Basics of Mechanical Ventilation RET Advanced Mechanical Vent Lecture 1 Reorientation and Basic Operational Principles Dr. J. Elsberry Special Thanks to: Joseph S. DiPietro, Ph.D., RRT & Jim Tolbert Southwest Virginia Community College

Some Common Ventilator Modes This is confusing so we will learn it a bit later!

It is about the Math ?

First off, Make sense of the Modes

The Guru of Ventilator Classification Robert L. Chatburn, RRT, FAARC Director of Research Cleveland Clinic A link to this text is posted on WebCT

Chatburn’s Classification of Mode I Breathing Pattern: I Breathing Pattern: Control---Volume, Pressure or Dual Breath Sequence---CMV, IMV or CSV II. Control Type: II. Control Type: Open Loop Closed Loop ( “Cruise Control” ) III. Control Strategy III. Control Strategy A. Phase variables (trigger, limit, cycle) B. Operational Logic

Exploring Chatburn’s Classification 1. Patient Support Level: Full VS, Partial VS or Spontaneous Breathing 2. Breathing Pattern: Control Target---Volume, Pressure or Dual Breath Sequence---CMV*, IMV** or CSV*** *CMV = Continuous Mandatory Ventilation **IMV = Intermitent Mandatory Ventilation ***CSV = Continuous Spontaneous Ventilation

If this happens, then … 3. Conditional Variables: Pressure, Volume, Time, Flow A. Phase variables (trigger, limit, cycle, baseline) A. Phase variables (trigger, limit, cycle, baseline) B. Operational Logic (varies for each ventilator) B. Operational Logic (varies for each ventilator) C. Patient Response (C L Raw, ABG’s ) C. Patient Response (C L Raw, ABG’s )

The Two Roads we Travel….

SPONTANEOUS (CSV) Not an actual mode since rate and tidal volume during spontaneous breathing are determined by the patient (Takes the place of aerosol “T-Piece”) Not an actual mode since rate and tidal volume during spontaneous breathing are determined by the patient (Takes the place of aerosol “T-Piece”) Role of ventilator during spontaneous vent. is to provide: Role of ventilator during spontaneous vent. is to provide: (1) flow to the pt. in a timely manner, (1) flow to the pt. in a timely manner, (2) flow adequate to fulfill a patient’s insp. demand, and (2) flow adequate to fulfill a patient’s insp. demand, and (3) provide adjunctive modes such as CPAP to complement the spontaneous effort (3) provide adjunctive modes such as CPAP to complement the spontaneous effort

SPONTANEOUS (cont’d.) Apnea ventilation is a safety feature used for spontaneous mode Apnea ventilation is a safety feature used for spontaneous mode The use of an ETT & ventilator for monitoring is seen in Adults and frequently in NEONATES The use of an ETT & ventilator for monitoring is seen in Adults and frequently in NEONATES

PEEP PEEP increases the end-expiratory or baseline airway press. to a value greater than ambient and is often used to improve the pt.’s O 2 status, esp. if refractory PEEP increases the end-expiratory or baseline airway press. to a value greater than ambient and is often used to improve the pt.’s O 2 status, esp. if refractory PEEP is not a stand-alone mode, but is used in conjunction with other modes PEEP is not a stand-alone mode, but is used in conjunction with other modes When PEEP is applied to spontaneous breathing pt., then it is called CPAP When PEEP is applied to spontaneous breathing pt., then it is called CPAP

PEEP (cont’d.) Two major indications for PEEP are: intrapulmonary shunt leading to refractory hypoxemia intrapulmonary shunt leading to refractory hypoxemia decreased functional residual capacity and lung compliance decreased functional residual capacity and lung compliance Complications assoc. with PEEP include: - ↓ venous return and C. O. - ↑ barotrauma - ↑ ICP - alterations of renal, hepatic, etc.

Lung Filling Characteristics Increasing Raw ? Increasing Raw ? Decreasing C L Decreasing C L Trauma Trauma Position of Patient Position of Patient Pneumo/Hemothorax Pneumo/Hemothorax

CPAP (CSV) If PEEP is applied to a spont. breathing pt: Indications are same as PEEP but in addition pt. must have adequate lung function to sustain eucapnic ventilation Indications are same as PEEP but in addition pt. must have adequate lung function to sustain eucapnic ventilation Can be used for adults with ET tube or facemask and nasal appliances as well as in neonates with ETT or nasal prongs Can be used for adults with ET tube or facemask and nasal appliances as well as in neonates with ETT or nasal prongs

BiPAP (PC-CSV) Allows one to apply IPAP and EPAP Allows one to apply IPAP and EPAP (P high and P low ) IPAP provides positive pressure breaths and it improves hypoxemia and/or hypercapnia IPAP provides positive pressure breaths and it improves hypoxemia and/or hypercapnia EPAP (essentially PEEP) improves oxygenation by increasing the FRC and enhancing alveolar recruitment EPAP (essentially PEEP) improves oxygenation by increasing the FRC and enhancing alveolar recruitment

BiPAP (cont’d.) Indications for BiPAP: - preventing intubation of end-stage COPD patient - supporting patients with chronic ventilatory failure - patient’s with restrictive chest wall disease - neuromuscular disease - nocturnal hypoventilation

BiPAP (cont’d) Three modes include: - spontaneous - timed - spontaneous/timed Three modes include: - spontaneous - timed - spontaneous/timed Initial settings: - if pt. breathing spont., set at 8 and 3 - use spont./timed as backup and set 2-5 breaths below pt.’s spont. Initial settings: - if pt. breathing spont., set at 8 and 3 - use spont./timed as backup and set 2-5 breaths below pt.’s spont. IPAP levels are determined by monitoring pt.’s clinical & physiologic response, not V T IPAP levels are determined by monitoring pt.’s clinical & physiologic response, not V T

BiPAP (cont’d) EPAP should be increased by 2 cm H 2 O increments to increase FRC and oxygenation EPAP should be increased by 2 cm H 2 O increments to increase FRC and oxygenation It is not possible to increase EPAP higher than IPAP It is not possible to increase EPAP higher than IPAP We’ll have a separate Lecture and Workshop on all forms of NIV later in the term. We’ll have a separate Lecture and Workshop on all forms of NIV later in the term.

