Ventilation of the Difficult-to-Oxygenate Patient

Why are your lungs so fluffy?

Ventilation of the difficult-to-oxygenate patient.

Written by Dr. Bryan Jarrett

A patient with unknown history was brought in by EMS after being found down by his brother in their apartment. He had agonal respirations with oxygen saturation in the 70s and HR in the 120s. He was being actively “bagged” after a failed EMS ET intubation and is non-responsive to painful stimuli.

Initial problem list:

• Bradypnea/agonal breathing
• Hypoxemia
• Tachycardia
• Altered mental status

The patient was rapid-sequence intubated (etomidate, succinylcholine) with settings of TV 500, PEEP 5, FIO2 100%, RR 16.(Editor’s note: Delayed-sequence intubation would have been a reasonable option here.)

Examination was significant for hypotension, diaphoresis, tachycardia, and diffuse rales. A fluid bolus was given, and a central line was placed for norepinephrine administration.

Additional history included a remote history of brain surgery. He was reportedly watching a movie with his brother, when the brother went to bedroom and took a nap. He returned to find the patient unresponsive on the couch and called 911. There was no reports of any illicit substances or drug use.

Differential:

• Seizure
  
• ICH/stroke
  
• Sepsis (pneumonia, meningitis)
  
• Intoxication
• Pulmonary edema (Vasogenic, ARDS, Pulmonary alveolar hemorrhage)
  

The RUSH exam showed hyperdynamic heart, no pericardial effusion or abdominal free fluid, no RV dilatation, collapsing IVC, lung sliding bilaterally, and diffuse B lines. A chest xray showed bilateral interstitial lung disease/infiltrates with the ETT in place.

Patient is still hypoxemic, why? What can you do to fix that?

Ventilatory strategies in the ED:¹

• Obstructive/COPD/asthma
  
• Lung protective/ARDS/ALI
  

Diagnosing ALI or ARDS² requires onset within 1 week of:

1. PaO2/FiO2 <300
   
   1. Mild             200 > PaO2/FiO2 < 300
      
   2. Moderate     100 > PaO2/FiO2 < 200
      
   3. Severe         PaO2/FiO2 < 100
      
2. New bilateral pulmonary infiltrates consistent with edema
   
3. No clinical evidence of LA hypertension (non-cardiogenic or fluid overload-related pulmonary edema)
   

35-65% of these patients die regardless of optimal ventilatory management (43% from Cochrane review in 2013).

Ventilator Settings

Mode (SIMV vs CMV vs HFOV)

• Synchronized Intermittent mechanical ventilation (SIMV) = Continuous mandatory ventilation (CMV) but reschedules mandatory breaths based on patient sensing
  
• Volume-assist control (V-A/C) is a version of CMV
  
• Large, multi-centered trial of almost 1600 patients comparing SIMV-PS vs A/C adjusted for propensity score due to the heterogeneity in indication and patient characteristics, showed no difference in in-hospital mortality.³
  
• Smaller, randomized controlled trial of SIMV+PS vs A/C in 40 pts with “moderate” ARDS (100>PaO2/FiO2<200) showed improved oxygenation at lower PEEP and FiO2 at 72hrs with SIMV, but no difference in mortality or ventilator days.⁴
  
• Cochrane review of PC (pressure control) vs VC (volume control) ventilation in ARDS showed that PC had a lower mortality compared to VC (RR 0.83 in hospital or 0.84 in ICU), although these differences were not significant and their conclusion was neither method provides a significant advantage.⁵
  

Volume & RR¹

• ARDSnet ARMA trial from 2000 showed that in patients with ALI and ARDS, TV of 6ml/kg ideal body weight vs 12ml/kg ideal body weight significantly improved mortality from 40% to 31% and decreased ventilator days from 12 to 10.⁶
  
• Cochrane review 2013 showed that mortality was significantly reduced in patients with ARDS or ALI (RR 0.74) by lung-protective ventilation with a TV of 7ml/kg or less compared to 10-15ml/kg.⁷
  
• One should lower TV at initial of ventilation even in patients WITHOUT ARDS as the majority of data favors lower TV to PREVENT progression to ARDS.⁸
  
• Given that lower TV will be used, RR must be increased to maintain minute ventilation and normocarbia/physiologic pH as much as possible
  
  • Can estimate minute ventilation from NIV if used before intubation
    
  • Average RR in ARDSnet was 30!
    
