exactly 41 - Rate and rhythm of breathing. Pulmonary and alveolar ventilation. Elastic and nonelastic resistance to breathing. Air flow during breathing. The work of breathing. Static lung volumes and capacities and their functional importance. Anatomical and physiological dead space. Estimation of external respiration.

sections

rate and rhythm of breathing

pulmonary and alveolar ventilation

compliance of lungs

work of breathing

elastic and non-elastic resistance

rate

• Alveolar ventilation per minute is the total volume of new air entering the alveoli and adjacent gas exchange areas each minute.

• It is equal to the respiratory rate x the amount of new air that enters the areas with each breath.

• Va= Frequency x (VT – VD)

• Va = Volume of alveolar ventilation per minute

• Frequency = frequency of respiration per minute

• VT= Tidal volume- volume of air inspired or expired per inspiration at rest- 500 ml

• VD= physiologic dead space volume

rhythm

• Eupnoea Normal respiration rate.

• Polypnoea- Rapid respiration rate.

• Tachypnoea- Very rapid and superficial respiration.

• Hyperpnoea- Deep and rapid respiration.

• Olygopnoea- Abnormally infrequent respiration.

• Beadypnoea -Abnormally slow respiration.

• Dysonoea- Difficult and laboured breathing.

• Apnea- Termination of breathing

• Asphyxia- suffocation and lack of oxygen in respired air

asphyxia

suffocation and lack of oxygen in respired air

apnea

termination of breathing

Dysonoea

difficult and laboured breathing

beadypnoea

abnormally slow respiration

olygopnoea

abnormally infrequent respiration

hyperpnoea

deep and rapid respiration

tachypnoea

very rapid and superficial respiration

polypnoea

rapid respiration rate

eupnoea

normal respiration rate

pulmonary and alveolar ventilation

• Pulmonary ventilation -inflow and outflow of air between the atmosphere and lung alveoli.

• Lungs can expand and contract in 2 ways.

  • Downward and upward movement of the diaphragm to lengthen or shorten the chest cavity.

  • Elevation and depression of the ribs to increase/decrease anteroposterior diameter of the chest cavity

• The main purpose for pulmonary ventilation is to continually renew the air in the gas exchange areas.

• These areas include the alveoli, alveolar sacs, alveolar ducts, and respiratory bronchioles. The rate at which the new air reaches these areas is called alveolar ventilation.

• Some air inhaled does not reach the gas exchange areas but simply fills the passages where gas exchange does not occur.

• Such as the nose, pharynx, and trachea. This air is called dead space air.

• On expiration, the air in the dead space is expired first, before any air from the alveoli.

• Therefore the dead space is very disadvantageous for removing expiratory gases from the lungs.

compliance of lungs

• change in lung volume per unit change in transpulmonary pressure

• Dependent on:

  • Elastic forces of the lung tissue itself- elastin and collagen fibres

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

work of breathing

• Work of breathing = energy needed to inhale or exhale a breathing gas.

• types of work:

  • Elastic work: work required to expand the lungs against the lung and chest elastic forces

  • Resistance work: work required to overcome the viscosity of the lungs and chest wall structures

  • Airway resistance work: work required to overcome airway resistance to movement of air into the lungs

elastic and non-elastic resistance

• Work against elastic resistance:

  • this work is usually generated during inhalation phase - stored as potential energy which is released during exhalation.

• Work against non-elastic resistance

  • pressure difference is required to overcome the frictional resistance to gas flow due to viscosity (major reason for non-elastic resistance)

  • to provide movement of non-elastic components of the airway tissues to make space for pulmonary volume change

sections

pulmonary volumes

pulmonary capacities

anatomical and physiological dead space

external respiration and estimation

pulmonary volumes

1. tidal volume: the volume of air that goes in and out of the lungs with each normal breath (0.5L)

2. inspiratory reserve volume: the max volume of air that can be inhaled after normal tidal volume inhalation (3L)

3. expiratory reserve volume: the max volume of air that can be exhaled after normal tidal volume inhalation (0.7-1L)

4. residual volume: volume of air remaining in the lungs after max exhalation (~1.2L)

5. Minute volume: the amount of air breathed during a minute while the person is at rest, 1216 breaths/minute, ~ 6-8 L/minute

6. Inspiratory capacity

7. TVC- theoretical vital capacity- calculed from body heigh using a coefficient

8. Vital capacity- volume change that occurs between max inhalation and max exhalation-

pulmonary capacities

• pulmonary capacities are a combination of two or more lung volumes together and are used in describing events in the pulmonary cycle.

• The important capacities are:

  1. Inspiratory capacity = tidal volume + inspiratory reserve volume(3.5L) IC=TV +IRV

  2. Functional residual capacity = expiratory reserve volume + residual volume (~2300ml)

  3. Vital capacity = inspiratory reserve volume + tidal volume + expiratory reserve volume the max.~4600ml VC=TV+IRV+ERV

  4. Total lung capacity = vital capacity + residual volume (~5800ml)

all of these just include tidal volume,residual volume, vital capacity and inspiratory and expiratory reserve volume

anatomical and physiological dead space

• Source of the air that’s inspired does not reach the sides of gas exchange instead this air fills up spaces – respiratory passages which do not participate in gas exchange.

• Theses passages include- the nose, pharynx and trachea.

  1. Anatomical dead space: it is the portion of airways which conducts gas to the alveoli but no gas exchange is possible in these spaces.

  2. Alveolar/pulmonary dead space: it is the sum of alveoli which have little or no blood flowing through their pulmonary capillaries and thus cannot take part in gas exchange. It is very low in normal healthy persons but can increase in lung diseases.

• The total dead space (physiological dead space) =sum of the anatomical dead space plus the alveolar dead space.

external respiration and estimation

• External respiration refers to gas exchange across the respiratory membrane in the lungs between alveoli and venous blood (deoxygenated blood).

• As venous blood flows through the pulmonary capillaries

• oxygen diffuses into the blood and carbon dioxide diffuses into the alveolar gas.

• Each gas diffuses down its own partial pressure gradient - that is, from a high to low partial pressure.