Oxygenation & Ventilation PDF

# Oxygenation & Ventilation ## Objectives: * Explain the difference between ventilation and oxygenation * Describe what stimulates ventilation in normal and hypoxemic patients. * List and describe the 5 causes of hypoxemia and examples of each. ## Oxygen Delivery $DO_2 = Cardiac Output \times Oxy...

# Oxygenation & Ventilation ## Objectives: * Explain the difference between ventilation and oxygenation * Describe what stimulates ventilation in normal and hypoxemic patients. * List and describe the 5 causes of hypoxemia and examples of each. ## Oxygen Delivery $DO_2 = Cardiac Output \times Oxygen Content$ $DO_2 = CO \times CaO_2$ $DO_2 = (HR \times SV) \times [(Hb)(SpO_2)(1.36) + 0.003 \times PaO_2]$ ## Gas Exchange * Oxygenation = oxygen * FiO2 * Transfer across alveolus * Ventilation dependent * Ventilation = Carbon dioxide * Rate and depth of breath ## Carbon Dioxide (PaCO₂) usually determines ventilation CO₂ produced H₂CO₃ HCO₃^- and H ⁺ ↑ H⁺ in CSF stimulates chemoreceptors Ventilation ## Effect of PCO₂ on minute ventilation An image of a graph showing the effect of PaCo2 on minute ventilation. The graph displays a normal response curve. ## Causes of hyperventilation * Pain, anxiety, excitement * Hyperthermia * Acidosis * Hypoxemia ## Causes of hypoventilation * Central neurologic * Brain (medulla, pons, cerebrum) * Cervical spinal disease * IVDD, Wobblers, AA subluxation * Drugs (Opioids, propofol, anesthesia) * Peripheral neurologic * Lower motor neuron disease * Botulism, M. gravis, polyradiculoneuritis, tick paralysis ## Causes of hypoventilation * Respiratory system disease * Airway obstruction * Parenchymal dz * Pleural space disease * Disorders of the thoracic cage/diaphragm ## Oxygen (PaO₂) determines ventilation if hypoxemia is severe An image of a diagram showing: * Severe hypoxemia (PaO₂ < 60 mmHg) * Aortic & carotid body chemoreceptors that sense low O₂. * Ventilation * PaCO₂ * Low SpO₂, as well as CO₂, anemia, and acidosis ## Effect of hypoxemia on minute ventilation An image of a graph showing the effect of hypoxemia on minute ventilation. The graph displays a curve where minute ventilation decreases as PaO₂ increases. ## Effect of minute ventilation on PO₂ An image of a graph showing the effect of minute ventilation on PaO₂. The graph displays curves of differing FiO₂ (0.21, 0.3, and 0.4), where PaO₂ increases as minute ventilation increases. ## Effect of PCO₂ on minute ventilation An image of a graph showing the effect of PaCo2 on minute ventilation. The graph displays normal response, raised threshold, and reduced sensitivity curves. ## Five causes of hypoxemia * Decreased FiO₂ * Alveolar hypoventilation * R to L Shunt * Diffusion impairment * Venous admixture (V/Q mismatch) ## Decreased FiO₂ * Under anesthesia * At altitude * PiO₂ = FiO₂ (Patm - PH₂O) * 150 = 0.21 (760-47) ## Five causes of hypoxemia * Decreased FiO₂ * Alveolar hypoventilation * R to L Shunt * Diffusion impairment * Venous admixture (V/Q mismatch) ## Effect of ventilation on PCO₂ An image of a graph showing effect of ventilation on PaCO₂. The graph shows that PaCO₂ decreases with increasing minute ventilation. ## Hypoventilation * Causes? ## Causes of hypoventilation * Central neurologic * Peripheral neurologic * Respiratory disease ## Diffusion impairment * Rarely a significant cause of hypoxemia in veterinary patients. * Oxygen exchange completed in first 1/3 of the alveolar capillary ## Diffusion impairment * Chronic obstructive pulmonary disease * Smoke inhalation ## R to L shunt * Abnormal circulation allows deoxygenated blood to enter systemic circulation. * Tetralogy of Fallot * Transposition of great vessels * Persistent truncus arteriosis * Tricuspid atresia * RL PDA An image of a diagram of the heart with arrows showing circulation. The diagram includes: * Vena Cava * Pulmonary