Respiratory Part 1

Respiratory part 1

Unit 3 objectives: to know, apply and interpret: • Pulmonary function symptoms • Pulmonary function tests. • Pulmonary diseases where laboratory contributes to good patient care.

NPLEx tests • • • •

Spirometry Blood gas analyses Pulse oximetry Lactate

How do you know you have a lung disease? One or more of • • • • • •

Cough Dyspnea – difficulty breathing Haemoptysis – spitting blood Sputum Cyanosis Sometimes chest pain

Investigations if respiratory disease seems likely: • • • • •

Spirometry Blood gases Lactate Pulse oximetry Other special tests for diagnosis

Pulmonary function: spirometry 1. Hold the spirometer and take a deep breath in 2. Place the mouth piece in your mouth, wrap your lips round it. 3. Breathe put as hard and fast as you can. 4. Repeat the measurement three times and record the best value.

Pulmonary function tests: Spirometry = measurement of breathing capacity of lungs. Forced expiration time FET – time to empty the lungs Peak expiratory flow rate (PEFR) – depends on age, height and gender Forced expiration volume (FEV1) expressed as % of non forced expiratory volume VC [vital capacity]/second

Spirometer traces 100 90 80 70 60 normal obstruction restriction

50 40 30 20 10 0

1 sec

2 sec

3 sec

4sec

Spirometer traces • Forced vital capacity (FVC) • Forced expiration volume in one second (FEV1) • Obstruction: FEV1/FVC reduced as in asthma. • Restriction: FEV1/FVC unchanged as in pulmonary fibrosis.

Spirometer

Respiratory function • Diurnal variation in bronchomotor tone – greatest in early morning. • In asthma this is exaggerated. Problems in early morning.

Arterial blood gases, north america versus the rest • • • •

pH or [H+] nmol/L, pH lethal levels: <6.8 or >7.65. pCO2 mm Hg or kPa. (kilo Pascals) Range 35-45 mm Hg. But could see 15 – 80 in diseases. • pO2 mm Hg or kPa. 90-100, below 60 dangerous

Acid base problems, the tests: • • • • •

Blood/serum/plasma electrolytes Blood pH (hydrogen ion concentration) Blood pCO2 Blood bicarbonate – calculated. Blood pO2 (oxygen saturat’n, pulse oximetry) • Blood lactate • Spirometry.

Pulse oximetry • Measures the red colour of oxyhaemoglobin. • Electrode clipped to ear lobe, finger tip or toe.

Acid-base: Kidney/metabolic problem: • Bicarbonate decreased then metabolic acidosis • Bicarbonate increased then metabolic alkalosis. Lung problem: • pCO2 increased then respiratory acidosis • pCO2 decreased then respiratory alkalosis. But compensation happens!

Respiratory acidosis • Acute could be choking. • Acute could be an asthma attack. • Chronic = bronchopneumonia.

Chronic • There is usually maximal renal compensation. pCO2 may be double normal and pO2 be depressed. • Chronic bronchitis COPD, usually “blue bloaters”. But could be emphysema SOB, “pink puffers”.

COPD