Oxygen Therapy and Airway Management Ventilator therapy

Oxygen Therapy and Airway Management, Ventilator therapy

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Dr.Dhaher JS Al-habbo
FRCP London UK
Assistant Professor in Medicine
DEPARTMENT OF MEDICINE

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Oxygen was discovered independently by the Swedish apothecary Karl W.Scheele, in 1772, and by the English amateur chemist Joseph Priestly,in August 1774.
Priestley first liberated oxygen by intensely heating 'mercurius calcinatus' (mercuric oxide) placed over liquid mercury in a closed vessel. He called this new gas "dephlogisticated air, "oxygenated."

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Basic Concepts of Oxygen

Oxygen Cascade:
Oxygen Cascade:


Inspired = 150 mmHg at Sea Level ↓ Alveolar PO2= 103
↓ Arterial=100
↓ Capillary= 51
↓ Mitochondrial= 1-10 ↓ Mitochondrial= 1-10

(FiO2 expressed as 0.21-1.0 or 21- 100%)

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Oxygen content of blood

The theoretical maximum oxygen carrying capacity is 1.39 ml O2/g Hb, but direct measurement gives a capacity of 1.34 ml O2/g Hb.1.34 is also known as Hüfner’s constant.
The oxygen content of blood is the volume of oxygen carried in each 100 ml blood.It is calculated by: (O2 carried by Hb) + (O2 in solution) = (1.34 x Hb x SpO2 x 0.01) + (0.023 x PaO2)
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Oxygen dissociation curve (ODC)

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Tachypnea

Cyanosis
Restlessness
Disorientation
Cardiac arrhythmias
Slow bounding pulse
Tachycardia
Hypertension
Dyspnea
Coma
Labored breathing (use of accessory muscles, nasal flaring)
Lethargy
Tremors/seizure activity
Indications for Oxygen Therapy


Oxygen Therapy
“Generally speaking”, a patient who is breathing less than 12 and more than 24 /minute needs oxygen of some kind
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A. THREE CLINICAL GOALS OF O2 THERAPY

OXYGEN THERAPY

1. TREAT HYPOXEMIA

2. DECREASE WORK OF BREATHING (WOB)

3. DECREASE MYOCARDIAL WORK

B. FACTORS THAT DETERMINE WHICH SYSTEM TO USE

1. PATIENT COMFORT

2. THE LEVEL OF FIO2 THAT IS NEEDED


3. THE REQUIREMENT THAT THE FIO2 BE CONTROLLED
BE CONTROLLED WITHIN A CERTAIN RANGE.

4. THE LEVEL OF HUMIDIFICATION AND OR NEBULIZATION

OXYGEN THERAPY

Oxygen therapy To ensure safe and effective treatment

Oxygen is required for the functioning and survival of all body tissues and deprivation for more than a few minutes is fatal.
In immediately life threatening situations oxygen should be administered.
Hypoxaemia. Acute hypotension.
Breathing inadequacy. Trauma. Acute illness. CO poisoning. Severe anaemia. During the peri-operative period.

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Oxygen therapy To ensure safe and effective treatment

Oxygen is a prescription drug.
Prescriptions should include – Flow rate.
Delivery system.
Duration.
Instructions for monitoring.
Monitoring resps oxygen sats not definitive tool need to be looking at other things acccessory muscles etc
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Oxygen therapy
Oxygen therapy Humidification Is recommended if more than 4 litres/min is delivered.
Helps prevent drying of mucous membranes.
Helps prevent the formation of tenacious sputum.
Oxygen concentrations will be affected with all delivery systems if not fitted correctly or tubing becomes kinked and ports obstructed.

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Methods of Oxygen Delivery

Most common methods of oxygen delivery include
Nasal Cannula
Venturi Mask
100% Non-Rebreather Mask
Mechanical Ventilation
Hyperbaric Oxygen Therapy(HBOT)

Nasal Cannula

Comfortable, convenient, mouth breathing will not effect % of O2 delivered
Liters/min = %
2 l/m = 24-28%
3 l/m = 28-30%
4 l/m = 32-36%
5 l/m = 36-40%
6 l/m = 40-44%
Cannot administer > 6 liters/minute (44%)


Oxygen Delivery Methods

Nasal Cannula

Provides limited oxygen concentration
Used when patients cannot tolerate mask
Prongs and other uses
Concentration of 24 to 44%
Flow rate set between 1 to 6 liters
For every liter per minute of flow delivered, the oxygen concentration the patient inhales increases by 4%
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Oxygen therapy

