PEC11 Chap 08 - Pathophysiology.pdf

(1)

Prehospital: Emergency Care

Eleventh Edition

Chapter 8

Pathophysiology

Slides in this presentation contain

(2)

Learning Readiness

• EMS Education Standards, text p. 177.

• Chapter Objectives, text p. 177.

• Key Terms, text p. 177-178.

• Purpose of lecture presentation versus textbook reading

(3)

Setting the Stage

• Overview of Lesson Topics

– Cellular Metabolism

(4)

Case Study Introduction

EMTs Patty Mirabal and Gus Oakes are on the scene of a

(5)

Case Study

(1 of 5)

• What purposes does breathing serve?

• In what ways does a problem with breathing affect the

(6)

Introduction

• Oxygen and glucose are necessary for normal cell

function.

• Illnesses and injuries can disturb the delivery of oxygen

and glucose and removal of waste by-products.

• A fundamental purpose of emergency care is maintaining

(7)

Cellular Metabolism

(1 of 7)

• Cellular metabolism is the process in which the body

breaks down molecules of glucose to produce energy.

– Aerobic metabolism takes place when oxygen is

available.

– When there is a lack of oxygen, the body uses a less

(8)

Cellular Metabolism

(2 of 7)

• Aerobic Metabolism

– The initial steps of cellular metabolism do not require

oxygen, but produce only small amounts of energy.

– Oxygen is required to complete the process of

(9)

A Aerobic Metabolism. Glucose Broken Down in the

Presence of Oxygen Produces a Large Amount of

(10)

Cellular Metabolism

(3 of 7)

• Aerobic metabolism

– The initial steps of cell metabolism take place in the

cytosol and are called glycolysis.

▪ Glycolysis produces a small amount of ATP.

▪ Then the process continues in the mitochondria,

(11)

Cellular Metabolism

(4 of 7)

– By-products of aerobic metabolism include

▪ heat, carbon dioxide, and water.

– The majority of ATP is used by the sodium-potassium

(12)

The Sodium/Potassium Pump

Energy (ATP) is required to pump sodium molecules out of

(13)

Cellular Metabolism

(5 of 7)

– By-products of aerobic metabolism include

▪ heat, carbon dioxide, and water.

– The majority of ATP is used by the sodium-potassium

pump.

(14)

Cellular Metabolism

(6 of 7)

• Anaerobic Metabolism

– The first stage of cell metabolism is anaerobic.

▪ The waste product produced is pyruvic acid.

▪ Without oxygen, pyruvic acid is converted to lactic

acid.

▪ Accumulation of lactic acid is harmful to body

(15)

Cellular Metabolism

(7 of 7)

• Anaerobic Metabolism

– Sodium/Potassium Pump Failure

▪ In anaerobic metabolism, the combination of

(16)

Anaerobic Metabolism

Glucose broken down without the presence of oxygen

produces pyruvic acid that converts to lactic acid and only a

(17)

Components Necessary for Adequate

Perfusion

(1 of 52)

• Perfusion

– Delivery of oxygen, glucose, and other substances to

the cells and the elimination of waste products from the cells.

(18)

Components Necessary for Adequate

Perfusion

(2 of 52)

• Components

1. Composition of ambient air

2. Patency of the airway

3. Mechanics of ventilation

4. Ventilation/Perfusion ratio

(19)

Components Necessary for Adequate

Perfusion

(3 of 52)

• Components

6. Blood volume

7. Pump function of the myocardium

8. Systemic vascular resistance

9. Microcirculation

(20)

Components Necessary for Adequate

Perfusion

(4 of 52)

• Any alteration in the components may lead to poor

cellular perfusion.

• Inadequate perfusion can shift cells from aerobic to

anaerobic metabolism.

• Emergency care focuses on restoring and maintaining

(21)

Case Study

(2 of 5)

(22)

Case Study

(3 of 5)

• What, specifically, will Gus be assessing to determine the

patient’s condition?

• How will Patty know what equipment and treatment the

patient needs?

• What is happening to the patient at the cellular level?

(23)

Components Necessary for Adequate

Perfusion

(5 of 52)

• Composition of Ambient Air

– The concentration of oxygen in the ambient air

influences oxygen that ends up in the alveoli for gas exchange.

