What can we learn from high-frequency ventilation? Dipartimento di Medicina Perioperatoria, Terapia Intensiva ed Emergenza Azienda Sanitaria Universitaria Integrata di Trieste Università degli Studi di Trieste, Italy U. Lucangelo MD, PhD
Historical Overview of High Frequency Ventilation Oberg and Sjöstrand: 1967 - first experimental application 1972 - first clinical application High Frequency Positive Pressure Ventilation (HFPPV ) Lunkenheimer: 1972 - High Frequency Oscillation (HFO) Klain and Smith 1977 High Frequency Jet Ventilation (HFJV)
The term High Frequency Ventilation is used to describe ventilation at higher than normal frequencies (above 60 cycles/min = 1 Hz) with reduced Tidal Volume (Vt) and Peak Airway Pressure (Ppeak)
Tidal Volume Tidal volume versus respiratory rate domain for different ventilatory strategies L F P P V + E C CO 2 R CV VD HFPPV HFJV HFOV 0 10 100 1000 10000 Respiratory Rate (b/min)
High Frequency Ventilation Techniques Overwiew Heterogeneous group of Techniques Gas Delivery System Design Frequency (60 2400 cycles/min)
Gas Transport During HFV most popular theories Bulk gas flow Diffusion Taylor dispersion Asymmetric velocity profiles Pendelluft Collateral ventilation Cardiogenic oscillation
Gas Transport During HFV The relative importance of each of these mechanisms is not clear!! These mechanics are not mutually exclusive All may be operative simultaneously Effects of lung disease on regional mechanics
High-frequency ventilation was developed in an effort to avoid many of the complications and limitations of conventional mechanical ventilation Alveolar overdistension Use of large tidal volume Failure to exceed the minimum end-expiratory lung volume needed to prevent tidal closure of alveolar units
Froese CMM 1997;25:906
High Frequency Ventilation HFJV HFPV HFOV
H.F.O.V. is the form of high-frequency ventilation most widely used in adult critical care.
HFOV The oscillatory pressure swings and thus VT are provided by a piston O 2 INLET CO 2 WASH OUT Pressure Static Mean Airway Pressure P Unilevel Adjustable %I-time P MAP time
Pressure transmission in HFOV The oscillating pressures in the circuit are significantly damped in alveolar regions. Indeed, the impedance in the endotracheal tube alone significantly reduces the pressure swings in the trachea to 5-16% of that in the circuit.
Equation of motion during HFOV Paw( t) V t Ers V t Rrs V t Irs
Does High-Frequency Ventilation Offer Benefits Over Conventional Ventilation in Adult Patients With Acute Respiratory Distress Syndrome? Many of the available human data on delivered VT during HFOV are from studies of neonates. Neonates : small and uncuffed endotracheal tubes higher frequencies (10 15 Hz). Adults: cuffed endotracheal tubes lower frequency (3 6 Hz). Very different lung and chest wall mechanics. Therefore, the very small VT reported in neonates could well be irrelevant to adult medicine. Fessler H.E. and Hess D.R. Respiratory Care 2007
Tidal volume delivery during high frequency oscillatory ventilation in adults with acute respiratory distress syndrome. Decreasing endotracheal tube internal diameter from 8 mm to 7 mm and from 7 mm to 6 mm caused a 15.3% ± 1.7% and 18.9% ± 2.1% reduction in tidal volume, respectively. A 2 Hz increase in frequency (4, 6, 8, 10, 12 Hz) was associated with a 23.1% ± 6.3% decrease in tidal volume. A 10 cmh 2 O increase in pressure amplitude (20, 30, 40 cmh 2 O ) caused a 21.4% ±3.4% increase in tidal volume. Tidal volumes are not uniformly small during HFOV (23-225 ml)!!! Hager DN et al. Crit Care Med 2007
Four methods of measuring tidal volume during high-frequency oscillatory ventilation. Measured VT varied with the pressure amplitude and varied strongly with the frequency. At a pressure amplitude of 90 cm H 2 O and a frequency of only 4 Hz, VT was 200 ml. At 10 Hz, the VT fell to about 80 ml, even at the pressure amplitude of 90 cm H 2 O. Hager DN, Fuld M, Kaczka DW, Fessler HE, et al. Crit Care Med 2006
Determinants of tidal volume during high-frequency oscillation. In an adult sheep model, was used HFVO management strategies that were identical to the ones used in early adult clinical trials by Fort and Mehta. These investigators found that quite large VT (ie, 6 ml/kg) were being delivered into the proximal airways. Sedeek KA et al. Crit Care Med 2003
