Cardiopulmonary Ventilation - MEDI221 PDF

Cardiopulmonary: Ventilation MEDI221/EXSC221 What You Need to Know How these processes/systems change (differ): from REST to EXERCISE for different types, modes and intensities of exercise for acute (during) and training adaptations  Revision: Lecture O...

Cardiopulmonary: Ventilation MEDI221/EXSC221 What You Need to Know How these processes/systems change (differ): from REST to EXERCISE for different types, modes and intensities of exercise for acute (during) and training adaptations  Revision: Lecture Objectives 1. Know the major terms and abbreviations 2. Review pulmonary structure and function (MEDI111&112) Explain why pulmonary and cardiovascular function important and how much these systems response in exercise Describe similarities and differences between exercise & rest for: Ventilatory and cardiovascular systems People (esp. Fitness) Different forms and intensities of exercise Understand how the body regulates and controls pulmonary function during rest and exercise Reading Chapter 14. Dynamics of Pulmonary Ventilation McArdle, W.D., Katch, F.I. and Katch, V.L. Exercise Physiology: Nutrition, Energy and Human Performance. Lippingcott, Williams and Wilkins, Sydney, NSW, 2014. ISBN/ISSN: 9781451191554. Terminology Respiration: Oxidative metabolism including transport processes: O2: Ventilate → diffuse → circulate → diffuse → Mitochondria CO2: Mitochondria → diffuse → circulate → diffuse → ventilate Pulmonary: Lungs Cardiac: Heart Cardiovascular system: Heart, pulmonary circulation, systemic circulation, blood and cardiovascular centers. A = Alveolar, a = arterial, v = venous, v = mixed venous Dot over a symbol denotes rate. Line denotes mean. Hyperventilation = over breathing (indicated by drop in PaCO2) Hyperpnea = increased rate and depth of breathing What do we regulate to stay alive? Ultimately, cellular homeostasis (internal stable environment) requires regulation of: Blood: Pressure Volume Content Especially: PaCO2 PaO2 [Glucose] Temperature PH Cardiopulmonary Function In Exercise Important because: Oxygen supply to cells (& removal of metabolites) governs exercise ability beyond seconds. ̇ 2max) Impacts performance (VO Oxygen consumption can ↑ 10-fold (sedentary) to 20-fold (athletes) Cardiopulmonary system has huge response capacity & variability: ̇ proportionately more than blood flow Air flow (ventilation; VE) Athletes less stressed at same absolute work rates & achieve higher rates for some factors (e.g., blood flow) but not others (e.g., peak ventilation) Role of the Pulmonary system Oxygenate blood and eliminate CO2 from cellular respiration (Metabolism) Mediated by ventilation of the alveoli Other roles: Acid:Base balance Blood reservoir Heat dissipation Filtration to remove thrombi (clots) Activates, synthesizes or catabolises many chemicals in the blood Aid stabilization of trunk/thorax in resistance exercise Mechanics of breathing Intrapleural pressure is a key feature, if air resistance is low Can get early airway closure (esp with forced expiration) High Low Powers & Howley Fig 10.6 Respiratory Cycle Inspiration = active Diaphragm, external intercostals Expiration = passive (rest) and active (exercise) Abdominal muscles + internal intercostals Breathing Duty cycle = 1/3 at rest, to 1/2 in exercise Respiratory rate is the number of breaths per minute. "Duty cycle" (ratio of time of inspiration to total breath time). Changes in breathing pattern during exercise Do Nasal Strips Improve Athletic Performance? The purpose of nasal strips Reduce nostril airway resistance Theoretically, would increase airflow into lungs No evidence of increased ventilation or performance Why? Because Vt is not limited by available volume! (and VE is normally not limiting factor for exercise performance) Potential psychological advantage? Do respiratory muscles fatigue during exercise? Historically believed that respiratory muscles do not fatigue during exercise Current evidence suggests that respiratory muscles do Your Turn fatigue during exercise Which muscles Prolonged (>120 minutes) will contribute to