Simple facemask Easy to use.
Allows administration of variable concentration dependant on flow of fresh gas up to 40%.
Nasal cannulae Easy to use. Well tolerated. Comfortable for long periods. Patient can eat and talk easily.
Possible to deliver oxygen concentrations of 24-40% at flow rates of 1-6 litres/min.
Flow rates in excess of 4 litres/min might cause discomfort and drying of mucous membranes and are best avoided.
Flow Rate: 10 L/Min
O2 Conc.: 40 – 60 %
Use: moderate FiO2, mouth breathers


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Venturi Mask

Mostly used in the hospital setting for COPD patients
Concerns
• Tight seal is a must
• Interferes with eating/drinking
• Condensation collection
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FiO2 Delivery
Blue 24% Yellow 28%
White 31% Green 35%
Pink 40%
• Provides precise concentrations of oxygen
• Entrainment valve to adjust oxygen delivery

Venturi Mask

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Red 40% 10/L/M

Blue 24% 2/L/M Yellow 35% 8/L/M
White28% 4/L/M Green 60% 15/L/M
Orange 31% 6/L/M

Partial rebreathing mask

6-10L /min
FiO2 0.35-0.60
Has no valves
Inspiration –O2 flows to mask and patient
Expiration – source O2 and expired gas enters the bag

Non rebreathing mask

6-10L/min
FiO2 0.55-0.70
Has 2 one way valves
Insp- insp valve opens provides O2 to patient
Exp- exp valve opens divert exp gas to atmosphere
Large air leaks

Oxygen therapy

Non-rebreathing mask Allows the delivery of high concentrations of oxygen (85% at 15 litres/min).
Has a reservoir bag to entrain oxygen. One way valves prevent room and expired air from diluting the oxygen concentration. A tight seal is essential.
Reservoir bag must be seen to expand freely.
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Oxygen Delivery MethodsMechanical Ventilation

Allows administration of 100% oxygen

Controls breathing pattern for patients who are unable to maintain adequate ventilation

Is a temporary support that “buys time” for correcting the primary pathologic process


Indications for Mechanical Ventilation
Mechanical Failure

Ventilatory Failure

Oxygenation Failure

General Anesthesia

Post-Cardiac Arrest

Mechanical Ventilation

Two categories of ventilators

Negative pressure ventilators

Iron lung
Cuirass ventilator
Positive pressure ventilators
Two categories
Volume-cycled (volume-preset)
Pressure-cycled (pressure-preset)



Iron Lung

Mechanical Ventilation PEEP

Description
Maintains a preset positive airway pressure at the end of expiration
Increases PaO2 so that FiO2 can be decreased
Increases DO2 (amt of delivered O2 to tissue)
Maximizes pulmonary compliance
Minimized pulmonary shunting
Indications
PaO2 < 60 on FiO2 > 60% by recruiting dysfunctional alveoli
Increases intrapulmonary pressure after cardiac surgery to decrease intrathoracic bleeding (research does not support this idea)

Mechanical Ventilation PEEP

Advantages
Improves PaO2 and SaO2 while allowing FiO2 to be decreased
Decreases the work of breathing
Keeps airways from closing at end expiration (esp. in pts with surfactant deficiency)
Disadvantages
Increased functional residual capacity (increases risk for barotrauma)
Can cause increased dead space and increased ICP
In pts with increased ICP, must assure CO2 elimination
Contraindicated: hypovolemia, drug induced low cardiac output, unilateral lung disease, COPD





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Mechanical Ventilation CPAP

Description
Constant positive pressure is applied throughout the respiratory cycle to keep alveoli open

Indications

To wean without having to remove the ventilator and having to connect to additional equipment




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Mechanical Ventilation CPAP
Advantages
Takes advantage of the ventilator alarm systems providing psychological security of the ventilator being there

Disadvantages

Patient may sense resistance as he breathes through the ventilator tubing

Respiratory arrest from disconnection

Respiratory infection (VAP)
Acid-base imbalances
Oxygen toxicity

Pneumothorax

GI bleeding
Barotrauma
Decreased cardiac output
Mechanical Ventilation Complications

Ventilator Weaning

Vital Capacity at least 10 – 15 ml/kg
Tidal Volume > 5 ml/kg
Resting minute volume > 10 L per minute
ABG’s adequate on < 40% FiO2
Stable vital signs
Intact airway protective reflexes (strong cough)
Absence of dyspnea, neuromuscular fatigue, pain, diaphoresis, restlessness, use of accessory muscles


Arterial blood gas Analysis
Which Artery to Choose?
The radial artery is superficial, has collaterals and is easily compressed. It should almost always be the first choice.
Other arteries (femoral, dorsalis pedis, brachial) can be used in emergencies.











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