Tutorial

Tutorial:

باطنية
د. ظاهر جميل

عدد الاوراق (4)

22/1/2013

Oxygen Therapy and Airway Management, Ventilator therapy

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 Hfners 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)

Clinical Conditions with Increased Risk of Hypoxia
Myocardial infarction
Acute pulmonary disorders
Sepsis
Drug overdose
Liver failure
Head trauma
CHF


Indications for Oxygen Therapy
Tachypnea
Cyanosis
Restlessness
Disorientation
Cardiac arrhythmias
Slow bounding pulse
Tachycardia
Hypertension

Oxygen Therapy
Generally speaking, a patient who is breathing less than 12 and more than 24 times a minute needs oxygen of some kind

Analysis Arterial Blood Gas results

Analysis Arterial Blood Gas results:
Pyramid points:
In acidosis, the PH is down.
In alkalosis, the PH is high.
The respiratory function indicator is the PCO2.
The metabolic function indicator is the HCO3.
Normal blood gas value:
PH: 7.35-7.45
PCO2: 35-45 mmHg
HCO3: 22-27meq/liter
PO2 : 80-100
If it does not reflect an opposite response to the PH; then move on to pyramid step 3.
Pyramid step 3:-
look at the HCO3.
Does the HCO3 reflect a corresponding response with the PH; if it does, then the condition is a metabolic imbalance.
Pyramid step 4:-
Remember, compensation has occurred if the PH is in a normal range of 7.35-7.45.
If the PH is not within normal range, look at the respiratory or metabolic function indicators.


Respiratory Imbalances :
If the condition is a respiratory imbalance look at the HCO3 to determine the state of compensation.
If the HCO3 is normal, then the condition is uncompensated.
If the HCO3 is abnormal, then the condition is partial compensation.

Metabolic Imbalance :

If the condition is metabolic imbalance, look at the PCO2 to determine the state of compensation.
If the PCO2 is normal, then the condition is uncompensated.
If the PCO2 is abnormal, then the is partial compensation.

Methods of Oxygen Delivery

Most common methods of oxygen delivery include
Nasal Cannula
Venturi Mask
100% Non-Rebreather Mask
Mechanical Ventilation

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%)
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%


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

Oxygen Delivery Methods100% Non-Rebreather
Delivery percentages
6 l/min = 55 60 %
8 l/min = 60 80 %
10 l/min = 80 90 %
>12 l/min = 90 + %
Benefit: Has a one way expiratory valve that prevents re-breathing expired gases
Concern
May lead to O2 toxicity


100% Non-Rebreather Mask
 SHAPE \* MERGEFORMAT 


Partial Rebreather Mask

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

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.
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.
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.
Oxygen Therapy Summary Oxygen therapy can be life saving therapy. Treat like any other drug. Be familiar with the principles of oxygen delivery and different device


Oxygen Delivery Methods
Mechanical 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)

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

Respiratory arrest from disconnection
Respiratory infection (VAP)
Acid-base imbalances
Oxygen toxicity
Pneumothorax
GI bleeding
Barotrauma
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
ABGs 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

Concentrators that Transfill











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Hypovolemic shock

Blunt chest trauma
Acute neuromuscular disease
Acute abdomen (splinting)
Acute pancreatitis
Spinal cord injury

Dyspnea

Coma
Labored breathing (use of accessory muscles, nasal flaring)

Lethargy

Tremors/seizure activity

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