Chapt 1 & 2 (RTH 162) Flashcards
What is the most common cause of increased airway resistance?
COPD. (Chronic obstructive pulmonary disease like emphysema chronic bronchitis chronic asthma and bronchiectasis)
What is one of the most frequent use of mechanical ventilation?
Management of postoperative patients recovering from anesthesia and medications.
Explain the Poiseuille’s law:
The work of breathing increases by a factor of 16 fold when the radius of the airway is reduced by half its original size.
What is the normal airway resistance in healthy adults?
Between 0.5 and 2.5 cm H2O/liter/second
Airway resistance :
Airway resistance varies directly with the length and inversely with the diameter of the airway or ET tube.
What is the equation of airway resistance, how is it calculated?
Pressure change / flow
Airway resistance and flow in the equation are inversely related.
What is the equation for pressure change?
Peak inspiratory pressure - plateau pressure.
When does ventilatory failure occur?
When the patients minute ventilation cannot keep up with CO2 production.
In the pressure/volume loop what does an increase bowing of the pressure/volume loop suggest?
And overall increase in airflow resistance.
What is lung compliance?
Volume change (lung expansion) per unit pressure change (work of breathing)
C= volume change / pressure change
What is the equation for static compliance?
Corrected tidal volume / (plateau pressure - peep)
What is the equation for dynamic compliance?
Corrected tidal volume / (peak inspiratory pressure - Peep)
What is a normal static compliance?
40 to 60 cm H2O
What is normal dynamic compliance?
30 to 40 cm H2O
In the pressure to volume slope what does a shift of the slope towards the pressure axis indicate?
A decrease in compliance.
In the pressure to volume slope what does a shift towards the volume axis indicate
An increase in compliance.
What is the critical percentage of shunting from one side of the heart to the other where it will require a mechanical ventilation?
Shunting of 15% or more blood will require a mechanical ventilation.
White is hypoxia?
Decrease of oxygen in the organs and tissue.
What is hypoxemia?
Reduced oxygen in the blood.
Why could we have oxygen failure without CO2 failure?
CO2 diffuses through capillary beds 20 times faster than O2.
What is the action of positive pressure ventilation on the intrathoracic pressure?
PPV causes an increase in intrathoracic pressure and compression of the pulmonary blood vessels.
And a decrease in ventricular output, stroke volume and pressure readings.
What is oliguria?
Urine output
less than 400 mL in 24 hours or less than 160 mL in eight hours.
What is the caloric cost of breathing for COPD patients?
About 10 times that of normal individuals
Normal = 38 to 72 cal per day COPD = 430 to 720 cal/Day
What will a sustained hyperventilation of less than 24 hours cause?
Respiratory alkalosis
Reduced cerebral blood flow
Intracranial pressure
What could be some causes of changes in patient’s mental status?
Hypoxia
Hypercapnia
Acidosis
What is one of the strategies to reduce airflow resistance?
During mechanical ventilation remove the secretion in the endotracheal tube.
What do patients with COPD or chronic airway obstruction typically do to compensate or accommodate for the airflow resistance?
Use a breathing pattern that is deep and slow.
On the pressure/volume loop what does an increase in Boeing of the inspiratory limb suggest?
In excessive inspiratory flow.
What is the target and the variable in a pressure-controlled ventilation?
During pressure-controlled ventilation the pressure is preset and the volume delivered by the vent is a variable.
In a volume -controlled ventilation which is preset and which one is the variable?
During volume-controlled ventilation the volume is preset and the pressure generated by the ventilator is variable.
In addition to elimination of waste, what what do kidneys do?
Regulation of
drug clearance
fluid and electrolyte balance
acid-base balance
What could PPV cause in the kidneys?
During positive pressure ventilation, hypoperfusion of the kidneys may decrease the rate of drug clearance leading to a higher drug concentration in the circulation.
Explain the action of peep on the liver.
The liver is perfused by about 15% of the total cardiac output, and this perfusion rate may be reduced when peep is added to positive pressure ventilation.
What is a nutritional consideration when it comes to PPV?
Nutritional balance is vital in the management of critically ill patients because, MALNUTRITION may cause MUSCLE FATIGUE, where as excessive nutritional support may cause excessive CO2 production.
Renal perfusion and PPV:
Blood flow to the kidneys is decreased when blood volume of cardiac output is low.
When renal perfusion or perfusion to the glomeruli of the kidneys is decreased, filtration becomes less efficient. Subsequently, the urine output is decreased, as the kidneys try to correct the hypovolemic condition by retaining fluid.
Hey Patrick or liver considerations with PPV and peep.
Hepatic perfusion accounts for about 15% of the total cardiac output.
PPV alone does not alter the blood flow to the liver.
When peep is added to mechanical ventilation, the blood flow to the liver is noticeably reduced.
What are the indicators of liver dysfunction?
Impairment of liver function is likely when coagulation time is increased.
Prothrombin time >4 seconds
Bilirubin level is increased >50 mg/L
Albumin level is decreased <20 g/L
TPN (total parenteral nutrition):
A fat based TPN should be considered for patients with significant or persistent CO2 retention, as fat emulsion may provide maximum caloric intake with minimum CO2 production.
What happens if hyperventilation is retained after 24 hours?
- Leftward shift of Oxyhemoglobin curve
- increased 02 affinity for hemoglobin
- reduced or two release to tissues
- cerebral tissue hypoxia
- neurologic dysfunction
- Hypophosphatemia
What are the components of mean arterial pressure?
- Inspiratory time
- respiratory frequency
- peak inspiratory pressure
- peep
What is ventilatory failure?
Failure of the respiratory system to remove CO2 from the body resulting in an abnormally high PaCO2.
