Lecture #3 Pulmonary system: response to exercise

Why do we breath?

• primarily to get rid of CO2

• also aerobic metabolism → break down food, get energy

What 2 things does out pulmonary system do?

ventilation

Respiration

Ventilation allows respiration to occur

What is ventilation?

• Breathing

• The process of inspiration and expiration

• Mechanical movement of gases into and out of the lungs

Inspiration

• active process

• increased volume inside thoracic cavity

• decreased pressure

• air comes in

Expiration

• usually a passive process

• relaxation of inspiratory muscles

• elastic recoil of lungs & surrounding tissues

• decreased volume inside thoracic cavity

• increased pressure

• air goes out

Process of inspiration and expiration

Boyle’s Law Equation

Muscles of Ventilation: Inspiration

Primary Muscles:

• diaphragm

• external intercostals

Accessory Muscles:

• SCM

• Scalenes

• Upper trap

• pec major & minor

• serratus anterior & rhomboids

• lats 

• serratus posterior superior

• thoracic erector spinae

Muscles of Ventilation: expiration

Primary Muscles: there are none!

• passive process in which there is relaxation of inspiratory muscles and elastic recoil of the lungs

Muscles of forced expiration:

• abdominals

• internal intercostals

Why do people do this?

Stabilizes the lats at the insertion so the origin can help with breathing

What moves first when you breath?

your abdomen

Usual Breath Sequence

1st: subtle rise of the upper abdomen

2nd: lateral costal expansion of the lower chest

3rd: subtle rise of the upper chest, mainly superior and anterior

Energy Cost of Breathing

• healthy people: 11-15% of energy towards muscles of ventilation

• COPD: 40% of energy used

What are the implications of COPD on functional mobility?

When energy is going to ventilatory muscles, it is NOT going to the limbs so…

• fatigued

• short of breath

• don’t want to do much physical activity

• get tired quicker

If the body has to chose between breathing or completing an action or activity, what will it chose?

breathing

What 3 important lung properties facilitate ventilation?

1. compliance: stiffness of lung tissue

2. Elastic recoil: ability to return to its initial size after being distended

3. surface tension: create a force that helps the lungs recoil during exhalation

What is pulmonary fibrous (fibrotic lungs)?

• people have low compliance or low distensibility of lung tissue (can’t inflate)

• work of breathing increases because of inability to increase lung volume

What is emphysema?

• over time, alveoli become overstretching and lose their elastic recoil

• air becomes trapped in lungs and people with emphysema have a hard time blowing air out

Babies and Infant Respiratory Distress Syndrome

• premature babies who lack surfactant are at increased risk for infant IRDS

• surfactant aides in decreasing surface tension in the alveoli

• without surfactant, alveoli collapse

Airway Turbulence

• collision of air molecules

• upper airway is responsible for most of the airway resistance

Additional causes:

• pathologies- asthma/bronchitis

• bronchial constriction

• mucus & edema

Tidal Volume (TV)

• volume of air inspired and expired each normal breath

• average: 0.4-1.0L per breath

Inspiratory Reserve Volume (IRV)

• maximum inspiration at the end of a tidal inspiration

• Avg: 2.5-3.5L

Expiratory Reserve Volume (ERV)

• maximum expiration at the end of a tidal expiration

• Avg: 2.5-3.5L

Vital Capacity

VC = TV+IRV+ERV

• greatest amount of air that can be expired after a maximal inspiration

• avg: male 4-5L, female 0.8-1.2L

Residual Lung Volume (RLV)

• volume in lungs after max expiration

• avg: male 0.9-1.4L, female 3-4L

Total Lung Capacity

TLC= VC+RLV

• volume in lungs after maximal inspiration

Inspiratory Capacity (IC)

IC= TV+IRV

• maximum volume inspired starting from a resting inspiratory position

Functional Residual Capacity (FRC)

FRC= RLV+ ERV

• volume in lungs after tidal expiration

Lung Volume Chart

What is responsible for keeping your lungs from collapsing?

residual volume

Obstructive Lung Disease

• difficulty exhaling all air from the lungs

• poor elastic recoil of alveoli (emphysema)

• chronic inflammation of airways (bronchitis)

• narrowing of airways (asthma)

Restrictive Lung Disease

• difficulty filling lungs with air due to inability to expand lungs

• low distensibility or stuff lung tissue (pulmonary fibrosis)

• postural restrictions limiting ability to expand (severe scoliosis or morbid obesity)

Forced Vital Capacity (FVC)

amount of air that can be forcefully exhaled as quickly as possible

Forced Expiratory Volume (FEV1)

