Mechanics of Breathing

Introduction Pulmonary ventilation: Moving air into and out of the lungs Breathing Inspiration = moving air into the lungs Expiration = moving air out of lungs

Pressure Relationships Intrapulmonary pressure Pressure within the alveoli (lungs) Changes with phases of breathing Always equalizes itself with atmospheric pressure Intrapleural pressure Pressure within intrapleural space Always 4mmHg less than intrapulmonary pressure

Atalectasis Any conditions that causes intrapulmonary pressure to equal intrapleural pressure will cause the lungs to collapse This means they lose the ability to move air since there is NO more pressure difference pneumothorax – air in the intrapleural space due to trauma

Atelectasis

Pulmonary ventilation Question: Why does breathing happen? ONLY acceptable answer: Volume changes lead to pressure changes which lead to the flow of gases to equalize the pressure

Inspiration Main inspiratory muscles Diaphragm & external intercostals Thoracic dimensions change to increase volume of thoracic cavity by 0.5 liters Intrapulmonary pressure drops 1-3 mmHg and air rushes info normal quiet inspiration A deep forced inspiration requires activation of accessory muscles

Expiration A passive process dependent on natural lung elasticity The lungs recoil, volume decreases, alveoli compress, intrapulmonary pressure rises, gas outflows to equalize the pressure with atmospheric pressure Forced expiration requires contraction of muscles of the abdominal wall

Physical factors influencing Pulmonary ventilation can be influenced by 4 physical factors Respiratory passage resistance Lung compliance Lung elasticity Alveolar surface tension forces

Respiratory passage resistance Friction as air moves through passages Smooth muscle bronchoconstriction and, Local accumulations of mucus, infectious material, and tumors will cause the air flow to be reduced Disorders such as asthma

Lung compliance The ease with which lungs can readily expand Affected by the elasticity of the lungs and the thoracic cage Diminished by 3 main factors: Fibrosis of the lung tissue Ossification and/or muscle paralysis impairs flexibility of the thoracic cage Blockage of the passageways

Lung fibrosis

Lung Elasticity Essential for normal expiration Emphysema: tissue becomes less elastic and more fibrous Read ALL the imbalances and info about emphysema within your handout

Page 415 in text

Alveolar Surface Tension Forces Surface tension – molecules of liquid hold together with hydrogen bonds Surfactant – substance which interferes with cohesion of water molecules so less energy is needed to expand the lungs IRDS – Infant Respiratory Distress Syndrome – read imbalance

Type II Cells

End of Quiz #3 Material

Gas Exchanges in the Body

Gas Exchanges Occur: Between the blood and the alveoli AND Between the blood and the tissue cells Takes place by simple diffusion Depends on partial pressures of oxygen & carbon dioxide That exist on opposite sides of the exchange membrane Diagrams on page 416-417 of text

Dalton’s Law Total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each individual gas (Ptotal = P1 + P2 + P3 + …) The partial pressure of each gas is directly proportional to its % in the mixture N2: 78.08%, O2: 20.95%, CO2: 0.04%

Henry’s law Each gas will dissolve in a liquid in proportion to its partial pressure and solubility coefficient of the liquid CO2 = .57 O2 = .024 N2 = .012 Solubility increases with increasing partial pressure Solubility decreases with increasing temperature

Hyperbaric Conditions Hyperbaric oxygen chambers – designed to force greater amounts of oxygen into patient’s blood

Life Applications Write down in detail the things we discuss!!!! Oxygen toxicity Nitrogen narcosis Decompression sickness High altitude sickness

Now what would happen if you breathed 100 percent oxygen? Exposed to 100 percent oxygen at normal air pressure for 48 hours A highly reactive form of the oxygen molecule, called a free radical destroys proteins and membranes in the epithelial cells.

In humans breathing 100 percent oxygen at normal pressure, here's what happens: Fluid accumulates in the lungs. Gas exchange in the alveoli slows down so person has to breathe more to get enough oxygen. Volume of exchangeable air decreases by 17 percent.

SCUBA In contrast, when 100 percent oxygen is breathed under high pressure (more than four times that of atmospheric pressure), acute oxygen poisoning can occur with these symptoms: Nausea Dizziness Muscle twitches Blurred vision Seizures/convulsions Such high oxygen pressures can be experienced by military SCUBA divers using rebreathing devices, divers being treated for the bends in hyperbaric chambers or patients being treated for acute carbon monoxide poisoning. These patients must be carefully monitored during treatment.

Nitrogen Narcosis As the total gas pressure increases with increasing dive depth, the partial pressure of nitrogen increases more nitrogen becomes dissolved in the blood. This high nitrogen concentration impairs the conduction of nerve impulses and mimics the effects of alcohol or narcotics.

Symptoms of nitrogen narcosis include: Wooziness Giddiness Euphoria Disorientation loss of balance loss of manual dexterity slowing of reaction time fixation of ideas impairment of complex reasoning. These effects are exacerbated by cold, stress, and a rapid rate of compression.

