PHTY 300 Wk 1 Lectures Arterial Blood Gas Components The test provides information on - Acid base balance - Oxygenation - Hemoglobin levels - Electrolyte blood glucose, lactate, renal function When initially assessing the results What is wrong and which system is responsible Is it an acute or chronic condition How sick is the patient Is the patient responding to treatment Acid base balance Homeostasis ph H 2 O + CO 2 <-> H 2 CO 3 <-> H + - + HCO 3 System involved Step 1 acid base - Ignore the O 2 Acidosis Respiratory - PaCO 2 > 45 Decreased gas movement overall - Low tidal volume without increased RR - Low RR without increased tidal volume Signs and symtpoms of respiratory acidosis - Cerebral vasodilation and increased ICP - Drowsiness / confusion - Headache - Unsteady / falls Metabolic - HCO 3 < 22 Acid gain or bicarbonate loss - Diabetic ketoacidosis - Methanol poisoning - Lactic acidosis (decreased oxygen to the tissues) - Starvation - Renal failure - Severe diarrhea
Signs and symptoms of metabolic acidosis - Cardiac arrhythmias and decreased contractility - Hyperventilation - Confusion and drowsiness - Decreased renal blood flow Alkalosis Respiratory - PaCO 2 < 35 Hyperventilation (blowing off too much CO 2 ) - Anxiety - Pain - Acute (severe) hypoxaemia - Sepsis Signs and symptoms of respiratory alkalosis - Tingling of the lips and fingers - Cerebral vasoconstriction dizziness and fainting - Arrhythmias Metabolic - HCO 3 > 28 Acid loss or bicarbonate gain - Gastrointestinal vomiting, nasogastric suction - Renal metabolic sydromes, drugs, not renal failure Signs and symptoms - Muscle cramps, weakness - Decreased minute ventilation (decreased RR and tidal volume) - Arrhythmias Discuss the difference between controlled (fixed) and uncontrolled (variable) O2 therapy Methods to improve PaO 2 Medical - Increased diffusion - Oxygen therapy o Increased fraction of inspired oxygen o Increased P atmospheric oxygen - Increased surface area (FRC) o PEEP o CPAP Outline the uses of oxygen
O 2 therapy used in acute and chronic hypoxemic respiratory failure PaO 2 < 60 mmhg is what is considered respiratory failure Also used for some cardiac conditions Medically prescribed drug Titrated to meet a target SpO 2 or PaO 2 (which will depend on the patients age, clinical condition or any risk factors for receiving supplemental oxygen) Discuss the use of high flow O2 therapy Spot test Physios Oxygen transport Venturi principles Dangers of oxygen therapy Domiciliary oxygen List the dangers and complications of O2 therapy CPOD patients with hypoxemia drive Toxicity - Adults: - Acute tracheobronchitis - Diffuse alveolar damage - Reduced ciliar activity - Neonates: - Bronchopulmonary dysplasia - Retrolental dysplasia Reduced matching of gas and blood movement via hyperoxie induced vasodilation Absorption atelectasis Fire hazard Complications: Related to both the F 1 O 2 and the length of the exposure The higher the F 1 O 2 the shorter the time and vice versa Clinically for adults keep the F 1 O 2 < 0.6 Oxygen therapy It is important to change the F 1 O 2 by mixing the oxygen with room air Cylinder and wall gas Cold and dry
Oxygen concentrator Uncontrolled variable performance - Nasal catheter / prongs / spectacles - Non venturi masks Controlled fixed performance - Venturi devices - Tents / head box / incubator - Mechanical ventilator Nasal prongs - Commonly used - Comfortable and non-invasive oxygen delivery system - Open system, oxygen is diluted by room aire and breathed in through the patients nose and mouth (variable) - Low flow device - Advantages: - Patients can eat and drink and communicate easily - Suitable for long term use - Natural humidification can occur via the nose - Disadvantages: - Only for delivery low flows ie less than 5 L/min - Unable to reliably record an accurate F 1 O 2 but often estimated as o 1L / min F 1 O 2-0.24 o 2L / min F 1 O 2-0.28 o 3L / min F 1 O 2-0.32 o 4L / min F 1 O 2-0.36 Simple face masks - These mix air and oxygen - For short term use ie post operative patients - Difficult to estimate the concentration of oxygen received - Must maintain a minimal flow rate of 5 L / min to ensure adequate CO2 removal - Masks act as a reservoir - More suited to mouth breathing - Short term use only Reservoir Masks - These delivery high concetrations of oxygen to spontaneously breathing patients - For short term use - The reservoir bag stores oxygen allowing a patient to receive high
concentrations of oxygen even when breathing rapidly - Small amount of room air entrained - High oxygen flow rates ie 10-15 L / min, F 1 O 2 06-0.9 - Either partial re-breathing valve in mask (PRB) or non re-breather valve (NRB) - Disadvantages very drying to mucosa ideally should change to a humidified system if required long term High flow devices - Air/ oxygen blenders - Nasal high flow o2 mix is delivered via nasal cannula at flow rates of up to 45 L/min - Essential to have humidification