Determining the Determining the appropriate level appropriate level

of PSVof PSVBy Elizabeth Kelley Buzbee By Elizabeth Kelley Buzbee

AAS, RRT-NPS, RCPAAS, RRT-NPS, RCP

According to Egan’s Fundamentals there are three methods According to Egan’s Fundamentals there are three methods to set appropriate levels of PSV for a patientto set appropriate levels of PSV for a patient

get an appropriate Vt [10-15 ml/kg] and titrate the PS level get an appropriate Vt [10-15 ml/kg] and titrate the PS level to achieve this Vtto achieve this Vt

increase the PS level till the respiratory rate is normalized increase the PS level till the respiratory rate is normalized [25 bpm or less][25 bpm or less]

[Egan’s page 1018] increase the PSV until you decrease the [Egan’s page 1018] increase the PSV until you decrease the work of breathing through the endotracheal tubework of breathing through the endotracheal tube To select the appropriate level of PSV to overcome the RAW To select the appropriate level of PSV to overcome the RAW

use this formulause this formulaPSV= PSV= (PIP - PPlat) x spont insp. Flow rate [lps](PIP - PPlat) x spont insp. Flow rate [lps]

Ventilator flow rate [lps]Ventilator flow rate [lps]

This tutorial will use case studies This tutorial will use case studies to go through each of these three to go through each of these three

methodsmethods Case study # 1Case study # 1

Mr. Casey is a 45 year old WM who has been Mr. Casey is a 45 year old WM who has been on CMV for several weeks following on CMV for several weeks following successful treatment for ARDS triggered successful treatment for ARDS triggered by smoke inhalation. He is alert and wants by smoke inhalation. He is alert and wants off the ventilator. His current ABG show a off the ventilator. His current ABG show a normal PaC02 and normal oxygenation on normal PaC02 and normal oxygenation on his current settings: A/C 10 Vt 700 ml and his current settings: A/C 10 Vt 700 ml and PEEP 5 Fi02 40%. He is breathing at a rate PEEP 5 Fi02 40%. He is breathing at a rate of 12 bpm with a return Vt of 705 mlof 12 bpm with a return Vt of 705 ml

You see that his lung compliance has You see that his lung compliance has risen from a low of 17 ml/cmH20 to a risen from a low of 17 ml/cmH20 to a current level of 45 ml/cmH02current level of 45 ml/cmH02

because he is ready to wean you because he is ready to wean you need to challenge him to breath by need to challenge him to breath by getting him off CMV onto some getting him off CMV onto some support mode. support mode.

You suggest what ventilator change?You suggest what ventilator change?

ANSWERANSWER

: change him from A/C of 10 to SIMV : change him from A/C of 10 to SIMV of 10 of 10

When his mode is changed from A/C When his mode is changed from A/C of 10, you see that his return Ve has of 10, you see that his return Ve has fallen from 8.4 Liters to 7.5 Liters. fallen from 8.4 Liters to 7.5 Liters.

Why?Why?

ANSWER:ANSWER:

his mechanical Ve dropped because his mechanical Ve dropped because he is now unable to trigger ventilator he is now unable to trigger ventilator breaths. He now has a spontaneous breaths. He now has a spontaneous Ve.Ve.

When you subtract Mr. Casey’s When you subtract Mr. Casey’s mechanical Ve [7.] from his total [Ve mechanical Ve [7.] from his total [Ve 7.5 L] you see that his spontaneous 7.5 L] you see that his spontaneous Ve is what?Ve is what?

ANSWER:ANSWER:

7.5 L – 7.0 L = spont. Ve of .5 L7.5 L – 7.0 L = spont. Ve of .5 L

Calculate his spontaneous VtCalculate his spontaneous Vt

ANSWERANSWER

: spont Ve/ spont RR = spont : spont Ve/ spont RR = spont Vt .5/10 = 50 ml VtVt .5/10 = 50 ml Vt

You see that his spontaneous You see that his spontaneous respiratory rate is 10. When added to respiratory rate is 10. When added to the 10 bpm of the mechanical the 10 bpm of the mechanical ventilator, he has a total respiratory ventilator, he has a total respiratory rate of what? Is it excessive? rate of what? Is it excessive?

