L9: Respiratory & Oxygenation Flashcards
What are 3 steps in the process of oxygenation?
Ventilation, perfusion, and diffusion
The exchange of respiratory gases occurs between the ___________ and the ________.
environment and the blood
What is Respiration?
the exchange of oxygen and carbon
dioxide during cellular metabolism.
Where in the lungs does is oxygen from the atmosphere get exchanged for carbon dioxide?
alveoli -
specifically the alveolar capillary membrane
How do the diaphragm and intercostal muscles work together during inspiration?
The diaphragm and external intercostal muscles contract to create a negative pleural pressure and
increase the size of the thorax for inspiration.
Is Intrapleural pressure less than or greater than atmospheric pressure,
Intrapleural pressure is negative, or less than atmospheric pressure, which is 760 mm Hg at sea level.
For air to flow into the lungs, intrapleural pressure becomes _______________.
more negative, setting up a pressure gradient between the atmosphere and the alveoli.
Ventilation
The process of moving gases into
and out of the lungs
Perfusion
The ability of the cardiovascular system to pump oxygenated blood to the tissues and return deoxygenated blood to the lungs
Diffusion
Exchange of respiratory gases in
the alveoli and capillaries
The major inspiratory muscle of respiration is
the diaphragm
The diaphragm is innervated by the _________.
phrenic nerve, which exits the spinal cord at the fourth cervical vertebra.
Diffusion moves respiratory gases from one area to another by ___________.
concentration gradients
Work of breathing is?
The effort required to expand and contract the lungs.
Inspiration
active process stimulated by chemical receptors in the aorta.
Expiration
a passive process that depends on the elastic recoil properties of the lungs
Surfactant
chemical produced in the lungs to maintain the surface tension of the alveoli and keep them from collapsing
Atelectasis
collapse of the alveoli that prevents normal exchange of oxygen
Compliance
ability of the lungs to distend or expand in response to increased intraalveolar pressure
Airway resistance
the increase in pressure that occurs as the diameter of the airways decreases from mouth/nose to alveoli. Any further decrease in airway diameter by bronchoconstriction can increase airway resistance
What can cause an increase in airway resistance?
Diseases causing airway obstruction such as ASTHMA and tracheal edema.
The amount of energy expended on breathing depends on ___________.
rate and depth of breathing, the ease with which the lungs can be expanded (compliance), and airway resistance.
What happens in patients with advanced chronic obstructive pulmonary disease (COPD)?
They lose the elastic recoil of the lungs and thorax. As a result, the patient’s work of breathing increases.
Pulmonary diseases that decreased surfactant production can sometimes cause _________?
atelectasis
What can cause a decrease in lung compliance?
diseases such as pulmonary edema, interstitial and pleural fibrosis, and congenital or traumatic structural abnormalities such as kyphosis or fractured ribs.
How does the thickness of the membrane affect the rate of diffusion?
Increased thickness of the membrane impedes diffusion because gases take longer to transfer across the membrane.
What can alter the amount of alveolar capillary membrane surface area?
Chronic diseases (e.g., emphysema), acute diseases (e.g., pneumothorax), and surgical processes (e.g., lobectomy)
The oxygen transport system consists of the _____ and _________________.
lungs and cardiovascular system
Carbon dioxide is a product of _______.
cellular metabolism
How is carbon dioxide transported?
CO2 diffuses into red blood cells and is rapidly hydrated into carbonic acid (H2CO3)
The carbonic acid then dissociates into hydrogen (H) and bicarbonate (HCO3-) ions. The (HCO3-) diffuses into the plasma.
Oxygen delivery depends on ______?
the amount of oxygen entering the lungs (ventilation), blood flow to the lungs and tissues (perfusion), rate of diffusion, and oxygen-carrying capacity.
What 3 things influence the capacity of the blood to carry oxygen?
the amount of dissolved oxygen in the plasma, the amount of hemoglobin, and the ability of hemoglobin to bind with oxygen.
What percent of the body’s oxygen is transported by hemoglobin?
approximately 97%
The hemoglobin molecule combines with oxygen to form ___________.
oxyhemoglobin
Deoxyhemoglobin
The process of hemoglobin and oxygen dissociating, which frees oxygen to enter tissues.
** Reduced hemoglobin**
What are the 2 types of respiratory regulation?
Neural regulation & Chemical regulation
Neural regulation
Central nervous system controls the respiratory rate, depth, and rhythm.
What part of the brain regulates the voluntary control of respiration?
Cerebral cortex
Chemical regulation
Maintains the rate and depth of respirations based on changes in the blood concentrations of CO2 and O2, and in hydrogen ion concentration (pH).
Chemoreceptors
Are located in the medulla, aortic body, and carotid body. They sense changes in the chemical content of O2, CO2, and H (pH) and stimulate neural regulators to adjust.