VC-CMV (timed trigger only) Ventilator delivers the preset tidal volume at a set time interval Ventilator delivers the preset tidal volume at a set time interval This mode should only be used when the pt. is properly medicated with a combination of sedatives, respiratory depressants and/or neuromuscular blockers This mode should only be used when the pt. is properly medicated with a combination of sedatives, respiratory depressants and/or neuromuscular blockers Indicated if: Indicated if: -pt. “fights” the vent. -pt. “fights” the vent. -tetanus or seizure disorder. -tetanus or seizure disorder. -complete rest for pt. for 24 hr. -crushed (flail) chest where spontaneous Vent. produces paradoxical movement. -crushed (flail) chest where spontaneous Vent. produces paradoxical movement.

IMV (VC or PC –IMV) Pt. breaths spontaneously at any tidal volume between the mechanical breaths Pt. breaths spontaneously at any tidal volume between the mechanical breaths Primary disadvantage is chance for breath stacking, therefore care should be taken to set high press. limit properly to reduce risk of barotrauma Primary disadvantage is chance for breath stacking, therefore care should be taken to set high press. limit properly to reduce risk of barotrauma

SIMV A mode in which the vent. delivers mandatory breaths to the pt. at or near the beginning of a spont. breath, mandatory breaths are synchronized with the pt.’s spont. efforts to avoid breath stacking A mode in which the vent. delivers mandatory breaths to the pt. at or near the beginning of a spont. breath, mandatory breaths are synchronized with the pt.’s spont. efforts to avoid breath stacking “synchronized window” refers to the time just prior to time triggering in which the vent. is responsive to the pt.’s effort (0.5 sec is typical) “synchronized window” refers to the time just prior to time triggering in which the vent. is responsive to the pt.’s effort (0.5 sec is typical)

SIMV (cont’d) gas source for spontaneous breathing is usually a demand valve that allows pt. to determine their tidal volume gas source for spontaneous breathing is usually a demand valve that allows pt. to determine their tidal volume Indications include providing partial vent. support, usually after 24 hr. of full vent. support Indications include providing partial vent. support, usually after 24 hr. of full vent. support Advantages include maintaining respiratory muscle strength, reducing V/Q mismatch, decreasing mean airway press., helps wean pt Advantages include maintaining respiratory muscle strength, reducing V/Q mismatch, decreasing mean airway press., helps wean pt

MMV (Mandatory Minute Ventilation) (DC-IMV) also called minimum minute ventilation also called minimum minute ventilation Provides a predetermined minute ventilation when the patient’s spontaneous breathing effort becomes inadequate Provides a predetermined minute ventilation when the patient’s spontaneous breathing effort becomes inadequate Useful for preventing hypoventilation and respiratory acidosis in the final stages of weaning with SIMV Useful for preventing hypoventilation and respiratory acidosis in the final stages of weaning with SIMV Need to watch spontaneous minute volume (a distressed pt. may increase f with lower tidal volume) This is a dual mode. Need to watch spontaneous minute volume (a distressed pt. may increase f with lower tidal volume) This is a dual mode.

PSV (PC-CSV) Used to lower the WOB and augment a patient’s spont. tidal volume Used to lower the WOB and augment a patient’s spont. tidal volume When PSV is used with SIMV, it lowers the O 2 consumption because of the decr. WOB When PSV is used with SIMV, it lowers the O 2 consumption because of the decr. WOB PSV applies a preset pressure plateau to the pt. during a spont. breath PSV applies a preset pressure plateau to the pt. during a spont. breath PSV breaths are patient triggered, pressure limited, and flow cycled PSV breaths are patient triggered, pressure limited, and flow cycled

PCV (PC-CMV) The pressure controlled breaths are time triggered by a preset f The pressure controlled breaths are time triggered by a preset f Once inspiration begins, a pressure plateau is created and maintained for a preset inspiration time Once inspiration begins, a pressure plateau is created and maintained for a preset inspiration time Typically used in ARDS (IRDS) where it takes excessive press. in volume cycled modes to ventilate a pt., leading to barotrauma Typically used in ARDS (IRDS) where it takes excessive press. in volume cycled modes to ventilate a pt., leading to barotrauma

APRV (airway pressure release ventilation) (PC-CSV) Combines two separate levels of PEEP and the pt. may breathe spontaneously from both levels, not a Volume Vent Mode Combines two separate levels of PEEP and the pt. may breathe spontaneously from both levels, not a Volume Vent Mode Periodically, pressure is dropped to the lower level, reducing mean airway press. Periodically, pressure is dropped to the lower level, reducing mean airway press. During spont. expiration, the PEEP is dropped (released) to a lower level which simulates an effective exhalation During spont. expiration, the PEEP is dropped (released) to a lower level which simulates an effective exhalation

Critical Care Ventilators vs. legacy Ventilators we use for Learning Which will You See in Clinic?