Pulmonary Systems

Chapter 9 in text

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Pulmonary Systems Review

Structure

Function

Pulmonary Structure and Function

Pulmonary Structure and Function

• The ventilatory system– Supplies oxygen required in metabolism – Eliminates carbon dioxide produced in

metabolism – Regulates hydrogen ion concentration [H+]

to maintain acid-base balance

Mechanics of Breathing

Breathing• At rest– Air in Trachea-

humidified and brought to body temperature

divides into 2 branches lungs

– Lungs hold 4-6 litres of ambient air- huge surface area

– 300 million alveoli– 250 ml oxygen in and

200 ml Carbon dioxide out each minute

Inspiration• Ribs rise• Diaphragm contracts

(flattens)

Moves downward (10cm)• Thoracic volume• Air in lungs expands • Pressure

to 5 mm Hg below atmospheric pressure

• Difference between outside air and lungs = air is sucked in until pressure inside and out is the same

Expiration

• Ribs move back down• Diaphragm relaxes (rises)• Thoracic volume• Pressure • Difference between outside air and lungs = air

is pushed out until pressure inside and out is the same

Lung Volumes

Lung VolumesLung Volumes

• Static lung volume tests– Evaluate the dimensional component for

air movement within the pulmonary tract, and impose no time limitation on the subject

• Dynamic lung volume tests– Evaluate the power component of

pulmonary performance during different phases of the ventilatory excursion

Spirometry

• Static and Dynamic lung volumes are measured using a spirometer

Static Lung Volumes

Dynamic lung volumes

• Depend on Volume of air moved

and the

• Speed of air movement

FEV/FVC ratio

MVV

FEV/FVC Ratio

• Forced Expiratory Volume

• Forced Vital Capacity

• Ratio tells us the speed at which air can be forced out of lungs

• Normal = 85% FVC can be expired in 1 second.

Maximal Voluntary Ventilation

• Breath as hard and fast as you can for 15 seconds

• Multiply by 4• And you have Maximal Voluntary

Ventilation• MVV-

– Males:140-180 Litres– Females: 80-120 Litres– Elite athletes up to 240 Litres

Minute Ventilation

At Rest• 12 breaths per minute• Tidal volume = 0.5L per

breath• = 6 Litres of air breathed

p/minDuring Exercise• 50 breaths p/ minute• Tidal Volume = 2 L per

breath• = 100L p/min

Alveolar VentilationAlveolar Ventilation

• Minute ventilation is just total amount of air

• Alveolar ventilation refers to the portion of minute ventilation that mixes with the air in the alveolar chambers

• Minute ventilation minus anatomical dead space (150-200 ml)- the air that is in the trachea, bronchi etc

Alveolar Ventilation =

Minute ventilation (TV x breathing rate) – dead space

Gas exchange

Gas Exchange in the Body Gas Exchange in the Body

• The exchange of gases between the lungs and blood, and their movement at the tissue level, takes place passively by diffusion

Oxygen Transport in the Blood Oxygen Transport in the Blood

• Blood transports oxygen in 2 ways:

• In physical solution — Dissolved in the fluid portion of the blood

• Combined with hemoglobin — In loose combination with the iron-protein hemoglobin molecule in the red blood cell

CO2 Transport in Blood CO2 Transport in Blood

• In physical solution– (~7%) dissolved in the fluid portion of the

blood

• As carbamino compounds – (~20%) in loose combination with amino acid

molecules of blood proteins

• As bicarbonate– (~73%) combines with water to form carbonic

acid

Regulation of Pulmonary VentilationRegulation of Pulmonary Ventilation

Regulation at rest: Plasma Pco2 and H+ Concentration

Regulation at rest: Plasma Pco2 and H+ Concentration

• The partial pressure of CO2 provides the most potent respiratory stimulus at rest

• [H+] in the cerebrospinal fluid bathing the central chemoreceptors provides a secondary stimulus driving inspiration

Ventilatory Regulation During Exercise

Ventilatory Regulation During Exercise

• Chemical control– Po2

– Pco2

– [H+]

• Nonchemical control

• Neurogenic factors– Cortical influence– Peripheral influence

Ventilation in steady rate exercise

Ventilation in steady rate exercise

• Of oxygen ( V E/ V O2)

– Quantity of air breathed per amount of oxygen consumed

– Remains relatively constant during steady-rate exercise- 25 L air breathed per 1L o2 consumed at 55% Vo2 max

• Of carbon dioxide ( V E/ V CO2)

– Remains relatively constant during steady-rate exercise

Ventilatory ThresholdVentilatory Threshold

• The point at which pulmonary ventilation increases disproportionately with oxygen uptake during graded exercise

• The excess ventilation relates to the increased CO2 production associated with buffering of lactic acid

Pulmonary adaptations to Exercise

Chapter 13

Adaptations to

Maximal exercise

• Minute ventilation increases

• Increased oxygen uptake

Submaximal Exercise

• Ventilatory muscles stronger

• Ventilatory equivalent for oxygen

( V E/ V O2) reduces indicates breathing efficiency– This leads to

• Reduced fatigue in ventilatory muscles• O2 that would have been used by those muscles

can be used by skeletal muscle.

Pulmonary Adaptations

• Increased tidal volume

• Decreased breathing frequency

• Increased time between breaths (Increased time for oxygen to get into bloodstream)

• Therefore less oxygen in exhaled air