Respiratory Acidosis and Alkalosis Flashcards Preview

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Flashcards in Respiratory Acidosis and Alkalosis Deck (17)
1

What is the Henderson Hasselbach equation?

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

2

What is the physiological cause of respiratory acidosis?

Carbon dioxide is produced constantly as a consequence of metabolism and therefore this CO2 will accumulate rapidly if the lungs don’t adequately dispel it; alveolar hypoventilation increased pCO2 (hypercapnia) respiratory acidosis

3

What is the cause of the symptoms associated with respiratory acidosis?

The signs and symptoms of respiratory acidosis are primarily due to low central nervous system pH, as although CO2 can cross the BBB in hypercapnia, bicarbonate cannot cross the BBB to buffer this; this can lead to headache, drowsiness, lethargy, memory loss etc.

4

What are the clinical signs of respiratory acidosis?

Slowed breathing, gait disturbance, disorientation, tremor, tachycardia, drop in BP

5

What are the main causes of respiratory acidosis?

Hypoventilation as a result of:
- drugs which suppress breathing e.g. powerful pain relief
- status asthmaticus and COPD
- scoliosis
- disease that affects the nerves/muscles involved in respiration
- severe obesity (restricts chest expansion)

6

What is the difference between acute and chronic respiratory acidosis?

In both types there is an elevated pCO2 but in acute respiratory acidosis there is also a pH less than 7.35, whereas in chronic this is compensated for by metabolic alkalosis so remains relatively normal.

7

What treatment may be given in order to treat respiratory acidosis?

The aim is to treat the underlying pathology, but this may include:

-Bronchodilators for airway obstruction
- Non-invasive positive pressure ventilation
- Oxygen
- Smoking cessation therapy

8

What is the physiological cause of respiratory alkalosis?

Generally occurs when an individual hyperventilates increased alveolar respiration increased carbon dioxide excretion. Hydrogen ions and bicarbonate (via carbonic anhydrase) react to produce more CO2 net effect is reduced H+ levels pH falls alkalosis

9

How do the signs and symptoms differ between acute and chronic respiratory alkalosis?

In acute respiratory alkalosis there may be hyperventilation, dizziness, cramps, muscle twitching, chest pain etc. Chronic respiratory alkalosis, however, is usually asymptomatic and has no distinctive signs.

10

What are the common causes of respiratory alkalosis?

Anything that causes hyperventilation e.g.:
• Intracerebral haemorrhage, meningitis ad stroke
• Salicylate and progesterone
• Anxiety, stress, pain
• Liver cirrhosis, sepsis
• Elevated body temperature (fever)
• Hypoxia and any lung disease that causes shortness of breath
• High altitude

11

What are the consequences of respiratory acidosis?

• Decrease in CO2 levels in the blood constriction of cerebral blood vessels
• Increased pH (alkalosis) shifts the oxygen dissociation curve to the left (greater affinity for oxygen) impaired oxygen delivery to tissues
• There is an increase in neuromuscular excitability
• Hypokalaemia (too little potassium) – this is because the increased H+ absorption in the kidney has to be electrically compensated for by another cation and subsequently K+ is excreted more in order to retain electroneutrality in the body

12

Define type 1 respiratory failure

A hypoxic respiratory failure with a normal to low pCO2 level

13

Define type 2 respiratory failure

A hypercapnic respiratory failure with or without hypoxia

14

What may cause type 1 respiratory failure?

Type 1 respiratory failure is the most common form at it can occur in most diseases of the lung which involve fluid filling or the collapse of alveolar units such as pulmonary oedema, pneumonia and pulmonary haemorrhage

15

What conditions may cause type 1 respiratory failure?

Pulmonary oedema, pneumonia and pulmonary haemorrhage

16

Can type 1 respiratory failure occur without pH change?

Yes

17

What is meant by ventilation-perfusion (VQ) mismatch? How may it exacerbate type 1 respiratory failure?

if a lobe in the lung becomes poorly ventilated, the capillaries and arterioles constrict to redirect blood flow to better oxygenated regions (adaptive response). However, in type 1 respiratory failure this can worsen the situation e.g. in asthma the downstream alveoli will be hypoxic (due to bronchiole constriction and spasm) and therefore the local capillaries will constrict, reducing gas exchange further. If large parts of the lungs are vasoconstricted due to hypoxia, AV shunts can open to prevent pulmonary arterial hypertension and right heart damage, but this doesn’t resolve the hypoxia