Decompression Sickness (the bends) As pressure increases, solubility of gases increase Larger quantities of Nitrogen are forced into the body fluid/blood but not used by the body Ascending rapidly causes nitrogen gas to become less soluble and “bubble” out of the blood too fast to be exhaled

Decompression sickness Gas collected in joint spaces and can also cause air embolisms which can lead to heart attack & stroke Treatment: Hyperbaric chamber Take back down to depth & bring up slowly

Internal & External Respiration

Factors influencing internal & external respiration Partial pressure gradients and gas solubilities cont’ Oxygen = has low solubility but steep partial pressure gradient (104 mmHg in alveoli – 40 mmHg in blood = 64 mmHg pressure gradient) Carbon dioxide = has solubility ~20x greater than oxygen but partial pressure gradient is only 5 mmHg

Factors influencing internal & external respiration Partial pressure gradients and gas solubilities Due to the ratios of solubility coefficients and pressure gradients: ~Equal amounts of gases are exchanged pH is not affected H2O + CO2 = H2CO3 (carbonic acid)

Factors influencing internal & external respiration Thickness of respiratory membranes 0.5 to 1.0 micrometers Hypoxia = oxygen deprivation Thickness – edematous (swollen) tissue can be caused by congestion and pneumonia Emphysema – infections can thicken membranes

Factors influencing internal & external respiration Surface Area 70-80 square meters for gas exchange Emphysema Walls of alveoli break down Less surface area to volume ratio

Transport of respiratory gases

Oxygen Transport Most oxygen is bound to hemoglobin for transport (blood is cherry red) Vocabulary to understand Loading = binding oxygen to hemoglobin for transport Unloading = releasing oxygen from hemoglobin to go into tissue cells

http://ems.lchospital.com/education/respiration.htm http://www.stemnet.nf.ca/~dpower/resp/exchange.htm http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter25/

Factors affecting hemoglobin transport Affects unloading rate 20-25% of oxygen unloaded to tissues in one systemic circuit Leaves a venous reserve of 75% This is why brain death will begin to occur 3-4 minutes after your heart stops CPR must begin ASAP!!

Factors affecting hemoglobin transport As the temperature increases – oxygen unloading increases Hard working tissues = high metabolism rate = heat produced = more oxygen unloaded Hard working tissues need more oxygen to produce more ATP = the heat is one way the tissues signal the body to bring more oxygen Cold tissues = low metabolism = less oxygen unloaded Nose & Cheeks are red when cold because the body is trying to bring them a little more heat = no additional oxygen is unloaded in this case

Factors affecting hemoglobin transport Active tissues = made lots of ATP so lots of carbon dioxide and hydrogen ions have been produced as a waste product = acidosis = increased oxygen unloading CO2 + H2O = H2CO3 (carbonic acid) Know the types of hypoxia and the symptoms & treatment of CO (fix this in notes) poisoning – see handout Also read the bracketed info on page 743 of handout

Carbon Monoxide poisoning

Carbon dioxide transport 7% dissolved in plasma ~20% bound to hemoglobin – aka. Carbaminohemoglobin 70% is in the form of the bicarbonate ion (HCO3-) Carbonic acid and bicarbonate ion work together as a buffer system to resists changes in pH

Hypoventilation Respiratory acidosis results Slow & shallow respiration Not adequate expiration so CO2 is not vented out of the body Production of excess acid H2O + CO2 = H2CO3 (carbonic acid) Respiratory acidosis results

Hyperventilation Respiratory alkalosis results Deep & rapid respiration Too much CO2 is vented out of the body Not enough acid production H2O + CO2 = H2CO3 (carbonic acid) Respiratory alkalosis results Treatment: trap the CO2 and rebreathe it till breathing returns to normal

Imbalances Pages 744-745 of handout

Chronic Bronchitis Symptoms: inflammation of mucosa – chronic mucus production Impairs ventilation and gas exchange Reduction of airway diameter “blue bloater” – hypoxia leads to cyanosis – CO2 retention leads to hyperinflation of chest wall Causative factors: cigarette smoking

Normal Bronchitis

Obstructive Emphysema “pink puffer” Gas exchange adequate until end stage so stay oxygenated and pink Breathing is very labored due to lack of alveolar recoil Barrel chest from hyperinflation of lungs Alveolar walls collapse = loss of surface area Causative factor: cigarette smoking

4 features in common Both emphysema and chronic bronchitis have: Smoking history Dyspnea = air hunger due to disfunctional breathing Apnea = no breathing Eupnea = normal breathing Coughing & pulmonary infections Will develop respiratory failure, hypoxia, acidosis

Lung Cancer Basic Info 1/3 of all cancer deaths are due to lung cancers 90% have a smoking history Metastasizes very rapidly due to vascularity of lungs

3 types Know the descriptions of these 3 types of lung cancers from your handout Squamous cell carcinoma Adenocarcinoma Oat cell (small cell) carcinoma

Squamous cell carcinoma

Adenocarcinoma

Oat cell carcinoma

Treatments Resection of diseased portion of lung Radiation therapy Chemotherapy

Lung Resection

Developmental Aspects

READ your handout Read through the Developmental Aspects section of your notes and your handout Know the related clinical terms on the back page of your handout

STUDY