Respiratory Acidosis and Alkalosis

Question 1

Normal Arterial blood gas

Answer 1

HCO3- = 24
PaCO2= 40
PaO2= 95

Question 2

Alveolar gas normal

Answer 2

PaCO2= 36
PaO2= 105

Question 3

Venous blood gas normal

Answer 3

PvCO2= 50
PvO2= 30-40

Question 4

Respiratory acidosis

Answer 4

Build up of CO2 in blood
pH more acidic
Brough about by some form of breathing difficulty

Question 5

Resp acidosis MOA

Answer 5

CO2 accumulates if lungs don’t dispel it through alveolar ventilation

Question 6

Alveolar hypoventilation

Answer 6

Increased PCO2- hypercapnia

–> decrease in blood pH

Question 7

Resp acidosis main causes

Answer 7

Hypoventilation due to drugs that suppress breathing
Diseases of airway
Diseases of chest (scoliosis)
Diseases that affect nerves + muscles that drive lungs to inflate or deflate
Severe obesity

Question 8

Degree of change in blood pH depends on

Answer 8

Body’s ability to buffer the excess CO2

Question 9

Henderson-Hasselbach equation

Answer 9

pH= 6.1 + log [(HCO3-)/0.03 x pCO2]

Question 10

pH

Answer 10

log(1/[H+])

Question 11

pKa

Answer 11

6.1 at body temp

Question 12

Resp acidosis chemicals

Answer 12

High PaCO2 (>40mmHg)
Slightly raised HCO3- (>24mmHg)
Ratio of [HCO3-]/pCO2 decreases -->pH also decreases

Question 13

Resp Acidosis symptoms explanation

Answer 13

CO2 lipid soluble gas- diffuse across BBB
HCO3- = ion, can’t enter CSF
–> CSF less buffered than blood so pH changes faster in response to CO2

Question 14

Resp acidosis symptoms

Answer 14

Headache
Drowsiness
Lethargy
Anxiety
Sleepiness

Question 15

Resp acidosis Signs

Answer 15

Slow breathing
Gait disturbance
Blunted deep tendon reflexes
Disorientation
Tremor
Myoclenic jerks
Papilloedema
Tachycardia
BP drop

Question 16

Resp Acidosis Diagnosis

Answer 16

pH<7.35
pCO2 >45mmHg
Blood sample for pH
ABG

Question 17

Resp Acidosis Treatment

Answer 17

Aimed at underlying lung disease

–> bronchodilators, ventilation, O2, smoking cessation

Question 18

Acute Resp acidosis findings

Answer 18

pCO2 > 6.3kPa/47mmHg

pH<7.35

Question 19

Acute resp acidosis

Answer 19

When an abrupt failure of ventilation occurs

Question 20

Acute resp acidosis Causes

Answer 20

Depression of central resp. centre by cerebral disease or drugs
Inability to ventilate adequately due to neuromuscular disease
Airway obstruction related to asthma or COPD

Question 21

Chronic Resp Acidosis findings

Answer 21

pCO2 > 6.3kPa/47mmHg

pH normal or near normal

Question 22

Chronic Resp Acidosis MOA

Answer 22

pH nearly normal because renal compensation–> produced a highly elevated serum bicarbonate

Question 23

Chronic resp acidosis Causes

Answer 23

Hypoventilation COPD
Obesity hypoventilation syndrome
Neuromuscular disorders
Severe restrictive ventilatory defects

Question 24

Metabolic compensation for Resp Acidosis

Answer 24

Kidneys generate + retain bicarbonate
Bicarb retention sometimes called “compensating metabolic alkalosis”
Maximum plasma HCO3- level reached this way is 45mmol/L

Question 25

Respiratory Alkalosis

Answer 25

Amount of CO2 in blood drops below normal pH more alkaline Usually due to hyperventilation

Question 26

Resp Alkalosis MOA

Answer 26

CO2 expelled too much H+ and HCO3- ions in plasma react (via carbonic anhydrase) to make more CO2 Decrease in circulation H+ --> increased pH

Question 27

Acute Resp Alkalosis Symptoms

Answer 27

``` Dizziness Lightheaded Agitation Confusion Cramps Tinging ```

Question 28

Acute Resp Alkalosis Signs

Answer 28

``` Muscle twitching Hyperpnoea Chest pain Blurred vision Spasms Weakness Seizures ```

Question 29

Chronic Resp Alkalosis Signs + symptoms

Answer 29

Asymptomatic | No distinctive signs

Question 30

Resp Alkalosis Main causes

Answer 30

``` Intracerebral haemorrhage Meningitis Stroke Drug usage Anxiety Stress Sepsis ``` Any lung disease that leads to shortness of breath

Question 31

Acute Resp Alkalosis

Answer 31

Rapid | Person may lose consciousness

Question 32

Chronic Resp Alkalosis

Answer 32

Asymptomatic due to metabolic compensation Kidneys excrete more bicarbonate --> gives a metabolic acidosis to compete with resp alkalosis Compensation complete in 7-10 days

Question 33

Resp Alkalosis body changes

Answer 33

Cerebral BV constriction Impaired O2 delivery Increase neuromuscular excitability Hypokalaemia

Question 34

K in Chronic Resp Acidosis

Answer 34

Protons excreted in kidney Potassium retained Hyperkalaemia

Question 35

K in Chronic Resp Alkalosis

Answer 35

Protons retained in kidney K excreted Hypokalaemia

Question 36

Resp Alkalosis Diagnosis

Answer 36

pH > 7.44 | pCO2 <35mmHg

Question 37

Resp Alkalosis Treatment

Answer 37

``` Treat underlying condition Hyperventilation- breathe into paper bag Pneumonia- antimicrobials Drug overdose- Poisoning treatment Mechanical ventilation if necessary ```

Question 38

Type 1 Resp Failure

Answer 38

Hypoxic pO2 < 60mmHg pCO2 normal or low Most common

Question 39

Type 2 Resp Failure

Answer 39

Hypercapnic pCO2 > 50mmHg pO2 normal or low

Question 40

O2 and CO2 diffusion in lungs

Answer 40

CO2 diffuses in and out much faster as steeper conc. gradient between blood + alveoli CO2 can be maintained at normal levels even with reduced ventilation

Question 41

Type 1 Resp failure examples

Answer 41

Pulmonary oedema Pneumonia Pulmonary haemorrhage

Question 42

Ventilation/perfusion mismatch

Answer 42

If lobe poorly ventilated, capillaries + arterioles constrict --> reduced blood flow

Question 43

Type 1 complications

Answer 43

If area of lung constricted then downstream alveoli hypoxic --> local capillaries constrict --> even less O2 to affected region

Question 44

Anion gap

Answer 44

[Na+] - ([Cl-] + [HCO3-]) = 12 mEq/L | Measures amount of unmeasured anions

Question 45

High anion gap

Answer 45

Loss of plasma bicarbonate - -> elevated of anions like lactate - -> METABOLIC ACIDOSIS

Question 46

Normal anion gap but still unwell

Answer 46

GI loss of bicarbonate due to vom Renal loss of bicarb due to renal damage Bicarb low but chlorine high