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High Frequency Oscillatory Ventilation in Pediatric Patients

John H. Arnold, MD

Department of Anesthesia, Childrens Hospital Boston and the

Departments of Anaesthesia and Pediatrics, Harvard Medical School, Boston, MA

Data supporting the feasibility of ventilating effectively with very small tidal volumes comes from the

observation that the need for adequate bulk gas flow in airways can be achieved by delivering tidal volumes

approximating the dead space at high frequency. While attempting to measure cardiac performance in large

animals by assessing the myocardial response to pericardial pressure oscillations, Lunkenheimer and

colleagues found in the early 1970s that endotracheal high frequency oscillations could produce efficient

CO2 elimination in the absence of significant chest wall excursion. These investigators determined that CO2elimination was related to changes in the frequency of oscillation as well as the amplitude of the vibrations.

In general, CO2 was cleared optimally at a frequency between 23-40 Hz, with smaller animals requiring

higher frequencies. Several years later, Butler and colleagues observed that gas exchange could be supported

in humans using frequencies up to 15 Hz, hypothesizing that this would enhance diffusive gas transport

while minimizing dependence on bulk convective gas flow in the airways. In this report, a series of patients9 years of age and older in an intensive care unit was successfully ventilated with tidal volumes in the range

of 50-100cc.

At the moment, there is a great deal of laboratory data to suggest that repetitive cycles of pulmonary

recruitment and derecruitment are associated with identifiable markers of lung injury, and experimental

models of ventilatory support which reverse atelectasis, limit phasic changes in lung volume, and prevent

alveolar overdistention appear to be less injurious. In addition, recent clinical investigations have brought

about an understanding that specific strategies for mechanical ventilation can have an important influence on

outcomes in patients with the acute respiratory distress syndrome (ARDS). In 2000, the ARDSnetwork

demonstrated a 22% relative reduction in mortality among adult patients with ARDS on conventional

mechanical ventilation who were randomized to receive relatively small tidal volumes (6 cc/kg ideal body

weight), compared to those who were ventilated with larger tidal volumes (12 cc/kg ideal body weight).These observations have led to the expectation that high frequency ventilation could limit excess lung injury

in the clinical arena because of its ability to provide efficient, low-stretch ventilation in the setting of

continuous alveolar recruitment. This open-lung strategy of ventilation offers the promise of lung

protection by its ability to preserve end-expiratory lung volume, minimize cyclic stretch, and avoid

parenchymal overdistension at end-inspiration by limiting tidal volume and transpulmonary pressure.

The major modalities of high frequency ventilation include high frequency flow interruption (HFFI), high

frequency positive pressure ventilation (HFPPV), high frequency jet ventilation (HFJV), and high frequency

oscillatory ventilation (HFOV). HFOV is the most widely used form of high frequency ventilation in clinical

practice today, and in this mode, lung recruitment is maintained by the application of relatively high mean

airway pressure, while ventilation is achieved by superimposed sinusoidal pressure oscillations that are

delivered by a motor-driven piston or diaphragm at a frequency of 3-15 Hz. HFOV is the only form of highfrequency ventilation in which expiration is an active process. As a result, alveolar ventilation is achieved

during HFOV with the use of tidal volumes in the range of 1-3 cc/kg, even in the most poorly compliant

lung.


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Summary of neonatal and pediatric high frequency oscillatory ventilation (HFOV) management

NEONATAL PEDIATRIC

INDICATIONS -Diffuse Alveolar Disease (Paw > 10)-Early intervention (ELBW)

-Air leak syndrome (including PIE)

- Diffuse Alveolar Disease (Paw >15)- Air leak syndrome

* do not use 3100B for < 35 kgMonitoring Obtain baseline VS, SpO2/PaO2, and PaCO2/TcPCO2

CardioVascular Insure adequate intravascular volume / C.O. (based on BP, HR, etc)

Airway - Verify ETT placement radiographically- Suction (consider in-line catheter)

Sedation Insure adequate sedation Sedation andmuscle relaxation

PRE HFOV

Lung VolumeRecruitment

Optimize lung volume with hand ventilation and inspiratory hold maneuvers as tolerated for DAD. Usecaution with air leaks and ELBW patients.

