RESPIRATION

Dr. Victoria G. GiangoChair, Dept. of Physiology

GOALS OF RESPIRATION

1. To provide oxygen to the tissues2. To remove carbon dioxide

MAJOR FUNCTIONAL EVENTS OF RESPIRATION

1. Pulmonary Ventilation – inflow and outflow of air between the atmosphere and lung alveoli

2. Diffusion of oxygen and carbon dioxide between the alveoli and the blood

3. Transport of oxygen and carbon dioxide in the blood and body fluids to and from the cells.

4. Regulation of Ventilation

RESPIRATORY SYSTEM – made up of:

1. Gas exchanging organ – Lungs2. Pump that ventilates the lungs – consists

of:a. Chest wallb. Respiratory Muscles – increase and decrease the size of the thoracic cavityc. Areas in the Brain – control the musclesd. Tracts and Nerves – connect the brain

to the muscles

MUSCLES OF INSPIRATION1. Diaphragm – 75%2. External intercostals3. Sternocleidomastoid4. Serratus (anterior)5. Scaleni

MUSCLES OF EXPIRATION

1. Internal intercostals

2. Abdominal recti

COMPLIANCE The extent to which the lungs

expand for each unit increase in transpulmonary pressure

Both lungs – 200 ml of air per cm of water transpulmonary pressure

Thorax and lungs together – 110 ml per cm of water transpulmonary pressure

FACTORS THAT DETERMINE COMPLIANCE:

1. Elastic forces of the lung tissue itself (elastin and collagen fibers interwoven among the lung parenchyma

2. Elastic forces caused by surface tension of the fluid that lines the inside walls of the alveoli and other lung spaces

Surface Tension accounts for 2/3 of total elastic forces in normal lung

SURFACTANT

- Surface active agent, when it spreads over the surface of a fluid, it reduces the surface tension

- Secreted by type II alveolar epithelial cells- Complex mixture of phospholipids,

proteins and ions- dipalmitoylphosphatidylcholine- surfactant apoproteins- calcium ions

SURFACTANT

1. Lowers surface tension2. Stabilizes the size of the alveoli3. Prevents the accumulation of

fluid

Surface Tension of Different watery fluids:

72 dynes/cm – pure water 50 dynes/cm – normal fluids lining

the alveoli but without surfactant 5 to 30 dynes/cm – fluids lining the

alveoli with surfactant included.

-Stabilize the sizes of the alveoli- inversely affected by radius of the alveolus- begin to be secreted between the 6th and 7th month of gestation

Collapse Pressure of Occluded Alveoli Caused by Surface Tension

Pressure = 2 x surface tension Radius

Respiratory Distress Syndrome of the Newborn - caused by little or no surfactant. The lungs of babies have extreme collapse tendencies, 30 mmHg or more

“WORK” OF BREATHING(work of inspiration)

1. Compliance work or Elastic work – that required to expand the lungs against the lung and chest elastic forces

2. Tissue resistance work – required to overcome the viscosity of the lung and chest wall structures

3. Airway resistance work – required to overcome airway resistance to movement of air into the lungs

Compliance and Tissue resistance work – increased by diseases that cause fibrosis of the lungs as in tuberculosis

Airway resistance work – increased by diseases that obstruct the airways as in asthma

3 to 5% of the total energy expended by the body is required to energize the pulmonary ventilatory process

LUNG VOLUMES

1. Tidal Volume (Vt) – is the volume of air inspired or expired with each normal breath - 500 ml

2. Inspiratory Reserve Volume (IRV) – the extra volume of air that can be inspired over and above the normal tidal volume when the person inspires with full force – 3000ml

3. Expiratory Reserve Volume (ERV)– is the maximum extra volume of air that can be expired by forceful expiration after the end of the normal tidal expiration - 1100 ml

