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Independent High-Frequency Oscillatory Ventilation in the Management of Asymmetric Acute Lung Injury

Terragni, Pierpaolo MD*; Rosboch, Giulio L. MD*; Corno, Eleonora MD*; Menaldo, Eleonora MD*; Tealdi, Andrea MD*; Borasio, Piero MD; Davini, Ottavio MD; Viale, Aurelio G. MD*; Ranieri, V Marco MD*

doi: 10.1213/01.ANE.0000151161.36330.CF
Critical Care and Trauma: Case Report

We present a case of independent lung ventilation in an adult with asymmetric acute lung injury. We applied a conventional protective ventilatory strategy to the more homogeneously infiltrated lung and high-frequency oscillatory ventilation to the almost totally collapsed lung, because a conventional protective strategy exposed this lung to plateau pressure more than 30 cm H2O, whereas high-frequency oscillatory ventilation provided sufficient gas exchange at safer pressure levels. Analysis of a lung computed tomography scan was used to evaluate the efficacy of the ventilatory strategy.

IMPLICATIONS: This case report demonstrates the feasibility and safety of independent lung ventilation set with high-frequency oscillation ventilation (HFO) in an adult acute respiratory distress syndrome patient with markedly asymmetric lung disease. HFO was initiated, set, and successfully discontinued on the basis of computed tomography analysis.

*Dipartimento di Discipline Medico-Chirurgiche, Sezione di Anestesia e Rianimazione, Università di Torino, Ospedale S. Giovanni Battista-Molinette, Torino, Italy; †Sezione di Chirurgia Toracica, Università di Torino, Ospedale S. Luigi, Torino, Italy; and ‡Servizio di Radiologia d’urgenza, Ospedale S. Giovanni Battista-Molinette, Torino, Italy

Accepted for publication November 5, 2004.

Address correspondence and reprint requests to V. Marco Ranieri, MD, Dipartimento di Discipline Medico-Chirurgiche, Sezione di Anestesiologia e Rianimazione, Università di Torino, Ospedale S. Giovanni Battista, Corso Dogliotti 14, 10126 Torino, Italy. Address e-mail to marco.ranieri@unito.it.

Independent lung ventilation (ILV) is often applied in asymmetric lung injury because application of tidal inflation and positive end-expiratory pressure (PEEP) to the heterogeneous lung may overdistend the uninvolved lung and divert pulmonary blood flow to the injured lung area, thus worsening ventilation/perfusion mismatch (1). High-frequency oscillation (HFO) uses tidal volume (Vt) close to the anatomic dead space and uses high respiratory rates and mean airway pressures to allow adequate alveolar ventilation; this minimizes the tidal recruitment of the collapsed lung and overdistension of the normal lung (2). We report the case of a 68-yr-old patient ventilated with both ILV and HFO.

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Case Report

A 68-yr-old man with a solid mass in the upper lobe of the left lung was scheduled for lobectomy; aortic valve replacement and coronary artery bypass surgery were performed at the same time as lung resection. Two days after surgery he had massive left pleural bleeding that necessitated 18 U of transfused blood. The patient developed severe hypoxemia (Pao2/fraction of inspired oxygen [Fio2] ratio of 91) 24 h after surgical revision of the left pleural space; chest radiograph showed the right lung to be homogeneously infiltrated and the left lung to be mostly collapsed. The patient was transferred to our institution for ILV.