– Ambient air contains approximately 79 percent

(24)

Table 8-1 Partial Pressure of Gases in

Ambient Atmosphere at Sea Level

Gas % Partial Pressure

Oxygen 20.95 159.2 millimetreHg

Nitrogen 78.08 593.4 millimetreHg

Argon 0.93 7.1 millimetreHg

Carbon Dioxide 0.03 0.2 millimetreHg

(25)

Components Necessary for Adequate

Perfusion

(6 of 52)

• Composition of Ambient Air

– FiO₂ is the fraction of inspired oxygen.

– FDO₂ is the fraction of delivered oxygen.

– One way to improve cellular oxygenation is to provide

(26)

Components Necessary for Adequate

Perfusion

(7 of 52)

• Patency of the Airway

– A patent airway is open and not obstructed by any

substance.

– Establishing an open airway is one of the first steps in

emergency care.

– Failure to establish or maintain a patent airway leads

(27)

Components Necessary for Adequate

Perfusion

(8 of 52)

• Patency of the Airway

– Locations of airway obstructions

▪ Nasopharynx

▪ Oropharynx

▪ Epiglottis

▪ Larynx

▪ Trachea

(28)

Airway Obstruction Can Occur at Several

Levels of the Upper and Lower Airway

(29)

Components Necessary for Adequate

Perfusion

(9 of 52)

• Mechanics of Ventilation

– An intact thoracic cavity is integral to normal

ventilation.

– Boyle’s Law defines and illustrates how ventilation

(30)

Components Necessary for Adequate

Perfusion

(10 of 52)

– Pleural linings

▪ Visceral pleura

▪ Parietal pleura

– Damage to one or both pleural linings can disrupt

(31)

Click on the Event that Occurs Just Prior to the

Movement of Air into the Lungs on Inhalation

A. The diaphragm relaxes.

B. The size of the chest cavity decreases.

C. Pressure within the chest decreases.

(32)

Components Necessary for Adequate

Perfusion

(11 of 52)

– Accessory muscles

▪ Used when extra effort is needed for inhalation or

exhalation

– Indication of a heighted ventilatory effort

(33)

Table 8-2 Accessory Muscles

(1 of 2)

Accessory Muscles of Inhalation

The following accessory muscles of inhalation are used to increase the size of the thoracic cavity and generate a

greater negative pressure, increasing the flow of air into the lungs.

• Sternocleidomastoid muscles lift the sternum upward.

(34)

Table 8-2 Accessory Muscles

(2 of 2)

Accessory Muscles of Exhalation

The following accessory muscles of exhalation are used to decrease the size of the thoracic cavity and to create a

more positive pressure, forcing air out of the lungs.

• Abdominal muscles contract and increase the pressure inside the abdominal cavity, forcing the diaphragm to

move higher against the lungs.

(35)

Components Necessary for Adequate

Perfusion

(12 of 52)

– Airway Compliance and Resistance

▪ High resistance and low compliance increase the

effort needed to breathe and lead to hypoxia.

▪ Compliance disorders make it hard for the lung

tissue to inflate.

▪ Resistance disorders result from constriction of

(36)

Components Necessary for Adequate

Perfusion

(13 of 52)

– Pleural Space

▪ Negative pressure is maintained in the pleural

space or cavity.

▪ An injury to the chest wall or lung that opens the

space can draw air, by way of negative pressure, into the space.

(37)

Components Necessary for Adequate

Perfusion

(14 of 52)

– Minute Ventilation

▪ The amount of air moved in and out of the lungs in

one minute.

▪ Minute volume = tidal volume × frequency of

ventilation.

▪ To ensure adequate ventilation, both the tidal

(38)

Components Necessary for Adequate

Perfusion

(15 of 52)

– A decrease in tidal volume decreases the minute

volume.

– A decrease in respiratory rate decreases the minute

volume.

– A decrease in minute volume reduces the air

(39)

Components Necessary for Adequate

Perfusion

(16 of 52)

– Alveolar ventilation

▪ The amount of air moved in and out of the alveoli

in one minute.

▪ Dead space air does not reach the alveoli during

breathing.

▪ An average of 350 milliLitre of a 500 milliLitre tidal volume

(40)

Components Necessary for Adequate

Perfusion

(17 of 52)

– Hypoxia can occur from:

▪ A low tidal volume.

▪ A slow ventilatory rate.

▪ A fast ventilatory rate.

– Typically pulmonary illnesses and trauma affect

(41)

Components Necessary for Adequate

Perfusion

(18 of 52)

• Regulation of Ventilation

– Breathing is an involuntary process controlled by

the ANS.

