Pulmonary VentilationPulmonary Ventilation

Week 2Week 2

Dr. Walid DaoudDr. Walid Daoud

A. ProfessorA. Professor

Pulmonary VentilationPulmonary Ventilation

Pulmonary ventilation is mass movement of Pulmonary ventilation is mass movement of air in and out of the lungsair in and out of the lungs..

Forces for Pulmonary VentilationForces for Pulmonary Ventilation::

Pressure gradient between alveoli and Pressure gradient between alveoli and atmosphereatmosphere..

Inspiration occurs when pressure in Inspiration occurs when pressure in atmosphere exceeds pressure in alveoliatmosphere exceeds pressure in alveoli..

Intra-alveolar PressureIntra-alveolar Pressure

At sea level, atm. pressure is 760 mmHg and At sea level, atm. pressure is 760 mmHg and all pressures in the respiratory system are all pressures in the respiratory system are expressed relative to atmospheric pressureexpressed relative to atmospheric pressure..

--During inspiration Palv. = - 1 mmHgDuring inspiration Palv. = - 1 mmHg

--During expiration Palv. = + 1 mmHgDuring expiration Palv. = + 1 mmHg

--At ends of inspiration & expiration= 0 mmHgAt ends of inspiration & expiration= 0 mmHg

Changes in intra-alveolar pressure are caused Changes in intra-alveolar pressure are caused by changes in volumes of lungsby changes in volumes of lungs..

Intra-pleural PressureIntra-pleural Pressure

It is the pressure inside pleural spaceIt is the pressure inside pleural space..

It is always negative under normal conditionsIt is always negative under normal conditions..

. .At end of normal expiration= - 4 mmHgAt end of normal expiration= - 4 mmHg

. .At end of normal inspiration= -6 to -8 mmHgAt end of normal inspiration= -6 to -8 mmHg

. .During forced inpiration with glottis closedDuring forced inpiration with glottis closed

- = - = 3030 to - 40 mmHg (Muller experiment)to - 40 mmHg (Muller experiment)..

. .During forced expiration with glottis closedDuring forced expiration with glottis closed

+ = + = 5050 mmHg (Valsalva experimentmmHg (Valsalva experiment))..

Importance of negative intra-Importance of negative intra-pleural pressurepleural pressure

- -It helps lung expansionIt helps lung expansion..

- -It helps venous and lymphatic return to theIt helps venous and lymphatic return to the

heartheart..

- -It is a measure of lung elasticity (recoilIt is a measure of lung elasticity (recoil

pressurepressure.(.(

Transpulmonary PressureTranspulmonary Pressure

It is difference between intralveolar and It is difference between intralveolar and intrapleural pressuresintrapleural pressures..

= =Palv. – PplPalv. – Ppl

= =00-) – -) – 44 = ( = ( 44 mmHgmmHg

Transpulmonary pressure is called Transpulmonary pressure is called distending pressure which is the force distending pressure which is the force acting to expand the lung against acting to expand the lung against elastic recoil of the stretched lungelastic recoil of the stretched lung..

Causes of Negative Intrapleural pressureCauses of Negative Intrapleural pressure

The negativity is due to continuous tendencyThe negativity is due to continuous tendency

of lungs to recoil inward against continuous of lungs to recoil inward against continuous tendency of chest wall to expand outward to tendency of chest wall to expand outward to reach their relaxation volumereach their relaxation volume..

Causes of recoil tendency of lungsCauses of recoil tendency of lungs::

11 - -Elastic tissues of lungsElastic tissues of lungs

22 - -Surface tension of fluid lining the alveoliSurface tension of fluid lining the alveoli..

Pulmonary SurfactantPulmonary SurfactantA detergent -like substance secreted byA detergent -like substance secreted by type II alveolar cellstype II alveolar cells..NatureNature::

Complex mixture of phospholipid dipalmitoyl Complex mixture of phospholipid dipalmitoyl lecithin, apoproteins and calcium ionslecithin, apoproteins and calcium ions..FunctionsFunctions::

- -Facilitation of lung expansionFacilitation of lung expansion.. - -Prevention of alveolar collapse during expPrevention of alveolar collapse during exp..

