Mechanical Ventilation

NIV: What’s the big deal?

EMKF

Terminology:

In general,
Type 1 RF requires CPAP type of NIV.

Type 2 RF requires BPAP type of NIV.

PEEP=EPAP=CPAP i.e. they all mean the same!

So you can say in Type 1 RF (Hypoxic failure), the pressure we provide is PEEP or just EPAP or CPAP. 

For Type 2 RF (Hypercapnic), we provide IPAP as well as EPAP. IPAP is greater than EPAP, PS (Pressure Support is the difference between IPAP and EPAP). For instance if IPAP = 15 and EPAP is 10 then PS = 15-10 i.e. 5cm H2O.

Non-Invasive Ventilation

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Noninvasive ventilation decreased endotracheal intubation rates and hospital mortality in acute hypoxemia non-hypercapnic respiratory failure excluding chronic obstructive pulmonary disease exacerbation and cardiogenic pulmonary edema patients. There is no sufficient scientific evidence to recommend bi-level positive airway pressure or helmet due to the limited number of trials available. Large rigorous randomized trials are needed to answer these questions definitely.

 

Heroic Medical Measures in the Crashing Asthmatic

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  1. Pre-oxygenate your patient with high flow nasal cannula at 20 – 30 LPM
  2. Next consider using IM Epinephrine 0.3 – 0.5mg of 1:1000. Severe asthmatics will have a hard time getting inhaled beta agonists into the small airways, but parenteral epinephrine will get into the circulation and get to where it needs to provide support.
  3. Non-Invasive Positive Pressure Ventilation (NIPPV)
  4. Corticosteroids
  5. 2g IV Magnesium and repeat it up to 2 more times over an hour
  6. Give IVF at a dose of 30cc/kg because patients with acute asthma exacerbations because patients will have insensible losses.

…and many more including intubating and ventilating the Crashing Asthmatic Patient…great read.

 

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Mechanical Ventilation- Terminology

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Volume controlled ventilation

We can put a certain volume of air into the patient with each breath in mechanical ventilation.

Pressure controlled ventilation

We can put air into the patient until the pressure reaches a certain value.

Rate

We can decide how often we give the patient a breath each minute.

Flow rate

For example, we can give a certain volume of gas , but the flow rate will determine whether we give that volume slowly or quickly over that breath.

FiO2

In other words, the oxygen concentration we give to the patient, from 21% (room air) to 100%.

What triggers the breath?

Do we have the patient decide when they want to breathe, or do we have the ventilator decide when to initiate a breath? Or indeed a combination of the two? Is it ventilator controlled or patient controlled?

 

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