RESPIRATION

• External respiration (Lungs):

- Pulmonary ventilation

- Gas exchange (lungs # blood # tissues)

- Gas transport

• Internal respiration (Mitochondria):

- O2 utilization.

Non respiratory functions of the lungs

• Acid base balance

• ACE (Activation : ATI ATII).

• Airway protection

• Vapor loss

• VR help

• Vocalization

Conducting & Respiratory Zones

Pneumocytes Types

Visceral & parietal pleura

Boyle’s Law

Pulmonary Pressures

Diaphragm

Pulmonary Pressures

Importance of Negative IPP

• Lung expansion

• Venous & lymph return

IPP become +ve in:

- Pneumothorax

- Valsalva manouver

Pneumothorax

Respiratory Muscles

Abdominal ms

Mechanism of Inspiration

Mechanism of Respiration

Inspiration Expiration

Process ActivePassive

Thorax +++_ _ _

IPPMore - veLess - ve

Lungs DistentionRecoil

IAP_ _ _+++

Air Rushes inRushes out

Pause

Surfactant

• Lipoprotein (phospholipid, apoproteins & Ca++).

• produced by alveolar type II cells.

• ST so prevents: - collapse of small alveoli in

expiration. - pulmonary edema.

Surfactant deficiency

• RDS• 100 % O2 inhalation.• Occlusion of pulmonary artery or major

bronchus.• Smoking.• Hyperinsulinism e.g baby of diabetic

mother.• Myxedema (hypothyroidism).• Hypocorticism

Physical Properties of the Lungs

–Elasticity. –Surface tension.

–Compliance (Distensibility).

Lung Compliance

• Definition change in lung volume/change in distending

pressure: C= V/P ml/cm H2O

• Types : # Static C ( lungs only, 200). # Dynamic C (lungs + thoracic wall, 110)

Static Lung Compliance

• 200 ml/cmH2O

• Hysteresis loop

• Surfactant conc. during deflation

Inflation

Deflation

Static Lung Compliance

Lung Compliance

++++++++ - - - - - - - - - - - - - -

Aging Lung fibrosisAtheletes Congestion

EmphysemaEdemaRDSPoliomyelitisobesity

Breath Work

• During inspiration or forced expiration.• 3 parts:1- Elastic work (or compliance).2- Air resistance work (medium bronchi).3- Tissue resistance work (viscosity).

• Air way resistance 1/a diameter of bronchi.• Breath work increases in : Surfactant

Compliance & Airway resistance.

Factors affecting bronchi diameters

Factors BronchodilationBronchoconstriction

ANSSymp. (B2 receptors).

Parasymp. (Muscarinic R)

PCO2 ++++++++++ - - - - - - - - - - - - -

RespirationInspiration (Lung expansion)

Expiration

Circadian rhythm

Max. at 6 PMMax. at 6 AM

Temp.Warm Cold

ChemicalsVIPHistamine,adenosine

Pulmonary Ventilation

• it is the air exchange (atmosphere & alveoli).• Normally: air vol. in insp. = air vol. in exp.• Spirometer measures lung volumes &

capacities.• High volumes in tall people, high altitude• low volumes in female, pregnancy, short & smokers

• The amount of air remaining in the lungs at the end of a maximum expiration.

• 1200 ml (30% TLC) during rest ( in exercise).

• in aging & obstructive lung diseases.

• Measured by Helium dilution method

(NOT spirometer).

Residual Volume

Helium Dilution Method

• RV = FRC – ERV

• TLC= FRC + IC

• Continuous gas exchange in between breathes.

• Prevent alveolar collapse.• D of asthma & emphysema ( 70%).• Medicolegal importance: lost in

pneumothorax but minimal air w is sufficient for floatation of lung in water & absent in stillbirth.

RV Significance

Vital Capacity

• Max. vol. of air can be expired after max. inspiration.

• Measured by spirometer.

• 4600 ml ( 2 - 2.5 L/m2).

• Index of pulmonary function & physical fitness.

Factors Affecting VC

+++++++++- - - - - - - - - -

Physiological Males Females

AtheletsPregnancy

Standing Recumbency

Pathological ______Chest/ lung diseases

Dead Space• The part of res. system with no gas

exchange.

• TYPES:

- Anatomical DS

- Alveolar DS - Physiological DS :Anatomical + Alveolar DS

Normally: Physiological = Anatomical DS

Lung diseases: Physiological > Anatomical DS

DS ImportanceWarms,filters & moistens inspired air.

Causes difference in composition between expired air & alveolar air (more CO2 & less O2).

Shallow rapid breath hypoxic hypoxia.

DS Measurement

• Anatomical DS : Fowler method (single breath N2 test).

• Physiological DS:Bohr equation.

• 150 – 167 ml.

• ANS can +++ or - - - - DS

Pulmonary Ventilation Tests

• Pulmonary ventilation ( minute respiratory volume):

RR X TV

• Alveolar ventilation:

RR X (TV – DS)

Pulmonary Function Tests

Pulmonary function tests

Static lung volumes

Dynamic lung volumes

Dynamic lung volumesVolume/unite time

Maximum breathing capacity

Breathing reserve

Timed vital capacity

Maximum flow rate

Maximum breathing capacity(Maximum ventilatory volume)

• Max. vol. of air inspired/expired using the deepest & fastest respiratory effort /min.

• Males: 80-180 L /min

• Females: 60-120 L /min

• Spirometer is used for 15 sec. to avoid fatigue & resp. alkalosis. Then X 4.

• Better index for physical fitness than VC.

Breathing Reserve

• BR = MBC - MV• BR/MBC > 90 %.• Dyspnic index : BR/MBC < 70 %.

• Max. velocity of expired air.• 10 L/m (by peak flowmeter).• --- in obstructive lung diseases.

Maximum flow rate

Timed vital capacity (Forced expiratory volume)

• % vol. of expired air at end of 1st sec.

• FEV1 (FEV/FVC) = 80 %.

• Measured by spirometer.

• Differentiates between restrictive & obstructive lung diseases.

FVC

<80% Normal

>80%

FEV1/FVC ratio

<80% Restrictive

>80% Obstructive

Spirometer Tests

FVC

<80% Normal

>80%

FEV1/FVC ratio

<80% Restrictive

>80% Obstructive

Forced expiratory flow

FEF 25%

FEF 50%

FEF 75%

Normal:70%

Small air ways obstruction <70%