High-intensity (90–100% VO2 max) respiratory muscle Do respiratory muscle adapt to training? fatigue the most? Yes! Why? Increased oxidative capacity improves respiratory muscle endurance Reduced work of breathing  May help with your group assignment if these interest you. Lean what is reliable or not. Consider this when searching for sources of information for Extended https://www.youtube.com/watch?v=nd5 Abstracts and Fact Sheets U7mDhFi4 Ventilatory response to exercise Ventilation = The amount of air moved in or out of the lungs per minute (V) - Tidal volume (VT) Amount of air moved per breath - Breathing frequency (f) Number of breaths per minute Cyclic relationship between tidal volume and breathing frequency Control of Ventilation Respiratory control At rest (revision), center Mainly by chemoreceptors (detect chemical state of arterial blood) Central chemoreceptors Peripheral chemoreceptors More sensitive to changes in CO2 than O2 Control of Ventilation During exercise: PaCO2 and PaO2 are stable. Unlike at rest, they’re NOT the major fact or controlling ventilation 1. Central command (feedforward control) Phase 1 and 2 – esp onset 2. Muscle ergoreceptors (feedback control) Phase 1 and 2 – Mechanoreceptors Phase 3 – Metaboreceptors (chemoreceptors) 3. Other ergoreceptors (fine tuning) Intercostal and diaphragm spindles, heart mechanoreceptors (pressure), Lung CO2, Temperature etc Three phases of exercise hyperpnea. Phase I: Rapid increase from rest and brief plateau from central command drive and input from active muscles. Phase II: Slower exponential rise begins approximately 20 s after exercise onset. Central command continues, along with feedback from active muscles plus the added effect of short- term potentiation of respiratory neurons. Phase III: Major regulatory mechanisms reach stable values; added input from peripheral chemoreceptors fine-tunes Chapter 14 Fig 14.4 Text book the ventilatory response.  Central Command Fig 14.1 Text book  Ventilatory Response to Continuous (sustainable exercise)  Ventilatory Response to Non- Sustainable Exercise  Ventilatory Response to ↑ Exercise Intensity Anaerobic Metabolism Aerobic Metabolism Fig 14.5 Text book Ventilatory Responses in Trained vs Untrained Exercise in a Hot/Humid Environment Recap Your Turn At rest what is mainly driving this response? Recap Your Turn During exercise what is mainly driving this response? Additional take home messages: The primary drive to increase ventilation during exercise probably comes from higher brain centers (central command). Also, humoral chemoreceptors and neural feedback from working muscles act to fine-tune ventilation. The major muscle of inspiration is the diaphragm. Air enters the pulmonary system due to intrapulmonary pressure being reduced below atmospheric pressure (bulk flow). At rest, expiration is passive. However, during exercise, expiration becomes active, using muscles located in the abdominal wall (e.g., rectus abdominis and internal oblique). The primary factor that contributes to airflow resistance in the pulmonary system is the diameter of the airway. Pulmonary ventilation refers to the amount of gas moved into and out of the lungs. Additional take home messages: The amount of gas moved per minute is the product of tidal volume times breathing frequency. An increase in pulmonary ventilation causes exhalation of additional CO2, which results in a reduction of blood PCO2 and a lowering of hydrogen ion concentration (i.e., pH increases). At the onset of constant-load submaximal exercise, ventilation increases rapidly, followed by a slower rise toward a steady-state value. Arterial PO2 and PCO2 are maintained relatively constant during this type of exercise. During prolonged exercise in a hot/humid environment, ventilation “drifts” upward due to the influence of rising body temperature on the respiratory control center. Incremental exercise results in a linear increase in VE up to approximately 50% to 70% of O2 max; at higher work rates, ventilation begins to rise exponentially. This ventilatory inflection point has been called the ventilatory threshold.