- -Prevention of pulmonary edemaPrevention of pulmonary edema..

Surfactant DeficiencySurfactant Deficiency

11 - -Respiratory distress syndrome (RDS)Respiratory distress syndrome (RDS)..

22 - -Long-term inhalation of 100% oxygenLong-term inhalation of 100% oxygen..

33 - -Occlusion of one pulmonary arteryOcclusion of one pulmonary artery..

44 - -Cigarette smokingCigarette smoking..

55 - -HypothyroidismHypothyroidism..

66 - -HypocoticismHypocoticism..

77 - -HyperinsulinismHyperinsulinism..

Mechanism of RespirationMechanism of Respiration

. .InspirationInspiration..

Active processActive process..

. .ExpirationExpiration..

Resting expiration is a passive processResting expiration is a passive process

while forced expiration is an active onewhile forced expiration is an active one..

SpirometrySpirometry

SpirometerSpirometer

ItIt is a device to measure lung volumes is a device to measure lung volumes and capacitiesand capacities . .

SpirometrySpirometry

ItIt is the used techniqueis the used technique. .

SpirogramSpirogram

ItIt is the recordingis the recording..

Pulmonary VolumesPulmonary Volumes

11 - -Tidal volume (VT)Tidal volume (VT)..

22 - -Inspiratory reserve volume (IRV)Inspiratory reserve volume (IRV)..

33 - -Expiratory reserve volume (ERV)Expiratory reserve volume (ERV)..

44 - -Residual volume (RV)Residual volume (RV)..

RV can not be measured by spirometryRV can not be measured by spirometry

but can be calculated by helium-dilution but can be calculated by helium-dilution method method..

Pulmonary CapacitiesPulmonary Capacities

11 - -Inspiratory capacity (IC)Inspiratory capacity (IC)..

22 - -Vital capacity (VC)Vital capacity (VC)..

33 - -Functional residual capacity (FRC)Functional residual capacity (FRC)..

44 - -Total lung capacity (TLC)Total lung capacity (TLC)..

FRC and TLC can not be measured by FRC and TLC can not be measured by spirometry spirometry..

Factors affecting vital capacityFactors affecting vital capacity

Physiological variationsPhysiological variations::

11 - -VC increases inVC increases in::

Males, athletes and standing positionMales, athletes and standing position..

22 - -VC decreases inVC decreases in::

Females, pregnancy and recumbentFemales, pregnancy and recumbent

positionposition..

Factors affecting vital capacityFactors affecting vital capacityClinical significance of VCClinical significance of VC::

VC is an index of lung function and strengthVC is an index of lung function and strength

of respiratory musclesof respiratory muscles::

11 - -Paralysis or myositis of resp. musclesParalysis or myositis of resp. muscles..

22 - -Bone deformities e.g, kyphosis or scoliosisBone deformities e.g, kyphosis or scoliosis..

33 - -Loss of lung elasticity e.g, emphysemaLoss of lung elasticity e.g, emphysema..

44 - -Restrictive lung diseases e.g, lung fibrosisRestrictive lung diseases e.g, lung fibrosis..

55 - -Obstructive lung diseases e.g, asthmaObstructive lung diseases e.g, asthma..

66 - -Abdominal tumorsAbdominal tumors..

Timed Vital capacityTimed Vital capacity - -Forced expiratory volume in first Forced expiratory volume in first

second (FEV1)second (FEV1).. - -Forced vital capacity (FVC)Forced vital capacity (FVC)..

Normally FEV1 = 80% of FVCNormally FEV1 = 80% of FVCIn diseasesIn diseases::

--Restrictive lung diseases: lung fibrosisRestrictive lung diseases: lung fibrosis:: . . Both FEV1 & FVC are reducedBoth FEV1 & FVC are reduced..

. . FEV1/FVC % is normalFEV1/FVC % is normal..--Obstructive lung diseases: brochial Obstructive lung diseases: brochial

asthmaasthma.. . . FEV1 is reduced more than FVCFEV1 is reduced more than FVC

. . FEV1/FVC % is lowFEV1/FVC % is low..