  • ETCO2 can be used as well, knowing that always PaCO2 ≤ ETCO2
    
• Permissive hypercapnia can be considered at the expense of increasing tidal volumes depending on the clinical scenario (ARDSnet tolerates pH down to 7.15)
  

Ideal body weight by ARDSnet calculator:

♂: PBW (kg) = 50 + 2.3 (height (in) – 60)

♀: PBW (kg) = 45.5 + 2.3 (height (in) – 60) }

FiO2 & PEEP

• ARDSnet ALVEOLI in 2004 studied patients with ALI or ARDS ventilated with 6ml/kg tital volumes and PEEP/FiO2 combinations from the following tables of high and low PEEP. There was no mortality benefit or decreased ventilator days associated with higher or lower PEEP.⁹
  
• Cochrane review from 2013 (metanalysis of 3 studies) again showed no difference in mortality between high and low PEEP at the same TV, but did demonstrate improved oxygenation on day 1, 3, and 7 in the high PEEP group. No increased incidence of barotrauma (pneumothorax or chest tube) was observed in the high PEEP group.¹⁰
  

Importance of plateau pressure

• Measure using inspiratory hold for at least 5 seconds (requires that patient be sedated adequately and not fighting vent)
  
• Must maintain plateau pressure <30 cmH2O to avoid volutrauma, barotrauma (i.e. pneumothorax)
  
• Ensure that patient is not breath stacking
  
• Can be falsely elevated in obesity or restrictive chest walls (pleural effusion or ascites)
  
• Mucous plugging can increase plateau pressure
  

Other Adjuncts to Improve Oxygenation

Prone positioning

• Cochrane review (9 RCTs) showed trend towards improved mortality with the prone position (RR 0.84-0.86; not significantly different)¹¹
  
  • Three groups had clear benefit: recruited within 48 hrs of meeting criteria (RR 0.75), prone for >16hrs/day (RR 0.77), patients with more severe hypoxemia at trial entry (RR 0.77)
    
  • Prone positioning increased pressure sores (RR 1.37) and tracheal tube obstruction (RR 1.78), but decreased risk of arrhythmia (RR 0.64)
    
• Meta-analysis (9 RCTs) showed that prone positioning decreased morality in severe ARDS patients (RR 0.71).¹²
  

Recruitment maneuvers

• Cochrane review of 7 trials showed no mortality benefit, no difference in risk for barotrauma, but that recruitment maneuvers did significantly increase oxygenation above baseline level for a short period of time.¹³
  

High frequency oscillatory ventilation (HSOV)

• Cochrane review (10 RCTs) showed no significant mortality difference, although 1 large RCT was terminated early because of increased mortality in the HFO group. It concluded that HFO should not be a first-line strategy in ARDS.¹⁴
  
• Multicenter RCT from 2013 showed increased use of sedation, neuromuscular blocade, and vasoactive medications in patients receiving HFOV, with a significantly increased mortality of in the HFOV group (47% vs 35% ).¹⁵
  

Paralysis

• Meta-analysis of 3 trials of 48hr infusions of cisatracurium in ARDS showed lower hospital mortality (RR 0.72), lower risk of barotrauma (RR 0.43), but no difference in ventilator days.¹⁶
  
• Multicenter double-blind trial of early cisatracurium (first 48 hours) in severe ARDS showed significantly reduced mortality (HR 0.68) and decreased ventilator days.¹⁷
  

