Respiratory Function Tests RFTs

Review Of Anatomy & physiology Lungs comprised of  Airways  Alveoli

Mechanics of Breathing Inspiration ◦ Active process caused mainly by contraction of diaphragm. Accessory muscles may used during exercise and distress Expiration ◦ Quiet breathing is a passive process but can become active, with forced expiration

Lung Volumes IRV TV ERV RV IC FRC VC TLC RV 4 Volumes 4 Capacities ◦ Sum of 2 or more lung volumes

Tidal Volume (TV) IRV TV ERV RV IC FRC VC TLC RV Volume of air inspired or expired during normal quiet breathing TV = 500 ml

The Inspiratory Reserve Volume IRV The extra volume of air that can be inspired over and above the normal tidal volume, when person inspires with full force IRV= 3000 ml IRV TV ERV RV IC FRC VC TLC RV

The extra volume of air that can be exhaled over normal tidal volume when person expires forcefully ERV= 1100ml Expiratory Reserve Volume (ERV) IRV TV ERV RV IC FRC VC TLC RV

Residual Volume (RV) IRV TV ERV Volume of air remaining in the lungs at the end of maximum expiration. RV =1200 ml RV IC FRC VC TLC RV

Vital Capacity (VC) IRV TV ERV The maximum amount of air a person can expel from the lungs after filling the lungs to their maximum extent and then expires to the maximum extent. Also called Forced vital capacity FVC VC=4600ml VC=IRV+TV+ERV RV IC FRC VC TLC RV

Inspiratory Capacity (IC) IRV TV ERV The amount of air a person can breathe in beginning at the normal expiratory level and distending the lung to the maximum amount. IC = IRV + TV IC= 3500ml RV IC FRC VC TLC RV

Functional Residual Capacity (FRC) IRV TV ERV Volume of air remaining in the lungs at the end of a normal expiration FRC = ERV + RV FRC= 2300 ml RV IC FRC VC TLC RV

Total Lung Capacity (TLC) IRV TV ERV Volume of air in the lungs after a maximum inspiration TLC = IRV + TV + ERV + RV =5800ml RV IC FRC VC TLC RV

Factors affecting lung volume Age Sex Height Weight Race Disease

CLINICAL SIGNIFICANCE VC% < 80% is abnormal RV/TLC% (residual air rate) normal : < 35% emphysema: > 40 % old person can be 50%. FRC ↑ : emphysema

Value of Respiratory function tests Evaluates 1 or more major aspects of the respiratory system ◦ Lung volumes ◦ Airway function ◦ Gas exchange

Indications Detect disease Evaluate extent and monitor course of disease Evaluate treatment Measure effects of exposures Assess risk for surgical procedures

PFTs 1. Arterial blood gases 2. Blood PH 3. Pulse oximeter 4. Peak flow meter measuring peaked expiratory flow rate. 5. Spirometry 1. Arterial blood gases 2. Blood PH 3. Pulse oximeter 4. Peak flow meter measuring peaked expiratory flow rate. 5. Spirometry

Peak flow meter measuring peaked expiratory flow rate PEFR This is extremely simple and cheap test It describes maximal airflow rate in a given time. It measures the airflow through the bronchi and thus the degree of obstruction in the airways. Is best for monitoring the progression of disease

Cont….. it can detect airway narrowing, commonly used in asthma, Even by the patient himself to know when he need an emergency interference. the effectiveness of a person's asthma management and treatment plan. when to stop or add medication, as directed by physician. what triggers the asthma attack (such as exercise-induced asthma )

To perform this test Loosen any tight clothing that might restrict your breathing. Sit up straight or stand while performing the tests Breathe in as deeply as possible. Mouthpiece is placed in mouth with lip sealed to prevent escape of air Blow into the instrument's mouthpiece as hard and fast as possible. Do this three times, and record the highest flow rate.

Normal values vary based on a person's age, sex, and size Normal person can empty their chest from full inspiration in 4 sec or less Prolongation to more than 6 sec indicates airflow obstruction A fall in peak flow can signal the onset of a lung disease flare, especially when it occurs with symptoms such as: Shortness of breath Increased cough Wheezing

SPIROMETRY  Simple, office-based  Measures flow, volumes  Volume vs. Time  Can determine: - Forced expiratory volume in one second (FEV1) - Forced vital capacity (FVC) - FEV1/FVC

Old version – spirometer bell – kymograph pen New version – portable

Indications of Spirometry: diagnostic and prognostic Evaluation of signs and symptoms of pulmonary diseases like asthma and COPD Screening at-risk populations male smokers >45 years Preoperative assessment Assess severity of diseases Follow up response to therapy Determine further treatment goals

A spirometer can be used to measure the following: ◦ FVC and its derivatives (such as FEV1, FEF 25-75%) ◦ Forced Inspiratory vital capacity (FIVC) ◦ Peak expiratory flow rate ◦ Maximum voluntary ventilation (MVV) ◦ Slow VC ◦ IC, IRV, and ERV ◦ Pre and post bronchodilator studies

Terminology Forced vital capacity (FVC): – Total volume of air that can be exhaled forcefully from TLC – The majority of FVC can be exhaled in <3 seconds in normal people, but often is much more prolonged in obstructive diseases – Measured in liters (L)

FVC Interpretation of % predicted: ◦ %Normal ◦ 70-79%Mild reduction ◦ 50%-69%Moderate reduction ◦ <50%Severe reduction

FEV1 Forced expiratory volume in 1 second: (FEV 1 ) ◦ Volume of air forcefully expired from full inflation (TLC) in the first second ◦ Measured in liters (L) ◦ Normal people can exhale more than % of their FVC in the first second; thus the FEV1/FVC can be utilized to characterize lung disease

FEV1 Interpretation of % predicted: ◦ >75%Normal ◦ 60%-75%Mild obstruction ◦ 50-59%Moderate obstruction ◦ <49%Severe obstruction

Technique Have patient seated comfortably Closed-circuit technique ◦ Place nose clip on ◦ Have patient breathe on mouthpiece ◦ Have patient take a deep breath ◦ Blow out the air as fast as possible and as hard and long as possible

Flow Volume Loop  “Spirogram”  Measures forced Inspiratory and expiratory flow rate  Augments Spirometry results  Indications: evaluation of upper airway obstruction (stridor, unexplained dyspnea)

Flow-Volume Loop Illustrates maximum expiratory and Inspiratory flow-volume curves

Obstructive Disorders ◦ Characterized by a limitation of expiratory airflow so that airways cannot empty as rapidly compared to normal (such as through narrowed airways from bronchospasm, inflammation, etc.) Examples: ◦ Asthma ◦ Emphysema ◦ Cystic Fibrosis Restrictive Disorders ◦ Characterized by reduced lung volumes/decreased lung compliance Examples: ◦ Interstitial Fibrosis ◦ Scoliosis ◦ Obesity ◦ Lung Resection ◦ Neuromuscular diseases ◦ Cystic Fibrosis

Obstructive Disorders Characterized by a limitation of expiratory airflow Decreased: FEV 1, FEV 1 /FVC ratio (<0.8) Increased or Normal: TLC

Spirometry in Obstructive Disease Slow rise in upstroke May not reach plateau

Restrictive Lung Disease Characterized by diminished lung volume Decreased TLC, FVC Normal FEV1 Normal or increased: FEV 1 /FVC ratio

Restrictive Disease Rapid upstroke as in normal Spirometry Plateau volume is low

Bronchial Dilation Test Method: to determine FEV1 and FEV1/FVC% before and after ß2-agonist inhalation Result: improved rate = after-before ×100% before Positive: >15% Reversible limitation: asthma