High-frequency oscillatory ventilation (HFOV) is an advanced mechanical ventilation strategy utilized in the management of respiratory failure, particularly in critically ill patients. It employs small tidal volumes delivered at rapid rates to maintain lung recruitment and gas exchange while minimizing the risk of ventilator-induced lung injury (VILI). HFOV is commonly employed in neonates, infants, and adults with acute respiratory distress syndrome (ARDS) or other conditions characterized by severe respiratory compromise.
The fundamental principle of HFOV involves the delivery of very small tidal volumes (often in the range of 1-3 mL/kg) at high frequencies (typically between 3 and 15 Hz). This approach differs from conventional mechanical ventilation, where larger tidal volumes are delivered at slower rates. The goal of HFOV is to provide adequate ventilation and oxygenation while minimizing the risk of lung injury associated with high tidal volumes and pressures.
In HFOV, gas is delivered into the airways in the form of rapid oscillations, creating small pressure changes that promote lung recruitment and gas exchange. These oscillations are superimposed on a baseline level of continuous positive airway pressure (CPAP), which helps to maintain lung volume and prevent atelectasis during expiration. The combination of high-frequency oscillations and continuous positive pressure facilitates gas exchange by improving alveolar ventilation and reducing intrapulmonary shunting.
The oscillations in HFOV are typically generated by a piston or a diaphragm within the ventilator circuit. The rapid oscillatory motion of the ventilator creates pressure fluctuations that are transmitted to the airways, causing the lungs to expand and contract at high frequencies. This cyclical stretching and relaxation of the lung tissue help to open collapsed alveoli, redistribute lung volume, and improve overall lung compliance.
One of the key advantages of HFOV is its ability to deliver ventilation while minimizing the risk of VILI. By using very small tidal volumes and high frequencies, HFOV reduces the mechanical forces applied to the lungs, thereby decreasing the likelihood of barotrauma (pressure-related lung injury) and volutrauma (overdistension of the alveoli). This makes HFOV particularly suitable for patients with ARDS or other conditions where lung injury may be exacerbated by conventional ventilation strategies.
HFOV can be used as a primary mode of ventilation or as a rescue therapy for patients who fail to respond to conventional ventilation. It is often initiated when patients exhibit severe respiratory distress, hypoxemia, or signs of impending respiratory failure. HFOV may also be used prophylactically in high-risk patients to prevent the development of ARDS or other complications.
Despite its potential benefits, HFOV requires careful patient selection, monitoring, and management to optimize outcomes.
2. CONTENTS
➔ Introduction
➔ Types of HFV
➔ What is HFOV?
➔ Indications of HFOV
➔ Contraindication of HFOV
➔ Settings &Parameters in HFOV
➔ Complication of HFOV
3. INTRODUCTION
DEFINITION OF HFV
High-frequency ventilation (HFV) is a type of ventilation that is utilized when
conventional ventilation fails. It is a technique where the set respiratory rate
greatly exceeds the normal breathing rate. In this rescue strategy, the tidal
volume delivered is significantly less and can also be less than dead space
ventilation.
4. TYPES OF HFV
Types of HFV are
1) High-frequency oscillatory ventilation(HFOV)
2) High-frequency positive pressure ventilation(HFPPV)
3) High-frequency jet ventilation(HFJV)
4) High-frequency percussive ventilation(HFPV)
5. WHAT IS HFOV?
DEFINITION OF HFOV
HFOV stands for High-Frequency Oscillatory Ventilation. It's a type of
mechanical ventilation used in intensive care units to support patients with
severe respiratory failure. HFOV delivers very small, rapid breaths at a set
frequency, allowing for greater lung recruitment and oxygenation while
minimizing barotrauma.
6. INDICATIONS OF HFOV
❏ Ventilator-associated lung injury
❏ Alveolar hemorrhage
❏ Large air leak with inability to keep lungs open
❏ Abdominal Compartment Syndrome
❏ Failure of conventional mechanical ventilation
❏ Refractory hypoxemia
❏ Increased intracranial pressure
❏ Persistent pulmonary hypertension
❏ Acute Respiratory Distress Syndrome
❏ Pulmonary Interstitial Emphysema
❏ Meconium aspiration
❏ Pulmonary hypoplasia
❏ Bronchopulmonary fistulae
9. SETTINGS AND PARAMETERS IN HFOV
The settings in hfov are
1. Bias flow
2. Mean airway pressure
3. Amplitude
4. Frequency
5. Inspiratory time
10.
11. 1.BIAS FLOW
❖ It is also called base flow
❖ Its supplies oxygen and remove exhale air
❖ Generate the Paw
❖ Initial flow 20L/min
❖ Maximum upto 60L/min
Parameters
❖ premature-10-15L/min
❖ <1yrs-15-25L/min
❖ 1 to 8 yrs-15-30L/min
❖ >8 yrs-25-40L/min
12. 2.MEAN AIRWAY PRESSURE
Its used to optmize lung volume & thus improves alveolar surfacearea for gas
exchange.
1) Neonates: 8-10cmH2o
2) infants:15-20cmH2o
13. 3.AMPLITUDE
❖ Distant the diaphragm moves
❖ Set the Pswing around MAP
❖ If is too low-under ventilation
❖ If its too high-VILI
❖ Determines Vt
PARAMETERS
❖ wt<2-0kg-2.5
❖ Wt2.1-2.5kg-3.0
❖ Wt2.6-4.0kg-4.0
❖ Wt4.6-5.0kg-5.0
❖ Wt5.1-10kg-6.0
❖ wt>20kg-7.0
14. 4.FREQUENCY
❖ Measured in Hertz(HZ)
❖ 1HZ=1cycle/sec=60breaths/min
❖ Increase in amplitude=decreasein frequency
❖ Decrease of age/wt=increase in frequency
❖ Decrease of compliance=increase in frequency
PARAMETERS
❖ Preterm neonates-15HZ
❖ Term neonates-12HZ
❖ infant/child-10HZ
❖ Older child-8HZ
15. 5.INSPIRATORY TIME
❖ Similar to conventional
❖ Ratio 1:2
❖ Insp time is 33%
❖ Increase in time will leads to air trapping
16. COMPLICATIONS OF HFOV
❖ Irritation
❖ Hypotension
❖ Pneumothorax
❖ ETT obstruction due to secretion
❖ Intracranial hemorrhage
❖ Bronchopulmonary dysplasia
❖ Necrotizing tracheo bronchitis
