You're doing an annual test at a hospital where the normal oxygen pressure is 55 psi. 

 You note that the area alarm does not activate when you put 60 PSI pressure to the sensor. 

 What should you do? 

A)  Tell the hospital that their pressures high in their oxygen system and adjust the oxygen system appropriately. 

B)  Note that there was a high alarm failure at 60 PSI in your report. 

C)  Raise the pressure on the sensor till you get a high alarm and note the activation point. 

D)  Notify the hospital that they need their system serviced in your report. 

Table

Section #5.1.11 The normal pressures for Oxygen are 50-55 psig.

So, 50 is normal, 51 is normal, 52 is normal,

53 is normal, 54 is normal and 55 is also normal

and within the standard code requirement.

WE SEE THIS EVERYDAY

Now:

Section #5.1.9.3.2 Is the requirement for the area alarm 20% increase and decrease set points from the normal line pressure. That is the 50-55 psig range. COOL

Numbers: 

Section #5.1.8.1.4 The accuracy of the digital indicators in the area alarm panel can be off scale by (+ or - 5 percent) of the operating pressures.

GOT TO LOVE THE NUMBERS

JUST A THOUGHT :

If a hospital has 50 area alarm panels and you do an annual on August 31 and the

oxygen line pressure is 50 psig, the alarm set points are 40 and 60 psig.

All is good right?

Now on September 01 the hospital has a procedure to rotate the final line regulators each month and that regulator is set for 53 psig.

Which is totally normal per #5.1.11.

So are you going to tell hospital to go back and to all 50 alarms and re-set the hi and low set point? Remember to take in to account the + or - 5% differential at the area alarm digital read out.

Is the hospital ready out of compliance ? 

Are the patient ready in danger ?

Is the equipment ready going to fail ?

Are their any real mortality or morbidity case studies on this ? (i.e. a white paper)

Conclusion In my opinion only.

A oxygen system that is within the normal ranges of 50 to 55 psig,

with the area alarm set at 40 psig low and 60 psig high is acceptable.

Steve and I win:

The effect on accuracy of flow due to variations in ambient temperature is standard accuracy +7.3% @ 32°F (0°C) and -3.0% @ 104°F (40°C). Most all USA flowmeters are calibrated at 50 psi (3.4 bar), 70°F (21°C), and standard atmospheric pressure.  

Agree, gas systems with nominal operating pressure of 50 -55 psig are fine with alarm set points of 40 and 60 psig.

This may be a good opportunity to briefly review how some respiratory care devises perform with changes in line pressure.

Medical 02 and med air flowmeters are “back pressure compensated” to 50 psig and read accurately at 50 psig and their flow reading will vary if pressure changes. Back pressure compensated means the gas pressure within the flow tube is always under line pressure, even when turned off. This is why you may see the flowmeter ball raise and fall rapidly when pressure temporarily changes as when nearby ventilators start their inspiratory cycle, particularly when the flowmeter is turned off. Will flowmeter flow readings change if pressure varies within the 40 to 60 psig range? Yes. Is it clinically significant? Probably not.

Ventilator inlet pressure requirements can vary somewhat from manufacturer to manufacturer and model to model, but generally will function as designed within the 40 and 60 psig range, but this should be verified for a specific vent. Flow, 02 concentration, and occasionally other parameters can vary as 02 and air inlet pressures change in relation to each other. Clinically significant within the 40 to 60 psig range? Maybe, maybe not.

Oxygen/air mixers (blenders) are devices separate from ventilators, used to control a precise and constant oxygen concentration to patients. Their range is 21 to 100% 02. These devises will typically give the set 02 concentration, within their stated accuracy, provided the difference between 02 and air inlet pressures are within +/- 20 psig of each other. This is providing the devices receive periodic maintenance (including replacing internal components) as required by the manufacturer.

Typically, ventilators and blenders will alarm when line pressure variation is significant.

George Scott