Resident lecture – requisite mandatory ventilatory parameters to order.

REMEMBER : Always discuss all aspects of respiratory care with the respiratory therapist, the resident, the nurse and the attending physician.

The physician should always order :

orders for initiation of mechanical ventilation to include :

type of ventilation : VCV vs. PCV vs. PRVC

mode of ventilation : full vs. partial vs. minimal ventilatory support (aka AC vs. SIMV vs. PSV)

RRset : 6 vs. 10 vs. 16

Vt(set) : 6ml/kg vs. 8ml/kg vs. 10ml/kg vs. 12ml/kg (and PBW(-predicted body weight) vs. IBW(ideal body weight) vs. actual weight)

alternatively to Vt(set), dP(set) : dP=30

alternatively to Vt(set), Time(inspiratory) : T(inspir) =2sec

FiO2 : 100% vs. 30% & appropriate PEEP (suggested=14cmH2O).

PEEP : 14cmH2O.

Pressure Support : targeted for tidal volume ~ 5ml/kg.


Resident lecture – what to set mandatory RR at.

REMEMBER : Always discuss all aspects of respiratory care with the respiratory therapist, the resident, the nurse and the attending physician.

Keeping it simple, there are only 3 general categories to set for mandatory RR.

RR= 16          as a transient solution to increased intracranial pressure (hyperventilation should cause cerebral vasoconstriction and thru the “mass effect”, allow a relative decrease in intracranial pressure to allow for the space occupying lesion that is the head injury.

RR= 6           for any patient deemed “difficult to ventilate” to include status asthmaticus and ARDS.  Lungs should be envision not as two organ systems but rather as individual alveoli.  Then, envision those alveoli inflating and deflating at 24 to 34 time per minute.  It is only a matter of time before a micro-tear appears and now the bioinflammatory cascade is evoked.  It will then be only a matter of time before early ARDS signs & symptoms appear.  Permissive hypercapnea should be entertained.  An acidic cellular milieu should be considered.  Acidemia in itself is a protective environment.  A slow RRmandatory will minimize mechanical trauma.

RR= 10         everyone else not mentioned above.

QoW 2015 – 003 (Where does APRV fit in the grid of modes vs. types of ventilation)

Where does APRV fit in the grid of Mode vs. Type of ventilation?

Modes of Ventilation

full                                         partial                                   minimal

Types                      VCV                        AC-VCV                                   SIMV-VCV                                VSV

of                             PCV                         AC-PCV                                  SIMV-PCV                                 PSV

Ventilation           PRVC                        AC-PRVC                              SIMV-PRVC                               VSV

Neural                                                                                                                            NAVA





Resident Lecture – spontaneous ventilatory modes

2015 nov 12 - modes spontaneous breathing

Spontaneous modes :

PSV (pressure support ventilation) – pressure is set and tidal volume is variable.

VSV (volume support ventilation) – tidal volume is set and the peak pressure is variable.

NAVA (neurally adjusted ventilatory assist) – this one is tricky – the unit of measure is cmH2o per unit of microvoltage.  In other words, if one were to set NAVA=1.0, the patient will get 1 cmH2o (1 centimeter of water pressure)  for every microvolt  the brain sends down the phrenic nerve.

If the NAVA level was set to NAVA=3.0, the patient will get 3cmH2o (3 centimeter of water pressure) for every microvolt the brain sends down the phrenic nerve.

However, when the brain feels it is adequately satiated with the size of the tidal volume and the stretch of the lung and acceptable pH and host of many other input receptors are satiated, the neural signal is tuned down.

Essentially, as one turns up the NAVA level (ex from NAVA=1.0 to NAVA=3.0), the more inverse the microvoltage signal from the brain to the diaphragm via the phrenic nerve (i.e. from 3microvolts to 1 microvolt) so that the tidal volume delivered is consistently the same (ex 250mls in both cases).

4 5uv

2015 nov - NAVA - 7 novel cases - j 012

Notice that in the above two screen captures :

NAVA=4.5 & Edi=2.3 & Vt~221.

NAVA=2.5 & Edi=3.7 & Vt~225.

Resident lecture – historical developement of PCV vs AC vs SIMV

2015 nov 12 - modes vs types of ventilation - ac vs simv vs pcv

During report, people continue to report that their patient is on AC or SIMV or PCV.

When people mention AC, they mean AC-VCV.

When people mention SIMV, they mean SIMV-VCV.

When people mention PCV, they mean AC-PCV.

This likely relates to the historical development of modes.  When there was originally PCV (aka AC-PCV) and then AC (aka AC-VCV) and then SIMV (aka SIMV-VCV).

However, with the advent of microprocessors, we have a myriad of ventilatory mode-types.

Resident lecture – modes vs. types of ventilation

2015 nov 12 - modes vs types of ventilation

Quite often, I hear medical residents reporting during morning rounds that their patients are on Assist Control or SIMV or PCV.  I remind them that is a very incomplete statement and that a qualifier word is needed in there during reporting.  Otherwise, the report is not very telling of the acuity of the patient.

I remind medical  residents that there are :

Modes of Ventilation :

AC  (full ventilatory support

SIMV (partial ventilatory support)

PSV (minimal ventilatory support)

and then, there are :

Types of Ventilation :

VCV (volume controlled ventilation)

PCV (pressure controlled ventilation)

PRVC (pressure regulated volume control)

When properly set up in the above grid (like a multiplication table) the relationship becomes obvious.

Types of Ventilation include :

Volume ventilation includes : AC-VCV ; SIMV-VCV ; VSV (volume support ventilation).

Pressure ventilation includes : AC-PCV ; SIMV-PCV ; PSV(pressure support ventilation).

Pressure Regulated ventilation includes : AC-PRVC ; SIMV-PRVC ; VSV (volume support ventilation).

Modes of Ventilation include :

full ventilatory support includes : AC-VCV ; AC-PCV ; AC-PRVC.

partial ventilator support includes : SIMV-VCV ; SIMV-PCV ; SIMV-PRVC.

minimal ventilatory support includes : VSV ; PSV (& NAVA).



QoW 2015 – 002 (How is this TRALI patient doing post trache?)

With regards to this TRALI patient post tracheostomy and trache-collar trial in progress for > 12hrs,

a) how do you think the patient is doing?

b) what do you think the physician thinks how this patient is faring?

c) how do you think the physician decided to manage this patient?

d) how would you handle this patient in the next 12hrs?


2015 nov 12 - trali hd17 tc

This is the patient who continued on a trache collar trial for approximately 18 hours.

The patient had stable vital signs with a HR=80-84, RRspont=18-22 and SpO2~95%.

The patient was sleeping very comfortablly and without signs of respiratory distress (no costal retractions and no nasal flaring).

The CXR and ABG are shown above.


2015 nov 12 - trali hd16

This is the patient the day after tracheostomy.  Note the lung fields are expanded even moreso due to having been “rested” on SIMV-VCV during the night.