BiPAP machine provides two kinds of pressure including IPAP (inspiratory positive airway pressure)and EPAP(expiratory positive airway pressure).
IPAP is the inspiratory pressure. The pressure conveyed by BiPAP when the patient inhales. Patients with chronic lung obstruction inhale less air because of small airway blockage. In order to solve this problem, the BiPAP needs to increase the pressure when the patient inhales to help them to inhale enough air.
In other words, the main function of IPAP pressure is to increase the patient's tidal volume, so that the patient can inhale enough air.
The more serious the patient's condition is, the higher the IPAP pressure needs to be set. At the same time, the patient's height and weight are also factors influencing the IPAP pressure value setting.
When the BiPAP machine is running, the two IPAP and PEEP are adjusted according to the patient's breathing state.
The EPAP pressure is the "expiratory pressure", which is quite different from the IPAP pressure.
When a person breathes normally, when exhaling, the gas in the lungs is discharged from the chest with high pressure until the pressure in the lungs is equal to atmospheric pressure.
On the pressure-time curve, the pressure in the expiratory phase gradually rises from the Abscissa level, then decreases gradually, and finally returns to the Abscissa.
That is to say, the end-expiratory pressure is supposed to be equal to zero.
When the end-expiratory gas is not fully discharged, a valve in the expiratory loop closes ahead of time, the remaining part of the gas cannot be discharged, and the pressure level cannot return to zero, which is greater than 0, so it is called positive pressure.
This occurs at the end of the breath, which is called the positive end-expiratory pressure (positive end-expiratory pressure, PEEP).
Patients with pulmonary diseases such as COPD have weak respiratory function, EPAP increases the solubility of oxygen which cross the membrane of the lung capillaries and increase the amount of oxygen in the blood.
The PEEP produced by the "closure" of the PEEP valve of a BiPAP machine is called extrinsic PEEP.
Extrinsic PEEP can dilate the respiratory tract and lung tissue, and its airway dilation effect is mainly concentrated in the expansion of lung tissue in the pharynx and larynx.
Its specific functions are as follows:
- Dilatation of the pharynx and throat-which can be used in the treatment of obstructive sleep apnea-hypopnea syndrome (OSAHS) and dilatation of lung tissue at the end can prevent and treat alveolar lung closure and can be used in the treatment of diseases such as ARDS.
- Extrinsic PEEP can redistribute lung water, reduce cardiac blood volume and reduce cardiac preload, which can be used in the treatment of acute pulmonary edema.
- PEEP also fights against intrinsic PEEP and is used in the treatment of asthma and COPD. It also plays a role in dilating airways, reducing airway resistance and improving man-machine synchronization.