Respiratory Flashcards
Hypoxia
Decrease in level of oxygen supply to tissues
Hypoxemia
Inadequate oxygenation of arterial blood
PaO2 less than 80mmHg (at sea level) or SaO2 or SPO2 of less than 95%
DO2
Delivery of oxygen to tissues
DO2 = CO x CaO2
General reasons for hypoxemia
hypoventilation, ventilation perfusion mismatch, diffusion impairment, decreased oxygen content of inspired air, and intrapulmonary shunt
How is arterial oxygen delivered to tissues?
Bound to hemoglobin Small fraction (0.003 x PaO2) is delivered unbound or dissolved in plasma
Nasal or transtracheal oxygen flow rate
50-150mL/kg/min
Five phases of oxygen toxicity
Initiation
-Free radicals cause damage to pulmonary epithelial cells and antioxidants become depleted
-24-72 hours of exposure to 100% oxygen
Inflammation
-Destruction of pulmonary epithelial lining causes airway inflammation and recruitment of activated inflammatory cells
-Release of inflammatory mediators causing increased permeability and development of pulmonary edema
Destruction
-Local destruction most commonly associated with patient mortality
Proliferation
-Type II pneumocytes and monocytes increase
Fibrosis
-Collagen deposition and interstitial fibrosis results in permanent damage to lungs
Retrolental fibroplasia
Retinal lesion seen in neonates after oxygen toxicosis
PaO2 <60mmHg or SaO2 or SpO2 <90%
Severe, potentially life-threating hypoxemia
PaO2
- Partial pressure of oxygen dissolved in plasma of arterial blood
- Measure of ability of lungs to move oxygen from atmosphere to the blood
- Normal PaO2 at sea level between 80-110mmHg
SaO2
Hemoglobin saturation with oxygen
SpO2
Pulse oximeter hemoglobin oxygen saturation
Commonly cited number for concentration of deoxygenated hemoglobin before cyanosis is present
5g/dL
Hypoventilation
elevated PaCO2 (45mmHg or higher) or elevated ETCO2 (5mmHg lower than PaCO2) or central venous PCO2 (5mmHg higher than PaCO2)
When can hypoventilation be eliminated as a cause of hypoxemia?
When the patient is breathing supplemental oxygen
Four causes of venous admixture
Low ventilation perfusion regions
Regions of zero ventilation/perfusion
Diffusion defects
Right to left shunting
Venous admixture
All the ways in which venous blood can get from right side to left side of circulation without being properly oxygenated
The 120 Rule
PaCO2 + PaO2 = 120 if lungs functioning normally
Used at room air at sea level
PaO2/FiO2 ratio
Compensates for variation in A-a gradient due to inspired oxygen
Use only if on supplemental oxygen
Normal = 500mmHg
Anatomic dead space
Upper airway, trachea, lower airway, to level of terminal bronchioles
Alveolar dead space
Inspired gas passing through anatomic dead space and mixing with gas in alveoli but no gas exchange
Physiologic dead space
Combination of anatomic and alveolar dead space - all portions of tidal volume not participating in gas exchange
In healthy lungs the amount of anatomic and physiologic dead space should be
Roughly equal
In diseased lungs with a ventilation perfusion mismatch - the amount of physiologic dead space ?
Increases
Bordetella bronchiseptica
Gram negative bacterium Extracellular Attaches to tracheal cilia Most common bacterial agent in infectious tracheobronchitis Treat with aerosolized gentamicin
How is tracheostomy tube size selected
Measurement of the tracheal lumen on radiograph
When placing a tracheostomy tube, what is a possible complication of inappropriate dissection?
Dissection lateral to trachea will cause injury to left recurrent laryngeal nerve and possibly disruption of the tracheal blood supply
Where is incision made for tracheostomy
Between 3 & 4th or 5th tracheal rings
What are possible complications of tracheal tube suctioning?
Anxiety, respiratory distress, vagal stimulation causing vomiting or retching
What must be done before initiating tracheal tube suctioning?
Airway humidified and preoxygenate for at least 3 minutes
When is thoracocentesis indicated?
When patient has fluid or air accumulation in pleural space believed to be causing or contributing to respiratory difficulties
How is tracheostomy site closed?
It is not, left open and heals on own
Where is thoracentesis performed if performed blindly?
7th - 9th intercostal spaces
If air suspected in middle to upper thorax
If fluid suspected in lower third of chest
Where are the internal thoracic arteries located?
Along ventral thorax a few centimeters to either side of the sternum
Where are the major vessels and nerves located in relation to the ribs?
Along the caudal end of the ribs
How many days of continuous suction with continued air production might indicate it is time for thoracotomy?
2-5 days
When should a thoracotomy tube be removed?
No air should be removed for 24 hours prior to tube removal
Fluid may continue to accumulate but no more than 2mL/kg/day
Imaging prior to pulling tube
