Special Thanks to: Nancy Hemmert, MPH, RRT Fundamentals of APRV (Airway Pressure Release Ventilation) or ‘CPAP with release’ Special Thanks to: Nancy Hemmert, MPH, RRT

APRV - Brief History of Mechanical Ventilation ca. 400 BC Hippocrates describes cannulation of the trachea ca. 1530-40 Fire bellows used to assist ventilation; Vesalius and Reed 1786 First volume limiting device used with bellows system 1864-1950 Negative Pressure ventilators are developed and refined 1886 First “cuffed” endotracheal tube 1906 Intermittent positive pressure ventilation device 1967 PEEP with mechanical ventilation is introduced 1971 CPAP introduced for the treatment of IRDS 1973 IMV used as technique to facilitate spontaneous breathing early 1980s Pressure Support introduced to augment Vt in spontaneously breathing patients 1986 APRV introduced @ conference on by Stock and Downs 1990 First ventilator with APRV is introduced

Importance of PEEP for Alveolar Recruitment PEEP vs ZEEP for Alveolar Recruitment

APRV Classic Definition: APRV is a pressure-limited spontaneous breathing mode (CPAP) with time-cycled pressure releases designed to enhance CO2 elimination and prevent alveolar collapse. …PC-CSV

APRV - waveforms

APRV – Indications for use RDS/ALI REFRACTORY HYPOXEMIA (R>L Intrapulmonary Shunt) SEVERE ATELECTASIS (Threshold Opening Pressure [TOP] and time) RESTORE FRC (increase alveolar surface area) O2 O2

PERFUSION WITHOUT VENTILATION RIGHT TO LEFT SHUNT PERFUSION WITHOUT VENTILATION Resulting in refractory hypoxemia PaO2 IS Decreased ! Responds only to PEEP Increases in FIO2 With Shunt Fractions >50% of Cardiac Output have little Effect on augmenting PaO2

RDS/ALI Disturbed oxygenation due to poor V/Q matching (refractory hypoxemia) Severe atelectasis w/high TOPs (threshold opening pressures) Chest x-ray - “white out” Non-homogenous lung disease (MRI) Reduced compliance with poor lung mechanics and high WOB Increased PCWP (pulmonary hypertension) With the "Breathing Support Package" Dräger offers a complete new philosopy in breathing support technique.

NORMAL V/Q RELATIONSHIP . . . NORMAL V/Q RELATIONSHIP 4LPM VA /5LPM QT = 0.8 .

Alveolar Dead Space - Over-distention Ventilation without Perfusion Leads to increase Vd/Vt ratio ultimately with HYPERCAPNIA (CO2) WOB INCREASES WITH A DEADSPACE QUOTIENT OF ~70%. SPONT. BREATHING IS NO LONGER POSSIBLE

PRESSURE / VOLUME CURVE FLAT LOWER PORTION OF CURVE V>Q MIDDLE STEEP PORTION OF CURVE V/Q normal FLAT UPPER PORTION OF CURVE V<Q

APRV P-V CT SCAN

APRV - Impact of spontaneous breathing

APRV – Impact of spontaneous breathing

APRV EIT image

APRV controls Dräger XL

APRV initial set-up Neonates Newly intubated Phigh—set at desired plateau pressure (typically 10–25 cm H2O) Plow—0 cm H2O Thigh—2–3 secs Tlow—0.2–0.4 Transition from conventional ventilation Phigh—plateau pressure in volume-cycled mode or peak airway pressure in pressure-cycled mode Transition from HFOVb Phigh—mPaw on HFOV plus 0–2 cm H2O Note: Phigh 25 cm H2O may be necessary in patients with decreased thoracic/abdominal compliance With a Phigh25 cm H2O, use of noncompliant ventilator circuit is recommended to minimize circuit volume compression

APRV initial set-up Pediatrics Newly intubated Phigh—set at desired plateau pressure (typically 20–30 cm H2O) Plow—0 cm H2O Thigh—3–5 secs Tlow—0.2–0.8 Transition from conventional ventilation Phigh—plateau pressure in volume-cycled mode or peak airway pressure in pressure-cycled mode Transition from HFOVb Phigh—mPaw on HFOV plus 2–4 cm H2O Note: Phigh 30 cm H2O may be necessary in patients with decreased thoracic/abdominal compliance or morbid obesity (73, 74). With a Phigh 25 cm H2O, use of noncompliant ventilator circuit is recommended to minimize circuit volume compression.

APRV initial set-up ADULTS Newly intubated Phigh—set at desired plateau pressure (typically 20–35 cm H2O) Plow—0 cm H2O Thigh—3–5 secs Tlow—0.2–0.8 (RLD) 0.8—1.5 (OLD) Transition from conventional ventilation Phigh—plateau pressure in volume-cycled mode or peak airway pressure in pressure-cycled mode Thigh—4–6 secs Transition from HFOVb*** use a non compliant ventilator circuit*** Phigh—mPaw on HFOV plus 2–4 cm H2O Note: Phigh 30 cm H2O may be necessary in patients with decreased thoracic/abdominal compliance or morbid obesity (73, 74). With a Phigh 25 cm H2O, use of noncompliant ventilator circuit is recommended to minimize circuit volume compression.

APRV MANIPULATION Pressure release cycles improve CO2 elimination. Increasing the number of cycles (reducedThigh) lowers PaCO2. Pdelta changes will affect the volume exhaled. Plow = 0 Mean airway pressure (Phigh) and FiO2 control oxygenation. Exhalation waveform is adjusted by Tlow to insure PEEPi, preventing alveolar collapse (50-75% PEFR). . .

APRV pre & post

What it would lild look like on other Vents:

APRV - Weaning Always decrease FiO2 to a non-toxic level. Phigh  in increments of 2cmH20 to maintain SpO2. Sudden abrupt changes could cause DE- RECRUITMENT and the patient could “CRASH” ! “Drop and stretch” Phigh gradually Thigh gradually

APRV - Weaning

APRV – short and simple Benefits of APRV and spontaneous breathing: Better distribution of Tidal Volume without regional over-distention Improves V/Q matching – TOP and time required for lung units to open Increases venous return/cardiac output CO2 removal is enhanced by allowing a pressure release The extremely short phase of the pressure release (Tlow) prevents alveolar collapse and de-recruitment Avoidance of cyclic de-recruitment avoids shear force tearing FRC is increased and V/Q mismatch is improved resulting in better oxygenation

APRV – Literature citations Downs JB, Stock MC: Airway pressure release ventilation: a new concept in ventilatory support. Crit Care Med 1987; 15:459–461 Habashi N : Other approaches to open-lung ventilation: Airway Pressure Release Ventilation. Crit Care Med 2005; vol. 33, No 3 (suppl.) s228-s240 Putensen C, Wrigge H: Clinical review: BiPhasic positive airway pressure and airway pressure release ventilation. Critical Care 2004, 8:492-497 Shultz T, et al: Airway pressure release ventilation in pediatrics. Pediatric Critical Care 2001; vol. 2, No. 3, pp 243-246

Fighting the Machine or Synchrony?