Paw High volume strategy(for DAD):3 - 5 cmH2O > Paw on CMV

Air leak strategy: Same or 2 - 3

cmH2

O > Paw on CMVEarly Intervention: 10 - 14 cmH2OFor all: if SpO2 falls rapidly and

below 90%, Paw incrementally

High volume strategy (for DAD):5 - 8 cmH2O > Paw on CMV

If SpO2

falls rapidly and below 90%, recruit withhand ventilation and Paw incrementally

Delta P Full term : 25 cmH2O or greaterPre-term : 16 cmH2O or greater

Set Powermid range; adjust to achieve vigorouschest vibrations

Frequency (HZ) Full term : 12 or 15 HzPre-term / ELBW: 15 Hz

Kg 3100A< 10: 10 - 12

11 - 20: 8 - 1021 - 40: 6 - 10

> 40: 5 - 8

Kg 3100B

35 - 50: 8 - 10> 50: 5 - 8

Bias Flow 8 - 15 L/min 15 - 20+ L/min, depending on patient size andrequired Paw

Inspiratory time 33 % 33%

INITIAL HFOV

SETTINGS

FiO2 1.0 1.0

High volume strategy: increase Paw by 1-2 cmH2O until FiO2 0.6 with acceptable PaO2/SpO2Oxygenation

Early intervention: adjust Paw to maintain FiO2 .30, SpO2 88-92%

Air leak strategy: tolerate FiO2 .8 - 1.0 (especially for first 12 - 24 ) to minimize Paw while achievingacceptable PaO2 / SpO2. Very difficult to achieve with pediatric patients

CO2 elimination Adjust Delta P: 2 - 5 cmH20 to achieve PaCO2 change of 3 - 5 mmHg;> 5 cmH2O to achieve PaCO2 change of 5 - 10 mmHg

Hz: decrease only if PaCO2 refractory to changes in Delta P

CXR Obtain1 - 2 hours post-initiation, as often as Q 6-8 hours until stable, then daily and after significantsettings changes (e.g. multiple Paw changes). Evaluate for lung expansion: 8-9 ribs optimal.

MANAGEMENT ON

HFOV

Suctioning Limit as much as possible, esp. during initial 24 hours. Consider for acute or progressive increase in

PaCO2. Perform recruitment maneuvers as tol

Delta P incrementally, as above; spontaneous breathing

may augment Ve

incrementally while maintaining acceptable

PaCO2

WEANING /

DISCON-

TINUATION Paw in 1-2 cmH2O increments

Full/Pre-term: to CMV when 10 -12

VLBW: CPAP with Paw 10,

weight gain, and absence of As&Bs

in 1-2 cmH2O increments to 15 - 20 cmH2O and

good recovery post suctioning; may see "plateau"


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References

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59:577-84.

Slutsky AS, Tremblay LN. Multiple system organ failure. Is mechanical ventilation a contributing factor? Am J Respir

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Doctor A, Arnold JH. Mechanical Support of Acute Lung Injury: Options for Strategic Ventilation. New Horizons

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McCulloch PR, Forkert PG, Froese AB. Lung volume maintenance prevents lung injury during high frequency

oscillatory ventilation in surfactant-deficient rabbits. Am Rev Respir Dis 1988; 137:1185-92.

Priebe GP, Arnold JH. High-frequency oscillatory ventilation in pediatric patients. Respir Care Clin N Am 2001; 7:633-

45.

Chang HK. Mechanisms of gas transport during ventilation by high-frequency oscillation. J Appl Physiol 1984; 56:553-

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Arnold JH. High-frequency ventilation in the pediatric intensive care unit. Pediatr Crit Care Med 2000; 1:93-9.

Arnold JH, Hanson JH, Toro-Figuero LO, Gutierrez J, Berens RJ, Anglin DL. Prospective, randomized comparison of

high-frequency oscillatory ventilation and conventional mechanical ventilation in pediatric respiratory failure. Crit Care

Med 1994; 22:1530-9.

Arnold JH, Truog RD, Thompson JE, Fackler JC. High-frequency oscillatory ventilation in pediatric respiratory failure.

Crit Care Med 1993; 21:272-8.

Courtney SE, Durand DJ, Asselin JM, Hudak ML, Aschner JL, Shoemaker CT. High-frequency oscillatory ventilation

versus conventional mechanical ventilation for very-low-birth-weight infants. N Engl J Med 2002; 347:643-52.

Johnson AH, Peacock JL, Greenough A, et al. High-frequency oscillatory ventilation for the prevention of chronic lung

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