Chapter 8

Pathophysiology

Copyright ©2010 by Pearson Education, Inc.All rights reserved.

Prehospital Emergency Care, Ninth EditionJoseph J. Mistovich • Keith J. Karren

Objectives

1. Define key terms introduced in this chapter.2. Explain the importance of understanding basic

pathophysiology.3. Differentiate between the processes of aerobic and

anaerobic cellular metabolism, including explanationsof (slides 13-17):a. The amount of ATP producedb. Removal of by-products of metabolism

4. Describe the consequences of failure of the cellularsodium/potassium pump (slides 18-19).

Objectives

5. Explain the concept of perfusion, including the physicaland physiological components necessary to maintainperfusion (slides 20-104).

6. Describe the composition of ambient air (slides 21-23).7. Apply the Boyle law to ventilation (slide 36)8. Explain how changes in compliance of the lungs and

chest wall and changes in airway resistance affectventilation (slides 41-42).

9. Describe the consequences of loss of contact betweenthe parietal and visceral pleura (slides 43-44).

10. Explain the concept of minute ventilation (slides 45-46).

Objectives

11. Differentiate between minute ventilation and alveolarventilation (slides 47-48).

12. Describe the roles of chemoreceptors, lung receptors,and the nervous system in the control of ventilation(slides 49-55).

13. Explain the concept of the ventilation/perfusion (VQ)ratio (slides 56-63).

14. Describe the transport of oxygen and carbon dioxide inthe blood (slides 64-70).

15. Explain the exchange of gases across thealveolar/capillary membrane and the exchange ofgases between capillaries and cells (slides 71-76).

Objectives

16. Describe the composition of blood, including thefunction of plasma and the formed elements (slides 79-80).

17. Explain the effects of changes in hydrostatic pressureand plasma oncotic pressure on the movement of fluidbetween the circulatory system and interstitial spaces(slides 83-86).

18. Discuss factors that affect cardiac output, includingheart rate, stroke volume, myocardial contractility,preload, and afterload (slides 87-93).

19. Describe the concept of systemic vascular resistanceand its relationship to blood pressure and pulsepressure (slides 94-97).

Objectives

20. Summarize the local, neural, and hormonal factors thatregulate blood flow through the capillaries (slides 98-99).

21. Explain the regulation of blood pressure bybaroreceptors and chemoreceptors (slides 100-104).

22. Explain the relationship between ventilation, perfusion,and cellular metabolism (slides 20-104).

Multimedia Directory

Slide 70 Transport of Carbon Dioxide AnimationSlide 73 Process of Gas Exchange AnimationSlide 76 Cellular Structures and Respiration VideoSlide 87 Starling’s Law Animation

Topics

Cellular MetabolismComponents Necessary for Adequate Perfusion

CASE STUDYCASE STUDY

Dispatch

EMS Unit 204

Respond to 143 Clovermeade Avenue for a 50-year-old who has been stabbed by his wife.

Time out 2136

Upon Arrival

• Police officer tells you wife is in custody• Daughter yells to you, “My father was stabbed in the

belly and he doesn’t look good”• She leads you to the back porch where you find the

patient lying on left side with blood on his shirt inabdominal area

How would you proceed to assessand care for this patient?

Back to Topics

Cellular Metabolism

Aerobic Metabolism

Back to Objectives

• Breakdown ofmolecules inthe presenceof oxygen

• Glycolysis• ATP• Aerobic

byproducts

Anaerobic Metabolism

• Breakdown ofmolecules in theabsence ofoxygen

• Glycolysis• Pyruvic acid• Lactic acid

Anaerobic Metabolism

Sodium/PotassiumPump Failure

Back to Objectives

• Function ofpump

• Failure ofpump

• Effect of failure

Back to Topics

ComponentsNecessary for

Adequate Perfusion

• Composition of ambient air• Patent airway• Mechanics of ventilation• Regulation of ventilation• Ventilation/perfusion ratio• Transport of oxygen and carbon dioxide by

the blood• Blood volume• Pump function of the myocardium• Systemic vascular resistance• Microcirculation• Blood pressure