▪ Receptors measure oxygen (O₂), carbon

dioxide (CO₂), and hydrogen ions (pH).

▪ Receptors send signals to the brain to adjust

(42)

Components Necessary for Adequate

Perfusion

(19 of 52)

– Chemoreceptors

▪ Central

▪ Peripheral

– Hypercapnic Drive

(43)

Components Necessary for Adequate

Perfusion

(20 of 52)

– COPD patients have a tendency to retain CO₂.

▪ They become insensitive to small changes in CO₂.

▪ Their respirations are controlled by decreased

(44)

Respiration is Controlled by the Autonomic

Nervous System

(45)

Components Necessary for Adequate

Perfusion

(21 of 52)

• Control of Ventilation

– Lung Receptors

▪ Three types of receptors within the lungs provide

impulses to help regulate respiration:

1. Irritant receptors

2. Stretch receptors

(46)

Components Necessary for Adequate

Perfusion

(22 of 52)

– Respiratory Centers in the Brainstem

1. Ventral respiratory group

2. Dorsal respiratory group

(47)

Case Study

(4 of 5)

The patient is working hard to breathe, and has pale, moist skin. He is using accessory muscles to breathe, but seems to be moving very little air. The patient appears sleepy as if on the verge of exhaustion.

(48)

Case Study

(5 of 5)

• What medical problems could lead a patient to have such

(49)

Components Necessary for Adequate

Perfusion

(23 of 52)

• Ventilation/Perfusion Ratio (V/Q)

– V/Q ratio is the relationship between alveolar

ventilation and perfusion of the alveolar capillaries.

▪ The relationship influences gas exchange.

(50)

(51)

Components Necessary for Adequate

Perfusion

(24 of 52)

– In an ideal state the amount of ventilation is equally

matched to the amount of perfusion.

▪ However, a perfect match does not actually occur.

▪ Overall, perfusion exceeds ventilation, but the

(52)

Components Necessary for Adequate

Perfusion

(25 of 52)

– When ventilation is better than perfusion, there is

wasted ventilation.

– When perfusion is better than ventilation, there is

(53)

(54)

Components Necessary for Adequate

Perfusion

(26 of 52)

– Pressure Imbalance

▪ If the air pressure in an alveolus exceeds the blood

pressure in the capillary bed, blood flow through the capillary stops.

– Occurs normally in the apex of the lungs.

– Occurs when the systemic blood pressure

(55)

Components Necessary for Adequate

Perfusion

(27 of 52)

– Ventilatory Disturbances

▪ A condition that decreases the amount of air

reaching the alveoli, such as asthma, results in wasted perfusion.

– Hypoxemia and hypoxia result.

– Treatment is aimed at increasing lung

(56)

Components Necessary for Adequate

Perfusion

(28 of 52)

– Perfusion Disturbances

▪ Ventilation is normal, or even increased, but blood

flow through the lungs is decreased.

▪ There is wasted ventilation, leading to hypoxemia

and hypoxia.

▪ Administering oxygen may help, but the perfusion

(57)

Components Necessary for Adequate

Perfusion

(29 of 52)

• Transport of O₂ and CO₂ by the Blood

– Oxygen must be continuously delivered by the blood

to the cells.

– Carbon dioxide must be carried back to the lungs to

be blown off in exhalation.

– A disturbance in the transport system may lead to

(58)

Components Necessary for Adequate

Perfusion

(30 of 52)

– Gases move from areas of higher concentration to

(59)

Components Necessary for Adequate

Perfusion

(31 of 52)

– Oxygen Transport

▪ O₂ is transported in the blood in two ways.

– 1.5 to 3 percent is dissolved in plasma.

– 97 to 98.5 percent is attached to hemoglobin

(60)

Components Necessary for Adequate

Perfusion

(32 of 52)

– Oxygen Transport

▪ Role of hemoglobin

– A protein molecule that contains iron.

(61)

Components Necessary for Adequate

Perfusion

(33 of 52)

– Carbon Dioxide

▪ Transported in the blood in three ways.

– 7 percent is dissolved in plasma.

– 23 percent is attached to hemoglobin in RBCs.

– 70 percent is transported by the lungs in the

(62)

Oxygen is Transported in the Blood Two

Ways

Attached to hemoglobin and dissolved in plasma. Carbon dioxide is transported in the blood three ways: as

(63)

Components Necessary for Adequate

Perfusion

(34 of 52)

– Alveolar/capillary gas exchange

▪ After inhalation, the alveolar air is high in O₂ and

low in CO₂.