Volume of air forcefully expired in the 1st second of FVC

• Normal: FEV1 > 2.0 liters

• Severe obstruction: FEV1 <1.0 liters

FEV1/FVC

80% or greater is considered normal

What would breathing be like?

hard

• diaphragm is very low

• lungs are narrow → not filling well

respiration

• gas exchange through the process of simple diffusion

• replenishment of oxygen for energy production and removal of CO2

Conduction zone pulmonary anatomy

• trachea

• bronchiole tree

• bronchioles

Respiratory Zone

• bronchioles

• alveolar ducts

• alveolli

Pulmonary diffusion

The process by which gases are exchanged across the respiratory membrane in the alveoli

1. replenishes blood’s O2 supply that has been depleted for oxidative energy production

2. removes CO2 from returning venous blood

Pulmonary circulation picture

Pulmonary diffusion and exercise

• oxygen diffuses from high pressure to low pressure

• oxygen diffusion rate increases with exercise

• when venous oxygen is depleted due to muscle uptake of oxygen, oxygen exchange at the alveoli is facilitated due to an increased pressure gradient

oxygen transport

bound to hemoglobin (>98%) or dissolved in plasma (<2%)

What determines the O2 carrying capacity of blood?

Hemoglobin

This is lower in people with anemia

Factors affecting oxygen uptake and delivery

• oxygen content of blood

• amount of blood flow

• local conditions within the muscle

  • increased H+ acidity and temperature of a muscle favors oxygen unloading in the muscle

Central and peripheral regulators of ventilation

Chemoreceptors

senses changes in blood pH, CO2, O2

Hypothalamus and Limbic system function

pain and emotions

What is normal ventilation driven by?

Co2 levels in the arteries as detected by peripheral chemoreceptors

Hypercapnia

chronically high CO2 levels in the blood

• people with severe COPD

O2 receptors become the primary means of regulating ventilation

What happens if you give someone with COPD O2?

increased O2 → decreased hypoxic drive → decreased drive to breath (ventilation) = increased risk of respiratory failure

what are the 3 Lung Receptors?

1. irritant

2. stretch

3. J receptor

Irritant receptor

initiates cough reflex, bronchial constriction, and increased respirator rate

Stretch receptor

protects the lung from excessive inflation during exercise

J receptor

senses pulmonary capillary pressures and congestion

• this initiates rapid, shallow breathing, and produces the cough reflex with fluid accumulation during pulmonary edema and pleural effusion

Joint and muscle receptors

• change in movement at the joints of the extremities → increased ventilation

• during exercise, there is an initial abrupt increase in ventilation due to signals from the joint and muscle receptors

What are 4 things that happen for pulmonary ventilation during dynamic exercise?

1. neurally-mediated increase in ventilation

2. increased metabolism generates CO2 and H+ 

   • stimulate chemoreceptors

3. Stimulated receptors increase in ventilation

4. Pulmonary ventilation returns to normal at a slower rate when exercise ceases

Ventilatory response graph

Ventilatory threshold

• point when ventilation increases disproportionately to oxygen consumption

• occurs at approximately the same point lactate begins to accumulate in the blood

• lactic acid is buffered by sodium bicarbonate

• ventilation increases due to increased CO2 stimulation the chemoreceptor

What are 3 breathing irregularities during exercise?

• dyspnea

• hyperventilation

• valsalva maneuver

Dyspnea (DOE)

exertional breathlessness caused by inability to readjust the blood PCO2 and H+

Hyperventilation

an increase in ventilation that exceeds the metabolic need for oxygen

Valsalva maneuver

a breathing technique where air is trapped in the lungs against a closed glottis, and intra-abdominal and intrathoracic pressure are increased

Respiratory Regulation of Acid-Base Balance

• Excess H+ (decreased pH) impairs muscle contractility and ATP generation

• increased H+ concentrations stimulate respiratory centers to remove CO2

• whenever H+ levels begin to rise, bicarbonate ions can buffer the H+ to prevent acidosis

• this increased CO2 to be removed through ventilation

Arterial blood gases

Normal:

• pH: 7.35-7.45

must buffer hydrogen ions to maintain this

What happens when a person fails to maintain acid-base balance?

they go on ventilatory system to get CO2 out or keep airways open

What are the benefits of mechanical ventilation?

decreased work of breathing (muscles rest), helps get oxygen into the body and CO2 out

What are the risks of mechanical ventilation?

Barotrauma, infection, difficulty weaning

Non-invasive positive- pressure ventilation CPAP and BiPAP

Invasive mechanical ventilation