ARDS in burn patients
Key Points
- ARDS is defined by the Berlin criteria (acute onset, bilateral opacities, PaO2/FiO2 stratification); in burns, distinguishing true ARDS from resuscitation-related pulmonary edema and inhalation injury is often clinically impossible [8]
- Apply lung-protective ventilation (Vt 6-8 mL/kg PBW, PEEP at least 5 cmH2O, plateau pressure less than 30 cmH2O) as a starting framework, but expect to modify for chest wall restriction in circumferential burns [1][3][7]
- No single ventilator mode has demonstrated superiority in burn patients; individualize settings based on pulmonary mechanics and response [2][5]
- Consider prone positioning in moderate-to-severe burn ARDS refractory to conventional ventilation, with coordinated wound care planning [9]
- Consider high-frequency percussive ventilation with low FiO2 as a protective strategy in patients requiring prolonged ventilation, particularly those with inhalation injury [4]
- Plan for tracheostomy at approximately 2 weeks if liberation from mechanical ventilation is not anticipated, with earlier tracheostomy when clinically indicated [2]
- Maintain a stepwise escalation approach: conventional ventilation, then HFPV/APRV, then ECMO as a last resort in well-resourced settings [6][11]
Definition
ARDS is defined by the 2012 Berlin Definition as acute-onset (within 1 week of a known insult), bilateral opacities on chest imaging not fully explained by effusions or atelectasis, respiratory failure not fully explained by cardiac failure or fluid overload, and impaired oxygenation classified by severity: mild (PaO2/FiO2 201-300 mmHg), moderate (101-200 mmHg), or severe (100 mmHg or less), all with PEEP of at least 5 cmH2O [8]. In burn patients, applying these criteria requires clinical judgment: bilateral opacities after massive resuscitation can reflect fluid overload, inhalation injury, or true ARDS, and distinguishing among these is often impossible at the bedside.
Overview
Acute respiratory distress syndrome in burn patients arises from pathophysiology that differs from typical medical ARDS. Burns and inhalation injury combine direct airway mucosal injury, chest wall restriction from circumferential eschar, systemic inflammation, and massive fluid resuscitation that compounds pulmonary edema [3][5]. Standard ARDS protocols developed in general ICU populations may not translate directly to this population.
The largest international prospective study of ventilation practices in burn patients (LAMiNAR, 160 patients from 28 ICUs across 16 countries) found that low tidal volume ventilation was used in 74% of patients but was not associated with a reduction in ventilator-free days at day 28, raising questions about whether the ARDSNet paradigm produces the same mortality benefit in burns as in medical ARDS [1].
Epidemiology
A survey of 46 North American burn centers found wide variation in mechanical ventilation practices, with no consensus on burn-specific ventilator guidelines [2]. For mild ARDS, the ARDSNet protocol and optimal PEEP titration were preferred. For severe ARDS, airway pressure release ventilation (APRV) and neuromuscular blockade were the most popular strategies [2].
Pathophysiology
Burns produce a unique combination of insults to the respiratory system. Chest wall restriction from circumferential burns and eschar may require higher airway pressures than standard ARDSNet settings allow [3]. Direct inhalation injury adds mucosal damage and cast formation to the alveolar injury typical of ARDS. Massive resuscitation volumes compound pulmonary edema beyond what is seen in medical ARDS [5].
Management
Conventional Ventilation
Lung-protective ventilation as established by the ARDS Network trial serves as the starting framework: tidal volume 6-8 mL/kg predicted body weight, PEEP at least 5 cmH2O, plateau pressure less than 30 cmH2O [7]. That landmark trial in 861 patients demonstrated a 22% relative reduction in mortality (31% vs 39.8%, P=0.007) and more ventilator-free days with lower tidal volumes [7]. However, burn patients may require modification for chest wall restriction from circumferential burns and eschar [1][3]. In the LAMiNAR cohort, median tidal volume was 7.3 mL/kg with 80% of patients maintaining maximum airway pressures below 30 cmH2O [1].
Alternative Ventilator Modes
High-frequency percussive ventilation (HFPV) combined with low FiO2 (0.25) showed promising results in 32 burn patients ventilated for more than 10 days: no patient developed ARDS, barotrauma, or died from respiratory failure, with a mean PaO2/FiO2 ratio of 395 [4]. This suggests that minimizing oxidative stress through aggressive FiO2 reduction combined with HFPV may be protective in prolonged burn ventilation.
APRV is used variably across centers without standardized indications or comparative effectiveness data [2].