▪ Venous blood in the capillaries surrounding the

(64)

Click on the Mechanism by Which Most of

the Oxygen in Blood is Transported

A. Bound to hemoglobin

B. In the form of bicarbonate

C. Dissolved in plasma

(65)

Components Necessary for Adequate

Perfusion

(35 of 52)

• Blood Volume

– A determinant of blood pressure and perfusion is

blood volume.

▪ Adults have 70 milliLitre of blood/kilogram of body weight.

(66)

Components Necessary for Adequate

Perfusion

(36 of 52)

• Blood Volume

– Blood Composition

▪ 45 percent formed elements

▪ 55 percent plasma

– Blood Distribution

▪ Majority of blood in the venous system

(67)

Table 8-3 Distribution of Blood in the

Cardiovascular System

Blood is distributed in the various components of the cardiovascular system as follows.

Venous 64%

Arterial 13%

Pulmonary vessels 9%

Capillaries 7%

(68)

Components Necessary for Adequate

Perfusion

(37 of 52)

• Blood Volume

– Hydrostatic Pressure

▪ Force inside the vessel or capillary bed generated

by the contraction of the heart and the blood pressure.

▪ Hydrostatic pressure exerts a “push” inside the

(69)

Components Necessary for Adequate

Perfusion

(38 of 52)

• Blood Volume

– Plasma oncotic pressure

▪ Keeps fluid inside the vessels to oppose

hydrostatic pressure.

▪ The large plasma proteins have the effect of

(70)

Hydrostatic Pressure Pushes Water out of the

(71)

Components Necessary for Adequate

Perfusion

(39 of 52)

• Pump Function of the Myocardium

– The myocardium must be an effective pump to

maintain perfusion.

▪ Cardiac output (CO) is the amount of blood ejected

from the heart in one minute.

(72)

Components Necessary for Adequate

Perfusion

(40 of 52)

maintain perfusion.

▪ Heart Rate

– Sympathetic

(73)

Components Necessary for Adequate

Perfusion

(41 of 52)

maintain perfusion.

▪ Stroke Volume

– Preload

– Contractility

(74)

(75)

(76)

Components Necessary for Adequate

Perfusion

(42 of 52)

– Factors that increase cardiac output

▪ Increased heart rate (to a point)

▪ Increased blood volume

▪ Increased myocardial contractility

▪ Sympathetic nervous system stimulation

▪ Beta₁ stimulation from epinephrine

(77)

Components Necessary for Adequate

Perfusion

(43 of 52)

– Factors that decrease cardiac output

▪ Decreased heart rate

▪ Decreased blood volume

▪ Decreased myocardial contractility

▪ Parasympathetic nervous stimulation

▪ Beta₁ blockade (beta blockers)

(78)

Components Necessary for Adequate

Perfusion

(44 of 52)

• Systemic Vascular Resistance (SVR)

– SVR is the resistance to blood flow through a vessel.

– Vasoconstriction increases SVR, increased SVR

increases BP.

– Vasodilation decreases SVR, decreased SVR

(79)

(80)

Components Necessary for Adequate

Perfusion

(45 of 52)

• Systemic Vascular Resistance Effect on Blood Pressure

– Pulse pressure is the difference between the systolic

and the diastolic BP readings.

▪ Systolic BP is a rough indicator of CO.

(81)

Components Necessary for Adequate

Perfusion

(46 of 52)

• Microcirculation

– Refers to the flow of blood through the arterioles,

(82)

Microcirculation is the Flow of Blood through the

Smallest Blood Vessels: Arterioles, Capillaries, and

Venules

(83)

Components Necessary for Adequate

Perfusion

(47 of 52)

• Microcirculation

– Precapillary sphincters

▪ Regulatory influences on sphincters

1. Local factors

2. Neural factors

(84)

Components Necessary for Adequate

Perfusion

(48 of 52)

• Blood Pressure (BP)

– Blood pressure = CO × S VR

▪ Relationship of SV & HR on CO

– Increased SV increases CO.

– Decreased SV decreases CO.

– Increased HR increases CO.

(85)

Components Necessary for Adequate

Perfusion

(49 of 52)

• Blood Pressure (BP)

– Blood pressure = CO × S VR

▪ Relationship of CO & SVR on BP

– Increased CO increases BP.