Veins * Right Atrium * Left Atrium * Right Ventricle * Left Ventricle * Aorta ## Venous admixture * Imbalance between blood flow and alveolar ventilation ## Venous admixture: High V/Q * Also called physiologic deadspace when Q=0 ## Venous admixture: High V/Q * Pulmonary thromboembolism * Pulmonary arterial hypertension ## Venous admixture: High V/Q * Also called physiologic deadspace when Q=0 ## Venous admixture: Low V/Q * Also called physiologic shunt when V=0 ## Venous admixture Low V/Q * Cardiogenic pulmonary edema * Non-cardiogenic pulmonary edema * Pneumonia * Inflammation * Atalectasis * ARDS * Airway obstruction ## Venous admixture: compensation * High V/Q → local hypocapnia → increased pH → local bronchoconstriction * Low V/Q → Increased CO₂→ stimulates increased ventilation → improves CO₂>O₂ * Low V/Q → hypoxic pulmonary vasoconstriction * Divert some bloodflow to better ventilated areas ## Using Respiratory Patterns to Identify Source of Dyspnea Amie Koenig, DVM, DACVIM (SAIM), DACVECC ## Today's objectives * How to recognize and interpret abnormal respirations and respiratory patterns * Recognize signs of impending respiratory arrest * How to relate breathing pattern to source of dyspnea. * Make stabilization plan based on location. ## Locations of Dyspnea Includes an image of a dog with the following labels: * Extrathoracic airway * Intrathoracic airway * Pulmonary parenchyma * Thoracic cage * Pleural space * Vascular ## Normal Respiration * Barely noticeable at rest * Ribs move cranially and outward * Diaphragm moves caudally * Abdomen moves passively outward * Thorax and abdomen move together ## Recognizing Respiratory Distress * Increased respiratory rate and effort. * Open mouth, flared nostrils. * Tail bobbing, hyperinflated airsacs (birds) * Anxiety, restlessness. * Orthopnea. * Cyanosis. * Noise. * Irregular pattern or rhythm ## Recognizing Respiratory Distress * Increased respiratory rate and effort. * Open mouth, flared nostrils. * Tail bobbing, hyperinflated airsacs (birds) * Anxiety, restlessness. * Orthopnea. * Cyanosis. * Noise. * Irregular pattern or rhythm ## Orthopnea An image of a dog and a cat showing orthopnea. ## Orthopnea An image of a cat showing orthopnea. ## Cyanosis * Insensitive. * Denotes severe oxygen deficiency, IF present. * PaO₂ ~40 mmHg * SpO₂ ~ 75% * 5 g/dl of deoxy Hb ## Cyanosis * Insensitive. * Denotes severe oxygen deficiency, IF present. * PaO₂ ~40 mmHg * SpO₂ ~ 75% * 5 g/dl of deoxy Hb An image of a graph showing total O₂, O₂ combined with HB, and dissolved O₂. ## Noise * Stridor * Stertor ## Stridor An image of a whistle and a dog demonstrating stridor. ## Stridor An image of a whistle and a horse demonstratig stridor. ## Stridor An image of a whistle and a horse demonstrating stridor. ## Stertor An image of flags blowing in the wind and a cat demonstrating stertor. ## Stertor An image of flags blowing in the wind and a dog demonstrating stertor. ## Irregular Patterns * Paradoxical respiration * Irregular rhythm * Irregular pattern ## Paradoxical respiration * Chest and abdomen move in opposite directions. * Ribs/intercostals move inward during inspiration. * Increased negative pressure * Weakness of the intercostal muscles (fatigue) * Outward movement of abdomen during inspiration, inward on expiration. * Abdominal musculature assists chest movement. * Not specific for location! ## Paradoxical respiration An image of a dog demonstrating paradoxical respiration. ## Paradoxical respiration An image of a dog demonstrating paradoxical respiration. ## Paradoxical respiration An image of a cat demonstrating paradoxical respiration. ## Irregular Patterns * Paradoxical respiration * Irregular rhythm * Irregular pattern ## Paradoxical respiration An image of a dog demonstrating paradoxical respiration. ## Not in reptiles * Non-ventilatory periods are NORMAL. * Duration