Pulmonary Function Pulmonary Function TestsTests

An Overview An Overview

Dr. Taher El NaggarDr. Taher El Naggar

Professor of Pulmonary Professor of Pulmonary MedicineMedicine

Ain Shams UniversityAin Shams University

What is Respiration ?What is Respiration ?

• It is a process by which cells It is a process by which cells utilize O2 produce Co2 & utilize O2 produce Co2 & exchange the gases with exchange the gases with atmosphere.atmosphere.

•External respirationExternal respiration a) Pulmonary ventilation b) Gas exchange across alveolar

capillary membrane. c) Carriage of O2 & CO2•Internal respirationInternal respiration Exchange of O2 & CO2 between

blood & tissues.

This achieved by :This achieved by :

(1)(1) VENTILATION VENTILATION ::

not only adequate in quantity not only adequate in quantity ( minute ( minute ventilation is 4 ventilation is 4 liters) ,but be efficiently liters) ,but be efficiently distributed distributed to all perfused alveoli.to all perfused alveoli.

(2)(2) PERFUSIONPERFUSION : :

Pulmonary capillary blood flow Pulmonary capillary blood flow being being delivered in adequate delivered in adequate volume volume (5Liters/m) and (5Liters/m) and distributed efficiently distributed efficiently to all to all ventilated alveoli.ventilated alveoli.

(3) (3) DIFFUSIONDIFFUSION : : It is concerned with the volume of It is concerned with the volume of gas transferred across the alveolar gas transferred across the alveolar capillary membrane. capillary membrane.

When expressed in terms of time and When expressed in terms of time and unit difference in partial pressure of the unit difference in partial pressure of the gas (ml/min/mm Hg) is known as diffusing gas (ml/min/mm Hg) is known as diffusing capacity.capacity.

Factors affecting diffusion:Factors affecting diffusion:

1.1. Pressure gradient of the gas.Pressure gradient of the gas.

2.2. Solubility of the gas.Solubility of the gas.

3.3. Surface area of the pulmonary Surface area of the pulmonary membrane.membrane.

4.4. Thickness of the pulmonary Thickness of the pulmonary membrane.membrane.

5.5. Ventilation perfusion ratio.Ventilation perfusion ratio.

Pulmonary function testing serves Pulmonary function testing serves 2 important clinical goals: 2 important clinical goals:

(1) categorizing the physiologic (1) categorizing the physiologic impairment from lung disease (i.e., impairment from lung disease (i.e., obstructive, restrictive, etc).obstructive, restrictive, etc).

(2) quantifying the degree of (2) quantifying the degree of functional impairment. functional impairment.

• SpirometrySpirometry : :

The most common pulmonary The most common pulmonary function function test.test.

It is quick, easy and non-It is quick, easy and non-invasive. invasive.

The more common lung function The more common lung function values measured with spirometry values measured with spirometry

areare::

•Forced vital capacity (FVC).Forced vital capacity (FVC).

•Forced expiratory volume (FEV). Forced expiratory volume (FEV).

•Forced expiratory flow 25% to Forced expiratory flow 25% to 75%. 75%.

•Peak expiratory flow (PEF). Peak expiratory flow (PEF).

•Maximum voluntary ventilation. Maximum voluntary ventilation.

Gas diffusion testsGas diffusion tests

Gas diffusion tests include :Gas diffusion tests include :

Carbon monoxide diffusing capacity ,Carbon monoxide diffusing capacity ,

Two different methods are used for Two different methods are used for this test. The single-breath or breath-this test. The single-breath or breath-holding method.holding method.

Body plethysmographyBody plethysmography

Body plethysmography may be used Body plethysmography may be used to measure:to measure:– Total lung capacity (TLC).Total lung capacity (TLC).– Residual volume (RV) .Residual volume (RV) .

Inhalation challenge testsInhalation challenge tests

• These tests are also called These tests are also called provocation studies.provocation studies.

• Inhalation challenge tests are done Inhalation challenge tests are done to measure the response of airways to measure the response of airways to allergens that may be causing to allergens that may be causing asthma.asthma.

Exercise stress testsExercise stress tests

• Exercise stress tests evaluate the Exercise stress tests evaluate the effect of exercise on lung function effect of exercise on lung function tests.tests.

• Spirometry readings are done after Spirometry readings are done after exercise and then again at rest. exercise and then again at rest.

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