Back to Objectives

Composition of Ambient Air

Composition of Ambient Air(at sea level)

Patency of the Airway

• Patency• Obstruction

Patency of the Airway

Nasopharynx

• Usuallydoes notpose amajorproblem

• Can lead toaspiration

• Alternativeairwaylocation

Patency of the Airway

Oropharynx and Pharynx

Any obstructionmust be removedimmediately.

Patency of the Airway

Epiglottis

• Can occludeairway

• May behelped byjaw-thrust orchin-liftmaneuver

Patency of the Airway

Larynx

• Thyroid cartilage• Cricoid cartilage• Laryngeal spasm

Patency of the Airway

Trachea and Bronchi

• Carina• Right and left mainstem

Respiratory Compromise Associatedwith Mechanics of Ventilation

Boyle’s Law Applied toVentilation

Back to Objectives

• Active inhalation• Passive exhalation

Respiratory Compromise Associatedwith Mechanics of Ventilation

Accessory Muscles

• Very energyintensive

• Will compoundrespiratoryproblems

Accessory Muscles of Inhalation

Accessory Muscles of Exhalation

• Normally passive butcan become active

• Active requiresenergy

• Can fatiguerespiratory musclesmore quickly

Respiratory Compromise Associatedwith Mechanics of Ventilation

Compliance andAirway Resistance

Back to Objectives

• Compliance• Airway resistance

Respiratory Compromise Associatedwith Mechanics of Ventilation

Pleural Space

Back to Objectives

Respiratory Compromise Associatedwith Mechanics of Ventilation

Minute Ventilation

Back to Objectives

Minute Ventilation = Tidal Volume (VT) x Frequency (f/min)

Minute Ventilation

MinuteVen)la)onTheamountofairmovedinandoutofthelungsinoneminute

TidalVolumeThevolumeofairinhaled

witheachbreath

FrequencyThenumberofven8la8ons

inoneminute

• In an average adult, tidal volume (VT) is ~ 500 mLand frequency is ~ 12 breaths per minute

• MV = 500mL x 12/min = 6,000 mL/min or 6 L/min

Respiratory Compromise Associatedwith Mechanics of Ventilation

Alveolar Ventilation

Back to Objectives

Alveolar ventilation =(tidal volume – dead air space) x frequency

of ventilation(f/min)

Regulation of Ventilation

Chemoreceptors

Back to Objectives

• Central• Peripheral

Chemoreceptors

• Hypercarbic drive• Hypoxic drive

Regulation of Ventilation

Lung Receptors

• Irritant receptors• Stretch receptors• J-receptors

Regulation of Ventilation

Respiratory Centers inthe Brainstem

• Dorsal respiratory group (DRG)• Ventral respiratory group (VRG)• Apneustic center• Pneumotaxic center

Ventilation/Perfusion Ratio

Back to Objectives

Ventilation / Perfusion(V/Q) Ratio

Ventilation/Perfusion Ratio

Pressure Imbalances

• Affected by air and pressure in alveoli• Affected by blood flowing through capillary

beds

Ventilation/Perfusion Ratio

VentilatoryDisturbances

• Less oxygenated air available• Can lead to hypoxia• Blood pressure not affected

Ventilation/Perfusion Ratio

PerfusionDisturbances

• Often due toblood loss

• Needs fluidreplacement toresolveperfusion issue

Transport of Oxygen andCarbon Dioxide by the

Blood

Back to Objectives

• Cells need O2 for normal cellular metabolism• Hypercarbia• Hypoxia

Transport of Oxygen and CarbonDioxide in the Blood

Oxygen Transport

• Oxyhemoglobin

• Deoxyhemoglobin

Transport of Oxygen and CarbonDioxide in the Blood

Carbon DioxideTransport

• Dissolved inplasma

• Hemoglobin• Bicarbonate

Transportationby Blood

Click here to view an animation of the transport of carbon dioxide.