between breaths gets shorter in reptiles with respiratory diseases. ## Not in reptiles * Non-ventilatory periods are NORMAL. * Duration between breaths gets shorter in reptiles with respiratory diseases. ## Signs of Impending Respiratory Arrest * Prey species! * Decreased mentation. * Restlessness, changing body position. * Vocalization * Lateral recumbency (cat) * Mydriasis (cat) * Puffed tail (cat) * Irregular breathing pattern. ## In Case of Impending Respiratory Arrest... * Discuss with client. * All dyspneic BIRDS and small mammals. * Intubate & Ventilate? * Prior to arrest!! * Low doses of drugs ## Locations of Dyspnea An image of a dog with the following labels: * Extrathoracic airway * Intrathoracic airway * Pulmonary parenchyma * Thoracic cage * Pleural space ## Birds * Unidirectional airflow. * Loss of voice (syrinx)/stridor → upper airway * Otherwise can't tell * Hx, PE, radiographs! ## Reptiles * Inc. RR and RE. * Shorter non-ventilatory periods. * Can visualized larynx. * Limited auscultation. * Need Hx, PE, radiographs. ## Respiratory Patterns * Normal * Obstructive * Restrictive * Hypoventilation ## Obstructive Pattern * Narrowing of airways. * Slow, deep breaths. * Lungs able to fully expand. * Large chest wall movements. ## Obstructive pattern * Dynamic * Obstruction moves and only impedes breathing during one phase of respiration. * Eg: Laryngeal paralysis, collapsing trachea, some tumors * Fixed * Obstruction does not change. * Concentric neoplasia * Some foreign objects * Crush injury ## Obstructive Pattern * Dynamic extrathoracic airway obstruction * Prolonged, pronounced inspiratory effort. * Intrathoracic airway obstruction * Prolonged, pronounced expiratory effort. * Fixed, or dynamic intra & extrathoracic obstruction * Increased inspiratory and expiratory effort. ## Obstructive Pattern An image of a dog demonstrating an obstruction. ## Obstructive Pattern An image of a dog demonstrating an obstruction. ## Obstructive Pattern An image of a dog demonstrating an obstruction. ## Extrathoracic Airway: Differentials * Nasal * Nasopharynx / Oropharynx * Extrathoracic trachea ## Extrathoracic Airway: Differentials | | Small Animals | Large Animals | |:--------------|:----------------------|:--------------------| | **Nasal** | Stenotic nares/stricture| Inflammation (snake bites/allergic) | | **Cavity** | Polyp | Neoplasia (rare) | | | Infection | Arytenoid chondritis | | **Pharyngeal**/| Laryngeal paralysis/ | Necrotizing laryngitis (cattle) | |**Laryngeal** | collapse | | | | Laryngeal edema/inflammation | Strangles (#1 in horses) | | | Everted saccules | -Strep equi equi | | | | Gutteral pouch dz/tympany | | | Elongated soft palate | Choanal atresia | | | Foreign body/trauma | Laryngeal paralysis (bilat) | | | Neoplasia | Neoplasia | ## Extrathoracic Airway: Nasal Differentials | | Small Animals | Large Animals | |:--------------|:----------------------|:--------------------| | **Extrathoracic** | Tracheal collapse | Tracheal collapse (miniature horses)| | **trachea** | Tracheal stenosis/stricture | Same as small animals, just uncommon | | | Foreign body | | | | Neoplasia | | | | Parasites | | | | Traumatic (rupture --> stricture) | | ## Intrathoracic Airway: Differentials | | Small Animals | Large Animals | |:--------------|:----------------------|:--------------------| | **Asthma** | (cats) | (horses) | | **Tracheal Stenosis/Stricture** | | | | | Traumatic (rupture --> stricture) | Same as small animals, just uncommon | | | Neoplasia | | | | Parasites | | | | Foreign body | | | | Bronchial disease | | ## Obstructive Pattern An image of a diagram with arrows showing the relationship between panic/anxiety, obstruction, can't move air, breathe harder, and inflammation. ## Worsening Obstruction An image of a diagram with arrows showing the relationship between hypoxemia, panic/anxiety, worsening