8 - ABGs and acid base Flashcards Preview

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Flashcards in 8 - ABGs and acid base Deck (15)
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1
Q

normal ABG values

A

PaO2 > 60 mmHg. SpO2/SaO2 > 90%. PaCO2 40 mmHg. HCO3 24 mmol/L. pH 7.4

2
Q

Pgas = (formula)

A

partial pressure o that gas = (barometric pressure - water vapor pressure) X Fgas

3
Q

PA vs Pa

A

A = alveolar. a = arterial

4
Q

how does partial pressure of O2 change with altitude?

A

increased altitude = decreased PAO2 and thus decreased PaO2

5
Q

7 causes of low PaO2

A

things that cause low PAO2: high PCO2 (displaces O2). low FIO2. low barometric alt. (with increased altitude). low exchange of CO2/O2 (decreased respiration). things that cause a mismatch of ventilation and perfusion: shunt, decreased V/Q, increased dead space

6
Q

what controls PaCO2

A

= VCO2/VA X 0.863. so depends on CO2 production, and ventilation

7
Q

how does PaCO2 change with exercise?

A

healthy person: it shouldn’t. increased production, but also increased ventilation

8
Q

A-aDO2? what is normal?

A

PaO2 minus PaO2. normally should be 0.4 X age

9
Q

effects of alveolar ventilation on PCO2 and PO2

A

increased ventilation = higher PA O2 and higher Pao2 (PAO2 goes up more = higher Aa-DO2). and lower PaCO2

10
Q

interpreting ABG: three steps?

A

PaCO2 to assess ventilation. PaO2 to determine if it is normal for FIO2 and ventilation rate (can also calculate A-aDO2. pH and assess it relative to PaCO2.

11
Q

fundamental relationship in acid/base physl

A

CO2 + H2O = HCO3 - + H+

12
Q

what is base excess? what does +/- BE mean?

A

concentration of bicarb caused by metabolic changes. + means excess of bicarb over what is produced by existing PCO2 so metabolic alkalosis. - means bicarb is lower than can be explained by existing PCO2 so metabolic acidosis.

13
Q

what is PCO2, pH and BE in pure respiratory acidosis? partially compensated resp acid? completely compensated?

A

pure: high PCO2, low pH, BE 0. part compensated: high PCO2, low pH (but slightly more normal), + BE. complete comp: high PCO2, normal pH, ++ BE

14
Q

what is PCO2, pH and BE in pure respiratory alkalosis? partially compensated resp acid? completely compensated?

A

pure: low PCO2, high pH, BE 0. partial: low PCO2, high pH, -BE. complete: low PCO2, normal pH, –BE

15
Q

what is PCO2, pH and BE in metabolic acidosis? metabolic alkalosis?

A

met acid: normal/low PCO2 with low pH, –BE. met alk: normal/high PCO2, high pH, ++BE