Return to Directory

Transport of Carbon Dioxide

Transport of Oxygen and CarbonDioxide in the Blood

Alveolar/Capillary GasExchange

Back to Objectives

Click here to view an animation showing the process of gas exchange.

Return to Directory

Process of Gas Exchange

Transport of Oxygen and CarbonDioxide in the Blood

Cell/Capillary GasExchange

Click here to view a video on the topic of cellular structures and respiration.

Return to Directory

Cellular Structures and Respiration

Blood Volume

An adult has approx 70mL of blood per kilogram.

Blood Volume

Composition of Blood

Back to Objectives

Composition of Blood• Formed elements• Plasma

Blood Volume

Distribution of Blood

Distribution ofBlood

Blood Volume

Hydrostatic Pressure

Back to Objectives

HydrostaticPressure

Blood Volume

Plasma OncoticPressure

Plasma OncoticPressure

Click here to view an animation showing Starling’s Hypothesis.

Return to Directory

Starling’s Hypothesis

Pump Function of the Myocardium

Cardiac Output

Back to Objectives

Cardiac output = heart rate x stroke volume

Pump Function of the Myocardium

Heart Rate

Heart Rate

• Sympathetic stimulation• Parasympathetic stimulation

Pump Function of the Myocardium

Stroke Volume

Stroke Volume

• Preload• Starling’s law• Afterload

Systemic VascularResistance

Back to Objectives

Systemic Vascular Resistance

Systemic VascularResistance Effect on

Pulse Pressure

Effect on Pulse Pressure

Systemicvascularresistance

Diastolicbloodpressure

Systemicvascularresistance

Diastolicbloodpressure

Microcirculation

Back to Objectives

• Site of exchange• Metarterioles• Precapillary

sphincters• Regulatory

influences

Blood Pressure

Back to Objectives

Bloodpressure

Cardiacoutput

Systemicvascularresistance

Blood Pressure

Regulation of BloodPressure by

Baroreceptors andChemoreceptors

Regulation of Blood Pressure

• Baroreceptors• Chemoreceptors

Case Study

Follow-Up

CASE STUDYCASE STUDY

Patient AssessmentCASE STUDYCASE STUDY

• Patient states his name is Paul• Patient is alert, oriented, has open

airway, breathing adequately• Respirations: 24 per minute; skin cool

and clammy• Heart rate: 122 and weak• Placed on nonrebreather mask at 15 lpm

Patient AssessmentCASE STUDYCASE STUDY

• BP: 102/88 mmHg• Cover stab wounds in abdomen• Transport to hospital• Give report

• 28-year-old construction worker whosustained a large, gaping laceration to hisleft upper leg

• Blood is spurting from the wound• Responds only with moans when you yell

his name

Critical Thinking Scenario

Vital signs:• BP: 98/76 mmHg• HR: 134 bpm, radial pulse is absent• RR: 26 per minute• Skin is extremely pale, cool, and clammy

Critical Thinking Scenario

1. In order to determine if his ventilation isadequate, what else must you assess?

2. Based on the ventilation/perfusion ratio,why would the cells in the patientbecome and remain hypoxic?

3. Why is the patient responding so poorly?

Critical Thinking Questions

4. How is the spurting blood affecting theperfusion of the cells?

5. What is causing a decrease in thesystolic blood pressure?

6. Is the pulse pressure narrow? If so,describe why.

7. Why is the skin pale, cool, and clammy?

Critical Thinking Questions

8. Why is the heart rate 134 bpm?9. Are the cells of this patient likely

undergoing aerobic or anaerobicmetabolism? Why?

10.Why does the patient have such a lack ofenergy?

Critical Thinking Questions

Reinforce and Review

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