When do you adjust IPAP and EPAP?
Your question: I have a question about adjusting IPAP and EPAP. How do I know when I need to adjust both?
My answer: Think of it this way:
1. IPAP is the same as Pressure support = increased ventilation = blow off more CO2
2. EPAP is the same as PEEP/CPAP = increased FRC = increased oxygenation
So when you want to blow off CO2 you increase IPAP, and when you want to increase oxygenation you increase EPAP
Normal starting settings are IPAP 10 EPAP 4
Indications for CPAP.
Hypoxemia that is refractory to high concentrations of oxygen by other means.
Obstructive Sleep Apnea to prevent the upper airway from collapsing
Adjusting CPAP settings. CPAP is increased or decreased to maintain a desired SpO2, which is usually greater than 90% SpO2 and 60 PaO2.
BiPAP: This is an acronym for Bi-level (or Biphasic) Positive Airway Pressure. It provides a combination of both IPAP and EPAP.
IPAP. This is Inspiratory Positive Airway Pressure. It is a pressure during inspiration that assists a patient obtain an adequate tidal volume. Because it provides assistance with inhalation, it therefore decreases the work of breathing required to get air in. Because it assures adequate ventilation, it is often prescribed to blow off carbon dioxide (CO2).
EPAP. This is Expiratory Positive Airway Pressure. It is the same thing as CPAP. EPAP is simply used here so you know your talking about CPAP on a BiPAP machine. EPAP is used to improve oxygenation.
Indications for BiPAP.
Respiratory Failure due to accessory muscles fatigue. It assures adequate ventilation to blow off CO2 and improve oxygenation.
COPD to decrease airway resistance, thereby decreasing work of breathing required to take in an adequate tidal volume. By increasing ventilations, it helps to blow off CO2. It also keeps airways patent to improve oxygenation.
Pulmonary Edema to help decrease cardiac output which decreases venous return to the right ventricle to reduce blood return to the heart. It also keeps airways patent to help improve oxygenation. It also helps keep alveoli patent to improve oxygenation (prevents alveolar collapse). By keeping alveoli patent, and redistributing alveolar fluid, it helps to reduce pulmonary compliance and reduce work of breathing.
Atelectasis to help keep airways patent to improve oxygenation
Pulmonary Embolis to improve oxygenation
Pneumonia to assure adequate ventilations and oxygenation
Adjusting BiPAP settings. As a rule of thumb, the following rules are true.
IPAP. Increase to blow off CO2. It should not be higher than 20 to prevent pressure from blocking the esophagus. By providing adequate tidal volumes it may also help improve oxygenation.
EPAP. Increase to improve oxygenation.
PS. Pressure Support. This is the gap between IPAP and EPAP. The greater the PS is the more CO2 will be blown off.
Patient Leak. It is important to have a small leak to prevent skin breakdown. Most modern machines will compensate for a small leak.
Alarms. Adjusted as appropriate for each patient.
Contraindications for BiPAP include.
Inability of patient to protect own airway (decreased level of consciousness). This includes the inability of the patient to pull off the mask if it becomes full of fluid, such as vomit or spit.
Increased secretions (i.e. pulmonary edema, increased sputum production)
Any patient at risk of vomiting (post stomach surgery, drug overdose). In this case you may be able to use BiPAP if an NG is inserted. Most machines will compensate just fine for the leak around the tube.
Bullous lung disease (emphysema) because the high pressure may cause a pneumothorax
Pneumothorax may be complication due to increased pressure;;may blow out rest of good lung
Hypotension; High pressures decrease cardiac output
Non-compliant patient. Surely you cannot force a patient to use this equipment.