Pharmacologic treatment

• Cochrane review 2004 (33 trials) showed no significant effect on mortality of prostaglandin E1, N-acetylcysteine, early high-dose corticosteroids, or surfactant. In single trials, corticosteroids given for late phase ARDS reduced mortality and pentoxifylline reduced 1-mo mortality in the setting of metastatic cancer with ARDS.¹⁸
  
• ARDSnet ALTA study was randomized placebo-controlled study (n=282) that compared albuterol vs saline q4 x10d.¹⁹ There was no decrease in ventilator-free days, so albuterol does not improve clinical outcomes in ALI.
• Meta-analysis (5 studies) of steroids after onset of ARDS showed a non-significant trend towards reduction in mortality (OR 0.62) and a decreased number of ventilator days (average diff 4 days).²⁰
  

Case follow-up:

An ABG was not performed until after his ventilator settings were changed to lung protective strategy (TV of 380, PEEP of 15, Fi02 100%, RR 18), however, his initial FiO2 was 100%, O2 saturation was low at 80%, new bilateral infiltrates were present, and left-sided systolic function was normal on bedside echo. ABG even after lung protective strategy had been initiated showed a P/F ratio of 76.6, suggestive of severe ARDS. Urine toxicology was positive for opiates and cocaine. Head CT demonstrated no acute findings. Patient was treated with broad-spectrum antibiotics for aspiration pneumonia vs aspiration pneumonitis. He did well and was extubated and discharged to a rehab facility.

Summary/Highlights

1. Difficulty oxygenating a patient in whom you do not suspect cardiogenic pulmonary edema should raise concern for ARDS
   
2. Low tidal volume and higher PEEP have been shown to significantly decreased mortality in ARDS patients
   
3. Ventilation mode does not seem to affect mortality, but there may be slight trend towards pressure control being better than volume control
   
4. Adjuncts which improve outcome include prone positioning, paralysis, and possibly steroids.
   

References

1. Weingart SD. Managing Initial Mechanical Ventilation in the Emergency Department. Ann Emerg Med. 2016 Jun 9.

2. Wright BJ. Lung-protective ventilation strategies and adjunctive treatments for the emergency medicine patient with acute respiratory failure. Emerg Med Clin North Am. 2014 Nov;32(4):871-87.

3. Ortiz G, Frutos-Vivar F, Ferguson ND, Esteban A, Raymondos K, Apezteguía C, Hurtado J, González M, Tomicic V, Elizalde J, Abroug F, Arabi Y, Pelosi P, Anzueto A; Ventila Group. Outcomes of patients ventilated with synchronized intermittent mandatory ventilation with pressure support: a comparative propensity score study. Chest. 2010 Jun;137(6):1265-77.

4. Luo J, Wang MY, Liang BM, Yu H, Jiang FM, Wang T, Shi CL, Li PJ, Liu D, Wu XL, Liang ZA. Initial synchronized intermittent mandatory ventilation versus assist/control ventilation in treatment of moderate acute respiratory distress syndrome: a prospective randomized controlled trial. J Thorac Dis. 2015 Dec;7(12):2262-73.

5. Chacko B, Peter JV, Tharyan P, John G, Jeyaseelan L. Pressure-controlled versus volume-controlled ventilation for acute respiratory failure due to acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Cochrane Database Syst Rev. 2015 Jan 14

6. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. The Acute Respiratory Distress Syndrome Network. N Engl J Med. 2000 May 4;342(18):1301-8.

7. Petrucci N, De Feo C. Lung protective ventilation strategy for the acute respiratory distress syndrome. Cochrane Database Syst Rev. 2013 Feb 28;(2)

8. Fuller BM, Mohr NM, Drewry AM, Carpenter CR. Lower tidal volume at initiation of mechanical ventilation may reduce progression to acute respiratory distress syndrome: a systematic review. Crit Care. 2013 Jan 18;17(1)

9. Brower RG, Lanken PN, MacIntyre N, Matthay MA, Morris A, Ancukiewicz M, Schoenfeld D, Thompson BT; National Heart, Lung, and Blood Institute ARDS Clinical Trials Network. Higher versus lower positive end-expiratory pressures in patients with the acute respiratory distress syndrome. N Engl J Med. 2004 Jul 22;351(4):327-36.

