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Lecture

Altered Ventilation and Diffusion.docx

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Department
Nursing
Course
NURS 2090
Professor
Heather Helpard
Semester
Fall

Description
Altered Ventilation and Diffusion Respiratory Structures Alveolar type 1: provide structure and air exchange Alveolar type 2: lubricant that coats the inner portion of the alveolus, promotes easy expansion, repels fluid accumulation ** inflation would be impossible w/out it Rate and volume of ventilation is regulated by: 1. Functioning respiratory control center (RCC): responds to chemical messages in the body. Composed of neurons in the pons/medulla. It sends impulses to diaphragm, muscles to contract/relax. (Constriction= Para, Dilation = Symp) 2. Lung receptors: Located in the epithelium/smooth muscle airways. 3. Chemoreceptors: detect gas exchange needs based on PaO2, PaCo2, pH levels. Central chemoreceptors: near RCC, respond to pH changes in the CSF. Detects CO2 levels in the blood. (↑ CO2 = ↑ ventilation to expel CO2) Peripheral chemorecepotrs: sensitive to O2 levels, located in aorta/carotid arteries. ( ↓ O2 = ↑ ventilation) Ventilation: Process of moving air in/out of lungs • Involves both acquiring oxygen (inspiration) and removing carbon dioxide (expiration) from the blood • Neuronal impulses are directed by lung receptors, which map the current state of breathing and lung function • Uses the intercostal muscles, diaphragm, and sternocleidomastoid muscles Inspiration • Breathing in to acquire oxygen • Unidirectional from high pressure to low pressure. • Chest cavity size changes to alter the pressure gradient • Neuronal stimulation/movement moves diaphragm down and out (reduces pressure inside lungs to pull air in) Expiration • Removing carbon dioxide out of the body through the lungs • The diaphragm and external intercostal muscles relax • Lungs compress and increase the pressure inside the airways • Chest wall moves in and diaphragm moves upwards. • Inside pressure is more than atm pressure (so air moves OUT) Measurement of Ventilation 1. Tidal volume (TV): the amount of air exhaled after passive inspiration (air in and out at rest) ** 500 mL 2. Vital capacity (VC): max amount of air in/out of lungs with forced inhale/exhale 3. Forced capacity (FVC): amount exhaled during forced exhale 4. Forced expiratory volume in 1 second (FEV1): amount exhaled from lungs in 1 sec 5. Residual volume (RV): volume of air left in lungs after maximal expiration 6. Total lung capacity: total air in lungs when they are maximally expanded (VC+ RV) Diffusion: Process of moving/exchanging O2/Co2 through membranes • Oxygen and carbon dioxide are exchanged at alveolar capillary junctions • Two major process occur: • Oxygen is trying to get to all the cells • Carbon dioxide is trying to escape the body through the lungs • Effectiveness depends on: Pressure (Co2, O2 in blood), Solubility (Co2 more soluble), and Membranes (thickness/SA) Partial Pressure • The collision of oxygen and carbon dioxide creates pressure • PaO2 • PaCO2 Perfusion: Process of supplying oxygenated blood to lungs and organ systems via blood vessels Respiration: Process in which cells in the body use O2 to make energy Oxygen Diffusion and Transport • Oxyhemoglobin (HbO2): As PaCO2 ↑ oxygen dissociates from the plasma and connects with hemoglobin molecules on RBC’s. Based on attraction to iron. When it is attached to hemoglobin, it is not available to the cell. • Oxygen Saturation (SaO2): Attraction of hemoglobin continutes until the hemoglobin molecules are completely saturated. It is NOT affected by blood volume. • Once saturation occurs, oxygen continues to diffuse and dissolve in the plasma, until the partial pressures in arteries = that in the alveoli Carbon Dioxide Diffusion and Transport • Dissolved in the plasma (10%) • Bound to hemoglobin (20%) • Diffused into the red blood cell as bicarbonate (70%): converted to either carbonic acid, bicarbonate ions (which helps regulate pH) Diffusing Capacity • The measurement of carbon monoxide, oxygen, or nitric oxide transfer from inspired gas to pulmonary capillary blood and is reflective of the volume of a gas that diffuses through the alveolar capillary membrane each minute. Impaired Ventilation • A problem of blocking airflow in and out of the lungs • Two major mechanisms implicated: • Compression or narrowing of the airways (↑ airway resistance, leading to difficulties with airway clearance, ie. Edema, exudates or inflammation) • Disruption of the neuronal transmissions needed to stimulate the mechanics of the airways (ignores messages sent by chemoreceptors/lung receptors, ie. Drug overdose) Impaired Ventilation-Perfusion Matching • Two possible scenarios: • Lung are ventilated, but not perfused • Lung is perfused, but not ventilated • Impaired ventilation: inadequate o2 comes from lungs even though the blood flow is ready and able to carry oz. • Impaired perfusion: the blood flow to the lungs is restricted in one or more areas. Oxygen might be coming in, but have no blood flow to carry it to the body. Altered Ventilation and Perfusion Impaired Diffusion • Restricted transfer of oxygen or carbon dioxide across the alveolar capillary junction • Dependent upon: • solubility and partial pressure of the gas: partial pressure is increased when molecules are packed in a space, temp increases, when barometric pressure increases. Decreased oxygen pp can occur in o2 deprevation, hypothermia. CO2 increases with metabolism increase/ exercise. • surface area and thickness of the membrane The Effects of Impaired Ventilation and Diffusion 1. Hypoxemia: is decreased oxygen in the arterial blood leading to a decrease in the PaO2. (caused by o2 deprivation, hypoventilation) 2. Hypoxia: When cells are deprived of adequate oxygen. (widespread hypoxemia) 3. Hypercapnia: a state of ↑CO2 in the blood (CO2 is more easily diffused, so it only really happens when there is severe alveolar hypoventilation followed by hypoxia). General Manifestations of Impaired Ventilation and Diffusion • Local manifestations: usually due to inflammatory processes • Cough (common, protective), mucus, hemoptysis • Dyspnea (feeling of SOB), orthopnea (the physical need to sit in an upright/standing position) • Adventitious lung sounds (altered) (ie. Wheezing= constricted airway) • Use of accessory muscles (retractions= the pulling in of accessory muscles to promote more effective inspiration) • Chest pain (can originate in the visceral/pleural/airway/chest wall. Pleural pain increases with deep inspiration and often described as sharp/stabbing pain) • Barrel chest: due to chronic dilation and distention of the alveoli (i.e emphysema) • Systemic manifestations: due to hypoxemia/ hypercapnia • Fever, malaise, leukocytosis • ↑ plasma proteins • Dusky/cyanotic mucus membrane color • Changes in arterial blood gases • Mental status changes • Finger clubbing (painless enlargement/flattening of tips of fingers/toes, caused by chronic hypoxia) Laboratory and Diagnostic Tests • History and physical examination • Visualization (bronchoscopy, x-ray, CT, MRI, nuclear medicine, etc.) • Pulmonary function tests • Pulse oximetry • Laboratory studies Treating Impaired Ventilation and Diffusion • Remove obstruction and restore physical integrity of airways, lung tissues • Decrease inflammation and mucus; treat infection • Supplemental oxygen • Mechanical ventilation Pneumonia Pathophysiology: • Acute infectious process on ventilation/diffusion (caused by miccrorganism, community acquired: strep/staph/influenza; nosocomial: pseudo/staph) • Respiratory droplet spread • Causes inflammation of the lungs • Occurs commonly in the bronchioles, interstitial lung tissue and/or the
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