Bronchopleural fistula (BPF): Vent mgmt [1,2]
BPF = Communication between bronchial tree and pleural space
Etiology: post-lung resection, chest tube, trauma, malignancy, infection, mech.vent.
Pneumonectomy pts: incidence 211%, mortality 2371%
Diagnosis: usually made clinically after 7d, confirmed by bronchoscopy.
o Persistent air leak (> 24h), dyspnea, subQ emphysema, tracheal deviation, air-fluid level on CXR, purulent sputum.
Size of BPF = Difference between inhaled and exhaled tidal volumes
May cause loss of VT or PEEP; transmission of chest tube suction to airways
May have flow through BPF >20L/min!
May need temporizing measures until definitive Tx
o Surgical: myoplasty (pec flap Clagett procedure), pneumonectomy; endobronchial closure, chemical pleurodesis
o Goals: maintain adequate chest tube drainage, full lung expansion, decrease pressure gradient from airway to pleural space
o Minimize flow through BPF, allow to heal
o Decrease airway pressures: ↓ VT, ↓ PEEP, ↓ I:E, ↓ RR
o Reduce chest tube suction (lowest level that expands lung)
Considered an absolute indication for double lumen tube.
Alternative vent modes: HFJV, HFOV, differential lung vent.
Low VT ventilation: Protect effect [3,4,5,6]
Lung protect vent: Pressure goal
Conventional VT: 10-15ml/kg
Ventilator induced lung injury (VILI)
o Macroscopic: barotrauma (extra-alveolar air)
PTX, pneumomediastinum, sub-Q emphysema
o Microscopic: epithelial or endothelial injury, alveolar-capillary barrier damage (2/2 overdistention, volutrauma), surfactant dysfunction (2/2 repetitive opening/closing atelectrauma), bronchiolar injury
o Excess alveolar stretch causes cytokine proliferation
1993 consensus conference: VT 5-7ml/kg, Pplat < 35 cmH2O
o Based on animal studies
1998 NEJM3: Brazilian RCT, 53 pts w/ early ARDS, VT 6ml/kg or 12ml/kg
o Low VT ↓d mortality (38% vs 71%), also less barotrauma, earlier weaning.
2000 NEJM MC RCT6:
o High VT: 12ml/kg & Pplat < 50cmH20 vs low VT: 6ml/kg & Pplat < 30 cmH20
o Stopped after 861 pts enrolled 2/2 ↓ mortality in low VT grp (31.% vs. 40%)
This strategy has also been used in H1N1 pts.
Therefore, generally accepted lung protective strategies include VT 6-8 ml/kg predicted body weight and Pplat < 30 cmH2O.
Keyword Challenge
Which of the following combinations of tidal volume (VT) and plateau pressure (Pplat) are part of a generally accepted lung protective ventilation strategy?
a. VT = 15ml/kg, Pplat < 50 cmH20
b. VT = 6 ml/kg, P¬plat < 50 cmH20
c. VT = 12 ml/kg, P¬plat < 30 cmH20
d. VT = 6 ml/kg, P¬plat < 30 cmH20
e. Whatever the respiratory therapist wants
References:
1. Millers Anesthesia pp. 1866-7
2. Jantz MA, Anthony VB. Pleural Disease in the Intensive Care Unit In: Civetta, Taylor and Kirby's Critical Care, 4th ed. Pp. 2181-2
3. N Engl J Med 1998;338:347-54
4. Halls Principles of Critical Care. Ch. 37
5. Slutsky AS: Mechanical ventilation. American College of Chest Physicians' Consensus Conference. Chest 104:1833, 1993. [PMID: 8252973]
6. The Acute Respiratory Distress Syndrome Network: 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, 2000.
Keywords Challenge Answer: D