Drugs pdf - د. منوع

Fifth stage

Medicine

Lec-9

د . منوع

1/1/2014

Oxygen Therapy and Airway Management, Ventilator therapy

• 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."

Basic Concepts of Oxygen

Oxygen Cascade:

Inspired = 150 mmHg at Sea Level

↓ Alveolar PO

= 103

↓ Arterial=100

↓ Capillary= 51

↓ Mitochondrial= 1-10 ↓ Mitochondrial= 1-10

(FiO

expressed as 0.21-1.0 or 21- 100%)

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)

Oxygen dissociation curve (ODC)

Indications for Oxygen Therapy

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

Oxygen Therapy

“Generally speaking”, a patient who is breathing less than 12 and more than 24 /minute
needs oxygen of some kind

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 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.

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

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.

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)

Oxygen Delivery Methods

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%)

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%

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

Venturi Mask

FiO2 Delivery

Blue 24% Yellow 28%

White 31% Green 35%

Pink 40%

Provides precise concentrations of oxygen

Entrainment valve to adjust oxygen delivery

Mostly used in the hospital setting for COPD patients

Concerns

Tight seal is a must Interferes with eating/drinking Condensation collection

Partial rebreathing mask

• 6-10L /min

• FiO

0.35-0.60

• Has no valves

• Inspiration –O

flows to mask and patient

• Expiration – source O

and expired gas enters the bag

Non rebreathing mask

• 6-10L/min

• FiO

0.55-0.70

• Has 2 one way valves

• Insp- insp valve opens provides O

to patient

• Exp- exp valve opens divert exp gas to atmosphere

• Large air leaks

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.

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

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)

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

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

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

Mechanical Ventilation Complications

1.  Respiratory arrest from disconnection
2.  Respiratory infection (VAP)
3.  Acid-base imbalances
4.  Oxygen toxicity
5.  Pneumothorax
6.  GI bleeding
7.  Barotrauma
8.  Decreased cardiac output

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.