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April 2010

Critical Care

Citation

Lucangelo U, Antonaglia V, Zin W, Confalonieri M, Borelli M, Columban M, Cassio S, Batticci I, Ferluga M, Cortale M, Berlot G.  High Frequency Percussive Ventilation Improves Perioperatively  Clinical Evolution in Pulmonary Resection. Crit Care Med. 2009 May;37(5):1663-9

Rationale

The perioperative period of patients requiring lung surgery is often complicated by hypoxemia and increased pulmonary secretions.  Both complications can lead to increased hospital stay and pneumonia.  High frequency percussive ventilation (HFPV) is a ventilatory mode that has been used to improve oxygenation in patients, including those with burn/smoke inhalation injury and with acute respiratory distress syndrome.  HFPV delivers small rapid volumes of gas at 300-600 cycles per minute and improves ventilation through a combination of convection and diffusion mechanisms.  To date, HFPV has not been examined in the setting of elective pulmonary surgery. 

Aim

To assess whether HFPV improves oxygenation and clearance of secretions in patients undergoing partial pneumonectomy (lobectomy or atypical resection that did not necessitate pneumonectomy).

Methods

44 patients were randomized to receive either continuous positive airway pressure (CPAP) or HFPV during elective partial pneumonectomy.  Study exclusion criteria included pulmonary hypertension, immunosuppresion, severe chest deformity, inoperable lung cancer diagnosed during surgery, unexpected pneumonectomy, and intubation with a single lumen tube. Arterial blood gases were measured at baseline, prior to thoracotomy during unilateral lung ventilation, after 15-minutes of unilateral lung ventilation with CPAP or HFPV, prior to and after lung reexpansion.  All staff outside the operating room was blinded to the patient’s mode of ventilation during surgery.  All patients received routine chest physical therapy.  Sputum volume and hospital length of stay were recorded.
 
Results

PaCO2, heart rate, and mean arterial pressure were comparable across both groups.  Just prior to lung reexpansion, PaO2 was greater in the HFPV group than in the CPAP group: 186 vs. 137 mm Hg; p = 0.02.  Although total sputum volume collected across both groups was comparable (296 cc vs. 336 cc), the volume of sputum collected in patients with COPD (n = 20) was greater in the HFPV group than in the CPAP group: 199 vs. 64 cc; p = 0.028.  Finally, the probability of early hospital discharge in the HFPV group was 3.14 times higher in the HFPV than in the CPAP group; p = 0.0007.

Discussion

Lucangelo et al found that, in patients undergoing partial pneumonectomy, HFPV can achieve three positive results.  First, it can increase oxygenation during surgery. Second, it can increase removal of bronchial secretions in patients with COPD.  Third, it can reduce hospital length of stay.  

The following points are worth noting.

1 – Both HFPV and CPAP delivered during partial pneumonectomy were safe and no patient developed hypoxemia.  The greater PaO2 recorded in the HFPV group just prior to lung reexpansion -- although statistically significant -- is of unclear clinical relevance.  Finally, it is unclear how improved oxygenation with HFPV and early hospital discharge are mechanistically linked.

2 – As the authors note, differences in the volume of collected sputum are subject to several factors including the patient’s ability to expectorate, collection methods, and variability in chest physical therapy.  Among all patients, volume of collected sputum was no different between the HFPV and the CPAP groups.  Only on subgroup analysis (in patients with COPD), was a beneficial effect of HFPV noted.  Larger trials are needed to further elucidate this potential positive effect of HFPV.

3 – Other questions regarding the usefulness of HFPV remain unanswered.  First, how feasible it is to apply HFPV in the ICU setting?  What is the risk of auto-PEEP during prolonged use of HFPV? What are potential pitfalls of pressure and volume monitoring of HFPV?  In addition, whether the purported enhanced clearance of secretions in patients with COPD decreases the rate of ventilator-acquired pneumonia remains to be investigated.
           
In conclusion, this interesting investigation of Lucangelo et al. supports the use of HFPV to shorten hospital stay in patients undergoing elective partial pneumonectomy.  The challenge now is to elucidate whether HFPV could indeed improve clearance of secretions (and/or pneumonia) in specific subsets of patients such as those with COPD.  Finally, the large-scale application of HFPV in the ICU setting remains to be evaluated.

Amit Goyal, MD
Research Fellow
Pulmonary and Critical Care Medicine
Loyola University Stritch School of Medicine
Maywood, IL

Franco Laghi, MD
Professor of Medicine
Pulmonary and Critical Care Medicine
Loyola University Stritch School of Medicine and Hines VAH
Hines, IL