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involves the integration and coordination of the pulmonary, cardiovascular, neurologic, hematologic and metabolic processes.
the process in which oxygen is being brought into the internal enviroment via the respiratory system
Pulmonary gas exchange
the intake of oxygen from the externa envroment into the internal enviiroment and is carried out by the processes of ventilation, diffusion, and perfusion
process of transportation of oxygen to cells and is dependant on Cardiac output, hemoglobin saturation with oxygen, and the partial pressure of oxygen in arterial blood
the use of oxygen at the cellular level to generate energy for cells to use to perform their specific functions.
movement of air to and from the atmosphere and the alveoli, requires breathing and ventilatory muscles thorax, lungs, conducting airways, and nervous system
the movement of gas across a pressure gradient from an area of high concentration to low concentration
mechanism- which oxygen moves across the alveoli and into the pulmonary capillar
Conditions that impair Pulmonary gas exchange- Ventilation Impairment
inspiratory muscle weakess or trauma (Guillian Barre, spinal cord injury)
Decreased level of consciousness
Obstruction or trauma to airways, lung, thorax (flail chest, mucous plug)
Restrictive Pulmonary disorders
Conditions that impair Pulmonary gas exchange-- Diffusion impairment
decrease in aveolar- capillary membrane surface area
ex. atlectasis, lung tumors, pneumonia
increase in alveolar-capillary embrane thickness
ex. acute respiratory distress syndome, pulmonary edema, pneumoni
decreased pressure gradiant for oxygen Ex. decreased FiO2
Conditions that impair Pulmonary gas exchange-
decreased Hb (anemia, carbon monoxide poisoning)
decreased perfusion (decreased cardiac output, hemorrhage, pulmonary emboli)
pulm. vasoconstriction (pulm. hypertension, hypoxemia)
process of transporting oxygen to cells
include cardiac ouput, autoregulation, oxygen content of arterial blood (CaO2), autonomic nervous system
the amount of blood pumped by the heart each minute
Ex. when tissue require more oxygen, heart rate will increase in an attempt to augment cardiac output in the delivery of more oxygenated blood
tissues have the ability to regulate their own blood supply by dilating or constricting local blood vessels
the saturation of hemoglobin with oxygen
Measurement of Sa02 by arterial bood gas analysis is a measure of the ratio of oxygenated hemoglobin to total hemoglobin
Ex. If SaO2 is 95 percent, it can be interpreted that 95 percent of the available seats on the hemoglobin seats are occcupied by oxygen
condition characterized by an inadequte amount of oxygen in the blood as a result of impaired gas exchange
PaO2 less than 60
can result in Hypoxia
inadequate amount of oxygen available at the ceullar level such that cells experience anaerobic metabolism
characterized by an inability of the cells to use oxygen properly despite adequate levels of oxygen delivery
Two goals in the assessment of oxygenation
to determine overral adequacy of oxygenation
to determine which component of oxygenation dysfunction should be manipulated
Assessment of pulmonary gas exchange
ABG (PaO2, PaCO2)
End tidal CO2
Pulmonary functon test
End tidal CO2
measure by placing a sensor at the end of the endotracheal tube to measure the amount of exhaled CO2
rapid shallow breathing index
accurate predctor of how well a patient is tolerating weaning form mechanical ventilation
- the ratio is expressed as the frequency of respiration divided by the tidal volume as measured during spontanous unsupported respiration
Weaning failure- greater than 105
porportion of blood that flows past alveoli without participating in gas exchange
normal value is more than 286
less than 200 suggesting a large intrapulmonary shunt
normal serum levels of lactate
less than 2mMol/L
cause: inadequate oxygen delivery to meet cellular oxygen needs
Measured using serial measurements for example four to eight hours can be used as an indicator of imporivng or worsening oxygen delivery in relation to to oxygen consumptoin
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