OXYGEN THERAPY AND AIRWAY MANAGEMENT, VENTILATOR THERAPY
* Dr.Dhaher JS Al-habbo FRCP London UK Assistant Professor in Medicine DEPARTMENT OF MEDICINE*
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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%) *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 Hьfner’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) 10OXYGEN DISSOCIATION CURVE (ODC)
*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 **
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.*
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 *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)
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%*
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/MinO2 Conc.: 40 – 60 %Use: moderate FiO2, mouth breathers *VENTURI MASK
Mostly used in the hospital setting for COPD patients Concerns Tight seal is a must Interferes with eating/drinking Condensation collection* 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
* Red 40% 10/L/MBlue 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 mask6-10L /minFiO2 0.35-0.60Has no valvesInspiration –O2 flows to mask and patientExpiration – 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.*
OXYGEN DELIVERY METHODSMECHANICAL VENTILATION
Allows administration of 100% oxygenControls breathing pattern for patients who are unable to maintain adequate ventilation Is a temporary support that “buys time” for correcting the primary pathologic processINDICATIONS FOR MECHANICAL VENTILATION
Mechanical Failure Ventilatory Failure Oxygenation Failure General Anesthesia Post-Cardiac ArrestMECHANICAL 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*
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*
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 tubingRespiratory 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/kgTidal Volume > 5 ml/kgResting minute volume > 10 L per minuteABG’s adequate on < 40% FiO2Stable vital signsIntact airway protective reflexes (strong cough)Absence of dyspnea, neuromuscular fatigue, pain, diaphoresis, restlessness, use of accessory musclesARTERIAL 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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