ANSWER:ANSWER:

20 bpm. It’s a bit fast, but not 20 bpm. It’s a bit fast, but not dangerously fastdangerously fast

When you get ABG on this setting When you get ABG on this setting you see that the PaC02 has risen you see that the PaC02 has risen from 40 to 45. He is looking a little from 40 to 45. He is looking a little anxious, and his breathing a little anxious, and his breathing a little labored at a SIMV 10 Vt 700labored at a SIMV 10 Vt 700

The doctor orders you to decrease The doctor orders you to decrease him from SIMV 10 to SIMV 5. Do you him from SIMV 10 to SIMV 5. Do you agree?agree?

ANSWER:ANSWER:

No, his current spontaneous Vt is No, his current spontaneous Vt is only 50 ml. His Vd is 150 so you only 50 ml. His Vd is 150 so you know that he doesn’t have enough Vt know that he doesn’t have enough Vt to get gas into his alveoli where it to get gas into his alveoli where it will do some good.will do some good.

Doctor disagrees and you put the Doctor disagrees and you put the patient on SIMV 5. You stick around patient on SIMV 5. You stick around because you want to see his reaction because you want to see his reaction to this. to this.

The patient increases his The patient increases his spontaneous respiratory rate from spontaneous respiratory rate from 10bpm to 35 bpm.10bpm to 35 bpm.

Why?Why?

ANSWER:ANSWER:

he must raise his spontaneous Ve he must raise his spontaneous Ve from .5 to 3.75 Liter to keep the total from .5 to 3.75 Liter to keep the total Ve that he had earlier. Because he Ve that he had earlier. Because he cannot breath any deeper than 50 cannot breath any deeper than 50 mL, he must increase his RR to 75 mL, he must increase his RR to 75 bpm—this is impossible and his C02 bpm—this is impossible and his C02 will rise and he will get exhausted.will rise and he will get exhausted.

What would you suggest at this What would you suggest at this point?point?

ANSWER:ANSWER:

give him enough PSV to raise his Vt, give him enough PSV to raise his Vt, that will drop his respiratory ratethat will drop his respiratory rate

The doctor agrees to add PS to him. The doctor agrees to add PS to him. He give you a free hand to select the He give you a free hand to select the appropriate level. You look at what?appropriate level. You look at what?

ANSWERANSWER

: put him on a PSV of 5 and watch his : put him on a PSV of 5 and watch his return Vt. Increase the PSV until his return Vt. Increase the PSV until his return Vt is 10 mL/kg IBW. return Vt is 10 mL/kg IBW.

Mr. Casey’s IBW is 65 kg. When you Mr. Casey’s IBW is 65 kg. When you select PSV 5 you see that his return select PSV 5 you see that his return spont Vt is now 200 ml. You increase spont Vt is now 200 ml. You increase his PSV to 10 and see that he now his PSV to 10 and see that he now gets 400 ml Vt. What do you do gets 400 ml Vt. What do you do next?next?

ANSWER:ANSWER:

you see that on PSV his dynamic C is you see that on PSV his dynamic C is 40 ml/cmH20 so you increase his PVS 40 ml/cmH20 so you increase his PVS to 16 [ 16 cmH20 x 40 = predicted to 16 [ 16 cmH20 x 40 = predicted 640 ml.640 ml.

At this point, the patient’s respiratory At this point, the patient’s respiratory rate goes from 36 bpm to 6 bpm. rate goes from 36 bpm to 6 bpm. Now is total respiratory rate is 5 + 6 Now is total respiratory rate is 5 + 6 = 11 bpm. His color gets better and = 11 bpm. His color gets better and he stops retracting.he stops retracting.

CASE STUDY # 2CASE STUDY # 2

Your patient is Mrs. Ortagus who has Your patient is Mrs. Ortagus who has been on A/C 15 and Vt 500 PEEP 5 been on A/C 15 and Vt 500 PEEP 5 and Fi02 45% for the last few days. and Fi02 45% for the last few days. She intubated and ventilated for viral She intubated and ventilated for viral pneumonia and is now getting better.pneumonia and is now getting better.

To wean her you request what mode To wean her you request what mode change? change?

