABG eligibility criteria, short transport distances common in the Danish prehospital system, and non-clinical operational barriers. The study did not establish whether prehospital NIV improves or harms patients with AECOPD-related respiratory acidosis — the primary physiological question remains unanswered. Results apply only to settings with prehospital physician capability and on-scene ABG analysis; they are not generalisable to paramedic-only systems or regions without prehospital blood gas infrastructure. Patients with very short transport times, immediate intubation need, or absence of life-prolonging treatment indication were explicitly excluded. No practice change is warranted from this study alone. The in-hospital evidence base for NIV in hypercapnic AECOPD (pH 7.25–7.35) remains robust and unaffected by these findings. Importantly, only an abstract and indexed excerpts were available for this summary; the full paper may contain additional outcome data not captured here, and clinicians should consult the published article directly before drawing further conclusions. __LIMITATIONS__ Premature termination due to low recruitment: only 14 of a planned (but not publicly reported) sample size were analysed — grossly underpowered for any efficacy or safety conclusion,Descriptive analysis only: inferential statistics for the primary outcome (pH change) are not reported; the trial cannot be interpreted as hypothesis-confirming or -refuting,High screen-to-randomisation failure rate (95/111 excluded): strict ABG criteria for respiratory acidosis (pH 6.0 kPa) and operational barriers substantially restricted eligible patients, raising questions about external validity and selection bias,Open-label design: blinding not feasible given the nature of the intervention, introducing potential performance and detection bias,Emergency enrolment without prior consent: although ethically approved, this introduces vulnerability concerns and limits contemporaneous patient preferences,Single prehospital system (Central Denmark Region physician-manned MECUs): findings on feasibility may not generalise to paramedic-staffed or resource-limited EMS systems,Short transport distances in the Danish system precluded enrolment of a meaningful proportion of eligible patients, creating inherent geographic selection bias,Post-randomisation exclusions (n=2) including one venous blood gas error suggest protocol implementation challenges that could affect data integrity in a larger trial,Surrogate primary endpoint (arterial pH at hospital arrival): clinical outcomes (intubation rate, ICU admission, mortality, length of stay) were not assessable given the sample size,Non-industry funding reduces sponsorship bias risk, but very small sample size and premature termination preclude any efficacy inference __BOTTOM_LINE_CATEGORY__ not_ready_for_clinical_application __BOTTOM_LINE__ The PRENIV trial was terminated early after enrolling only 14 evaluable patients, making it impossible to draw any conclusion about the efficacy or safety of ABG-guided prehospital NIV for AECOPD-related respiratory acidosis. The trial's primary contribution is documenting the substantial operational barriers — stringent ABG eligibility thresholds, short transport distances, and clinical team implementation challenges — that must be addressed before a definitive prehospital NIV trial is feasible. No change to current in-hospital NIV practice for AECOPD is indicated or implied by these results.