obstruction, can't move air, breath harder, hyperthermia, and inflammation. ## Obstruction Worsens An image of a diagram with arrows showing the relationship between hypoxemia, panic/anxiety, obstruction worsens, can't move air, breathe harder, hyperthermia, and inflammation. ## Airway: Initial Treatment * Ensure patent airway!! * Verify air flow * Intubate small animals if... * Not passing air * Cyanotic * Distressed/panic * Fatigued * Tracheostomy * Rarely needed in SA. * More common in LA. ## Airway: Initial Treatment * Oxygen! * Sedation or anxiolytic * Butorphanol or acepromazine in SA. * Cooling as needed. * +/- anti-inflammatory corticosteroids * Prednisone or dexamethasone. * +/- bronchodilator (feline asthma) * Aminophylline or terbutaline. ## Restrictive Pattern * Prevent lungs from fully expanding. * Shallow chest wall excursion. * Chest wall does not fully expand. * Large abdominal effort. * Parenchymal disease * Pleural space disease ## Restrictive Pattern An image of a dog demonstrating a restrictive pattern. ## Restrictive Pattern An image of a dog demonstrating a restrictive pattern. ## Restrictive Pattern An image of a cat demonstrating a restrictive pattern. ## Restrictive Pattern * Parenchymal disease or Pleural space disease. * Differentiated by ?? ## Pleural Space: Differentials * AIR.....FLUID.....TISSUE * Pneumothorax * Pleural effusion * Blood, pus, chyle, pure or modified transudates * Pleuropneumonia in the horse * Thymoma related – goat * Neoplasia * Diaphragmatic hernia ## Pleural Space Disease Stabilization * Oxygen supplementation * AND... An image of a dog during pleural space disease stabilization. ## Pulmonary Parenchyma: Differentials | | Small Animals | Large Animals | |:---------------|:----------------------|:--------------------| | **Pneumonia** | (viral, bact, fungal, parasitic) | (#1) | | **Aspiration Pneumonia** | (dogs) | (usu young or choke patients, colic (tubing)) | | **Congestive Heart Failure** | | (occ) | | | Noncardiogenic edema | Noncardiogenic edema | | | Hemorrhage/contusions | Equine multinodular pulmonary fibrosis (EHV5?) | | | Neoplasia | ARDS (foals) | | | ARDS/Inflammation (PIE) | Atypical pneumonia (ruminants) | | | Heartworm | Silicosis | | | Thromboembolic disease | Lung worm/parasite migrations | ## Pulmonary vascular: Differentials | | Small Animals | Large Animals | |:---------------|:----------------------|:--------------------| | **Thromboembolic disease** | | Core pumonale (cattle) | | **Pulmonary hypertension** | | (horse) | | | Heartworm | | ## Pulmonary Parenchyma: Stabilization * Oxygen * +/- sedation – butorphanol. * Disease specific. * Diagnostics usually necessary. * May try empiric treatment. * History * Other physical exam findings. ## Hypoventilation * Reduced/absent chest wall movements * Usually shallow abdominal movements * No or minimal signs of distress. ## Hypoventilation An image of a cat demonstrating hypoventilation. ## Hypoventilation: Differentials * Central nervous system * Brain * Cervical spine * Phrenic nerve * Neuromuscular causes * Myasthenia gravis, botulism * Tick paralysis, polyradiculoneuritis (coonhound paralysis) * Hypokalemia, polymyositis ## Hypoventilation Treatment * Oxygen. * Treat underlying cause. * Intubate and ventilate. * Monitor. ## Masqueraders.... * Hyperthermia * Pain * Metabolic Acidosis * Fear/ Excitement * Anemia/Hemoglobinopathy * Hypoglycemia (esp neonates) * Purring * Display/threat behavior ## Masqueraders.... An image of a cat demonstrating a masquerader. ## Masqueraders.... An image of a lizard demonstrating a masquerader. ## Masqueraders.... An image of a cat demonstrating a masquerader. ## Masqueraders.... An image of a cat demonstrating a masquerader. ## Masqueraders.... An image of a bird demonstrating a masquerader. ## Masqueraders.... An image of a dog demonstrating a masquerader.