Non-Invasive Ventilation - CPAP-BiPAP

Introduction to Non-Invasive Ventilation

• Presenter: San Fernando, Emergency Physician in South West Sydney.

• Focus: Non-Invasive Ventilation (NIV) in emergency medicine, specifically CPAP and BiPAP.

Reasons for Using Non-Invasive Ventilation

• Ventilatory Failure:

  • Patients experience respiratory difficulty and become fatigued or weak, unable to handle respiratory challenges.

  • The forces opposing ventilation surpass the respiratory effort of the patient.

• Failure of Gas Exchange:

  • Occurs when alveoli are compromised due to substances like pus, phlegm, fluid, or blood.

  • Gas exchange between the alveoli and bloodstream is disrupted.

  • Often, both ventilatory failure and gas exchange failure are present.

Mechanism of Action of Non-Invasive Ventilation

• NIV can help mitigate further pulmonary complications by:

  • Keeping airways open and preventing collapse, particularly during expiration.

  • Enhancing alveolar ventilation and reducing the work of breathing.

  • Offering beneficial effects on cardiac function.

Application of CPAP and BiPAP

• CPAP (Continuous Positive Airway Pressure):

  • Best suited for treating hypoxia, which is low oxygen supply.

  • Example: Used in acute pulmonary edema, especially cardiogenic types.

  • Mechanism: Improves movement of alveolar fluid into interstitium, increases surfactant production, and recruits collapsed alveoli.

  • Recommended in isolation without hypercapnia.

• BiPAP (Bilevel Positive Airway Pressure):

  • Designed for hypercapnia (high CO2 levels).

  • Provides both inspiratory and expiratory pressures, helping to reduce the work of breathing.

  • Comprises inspiratory pressure and an expiratory pressure, where the difference defines pressure support.

  • Particularly effective for COPD exacerbations, addressing both hypoxia and hypercapnia simultaneously.

Case Study Example

• Hypothetical Patient: 68-year-old man with acute pulmonary edema.

  • Symptoms: Shortness of breath, high respiratory rate (40), sweating, oxygen saturation at 90% despite supplemental oxygen.

  • Initial treatment: Established on CPAP (5-10 cm H2O, FiO2 at 40%).

• Initial Blood Gas Results:

  • PaO2: 55, PaCO2: 72, indicating both hypoxia and hypercapnia.

  • Transitioned to BiPAP (initial IPAP 12 cm H2O, EPAP 6 cm H2O).

  • Adjusted FiO2 to 22%.

  • Improvement in O2 saturation and reduction in work of breathing observed.

Adjustments to Treatment

• One hour later, patient appears to tire despite improved oxygenation.

  • Repeat arterial blood gas indicates an elevated CO2 (75).

  • Correct response: Increase pressure support by adjusting IPAP and EPAP.

  • Increase IPAP to 15 cm H2O and decrease EPAP to 5 cm H2O, achieving an increased pressure support of 10 cm H2O.

Conclusion

• Summary of treatment approach:

  • CPAP is used for hypoxia.

  • BiPAP is utilized for hypercapnia, leveraging pressure support to minimize the work of breathing.

  • Emphasis on continuous assessment and adjustment of ventilation settings.

Applying CPAP Mask

• Understanding the Device

  • Patients often bring their own CPAP machines.

  • Patients are typically knowledgeable about their devices and masks.

  • Consult the patient for best practices in fitting the mask.

Importance of Good Seal

• Achieving a proper seal is crucial for the effectiveness of the CPAP therapy.

• Modern masks feature soft silicone or rubber edges for better sealing capabilities.

Mask Application Steps

1. Positioning the Mask

   • Place the mask gently over the patient's nose and mouth.

   • Ensure a smooth fit, adjusting as necessary.

   • Tuck the back of the mask under the patient’s head securely.

2. Securing the Straps

   • Reapply the magnetic clip for secure attachment.

   • Adjust the lower strap to be snug, but not overly tight.

   • Ensure comfort by adjusting the rear straps over the patient’s head.

   • Finetune the top straps for a snug fit.

3. Patient Feedback

   • Ask the patient if the mask feels smooth, comfortable, and well-fitted.

   • Communication is key, especially if the patient is accustomed to using a CPAP mask.

Setting Up the CPAP Machine

• Familiarize with Machine Features

  • CPAP machines vary in designs and settings.

  • Two essential settings:

    • Mask Fit:

      • A button that checks if the mask has a proper seal.

      • Note: A mannequin will not provide accurate fitting feedback.

    • Comfort Settings:

      • Choose appropriate mask type:

        • Full face

        • Nasal

        • Pillow types

      • Select settings based on the mask type being used.

• Adjusting Machine Settings

  • Most settings will be preset by a senior clinician or doctor.

  • Avoid altering settings unless you have knowledge of what you are doing.

  • To start the machine, typically press the top button or use the settings on the side, depending on the machine model.

What are some of the common uses for NIV devices such as CPAP/BiPAP in the home and hospital setting?

• Autoimmune neuromuscular conditions (Cystic Fibrosis, Motor Neuron Disease (MND) and muscular dystrophy) can affect the lungs and NIV can help expand the lungs and decrease respiratory distress.

• NIV will greatly support respiration rate and oxygenation levels. Patients with Sleep apnoea, obesity hypoventilation syndrome, Bronchiectasis, Chronic Obstructive Pulmonary Disease (COPD), Asthma and Chronic Heart Failure (CHF) can have fluid build up in the lungs and as such NIV can help recruit alveoli and expand the lungs.

• NIV is contraindicated in respiratory arrest, instead the patient needs to be intubated and placed on a ventilator.

• NIV is contraindicated in upper airway obstruction. In case of a foreign object blocking the airway, it needs to be removed. NIV could cause a foreign object lodged in the airway to move into the lungs. In case of narrowing of the airway, the patient may need to be intubated or have a tracheostomy.