3-19-26 Kopp intro to NIV

Mismatch: A condition where there is a delay or obstruction in oxygen crossing the alveolar-capillary membrane.
- Treatment: Administration of additional oxygen can alleviate this issue, as the highway (alveoli) and exit ramp (capillaries) are functioning but congested.
Shunt: Refers to a collapsed airway that prevents the delivery or uptake of oxygen despite increased FiO2 (fraction of inspired oxygen).
- Administration of high concentrations of oxygen will not help if the airways are collapsed, necessitating the use of mechanical devices for intervention.

When assessing a patient with poor PO2 levels, it is critical to determine the underlying cause, which may include:
- Secretions present in the airways.
- Bronchospasm.
- Areas of the lung not participating in gas exchange.

Hypoventilation: Leads to two main physiological effects:
- Increased PCO2 (carbon dioxide concentration) due to inadequate ventilation.
- Decreased O2 levels (hypoxemia).
Conversely, if a patient hyperventilates, their brain perceives low oxygen levels, prompting an increased respiratory rate:
- Results in lowered PCO2 levels.

In cases of pulmonary embolism (blood clot in the vasculature), oxygen levels may be critically low:
- Patients will attempt to breathe more but will be unable to transfer oxygen from the alveoli to the bloodstream due to a lack of blood flow.

Venous Admixture: It is a natural occurrence where venous blood mixes with arterial blood, resulting in discrepancies between the partial pressure of oxygen in arterial (PaO2) and alveolar blood (PAO2).
- There are anatomical shunts present, such as tiny veins draining directly into arterial circulation without oxygenation.
- The V/Q (ventilation/perfusion) mismatch, where areas of the lung are ventilated but not perfused, leads to symptoms such as:
- Dyspnea (difficulty breathing).
- Tachycardia (rapid heart rate).
- Tachypnea (rapid breathing).
- Accessory Muscles of Respirations: Use of neck and back muscles, e.g., scalene and sternocleidomastoid, indicates respiratory distress.

NIV: Non-invasive ventilation refers to providing positive pressure ventilation without the use of an endotracheal tube.
- Terminology: Can also be referred to as NIPPV (non-invasive positive pressure ventilation).
- Devices: Will not typically see the term BiPAP on examinations; focus should be on the correct understanding of NIV principles.

CPAP (Continuous Positive Airway Pressure):
- Delivered at a constant pressure.
- Commonly used for conditions like sleep apnea and when addressing upper airway problems.
- Effective primarily for patients who are able to breathe adequately despite having a shunt or collapsed alveoli.
BiPAP (Bilevel Positive Airway Pressure):
- A more modern approach providing two levels of pressure: Inspiratory (IPAP) and Expiratory (EPAP).
- Benefits include improved patient comfort and functionality, allowing for enhanced ventilation support.
- Easy adjustment of inspiratory and expiratory pressures:
- Starting pressure generally suggested:
  - IPAP: 10-12 cm H2O.
  - EPAP: 6 cm H2O.

If the patient has a significant ventilation problem (e.g., low tidal volumes):
- Adjust IPAP upward to improve tidal volume and ventilation.
If oxygen saturation starts to decline despite an adequate tidal volume:
- Increase EPAP to maintain oxygenation.
The concepts of fresh pressure support relate to the increase in pressure given to assist patient breathing in BiPAP scenarios.

Ventilators can be powered by gas or electricity.
Manual-Powered Ventilator: Bird Mark 7 is an example that operates without electricity and is primarily designed for lung expansion.
Each ventilator requires:
- An inspiratory cycle.
- An expiratory cycle.

The standard hospital outlet typically operates at 50 psi.
Ventilation techniques reduce this to safe levels using flow meters.
Ventilators can feature manifold systems to mix gases and achieve desired FiO2 levels for patients.

Peak Inspiratory Pressure (PIP): The maximum pressure recorded during a ventilatory breath delivery.
- Static Pressure: Measured at the end of inspiration with no airflow, important for assessing lung compliance (stiffness of lungs due to conditions like ARDS).

Static Compliance: Measurement at the end of inspiration when flow ceases; reflects the lung's ability to inflate:
- High static pressure indicates compliance issues (stiff lungs).
- Low static pressure may indicate increased airway resistance (bronchospasm, secretions).
Resistance: The obstruction in the airways that affects airflow, leading to increased pressures in the ventilator.

Waveforms will provide real-time insights into:
- Pressure.
- Flow rate (volume over time).
- Minute ventilation formula:
  $ext{Minute Ventilation} = ext{Tidal Volume} imes ext{Respiratory Rate}$
An alarming low minute ventilation reading (e.g., 1.6 L/min) indicates a lifesaving necessity for intervention.

Clear understanding of settings like tidal volume, PIP, and minute ventilation is necessary for effective patient management.
- Tidal Volume: Desired volume delivered per breath; normally around 500-600 cc.
- Keep in mind states of compliance and resistance during patient evaluations to ensure accurate responses to ventilatory changes.

Discussion emphasizes the importance of hands-on experience with ventilators, practicing adjustments in real-time, and troubleshooting for optimization of patient care.
The critical nature of maintaining equipment hygiene and function is highlighted, including the placement and securing of tubing to avoid disconnections and prevent contamination.