On his arrival, a tracheostomy was performed, and a left double-lumen tube was placed (Fig. 1). Conventional ILV was initiated, with the respiratory rate set at 20 breaths/min and Fio2 at 1; Vt and PEEP were 3 mL/kg (predicted body weight) and 15 cm H2O for the right lung and 2 mL/kg and 18 cm H2O for the left lung, respectively. These settings resulted in a Pao2/Fio2 ratio of 112, with an end-inspiratory plateau pressure (Pplat) of 28 cm H2O in the right lung and 43 cm H2O in the left lung. His Paco2 was 38.8 mm Hg, and arterial pH was 7.49. Because of the risk of ventilator-induced lung injury (VILI) in the left lung, HFO ILV was initiated. The right lung was ventilated with conventional ventilation (Vt, 3 mL/kg; PEEP, 15 cm H2O; respiratory rate, 30 breaths/min), and the left lung was ventilated with HFO (3100B; SensorMedics; mean airway pressure, 30 cm H2O; oscillation frequency, 8 Hz; bias flow, 35 L/min). These settings further improved the Pao2/Fio2 ratio to 148; Paco2 was 48.3 mm Hg, and arterial pH was 7.38. Computed tomography (CT) images of the lung were acquired during conventional ILV (Fig. 2; top left) and HFO ILV (Fig. 2; top right). Analysis of the left lung images showed that HFO set with a mean airway pressure smaller than the Pplat developed during conventional ventilation, decreased the amount of nonaerated tissue, and increased the amount of normally aerated tissue (Fig. 2; bottom). Afterward, CT scans comparing conventional ILV and HFO ILV were repeated every 8–10 days. These confirmed that the amount of nonaerated tissue was smaller and the amount of normally aerated tissue was larger during HFO ILV than during conventional ILV.

Figure 1

Figure 1

Figure 2

Figure 2

After 40 days, the right lung was ventilated with a Vt of 3 mL/kg, a respiratory rate of 30 breaths/min, and a PEEP of 6 cm H2O, and the left lung was ventilated with HFO set with a mean airway pressure of 25 cm H2O, an oscillation frequency of 6 Hz, and a bias flow of 35 L/min; Fio2 was 0.5 for both lungs. The Pao2/Fio2 ratio, Paco2, and arterial pH were 280, 41 mm Hg, and 7.41, respectively. CT analysis revealed that the aeration pattern during HFO was similar to the one obtained while the left lung was ventilated with a breathing pattern that led to a Pplat of 20–22 cm H2O (Fig. 3; bottom) (Vt, 3 mL/kg; PEEP, 10 cm H2O; respiratory rate, 20 breaths/min). On the basis of these results, HFO ILV was discontinued, and the patient was ventilated with conventional ILV (right lung: Vt, 3 mL/kg; respiratory rate, 30 breaths/min; PEEP, 6 cm H2O; left lung: Vt, 3 mL/kg; respiratory rate, 20 breaths/min; PEEP, 10 cm H2O; Fio2 was 0.5 for both lungs). Two days later conventional ventilation was reestablished, and the patient was successfully disconnected from the ventilator. He was discharged alive from the intensive care unit 64 days after admission.

Figure 3

Figure 3

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Discussion

Reports of the concurrent use of ILV and HFO are limited to the management of severe air leak or asymmetric lung injury in pediatric patients (3–6). Graciano et al. (3) used two HFO ventilators to independently ventilate the lungs of a 17-year-old, 87-kg patient with trisomy 21 and unilateral pneumonia.

To minimize VILI, alveolar overdistension, cyclic alveolar collapse, and reopening should be avoided. HFO theoretically achieves these goals by keeping the lung open with high mean airway pressure and by applying small alveolar pressure swings (2). We observed that conventional ILV exposed the most injured lung to a Pplat >30 cm H2O, which would potentially lead to VILI, whereas application of HFO provided sufficient gas exchange at safer pressure levels. Improvement of gas exchange could have been achieved with the selective administration of nitric oxide or right-side positioning, but this would have left the lungs exposed to high ventilator pressure.

In the setting of unilateral lung injury, the mechanical impairment of the injured parts of the lung cannot be specifically assessed. We showed that pulmonary CT scanning provides useful information on the efficacy of ILV HFO ventilation in an adult patient with asymmetric acute lung injury.

In conclusion, this case report demonstrates the feasibility of HFO for ILV in an adult patient. Attention should be paid to the risk of airway harm caused by prolonged ILV.

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References

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