PULMONARY FUNCTION TESTS D.mohamed said

Lung Volumes and Capacities PFT tracings have:  Four Lung volumes: tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume  Five capacities:, inspiratory capacity, expiratory capacity, vital capacity, functional residual capacity, and total lung capacity Addition of 2 or more volumes comprise a capacity.

Lung Volumes Tidal Volume (TV): volume of air inhaled or exhaled with each breath during quiet breathing (6- 8 ml/kg) Inspiratory Reserve Volume (IRV): maximum volume of air inhaled from the end-inspiratory tidal position.( ml) Expiratory Reserve Volume (ERV): maximum volume of air that can be exhaled from resting end-expiratory tidal position.( ml).

Lung Volumes Residual Volume (RV): – Volume of air remaining in lungs after maximium exhalation (20-25 ml/kg) ( ml) – Indirectly measured (FRC-ERV) – It can not be measured by spirometry

Lung Capacities Total Lung Capacity (TLC): Sum of all volume compartments or volume of air in lungs after maximum inspiration (4-6 L) Vital Capacity (VC): TLC minus RV or maximum volume of air exhaled from maximal inspiratory level. (60-70 ml/kg) ( ml) Inspiratory Capacity (IC): Sum of IRV and TV or the maximum volume of air that can be inhaled from the end-expiratory tidal position. ( ml). Expiratory Capacity (EC): TV+ ERV

Lung Capacities (cont.) Functional Residual Capacity (FRC): – Sum of RV and ERV or the volume of air in the lungs at end-expiratory tidal position.(30-35 ml/kg) ( ml). – Measured with multiple- breath closed-circuit helium dilution, multiple-breath open-circuit nitrogen washout, or body plethysmography. – It can not be measured by spirometry)

VOLUMES, CAPACITIES AND THEIR CLINICAL SIGNIFICANCE

DIFFERENT POSTURES AFFECTING VC POSITION  TRENDELENBERG  LITHOTOMY  PRONE  RT. LATERAL  LT. LATERAL DECREASE IN VC  14.5%  18%  10%  12%  10%

VC CONTINUED……. VC correlates with capability for deep breathing and effective cough. So in post operative period if VC falls below 3 times VC– artificial respiration is needed to maintain airway clear of secretions.

CONTINUED…… FUNCTIONAL RESIDUAL CAPACITY (FRC):  Volume of air remaining in the lungs after normal tidal expiration, when there is no airflow.  N L OR ml/kg.  FRC = RV + ERV  Decreses under anaesthesia with spontaneous Respiration – decreases by 20% With paralysis – decreases by 16%

FACTORS AFFECTING FRC FRC INCREASES WITH Increased height Erect position (30% more than in supine) Decreased lung recoil (e.g. emphysema) FRC DECREASES WITH Obesity Muscle paralysis (especially in supine) Supine position Restrictive lung disease (e.g. fibrosis, Pregnancy) Anaesthesia FRC does NOT change with age.

FUNCTIONS OF FRC Oxygen store Buffer for maintaining a steady arterial po2 Partial inflation helps prevent atelectasis Minimise the work of breathing Minimise pulmonary vascular resistance Minimised v/q mismatch Keep airway resistance low (but not minimal

FORCED VITAL CAPACITY IN 1 SEC. (FEV1)  Forced expired vol. In 1 sec during fvc maneuver.  Expressed as an absolute value or % of fvc.  N- FEV1 (1 SEC) % OF FVC  FEV2 (2 SEC)- 94% OF FVC  FEV3 (3 SEC)- 97% OF FVC

CONTINUED…… CLINICAL RANGE (FEV1) L 1.5 – 2.5 L <1 L 0.8 L 0.5 L PATIENT GROUP NORMAL ADULT MILD – MOD.OBSTRUCTION HANDICAPPED DISABILITY SEVERE EMPHYSEMA

CONTINUED…… FEV1 – Decreased in both obstructive & restrictive lung disorders. FEV1/FVC – Reduced in obstructive disorders. NORMAL VALUE IS 75 – 85 % (FEV1/FVC) < 70% OF PREDICTED VALUE – MILD OBST. < 60% OF PREDICTED VALUE – MODERATE OBST. < 50% OF PREDICTED VALUE – SEVERE OBST.

CONTINUED…… DISEASE STATES FVC FEV1 FEV1/FVC 1)OBSTRUCTIVE NORMAL ↓ ↓ 2) STIFF LUNGS ↓ ↓ NORMAL 3 ) RESP. MUSCLE WEAKNESS ↓ ↓ NORMAL

FLOW VOLUME LOOP

Flow-volume loops and upper airway obstruction Extrathoracic obstruction – vocal cord dysfunction, goiter, cause flattening of inspiratory limb of flow/volume loop Intrathoracic obstruction – bronchogenic cancer in right mainstem bronchus, flattening of expiratory limb of flow/volume loop

Extrathoracic Intrathoracic

Pulmonary Function Tests The term encompasses a wide variety of objective tests to assess lung function Provide objective and standardized measurements for assessing the presence and severity of respiratory dysfunction.

GOALS  To predict the presence of pulmonary dysfunction  To know the functional nature of disease (obstructive or restrictive. )  To assess the severity of disease  To assess the progression of disease  To assess the response to treatment  To identify patients at increased risk of morbidity and mortality, undergoing pulmonary resection.

 To wean patient from ventilator in icu.  Medicolegal- to assess lung impairment as a result of occupational hazard.  Epidemiological surveys- to assess the hazards to document incidence of disease  To identify patients at perioperative risk of pulmonary complications GOALS, CONTINUED……..

INDICATIONS OF PFT Last GUIDELINES FOR PREOPERATIVE SPIROMETRY  Age > 70 yrs.  Morbid obesity  Thoracic surgery  Upper abdominal surgery  Smoking history and cough  Any pulomonary disease

BED SIDE PFT

BED SIDE PFT 1) Single breath count: After deep breath, hold it and start counting till the next breath.  N COUNT  Indicates vital capacity

BED SIDE PFT 2) SCHNEIDER’S MATCH BLOWING TEST: MEASURES Maximum Breathing Capacity. Ask to blow a match stick from a distance of 6” (15 cms) with-  Mouth wide open  Chin rested/supported  No purse lipping  No head movement  No air movement in the room  Mouth and match at the same level

BED SIDE PFT Can not blow out a match – MBC < 60 L/min – FEV1 < 1.6L Able to blow out a match – MBC > 60 L/min – FEV1 > 1.6L MODIFIED MATCH TEST: DISTANCE MBC 9” >150 L/MIN. 6” >60 L/MIN. 3” > 40 L/MIN.

BED SIDE TEST 3) COUGH TEST: DEEP BREATH F/BY COUGH  ABILITY TO COUGH  STRENGTH  EFFECTIVENESS INADEQUATE COUGH IF: FVC<20 ML/KG FEV1 < 15 ML/KG PEFR < 200 L/MIN. A wet productive cough / self propagated paraoxysms of coughing – patient susceptible for pulmonary Complication.

BED SIDE PFT 4) MICROSPIROMETERS – MEASURE VC. 5) BED SIDE PULSE OXIMETRY 6) ABG.

Questions 1- What are the bed side testes to evaluate PFT ? 2- mention PFT, its interpretions and indications ?

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