Why would a patients respiratory rate be set at 28 on a mechanical ventilator?


Mechanical ventilators are usually set between 12-16 breaths per minute but one patient in a case study I am working on, has her ventilator set at 28.

The Patient Bicarbonate level is low at 7 and is in respiratory acidosis. Just wondering. I have not been to a ICU floor nor can I find the answer in the book.

Just wondering why would they set a patients respiratory rate so high on a mechanical ventilator.

:unsure: please help

confused nursing student


207 Posts

You can bring down high CO2s with higher volumes, increased respiratory rate, and longer expiratory times. If the patient is maxed out on volume then the next step would be to adjust respiratory times. This will increase their expiratory minute volumes and blow off more CO2.

babyNP., APRN

1,921 Posts

Specializes in NICU. Has 15 years experience.

Have you learned about acid/base balance yet? What would a patient present with in respiratory acidosis?

edmia, BSN, RN

827 Posts

Specializes in Emergency, ICU. Has 10 years experience.

Go to your A&P book and review the physiology of acid/base balance.

What builds up with acidosis?


207 Posts

I wanted to clarify that I mean respiratory rate and not time.


120 Posts

I can promise you that if your patient's bicarbonate is 7, there's a 99 percent chance he's not in respiratory acidosis. Please provide the rest of the ABG values.


10 Posts

Sorry i meant metabolic acidosis... typo


10 Posts

But her bicarbonate is low. so a higher resp rate on the ventilator would lower it even more according to your answer, no? Also i meant metabolic acidosis.


10 Posts

. Ms. C is on a mechanical ventilator set on assist-control of 14, respiratory rate of 28, volume 650, oxygen 40%, and a positive end-expiratory pressure (PEEP) of 5


20 Posts

Specializes in SI/CV ICU and ER. Has 5 years experience.

The vent is acting as a temporary fix for the acidosis. The underlying problem is what needs to be fixed, a lot of intensivists don't like to give the patient exogenous bicarbonate because it really skews what is wrong. The problem could be something as simple as dehydration, or it could be something much more complex like renal failure. The short answer is they are blowing off c02 as a temporary fix.


10 Posts

Thank you so much!

Esme12, ASN, BSN, RN

4 Articles; 20,908 Posts

Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma. Has 43 years experience.
. Ms. C is on a mechanical ventilator set on assist-control of 14, respiratory rate of 28, volume 650, oxygen 40%, and a positive end-expiratory pressure (PEEP) of 5
Looking at these settings....the machine is set at assist control of 14, so the machine will give exactly 14 breaths per minute, however the patient is over breathing at a total rate of 28 breaths per minute. A +5 of peep is really noting it just "removes" (compensates for) the dead space of the vent tubing.

The overall respiratory rate is high but the vent is set at 14....why is the patient breathing more/over the vent? .....to compensate for metabolic acidosis.

5.5 Metabolic Acidosis - Compensation