L11. Lung function tests Flashcards
What are the four aspects of pulmonary function being tested and why are they tested
Ventilation, gas exchange, perfusion, respiratory control.
Tests assess:
impact of a pathological/ aging process, degree of risk associated with specific activity or intervention, progress of disease/ treatment regimen
What is the basic principle and special indications for Spirometry
Measures flow and volume during a max expiration (starting at TLC) followed by a max inspiration, for FVC, FEV1, flow volume loop.
Indications: diagnosis for obstructive ventilatory defect= but also show restrictive conditions and obstructions in different places
What is the basic principle and special indications for measurement of Static lung volumes and TLC + ways this is done
He dilution and N washout use and plethysmography measure FRC using slow vital capacity. Therefore find TLC and RV. If restrictive disease then the max lung volume > 6x RV
Indication: Diagnosis of restrictive ventilatory defect. Can also differentiate
What is the basic principle and special indications for Alveolar Capillary diffusion assessment (DLCO)
Evaluates the transfer of gas from the air spaces into the pulmonary capillaries through max insp of CO and CH4.
dlco= area/ thickness and also rate of diffusion/ concentration gradient.
Indications: Evaluation of parenchymal lung disease, pulmonary involvement in systemic diseases, prediction of arterial desaturation.
Differentiating between chronic bronchitis, emphysema: reduced dlco and asthma: normal.
Why use CO for alveolar capillary diffusion assessment
Follows the same diffusion path as O2 but amount across alveolar capillary is diffusion limited so never fully equilibrated with pul. cap. plasma.
Due to strong binding to hb, free conc in plasma = 0
What is the basic principle and special indications for Bronchodilator response
Measures the degree to which bronchodilators can make airway obstruction better with PFT. Positive if FEV1 is increased 12-15% and FEV1 is increased by 200mL or
What is the basic principle and special indications for Bronchoprovocation test
Evaluates airway hyper responsiveness Uses Direct pharmacological agents (nonspecific) and indirect : dries out airways to cause bronchospasm.(specific)
Indications:
to diagnose asthma in patients with unclear symptoms, but there is some overlap with COPD
Whats the difference between sensitivity and specificity
Sensitivity: % of asthmatics who test positive to a specific test. Remainders are false positive
Specificity: % patients without disease that test negative to specific test. Remainder are false negatives
What is the basic principle and special indications for Progressive Exercise test
Assesses cardiopulmonary function during incremental exercise: Looks at arterial haemoglobin saturation, ventilation: O2, CO2 volumes, Heart rate and SV analogue, ECG, BP.
Indications: breathlessness on exertion, exercise impairment, post surgery evaluation.