Cardiac output (CO)
Amount of blood ejected from the left ventricle each minute
CO = SV × HR
Normal cardiac output is _______ L/min in the healthy adult at rest.
4 - 8
Stroke volume (SV)
Amount of blood ejected from the left ventricle with each contraction
What are 3 things that affect stroke volume?
preload, afterload, and myocardial contractility
Preload
the amount of blood in the left ventricle at the end of diastole, often referred to as end-diastolic volume.
What is Starling’s law?
The ventricles stretch when filling with blood. The more stretch on the ventricular muscle, the greater the contraction and the greater the stroke volume.
Afterload
The resistance to left ventricular ejection. ie the pressure that the heart must overcome to pump blood out during systole.
What is a good measure of afterload?
diastolic aortic pressure
How does hypertension affect cardiac workload?
In hypertension the afterload increases, making cardiac workload also increase.
How does myocardial infarction affect SV and CO?
Poor ventricular contraction decreases the amount of blood ejected. Injury to the myocardial muscle such as an acute MI causes a decrease in myocardial contractility.
he myocardium of the older adult is _______________.
stiffer with a slower ventricular filling rate and prolonged contraction time.
How does HR affect blood flow?
With a sustained heart rate greater than 160 beats/min, diastolic filling time decreases, decreasing stroke volume and cardiac output.
What is the role of the cardiac conduction system?
The cardiac conduction system generates and transmits electrical impulses that control the rhythmic relaxation and contraction of the atria and ventricles.
How does the autonomic nervous system affect the heart?
The autonomic nervous system influences the rate of impulse generation, speed of transmission, and strength of atrial and ventricular contractions.
What is the effect of sympathetic nerve fibers on the heart?
Sympathetic nerve fibers increase the rate of impulse generation and speed of transmission.
What is the effect of parasympathetic nerve fibers on the heart?
Parasympathetic nerve fibers, originating from the vagus nerve, decrease the rate of impulse generation.
What is considered the “pacemaker” of the heart?
sinoatrial (SA) node
Where is the sinoatrial (SA) node located?
The SA node is located in the right atrium next to the entrance of the superior vena cava.
What is the intrinsic rate of the SA node in an adult at rest?
The SA node initiates impulses at an intrinsic rate of 60 to 100 cardiac action potentials per minute in an adult at rest.
What is the function of the atrioventricular (AV) node?
The AV node mediates impulses between the atria and the ventricles and assists atrial emptying by delaying the impulse before transmitting it.
What pathways do electrical impulses follow after the SA node?
Electrical impulses are transmitted through the atria along intraatrial pathways to the AV node.
What structures are involved in transmitting impulses from the AV node?
The impulses are transmitted through the bundle of His and the ventricular Purkinje network.
What does an electrocardiogram (ECG) do?
An ECG reflects the electrical activity of the conduction system and monitors the regularity and path of the electrical impulse through the conduction system.
What does an ECG not reflect?
An ECG does not reflect the muscular work of the heart.
What is the normal sequence on the ECG called?
The normal sequence on the ECG is called the normal sinus rhythm (NSR).
What does NORMAL SINUS RHYTHM (NSR) imply?
NSR implies that the impulse originates at the SA node and follows the normal sequence through the conduction system.
What does the P WAVE represent?
The P WAVE represents the electrical conduction through both atria. Atrial contraction follows the P wave.
What does the PR INTERVAL represent?
The PR INTERVAL represents the impulse travel time from the SA node through the AV node, through the bundle of His, and to the Purkinje fibers.
What is the normal length for the PR interval?
The normal length for the PR interval is 0.12 to 0.2 seconds. A PR interval time greater than 0.2 seconds indicates a block in the impulse transmission through the AV node.
What does a decrease in PR interval time less than 0.12 seconds indicate?
It indicates the initiation of the electrical impulse from a source other than the SA node.
What does the QRS complex indicate?
The QRS complex indicates that the electrical impulse traveled through the ventricles.
What is the normal QRS interval and what does an increase in QRS duration indicate?
Normal QRS duration is 0.06 to 0.1 seconds. An increase in QRS duration indicates a delay in conduction time through the ventricles.
What usually follows the QRS complex?
Ventricular contraction usually follows the QRS complex.
What is the normal QT interval and what does the QT INTERVAL represent?
The QT INTERVAL represents the time needed for ventricular depolarization and repolarization. The normal QT interval is 0.12 to 0.42 seconds.
What changes in older adults affect cardiac function?
Calcification of conduction pathways, thicker and stiffer heart valves due to lipid accumulation and fibrosis, and a decrease in the number of pacemaker cells in the SA node.
What are rhythm disturbances called?
Dysrhythmias, meaning a deviation from the normal sinus heart rhythm.