10. Santa Cruz R, Rojas JI, Nervi R, Heredia R, Ciapponi A. High versus low positive end-expiratory pressure (PEEP) levels for mechanically ventilated adult patients with acute lung injury and acute respiratory distress syndrome. Cochrane Database Syst Rev. 2013 Jun 6

11. Bloomfield R, Noble DW, Sudlow A. Prone position for acute respiratory failure in adults. Cochrane Database Syst Rev. 2015 Nov 13

12. Hu SL, He HL, Pan C, Liu AR, Liu SQ, Liu L, Huang YZ, Guo FM, Yang Y, Qiu HB. The effect of prone positioning on mortality in patients with acute respiratory distress syndrome: a meta-analysis of randomized controlled trials. Crit Care. 2014 May 28;18(3):R109.

13. Hodgson C, Keating JL, Holland AE, Davies AR, Smirneos L, Bradley SJ, Tuxen D. Recruitment manoeuvres for adults with acute lung injury receiving mechanical ventilation. Cochrane Database Syst Rev. 2009 Apr 15

14. Sud S, Sud M, Friedrich JO, Wunsch H, Meade MO, Ferguson ND, Adhikari NK. High-frequency oscillatory ventilation versus conventional ventilation for acute respiratory distress syndrome. Cochrane Database Syst Rev. 2016 Apr 4

15. Ferguson ND, Cook DJ, Guyatt GH, Mehta S, Hand L, Austin P, Zhou Q, Matte A, Walter SD, Lamontagne F, Granton JT, Arabi YM, Arroliga AC, Stewart TE, Slutsky AS, Meade MO; OSCILLATE Trial Investigators; Canadian Critical Care Trials Group. High-frequency oscillation in early acute respiratory distress syndrome. N Engl J Med. 2013 Feb 28;368(9):795-805.

16. Alhazzani W, Alshahrani M, Jaeschke R, Forel JM, Papazian L, Sevransky J, Meade MO. Neuromuscular blocking agents in acute respiratory distress syndrome: a systematic review and meta-analysis of randomized controlled trials. Crit Care. 2013 Mar 11;17(2)

17. Papazian L, Forel JM, Gacouin A, Penot-Ragon C, Perrin G, Loundou A, Jaber S, Arnal JM, Perez D, Seghboyan JM, Constantin JM, Courant P, Lefrant JY, Guérin C, Prat G, Morange S, Roch A; ACURASYS Study Investigators. Neuromuscular blockers in early acute respiratory distress syndrome. N Engl J Med. 2010 Sep 16;363(12):1107-16.

18. Adhikari N, Burns KE, Meade MO. Pharmacologic therapies for adults with acute lung injury and acute respiratory distress syndrome. Cochrane Database Syst Rev. 2004 Oct 18;(4)

19. National Heart, Lung, and Blood Institute Acute Respiratory Distress Syndrome

(ARDS) Clinical Trials Network, Matthay MA, Brower RG, Carson S, Douglas IS,

Eisner M, Hite D, Holets S, Kallet RH, Liu KD, MacIntyre N, Moss M, Schoenfeld D, Steingrub J, Thompson BT. Randomized, placebo-controlled clinical trial of an aerosolized β₂-agonist for treatment of acute lung injury. Am J Respir Crit Care Med. 2011 Sep 1;184(5):561-8.

20. Peter JV, John P, Graham PL, Moran JL, George IA, Bersten A. Corticosteroids in the prevention and treatment of acute respiratory distress syndrome (ARDS) in adults: meta-analysis. BMJ. 2008 May 3;336(7651):1006-9.

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emergencydrb

Emergency Medicine Resident

Latest posts by emergencydrb (see all)

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