ANSWER:ANSWER:

switch her to SIMV and get a gas. If it switch her to SIMV and get a gas. If it is good reduce the SIMV rateis good reduce the SIMV rate

The doctor agrees and when she is The doctor agrees and when she is on SIMV 10 bpm, she starts to breath on SIMV 10 bpm, she starts to breath on her own. You see that her spont on her own. You see that her spont Ve is 3.0 and her spont respiratory Ve is 3.0 and her spont respiratory rate is 12 bpm. What is her spont Vt?rate is 12 bpm. What is her spont Vt?

ANSWER:ANSWER:

Ve / rate = Vt so 3.0 L/ 12 = 250 mlVe / rate = Vt so 3.0 L/ 12 = 250 ml

The doctor orders her down from The doctor orders her down from SIMV 10 to SIMV 5 and her SIMV 10 to SIMV 5 and her respiratory rate rises to 23 bpm. respiratory rate rises to 23 bpm. What do you suggest?What do you suggest?

ANSWER:ANSWER:

put her on SIMV + PSVput her on SIMV + PSV

The doctor gives you permission to The doctor gives you permission to adjust the PSV. What do you do?adjust the PSV. What do you do?

ANSWER:ANSWER:

start at PSV 5 or 10 watch the start at PSV 5 or 10 watch the respiratory rate for a few minutes. respiratory rate for a few minutes. Increase the PS until the respiratory Increase the PS until the respiratory rate drops to less than 25 bpmrate drops to less than 25 bpm

When you select PSV 5 you see her When you select PSV 5 you see her rate decreases to 20 bpm [total is 5 rate decreases to 20 bpm [total is 5 + 20 = 25]+ 20 = 25]

Are you happy with this?Are you happy with this?

ANSWER:ANSWER:

if the gas is good and she is not if the gas is good and she is not working too hard to breath. working too hard to breath.

CASESTUDY # 3CASESTUDY # 3

Your patient is Mr. Blake a 50-year-old BM Your patient is Mr. Blake a 50-year-old BM with a history of COPD. He was placed on with a history of COPD. He was placed on SIMV 12, Vt 500, Fi02 34% and has been SIMV 12, Vt 500, Fi02 34% and has been on these settings for two weeks. The on these settings for two weeks. The doctor orders you to decrease his rate to 8 doctor orders you to decrease his rate to 8 bpm. When you do this he starts to breath bpm. When you do this he starts to breath on his own. He seems to be working hard on his own. He seems to be working hard to breath and the doctor asks you to put to breath and the doctor asks you to put him on enough PSV to overcome the RAW him on enough PSV to overcome the RAW of the endotracheal tube.of the endotracheal tube.

What information do you need to do this?What information do you need to do this?

ANSWER:ANSWER:

look at his look at his flow/timeflow/time curve and find curve and find his spontaneous inspiratory flow ratehis spontaneous inspiratory flow rate

look at the look at the flow/timeflow/time curve and find curve and find his ventilator flow ratehis ventilator flow rate

look at the look at the pressure/timepressure/time curve and curve and find his PIPfind his PIP

put him on .5 seconds of pause time put him on .5 seconds of pause time and find his Pplatand find his Pplat

You get the following information:You get the following information: spontaneous inspiratory flow rate 20 spontaneous inspiratory flow rate 20

lpm /60 = .33L/seclpm /60 = .33L/sec ventilator flow rate = 50 lpm/60 = .83 lpsventilator flow rate = 50 lpm/60 = .83 lps PIP 45PIP 45 Pplat 23Pplat 23

Calculate the PSV he needs through Calculate the PSV he needs through this endotracheal tube to over come this endotracheal tube to over come resistance.resistance.

PSV= PSV= (PIP - PPlat) x spont insp. Flow (PIP - PPlat) x spont insp. Flow rate [lps]rate [lps]

Ventilator flow rate [lps]Ventilator flow rate [lps]

ANSWER:ANSWER:

PSV= PSV= (45 - 23) x .33 [lps](45 - 23) x .33 [lps]

.83 [lps].83 [lps]

PSV= PSV= 22 cm H20 x .33 [lps]22 cm H20 x .33 [lps]

.83 [lps].83 [lps]

PSV= PSV= 7.267.26

.83.83

PSV = 8.7 cm H20PSV = 8.7 cm H20