VT is technically difficult to measure and is not monitored during HFOV. Reliable tidal volume estimates at the airway opening with an infant monitor during high-frequency oscillatory ventilation. Scalfaro P, Pillow JJ, Sly PD, Cotting J. Crit Care Med 2001. In the clinical practice, HFOV is not an intuitive ventilatory modality Four methods of measuring tidal volume during high-frequency oscillatory ventilation. Hager DN, Fuld M, Kaczka DW, Fessler HE, et al. Crit Care Med 2006 and the absence of real-time delivered volume monitoring Portable instrument for the volume measurement of high-frequency percussive produces disaffection among the physicians. ventilators. Riscica F, Lucangelo U, Accardo A. Biomed Sci Instrum 2010
Comparison of prone positioning and high-frequency oscillatory ventilation in patients with acute respiratory distress syndrome. Prospective randomized study that enrolled 39 ARDS patients with a PaO2/FIO 2 < 150 mm Hg at PEEP > 5 cm H 2 O. After 12 hours on conventional lung-protective mechanical ventilation (VT of 6 ml/kg, Pplat 35 cmh 2 O, with supine conventional ventilation). 12 patients received conventional lung protective mechanical ventilation in prone position. 13 patients received HFOV in supine position 12 patients received HFOV in prone position Papazian L, et al. Crit Care Med 2005
* * PaO 2 /FiO 2 Sup-CV Pro-CV Sup-CV Sup-CV Papazian L, et al. Crit Care Med 2005
Neutrophil counts in bronchoalveolar lavage fluid Papazian L, et al. Crit Care Med 2005
OSCAR/OSCILLATE, Both Imperfect Trials OSCILLATE (> 72 h excluded) OSCAR ( up to 7 days) CMV HFOV CMV HFOV PaO 2 /FiO 2 113±38 113±37 114±38 121±46 Hospital mortality 35% 47% 41.1% 41.7% Apache II 29±7-21±6.1 - VT (ml/kg) 7.1±1.8-8.3±3.5 - PREMATURELY STOPPED
Finally, the epiphenomena of HFOV include the potential for circulatory depression from high airway pressure and the need for heavy sedation or paralysis during HFOV.
Efficacy and adverse events of high-frequency oscillatory ventilation in adult patients with acute respiratory distress syndrome: a meta-analysis Huang et al. Critical Care 2014, 18:R102
Efficacy and adverse events of high-frequency oscillatory ventilation in adult patients with acute respiratory distress syndrome: a meta-analysis Huang et al. Critical Care 2014, 18:R102
The effect of HFOV on 30-day or hospital mortality Huang et al. Critical Care 2014, 18:R102
The application of HFOV was associated with a trend toward increased risk of barotrauma and unfavorable hemodynamics. Huang et al. Critical Care 2014, 18:R102
The application of HFOV was associated with a trend toward increased risk of barotrauma and unfavorable hemodynamics. Huang et al. Critical Care 2014, 18:R102
Current evidence did not support the routine use of HFOV for ARDS patients in the era of lung-protective ventilation because of its potential harm.
High Frequency PercussiveVentilation Delivers high frequency ventilation (200-1200 cycles/min) in combination with low frequency breath cycles. I E
Male, 58yrs old, BMI 27,7 Essential hypertension, paroxystic atrial flutter, mild mitral and aortic insuffciency Bilateral bronchopneumonia Nasal swab positive for influenza virus A (H1N1)
ph 7.310 PaCO 2 62.5 mmhg PaO 2 46.8 mmhg HCO - 3 26.7 meq/l BE 4.5 and SaO 2 77.2 % Oxygenation index = 39 Lung injury score = 3.25 FiO 2 = 1
PCV
HFPV
Electrical impedance tomography during VCV
Electrical impedance tomography during HFPV
The Evidence for New Ventilator Modes It s not the ventilator mode that makes a difference It s the skills of the clinician that makes the difference. Any ventilator mode has the potential to do harm! Dean Hess 2010
To ventilate, oscillate, or cannulate? Given the heterogeneity of acute respiratory distress syndrome, each of these modalities may play a role in an individual patient. Future studies comparing LPV, HFOV, and VV ECMO should not only focus on defining the patients who benefit most from each of these therapies but also consider long-term functional outcomes. Shekar K et al. Journal of Critical Care 2013
HFOV should be reserved for patients failing conventional ventilation and applied by clinicians with considerable experience with the device. Respir Care 2016