– Decreased CO decreases BP.

– Increased SVR increases BP.

(86)

Components Necessary for Adequate

Perfusion

(50 of 52)

• Blood Pressure

– The general effect of blood pressure on perfusion is:

▪ Increased BP increases cellular perfusion.

(87)

Components Necessary for Adequate

Perfusion

(51 of 52)

• Blood Pressure

– Regulation of BP by Baroreceptors.

▪ Baroreceptors located in the aortic arch and

carotid sinuses detect changes in blood pressure.

▪ Signals are sent to the vasomotor and

(88)

Baroreceptor Function and Influence on

(89)

Components Necessary for Adequate

Perfusion

(52 of 52)

• Blood Pressure

– Regulation of BP by Chemoreceptors

▪ A decrease in blood oxygen level stimulates the

sympathetic nervous system.

▪ Heart rate increases and blood vessels constrict.

▪ Hypoxia can present with pale, cool skin, and

(90)

(91)

Review of Aerobic Metabolism

Components

(1 of 4)

1. Oxygen content in ambient air

2. Patency of the airway

3. Minute ventilation

– Ventilatory rate

– Tidal volume

4. Alveolar ventilation

(92)

Review of Aerobic Metabolism

Components

(2 of 4)

5. Perfusion in the Pulmonary Capillaries

– Venous volume

– Right ventricular pump function

6. Gas Exchange Between the Capillaries and the Alveoli

7. Content of blood

– Red blood cells and Hemoglobin

(93)

Review of Aerobic Metabolism

Components

(3 of 4)

8. Cardiac Output and Determinants

– Heart rate

– Preload

– Stroke volume

– Myocardial contractility

(94)

Review of Aerobic Metabolism

Components

(4 of 4)

9. Systemic Vascular Resistance

– Sympathetic nervous system stimulation

– Parasympathetic nervous system stimulation

(95)

Case Study Conclusion

(1 of 2)

The patient has a history of chronic obstructive lung

disease and heart failure. He has been increasingly short of breath for two days, with a sudden worsening today.

With the assistance of an engine crew, Patty and Gus

(96)

Case Study Conclusion

(2 of 2)

The crew recognizes the seriousness of the patient’s condition and is prepared to take further measures, if needed, to maintain the patient's airway.

Gus calls in a report to the receiving hospital. When they

arrive at the ED, a physician, nurse, and respiratory

(97)

Lesson Summary

• Cells require oxygen and glucose to produce energy and

perform work.

• Without adequate ventilation and perfusion, cells engage

in anaerobic metabolism, which produces less energy and more waste.

• A fundamental purpose of emergency care is to restore

(98)

Correct!

(1 of 3)

• Your answer is supported by two principles of physics.

– First, according to Boyle’s law, the pressure of a gas

varies inversely with its volume.

– Second, air (a mixture of gases) moves from areas of

(99)

Correct!

(2 of 3)

• When the diaphragm and intercostal muscles contract,

the thoracic cavity increases in volume, which lowers the pressure in the thorax and lungs. Air flows from the

higher atmospheric pressure into the area of lower pressure within the lungs.

(100)

Incorrect

(1 of 4)

• When the diaphragm relaxes, it rises into the chest

cavity, making it smaller, which promotes exhalation.

(101)

Incorrect

(2 of 4)

• According to Boyle’s law, when the volume of a gas

decreases, such as happens to the gas within the thorax when the size of the thorax decreases, the pressure of the gas increases. In the case of ventilation, this action promotes exhalation.

(102)

Incorrect

(3 of 4)

• When the intercostal muscles relax, the volume of the

thoracic cavity decreases in size, which increases the pressure within thorax. This action promotes exhalation.

(103)

Correct

• Most oxygen transported in the blood is carried by

hemoglobin. Each molecule of hemoglobin contains iron, to which the oxygen can bind. Each hemoglobin molecule provides four binding sites, which allow it to carry up to four molecules of oxygen.

(104)

Correct!

(3 of 3)

• The loss of hemoglobin-containing red blood cells, such

as through hemorrhage, is a loss of oxygen-carrying capacity. Controlling bleeding is a critical way to help preserve a patient’s ability to deliver oxygen to his cells.

(105)

Incorrect

(4 of 4)

• This is not the way most oxygen is transported in the

blood. Return to the quiz to try again.

(106)