Journey ABG and Mechanical Ventilation

Mixed acidosis / alkalosis

Acid + acid = mixed acidosis
Alk + alk = mixed alkalosis

Basic A & P of the pulmonary system: Alveoli, terminal bronchioles

Alveoli is where the cellular level of gas exchange occurs

Terminal bronchioles are last bronchi before they hit alveoli.

Physiology of breathing

Gases travel from an area of higher pressure to lower pressure

Inspiration: Diaphragm flattens out (Active)
Expiration: Relaxes (Passive)

Diffusion

High concentration to low concentration, the greater the difference, the greater the movement

What do we need to breathe?

Lungs, air, airway, muscles, brain (phrenic nerve) and adequate blood supply.

C3 - C5

Keep the diaphragm alive

C1 - C5 Paralysis

C1 - C3: Ventilator dependent
C4 - C5: Depends
Below C5: Breathe on their own

Gas Exchange in 4 steps

Ventilation: Movement in and out of the lungs
Diffusion: O2 and CO2 occur at the pulmonary capillary membrane (gas exchange)
Transport: Oxygenated blood is perfused or transported to the tissues
Diffusion: At the cells (cellular level) (gas exchange)

SaO2 and PaO2

SaO2 - Arterial Oxygen Saturation: Bound to Hgb, 95-100% (97%)
PaO2 - Partial Pressure of Oxygen: Dissolved- 80-100 mmHg (3%)

O2 Dissociation Curve

A graph that illustrates the relationship between the partial pressure of oxygen (PaO2) and the saturation of hemoglobin (SaO2), indicating how readily hemoglobin binds to and releases oxygen under varying conditions.

If O2 sat drops below 92%: watch it! That’s when it starts to rapidly decline.

Left shift: Decreased temp, decreased 2-3 DPG (by product of glucose metabolism), Decreased [H+], CO

Right shift: Reduced affinity, Increased temp, Increased 2-3 DPG, Increased [H+]

Vital capacity

The maximum amount of air a person can exhale after taking the deepest possible breath in

Tidal Volume

Amount of air inhaled and exhaled during a normal, unforced breath

IRV

Inspiratory reserve volume - Extra air breathed in beyond normal, resting breath

ERV

Expiratory reserve volume: volume of air you can forcefully exhale after a normal breath, leaving only RV (residual volume) remaining in lungs.

MV = TV x RR

Minute ventilation = tidal volume x respiratory rate

Measured in Liters/min

If patient is on 2L NC, what is the FiO2?

28%, goes up by 4% for each liter

Vent modes

PRVC (Pressure Regulated Volume Control [Full Control]), PS (Pressure support [Full Control]), PC (Pressure control).

Alarms: Flashing red

Check patient, call RRT stat!
Means: Apnea, low minute ventilation

Alarms: Flashing yellow

High pressure alarm, high minute ventilation

Low Volume Alarm

Patient does not receive preset tidal volume

Causes: Line disconnection, Leak in cuff, Tube out of position

Fix the cause

High pressure alarm

High pressure alarm sound if pre-set pressure limit is exceeded

Causes: secretions and mucus plugs, kinks in ETT tube or tubing, Talking, Dyssynchrony, and Barotrauma

Responsibilities of nurse r/t vent

Prevent aspirations, assessing et tube at lip, monitor O2, Maintain integrity of tube, suctioning

SAT safety screen exclusion criteria

I:E ratio greater than 1:1
Continuous sedation for seizure management
On neuromuscular blocking agent/chemically paralyzed
Targeted temperature management w/ active shivering
ICP sustained greater than or equal to 20 or if labile
Active or unresolved myocardial ischemia
Comfort care
RASS > (+)2/escalating doses
CHECK w/ provider if FiO2 greater than or equal to 70% or critical airwayS

SAT failure

RASS greater than 2 for 5 min
New arrhythmia
Resp. Rate greater than 35 for 5 mins
O2 Sat less than 88% for 5 min
Resp. Distress (2 change from baseline)
- Tachycardia
- Bradycardia
- Use of accessory muscule
- abnormal paradox
- Diaphoresis
- Marked dyspnea

IMPORTANT Consideration: Consider dexmedetomidine (Precedex) infusion

SBT SAFETY SCREEN Exclusion criteria

RASS less than (-) 2
SpO2 less than 88%
PEEP Greater than 8 cmH2O
FiO2 greater than 50%
Active or unresolved Myocardial Ischemia
Known lack of inspiratory effort
Trach Collar
Provider order
VE greater than 15 LPM
Failed SAT

SBT Failure

Resp. Rate greater than 35 greater than 5 min
Resp. Rate less than 8
Increase HR of 20% > 10 min
MAP less than 60 mmHg or SBP greater than 180 mmHg greater than 10 min
SpO2 less than 88% greater than 5 min
ETCO2 change greater than 20 mmHg greater than 5 min
HR less than 60 greater than 10 min
VE greater than 15 lpm greater than 5 min
RSBI greater than 105
Provider order to end SBT

End-tidal CO2 monitoring

Confirming ET tube placement, monitoring sedation, and assessing respiratory status

Measures partial pressure of CO2 at the end of an exhaled breath (35 - 45 mmHg)

SpO2

Measures percent of oxygen in blood (95 - 100 %)