4. Residual Volume (RV) – the volume of air remaining in the lungs after the most forceful expiration – 1200ml

CAPACITIES1. Inspiratory Capacity (IC) I C = Vt + IRV = 3, 500 ml2. Functional Residual Capacity (FRC) = 2,300

mlFRC = ERV + RV

3. Vital Capacity (VC) VC = IRV + Vt + ERV

= IC + ERV4. Total Lung Capacity (TLC) = 5, 800ml

TLC = Vt + IRV + ERV + RV = IC + FRC = VC + RV

HELIUM DILUTION METHOD – determination Functional Residual capacity, Residual volume, Total Lung Capacity

FRC = Initial conc. Of Helium in spirometer

Final conc. Of Helium

FRC = CiHe __ - 1 ViSpir

CfHe

RV = FRC – REVTLC = FRC + IC

FACTORS AFFECTING LUNG VOLUMES AND VITAL

CAPACITY

1. Body build or physique2. Position of the body3. Strength of respiratory muscles4. Pulmonary compliance

Minute Respiratory Volumeis the total amount of new moved into

the respiratory passages each minute

= Tidal volume x Respiratory rate/minute

= 500 x 12

Alveolar Ventilation

Total volume of new air entering the the alveoli and adjacent gas exchange areas each minute

V A= Freq . (VT – VD )

Respiratory Dead Space – space in the conducting zone of the airways occupied by gas that does not exchange with the blood in the pulmonary vessels

Vital Capacity – the largest volume of air that can be expired after a maximal inspiratory effort. It is frequently measured clinically as an index of pulmonary function. It gives useful information about the strength of the respiratory muscles and other pulmonary functions.

Maximal Voluntary Ventilation –(MVV) or Maximal breathing Capacity – largest volume of gas that can be moved into and out of the lungs in 1 minute by voluntary effort – 125 – 170 L/min.

ANATOMIC DEAD SPACE – space of the respiratory system besides the alveoli and other gas exchange areasDead space air = 15 0 m

PHYSIOLOGIC DEAD SPACE – alveolar dead space and anatomic dead space

In normal person the Anatomic and Physiologic dead spaces are nearly equal

In person with partially functional or nonfunctional alveoli the Physiologic dead space is much as 10 x the volume of Anatomic dead space

FUNCTIONS OF THE RESPIRATORY PASSAGEWAYS

ANATOMY:Trachea, Bronchi, Bronchioles

between trachea and alveolar sacs airways divide 23 times – first 16 generations made up of bronchi, bronchioles, and terminal bronchioles.

Last 7 generations are made up of respiratory bronchioles, alveolar ducts, and alveoli

Muscular Wall of the Bronchi and Bronchioles and its Control

Resistance to Airflow in the Bronchial TreeNervous and Local Control of the Bronchiolar

Musculature – “Sympathetic” Dilatation of the Bronchioles

Parasympathetic constriction of the Bronchioles

Local Secretory Factors Often Cause Bronchiolar Constriction

- Histamine- Slow Reacting Substance of

Anaphylaxis

FUNCTIONS:

1. Mucous Lining of the Respiratory Passageways and Action of Cilia to Clear the Passageways

2. Cough Reflex – Vagus Nervea. Irritationb. Inspiration – 2.5 liters of air are rapidly inspired. Epiglottis closes and the vocal cords shut tightly to entrap the air within the lungs.c. Compression – abdominal muscles contract forcefully. Pushing against the diaphragm. Pressure rises to 100 mmHg or more.d. Expulsion – air under high pressure in the lungs explude outward

3. Sneeze Reflex – Trigeminal NerveUvula is depressed so large amounts

of air pass directly through the nose helping to clear the nasal passages of foreign matter,

4. Normal Respiratory Functions of the Nose – Air Conditioning Function of the Upper Respiratory Passages

a. Air is warmedb. Air is Humidifiedc. Air is Filtered

- turbulent precipitation- gravitational precipitation

5. Vocalization

a. Phonation – larynx is adapted to act as vibrator (vibrating element is the vocal cord)

b. Vocalization and resonance – organs of articulation are the lips, tongue, and soft palate