Comparison of four methods of lung volume  recruitment during high frequency oscillatory  ventilation.
OBJECTIVE
To compare four methods of volume recruitment upon initiation of high frequency oscillatory ventilation (HFOV).


METHODS
Anesthetized intubated neonatal piglets (n = 10) underwent repeated saline lavage, followed by conventional mechanical ventilation (CMV). After transition to HFOV at a mean airway pressure 8 cmH2O above CMV (P(basal)), four methods of lung volume recruitment were tested in each animal in random order: Escalating--step-wise pressure increments over 6 min to a peak mean airway pressure 12 cmH2O above P(basal); Sustained dynamic inflation (DI)--a 20 s inflation to the same peak pressure; DI repeated six times for 1 s; Standard--mean airway pressure set directly at P(basal). After each recruitment method, HFOV continued at P(basal) for 15 min. Thoracic gas volume and distribution of aeration were determined by single slice computed tomography, and oxygenation by arterial blood gas sampling.


RESULTS
Escalating recruitment resulted in the greatest thoracic gas volume 15 min post recruitment [77 +/- 3.3% of total lung capacity vs. 70 +/- 4.2% (Sustained DI), 65 +/- 3.5% (Repeated DI),63 +/- 5.1% (Standard); mean +/- SEM; P = 0.042, ANOVA]. All methods resulted in a reduction in non-aerated lung, with the greatest redistribution to normally aerated lung being with Escalating recruitment. Oxygenation 15 min post recruitment was better with the Escalating method than with Repeated DI or Standard recruitment (pO2 307 +/- 41 vs. 159 +/- 36 vs. 134 +/- 39 mmHg, respectively; P = 0.016, ANOVA).


CONCLUSIONS
Escalating recruitment produced the greatest increase in lung volume and resolution of atelectasis, and is recommended for lung volume recruitment upon initiation of HFOV.
Pellicano
Anastasia
A
Department of Neonatology, Royal Children's Hospital, Melbourne, Australia. peter.dargaville@dhhs.tas.gov.au
Tingay
David G
DG
Mills
John F
JF
Fasulakis
Stephen
S
Morley
Colin J
CJ
Dargaville
Peter A
PA
D000403:Airway Resistance / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001784:Blood Gas Analysis; D018592:Cross-Over Studies; D004195:Disease Models, Animal; D006612:High-Frequency Ventilation / Q000009:adverse effects / Q000379:methods*; D006801:Humans; D007231:Infant, Newborn; D008176:Lung Volume Measurements; D010102:Oxygen Inhalation Therapy / Q000379:methods; D001261:Pulmonary Atelectasis / Q000175:diagnosis / Q000378:metabolism / Q000628:therapy*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D011897:Random Allocation; D012127:Respiratory Distress Syndrome, Newborn / Q000175:diagnosis / Q000378:metabolism / Q000628:therapy*; D013552:Swine; D013990:Tidal Volume / Q000502:physiology; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D014109:Total Lung Capacity / Q000502:physiology; D016896:Treatment Outcome; D014692:Ventilation-Perfusion Ratio / Q000502:physiology; D055397:Ventilator-Induced Lung Injury / Q000209:etiology / Q000517:prevention & control