ICU

BiPAP: (IPAP, EPAP), Principle, Operation, Pros, Cons, Handling

Non-Invasive Positive Pressure Ventilation (BiPAP)

BiPAP stands for Bilevel Positive Airway Pressure. Unlike the CPAP machine, it provides two levels of air pressure to the patient. Nowadays, a single machine can have the features of both CPAP and BiPAP.

Levels of pressure

  • Inspiratory Positive Airway Pressure (IPAP):- It is the pressure that is applied during inspiration. The set value for IPAP generally ranges from 10 to 20 cm H2O.
  • Expiratory Positive Airway Pressure (EPAP):- It is the pressure that is applied during expiration. The set value for EPAP generally ranges from 5 to 12 cm H2O.

(Inspiration is an active process that needs more energy than expiration. Similarly, expiration is a passive process that does not need much energy. Thus IPAP is always greater than EPAP.)

BiPAP Setting

1. Modes of BiPAP

  • CPAP mode
  • S mode: Spontaneous mode in which the patient controls the breathing cycle
  • S/T mode: (Spontaneous/ Timed) Mode causes alteration between IPAP and EPAP based on the set timing

2. Parameters

Different models of the machine allow the users to set different parameters. Some, of the major ones, are as follows:

  • EPAPmin = 4 cm H2O
  • IPAPmax = 20 cm H2O
  • PSmin = 3 cm H2O
  • PSmax = 15 cm H2O

The above are my opinions for setting the values. However, the values can differ from patient to patient.

  • Inspiratory to Expiratory  (I: E) Ratio

The machine can also have the following features

  • Actual Breathing Rate
  • Estimated Tidal Volume, Minute Volume, and Air Leakage
  • No. of Apneas
  • Alarm button, alarm reset, etc.

Difference between CPAP and BiPAP

( BiPAP VS CPAP )

CPAP BiPAP
Stands for Continuous Positive Airway Pressure Stands for Bilevel Positive Airway Pressure
It continuously provides a single airway pressure to the patient. However, the set value can be changed as per the requirement of the patient. It continuously provides two airway pressures to the patient. One is during the inspiration, while the other one is during expiration.
CPAP is useful for the treatment of patients with normal breathing problems such as sleep apnea. If the condition of the patient becomes much more complex, then BiPAP is better.
Since a single high positive pressure is applied continuously, expiration might be difficult. Since a lower airway pressure is applied during expiration, breathing becomes much easier.
It is cheaper to purchase It is much more expensive in comparison to the CPAP.

BiPAP Mask

Mainly, two types of BiPAP masks are in use.

These masks are also used in CPAP machines.

How does BiPAP work?

Block Diagram of CPAP, BiPAP
Image Source: https://www.researchgate.net/figure/The-block-diagram-of-the-experimental-CPAP-setup_fig1_221797667

 

Atmospheric air goes to the blower of the machine through the filters. The blower compresses the air and sends high-pressure air to the connecting tube. Then the air goes to the patient through the nasal mask.

The pressure sensor senses the air pressure in the connecting tube. This sensed pressure goes to the microprocessor. Then the microprocessor analyzes the variation among the set and obtained pressure value. In case of any variation, it either increases or decreases the voltage signal of the driver motor. This, in turn, controls the speed of the blower. Based on the companies there can be some variations in the above block diagram.

Breathing Cycle Under BiPAP

Inspiration increases the volume of the lungs. This causes a sudden drop in intra-alveolar pressure. On sensing this drop of pressure, the machine applies pressure equal to IPAP. The pressure gradient (IPAP> intra-alveolar pressure) causes air to flow from the machine to the lungs. At the end of the inspiration, intra-alveolar pressure becomes equal to IPAP.

The expiration might be triggered by the drop in the air inflow to the threshold value. On, detecting the decreased air inflow, EPAP is applied by the machine. The expiration causes a fall in the intra-alveolar pressure. Once the pressure lowers below EPAP value, IPAP pressure activates again for the next breathing cycle.

Also, EPAP ≈ CPAP ≈ PEEP

 Pressure Support (PS) ≈ IPAP – EPAP

Operation 

  • Connect the AC cord to the machine and the power supply
  • Connect connecting tube, mask, and humidification tank (if needed)
  • Turn on the machine
  • Pre-heat the water of the humidifier before use (30 mins earlier)
  • Set the parameters in your setting option. The values will be prescribed by your doctor.

Drawbacks

  • Continuous high airflow might cause patients, difficult sleep
  • High air pressure might cause patients, difficult to expire
  • Chance of air leakage from the BiPAP masks
  • Dry nose and mouth
  • Headache to some patients

Handling

  • Use soap water to clean mask and humidification tank
  • Do not use alcohol to clean the machine. You can use Collins.
  • Always use distilled water in the humidification tank
  • An ultra-fine filter is disposable
  • The film filter is washable (life span: 6 months)
  • Check for any leakage in the tubing system.

You may not be able to manually wash the tubing, mask, and humidification tank properly. Thus in that case you can use a CPAP Cleaner to get the job done.

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