mechanical ventilation Flashcards
perfusion
blood supply
shunt
normal perfusion but decreased or no ventilation
physiological eg: normal shunting from pleural coronory circulation, dormant alveoli
pathologic: atelectasis secretion
emphysema
dead space
ventilation but no perfusion
partial pressure
partial pressure is the individual pressure exerted independently by a particular gas within a mixture of gases
oxygen saturation
oxygen saturation measures the percentage of hemoglobin bound to oxygen in the blood.
At low partial pressure of oxyegen most hemoglobin is deoxygenated
how many o2 molecule carry haemoglobin?
4
mechanical ventilation or assisted /artificial ventilation
term used when mechanical means are used to assist or replace spontaneous breathing
what is respiratory failure?
inability to maintain p02 of more than 60 mmhg &
pco2 of less than 45 mmhg
what are type of respiratory failure?
hypoxemic (type 1) - pa02 <60 mmhg with normal or subnormal paco2
hypercapnic (type 2): paco2 >50 mmhg
hypoxemia
lung failure (gas exchange failure manifested by hypoxaemic)
occur at lung
hypercapnia
pump failure
ventilatory failure manifested by hupercapnia
occur outside a lung
what baro receptor do?
sensing the pressure
chemoreceptors & baroreceptor?
baroreceptor (sense the increase & decrease pressure of o2 level)
chemoreceptors (check the saturation ) send signal to brain send to respiratory muscle
then muscle are work harder
causes of respiratory failure?
failure of lung caused by a variety of lung disease (e.g pneumonia, ild & emphysema) leads to hypoxaemia with normal normocapnia or hypocapnia
failure of pump (e.g drug overuse) results in alveolar hypo ventilation & hypercapnia
although there is coexistence hypoxaemia the hallmark
if ventilatilatory failure is the increase in pa co2
indication of mechanical ventilation?
loss of airway anatomy- edema , direct/indirect trauma, burns , infection
loss of protective airway mechanisms-intoxicants, brain injury, stroke
expected clinical course or prophylactic ventilatory support- e.g post anaesthesia recovery, muscle fatigue
inability of oxygenate appropriately (hypoxaemic respiratory failure)
-shunt ,alveoli filled with anything apart from air like secretion, infection etc (condition like ARDS , COPD , cardiac disease etc)
inability to ventilate appropriately (hypercapnia respiratory failure)
cns disease e.g head injury, cerebral hemorrhage , drug overuse (decreased central respiratory drive)
neuromuscular disease e.gbs, poliomyelitis etc (impaired mechanical performance of inspiratory muscle)
musculoskeletal disease e.g chest wall trauma (mechanical defect in chest wall)
goals of mechanical ventilation
relive respiratory distress decrease work of breathing improve pulmonary gas exchange reverse respiratory muscle fatigue permit lung healing avoid complications
criteria for starting mechanical ventilation
respiratory rate >35 or <5 breath/ min
exhaustion with laboured pattern of breathing
hypoxia- central cyanosis, sa02 <90% on oxygen or pa02 <80 mmhg
hypercarbia -paco2 >50 mmhg
decreasing conscious level
significant chest trauma
tidal volume <5ml/kg or vital capacity <15ml/kg
control of intracranial pressure in head injury
airway protection following drug overdose
following cardiac arrest
for recovery after prolonged major surgery or trauma
how normal breathing happens?
when the pressure in the lung di decreases the outside air come inside
when the pressure in the lungs more than atmospheric pressure
air goes out
physical breathing
- movement of air in & out of the lungs by respiratory muscle depending on the body requirements
- initiation & termination of breath, rate & depth of breathing are partly voluntary & depand on level of pco2 , p02 and lung inflation
- air is sucked into lungs during inspiration because of negative pressure
increase in pulmonary pressure is minimal between -3 to +5 cm of water
venous return increase during inspiration
mechanical ventilation ?
work of respiratory muscle carried out by ventilator
initation & termination of breath rate and depth of breathing are machine /clinical determined
air is sucked into lungs during inspiration because of positive pressure
increase in pulmonary pressure is high between 15 to 40 cm of water
venous return decrease during inspiration
dead space
normal ventilation but decreased or no perfusion
physiologic e.g peripheral airway like trachea, bronchi
pathologic: pulmonary embolism
mechanical ventilation classification
invasive
ventilatory support given through ETT(endo tracheal tube) or tracheotomy
NON invasive
ventilatory support given without establishing ETT or tracheotomy, generally given through maks
where tube coke ate end?
carina where bifurcate into two bronchioles
invasive positive pressure ventilation types
volume cycle
pressure cycle
time cycle
