DR.NILESH KATE. M.D.

ASSOCIATE PROFESSOR,DEPARTMENT OF PHYSIOLOGY,

ESIC MEDICAL COLLEGE& HOSPITAL,SEDAM ROAD, GULBARGA.

OBECTIVES Introduction- Mechanics of respiration-Inspiration,

expiration. Muscles involved in pulmonary

pressure. Pressure changes during ventilation. Intrapleural & intrapulmonary

pressure. Measurements. Normal values. Applied aspects.

INTRODUCTION – PASSSAGE OF AIR.

EXTERNAL AND INTERNAL RESPIRATION

EXTERNAL RESPIRATION

External respiration-Ventilation or breathing: air moved in and out of lungs

Exchange of gases -Oxygen and Carbon Dioxide exchange in the lungs

Transport of gases- Oxygen and Carbon Dioxide transported by blood to and from tissues

Internal respiration- Exchange of Oxygen and Carbon Dioxide between tissue and blood

INTERNAL RESPIRATION

Cellular metabolism

Anaerobic glycolysis

Aerobic oxidative metabolism in the mitochondria

EXTERNAL AND INTERNAL RESPIRATION

HEARTTISSUECELL

O2 + FOOD

CO2 + H2O+ ATP

LUNGS

ATMOSPHERE

PULMONARYCIRULATION

SYSTEMICCIRCULATION

AIR IS A COMPRESSABLE GAS WHICH OBEYS BOYLE’S LAW

P1V1 = P2V2

If Volume increases, Pressure must decrease

As lungs expand, pressure inside falls

BAROMETRIC PRESSURE

Mercury Hg

VACUUM

WEIGHT OF COLUMNOF AIR = FORCE

FORCE/AREA = PRESSURESea Level

760 mm

RESPIRATORY PRESSURES TWO TYPES 1) Intraalveolar

pressure or Intra pulmonary pressure (760 mm Hg)

2) Intrapleural pressure or Intrathoracic pressure(758 mm Hg)

Atmospheric pressure.760 mm Hg.

REST PRESSURES

760 MM Hg

758 mmHg

Lungs

Intrapleural pressure

Airways

Atmosphere

Pleural Sac

ThoracicWall

MECHANICS OF BREATHING.

Eupnoea.- Inspiration.- active

process. Expiration.- passive

process.

THE TRANSMURAL PRESSURE GRADIENT INFLATES THE LUNGS

Thoracic cavity larger than lungs Transmural (Across Lung Wall) pressure

gradient holds thoracic wall and lungs in close apposition

This pressure gradient is balanced by the elastic forces in the alveoli producing equilibrium

INSPIRATION

760 mm Hg

754 mmHg

Lungs

Intrapleural pressure

Airways

Atmosphere

Pleural Sac

ThoracicWall

759mm Hg

MECHANISM OF INSPIRATION.

Active process,

Thorax – enlarged by

1) Rib movement,

2) Diaphragmatic movement.

According to property of gasesP= nRT/ V

MECHANISM OF INSPIRATION.

Rib movement.

1 Pump handle movement.(2-6th)

2 Bucket handle movement.(7-10th)

Contraction of external intercostal muscles.

RIB MOVEMENT.

MECHANISM OF INSPIRATION.( CONT..)

Diaphragmatic movement.

downward movement

1.5 cm in eupnoea.

7 cm in deep inspiration.

1cm decent = 200-300 ml air sucked in. (75% of tidal volume)

DIAGRAM

CLINICAL SIGNIFICANCE.

Transection of spinal cord.

above 3rd cervical spinal segment- fatal – needs artificial respiration.below 5th cervical spinal segment – not,

Phrenic nerve that innervate diaphragm ( C 3,4,5)

ACCESSORY MUSCLES OF INSPIRATION.

Scalene & sternocleidomastoid

Intrinsic muscles of larynxAbductors of vocal

cords – post cricoarytenoids – supplied by recurrent laryngeal nerve, branch of vagus.

Paralysis – Inspiratory Stridor.