Prone Positioning
Prone positioning for at least 16 hours per day reduces mortality in moderate-to-severe ARDS. The PROSEVA trial (466 patients, PaO2/FiO2 less than 150 mmHg) demonstrated 28-day mortality of 16% prone vs 32.8% supine (P<0.001), making it one of the strongest mortality-reducing interventions in ARDS [9]. In burn patients, prone positioning presents practical challenges: open wounds on the anterior trunk and face require protective dressings, central venous catheters and arterial lines risk dislodgement during turns, and recently grafted areas may be at risk from pressure and shear. Despite these logistics, prone positioning should be considered in burn patients with moderate-to-severe ARDS who are not responding to conventional ventilation, with coordinated nursing and surgical planning around wound care schedules.
Neuromuscular Blockade
Early neuromuscular blockade with cisatracurium is the most popular severe ARDS strategy reported across burn centers [2], but the evidence base comes from general ICU populations with conflicting results. The ACURASYS trial (340 patients) showed improved 90-day survival with 48-hour cisatracurium infusion in early severe ARDS [10]. The subsequent larger ROSE trial (1006 patients, PETAL Network) found no mortality benefit from early continuous cisatracurium compared with a lighter sedation strategy, and the trial was stopped for futility [10]. Current practice favors a trial of neuromuscular blockade in severe refractory hypoxemia rather than routine early use, with attention to the increased risk of ICU-acquired weakness in burn patients who already face prolonged immobility and catabolism.
Tracheostomy
The most common threshold for tracheostomy was 2 weeks, though all surveyed centers acknowledged clinical situations warranting earlier tracheostomy [2].
Escalation Therapies
A stepwise escalation approach is recommended: conventional ventilation, then HFPV/APRV, then extracorporeal membrane oxygenation (ECMO) as a last resort [6]. ECMO and other extracorporeal organ support technologies show promise but remain in early implementation phases and are restricted to well-resourced centers [11].
Controversies and Evidence Gaps
Despite the widespread adoption of lung-protective ventilation in burn ICUs, the LAMiNAR study found no association between low tidal volumes and improved ventilator-free days, leaving open the question of whether the ARDSNet survival benefit extends to burn patients [1]. Permissive hypercapnia, a cornerstone of lung-protective ventilation in medical ARDS, has not been adequately studied in the setting of traumatic brain injury co-occurring with burns or in patients with severe metabolic acidosis from burn shock. The role of HFOV has diminished after the OSCILLATE trial showed harm in general ARDS, but burn-specific data remain sparse. ECMO candidacy criteria for burn patients are undefined: massive wounds, coagulopathy, and infection risk complicate anticoagulation requirements. Alternative ventilator modes such as APRV and HFPV are used variably across centers without standardized indications or comparative effectiveness data. The conflicting results between ACURASYS and ROSE leave neuromuscular blockade without a clear evidence-based role in burn ARDS specifically.
References
[1] Schultz MJ et al. (2021). Ventilation practices in burn patients -- an international prospective observational cohort study. PMID: 34926707 [2] Chung KK et al. (2016). A Survey of Mechanical Ventilator Practices Across Burn Centers in North America. PMID: 26135527 [3] Peck MD, Koppelman T. (2009). Low-tidal-volume ventilation as a strategy to reduce ventilator-associated injury in ALI and ARDS. PMID: 19060729 [4] Starnes-Roubaud M et al. (2012). High frequency percussive ventilation and low FiO2. PMID: 22766403 [5] Velamuri SR et al. (2024). Inhalation Injury, Respiratory Failure, and Ventilator Support in Acute Burn Care. PMID: 38429045 [6] Nayyar A et al. (2017). Management of Pulmonary Failure after Burn Injury: From VDR to ECMO. PMID: 28576240 [7] Acute Respiratory Distress Syndrome Network. (2000). Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 342:1301-8. PMID: 10793162 [8] ARDS Definition Task Force; Ranieri VM et al. (2012). Acute respiratory distress syndrome: the Berlin Definition. JAMA. 307(23):2526-33. PMID: 22797452 [9] Guerin C et al. (2013). Prone positioning in severe acute respiratory distress syndrome. N Engl J Med. 368(23):2159-68. PMID: 23688302 [10] Papazian L et al. (2010). Neuromuscular blockers in early acute respiratory distress syndrome. N Engl J Med. 363(12):1107-16. PMID: 20843245. See also: National Heart, Lung, and Blood Institute PETAL Clinical Trials Network. (2019). Early neuromuscular blockade in the acute respiratory distress syndrome (ROSE). N Engl J Med. 380(21):1997-2008. PMID: 31112383 [11] Britton GW et al. (2024). Extracorporeal Organ Support for Burn-Injured Patients. PMID: 39599979