BiPAP or Bi-level Positive airway pressure is used to restore functional residual capacity (FRC) – the volume left in the lungs at the end of a resting exhalation. This residue allows more efficient gas exchange at the alveoli and hence improves oxygenation.
It is also known as non-invasive positive pressure ventilation (NPPV).
It differs from Continuous Positive Airway Pressure (CPAP) in that it provides assistance with ventilation. CPAP only provides a constant positive pressure.
BiPAP is used to treat hypercapnoeic respiratory failure. Examples of this might include: Sleep apnoea, chronic airway limitation (CAL) and some neuromuscular disorders. Recent studies have found it effective in the treatment of hydrostatic pulmonary oedema and pneumonia.To achieve BiPAP a patient ventilator interface (known in the business as the face mask) is secured snugly to the patients face (usually with the aid of elastic straps).
Fractional concentration of inspired oxygen (FiO2) is titrated via a flow valve to meet patient requirements.
When the patient begins to breathe in a transducer in the unit senses the decrease in airflow within the circuit and delivers IPAP supporting the patient’s inspiratory effort and producing a larger tidal breath. As the patient finishes her inspiration the transducer senses the drop in inspiratory flow and allows the patient to exhale with pressure support (PS) to the EPAP level.(IPAP-EPAP=PS)
Most machines permit spontaneous breathing by the patient (assist mode) or degrees of machine cycled ventilation (control mode).
IPAP is usually set at 5-10 cmH2O.
EPAP is commenced at 3-5cmH2O.
Settings are increased in 3-5cmH2O increments if the patient is not improving.
If no improvement is seen after around and hour, other interventions should be considered.
With a multitude of facial contours, it is important that the mask fits tightly with minimal air leakage. In order to ensure patient compliance the patient must be made as comfortable as is possible. Reassurance, explanation and vigilance are mandatory.
- Pressure areas around the mask. Most modern BiPAP machines will compensate for some gas leakage around the mask but even so they must still be applied fairly firmly.
- Dryness of lips and nasal passages.
Consider some lip balm or perhaps a saline spray to moisten the oral mucosa.
- Gastric distension from swallowing air (aerophagia) which may lead to…
- Risk of aspiration.
Watch for signs of nausea and consider and anti-emetic. Always use a clear mask to make sure you are not ventilating your patient with her breakfast.
- Hypoventilation due to air leaks around the mask.
- Corneal irritation from air constantly blowing onto the eyes.
Constantly use your clinical expertise to evaluate the effectiveness of BiPAP therapy.
Watch respiratory rate and effort (paradoxical breathing and accessory usage) as well as level of consciousness and Sa02.
Auscultate the lung fields.
Monitor arterial blood gasses.
If you feel your patient is deteriorating.. get them reviewed by a senior doctor.