EXPIRATION

Return of ribs to rest position causes diminishing of lung volume

Return of diaphragm to rest position also causes diminishing of lung volume

Diminishing of lung volume causes pressure in lung to raise to a higher value than atmospheric pressure

Air flows out of the lungs

EXPIRATION

760 mm Hg

758 mmHg

Lungs

Intrapleural pressure

Airways

Atmosphere

Pleural Sac

ThoracicWall

761 mm Hg

MECHANISM OF EXPIRATION.

Anterior abdominal wall muscles.

Internal intercostal muscles.

Accessory muscles of respiration.○ Adductors of vocal

cords.

DIAGRAM

PRESSURE AND VOLUME CHANGES DURING VENTILATION

PRESSURE CHANGES DURING VENTILATION

INTRAPULMONARY PRESSURE,( INTRA-ALVEOLAR PRESSURE)In quite breathing = 0 atmospheric pressure i.e.

760 mm Hg.During inspiration -- 759 mm Hg.During expiration -- 761 mm Hg.

Factors affecting intrapulmonary pressure.Valsalva manoeuvre (+100 mm Hg)Muller’s manoeuvre (-80 mm Hg)

PRESSURE CHANGES DURING VENTILATION

INTRAPLEURAL PRESSURE,(INTRA-THORACIC PRESSURE)In quite breathing (-2 mm Hg.) Reason – balance between ○ Lung – Tendency to collapse due to Intraalveolar

negative pressure.. ○ Thoracic cage – Tendency to expand due to ribs and

elastic tissue.

INTRAPLEURAL PRESSURE,(INTRA-THORACIC PRESSURE)

Factors affecting intra pleural pressure.

PhysiologicalDeep inspiration (-30 mm Hg.)Valsalva manoeuvre (+60-70 mm Hg.)Effect of gravity. (-7 apex, -2 Base)○ Clinical significance – during first part of

inspiration more of inspired gas goes to apices than to bases.

INTRAPLEURAL PRESSURE,(INTRA-THORACIC PRESSURE) cont…

PathologicalEmphysema – loss or decrease in lung elasticity.

decrease in Intrapleural pressure.

leads to expansion of thoracic cage, i.e. barrel shaped chest.

Injury to thoracic wall. (Pneumothorax)

leads to collapse of lung.

MEASUREMENT OF INTRA PLEURAL PRESSURE.

1 NEEDLE IN INTRAPLEURAL SPACE.

2 INTRA-ESOPHAGEAL PRESSURE

APPLIED PHYSIOLOGY.

AIRWAY RESISTANCE

Flow of air depends on the pressure gradient (atmospheric, Pa, and intra-alveolar, Pi) and the airway resistance, R

F = (Pa - Pi)/R

Resistance depends primarily on the radius of the conducting airways

Parasympathetic stimulation constricts, while sympathetic dilates

APPLIED PHYSIOLOGY. What happens when you try to

exhale below the FRC?Dynamic airway collapse”.

What is the closing volume?

Whats the use of knowing mechanics

of breathing.

MECHANICAL VENTILATION

TYPES OF VENTILATORSHand control-○ Bag valve mask○ Continuous flow or anesthesia bag (T-piece)

Mechanical ventilators○ Transport ventilators○ ICU ventilators○ PAP ventilators – for home use in sleep apnoea

Modes of ventilation Breath termination

Volume ventilationPressure ventilation

Breath initiation.Assist Control(ac)Synchronized Intermittent Mandatory

Ventilation (SIMV)Controlled Mechanical Ventilation (CMV)Pressure Support Ventilation.(PSV)Continuous Positive Airway Pressure (CPAP)Positive End Expiratory Pressure. (PEEP)

Resistance and Disease COLDS ASTHMA: Constriction of small airways, excess mucus,

and histamine-induced edema BRONCHITIS : Long term inflammatory response

causing thickened walls and overproduction of mucous EMPHYSEMA: Collapse of smaller airways and

breakdown of alveolar walls ALVEOLAR SURFACE TENSION – Deficiency leads to

increase in negative Intraalveolar pressure and collapse of lung.

SUMMARY Mechanics of respiration-Inspiration,

expiration. Muscles involved in pulmonary

pressure. Pressure changes during ventilation. Intrapleural & intrapulmonary

pressure. Measurements. Normal values. Applied aspects.

THANK YOU.