If arytenoid folds do not open adequately, then air flow is compromised as a function of R 1

1. If arytenoidfolds do notopenadequately,then air flowis compromisedas a function of R = 1/r4

2. The smallerthe radiusof thetrachea,the moreresistanceis increasedand the lessair is conductedto lungs for gas exchange

3. Vocal folds Vibrate asair moves past Functionin phonation Potentialto restrict airway

4. Larynx Cartilageand lotsof muscleto controlairmovement through larynx and into trachea Easily palpated beneath mandible

5. Larynx is the narrowest portion of conductive airway Air has to travel over the epiglottis, past arytenoid folds, past vocal folds, into trachea Most restrictive, most air resistance Pathology here = significant impact on performance

7. Normal lung volumes 450 kg horse Tidal volume at rest 5-6 L During exercise tidal volume double to 10-12 L/breath Humans at rest 500 ml �Tidal� because moves forward and backwards Volume of each normal passive breath (Diagram of respiration volumes?)

9. Inspiratory reserve The extra volume when you take a deep breath Expiratory reserve The extra volume when you maximally exhale

10. Vital capacity = maximum inspiration/expiration volume Tidal volume + inspiratory reserve + expiratory reserve Total lung volume available for air exchange This is the volume measured during compliance testing

11. Residual capacity The volume left over in tissues that you can�t entirely flatten during expiration

12. Respiratory rate at rest average 12-16 breaths per minute Minute ventilation = Ve Tidal volume x breaths per min 5 liters x 12 bpm = 60 liters/min

13. During galloping exercise Respiratory rate is coupled to stride frequency at gallop => one breath per stride

14. Duringstancephase ofgallop,viscera inabdominalcavity actas a pistonmovingagainst thediaphragm to assist expiration

15. Asforelimbsmoveforward,ribs areliftedforward andupward to expand thorax and assist in inspiration

16. Respiratory - stride coupling only occurs during cantering or galloping Doesn�t occur during walk or trot Rhythmic respiration occurs, but not strictly related to piston-pendulum movement

17. At submaximal levels, coupling may be 1:1 or 1:2 One breath per stride; or one breath every two strides Less than 1:1 coupling may also occur with respiratory disease Airway obstruction COPD, �heaves� Decreased compliance

18. Respiratory-stride coupling saves energy, but may also limit VO2max Cannot increase resp rate above stride frequency Once horse reaches maximal stride frequency, cannot further increase Ve Favors horses with longer stride Slower stride frequency allows deeper (more efficient) breathing

19. At maximal levels, always 1:1 Cannot take more than one breath per gallop stride

20. Tidal volume linear increase as speed increases from 5 => 12 L 2-fold increase from rest to maximal exercise Respiratory rate may increase from 12 at rest up to 120 breaths per minute 10-fold increase

21. Minute ventilation = Ve Tidal volume x breaths per min (GTQ) 5 liters x 12 bpm = 60 liters/min The majority of increase in Ve between rest and maximal exercise is a function of the increase in respiratory rate; a relatively small proportion is due to increase in tidal volume (GTQ)

22. Air to lungs is not uniformly distributed Dorsal portions receive more air than ventral portions In humans, upper portions (superior) of lungs receive more air than lower (inferior) portions

23. Dorsal portions receiving more air flow also receive more blood circulation for optimum gas exchange Blood circulating through lungs = perfusion

24. Ideally, you want ventilation and perfusion to �match� in a 1:1 ratio V/Q ratio Not more blood flow than can be ventilated for gas exchange Not more air flow than blood can exchange gases with

25. Units of measurement mmHg measured as gas pressure of O2 and CO2 at alveolus; and within capillary Ventilation � perfusion

26. If ventilation-perfusion ratio is perfect, then �1.0� ration In reality, this is hard to attain Gravity makes it more difficult for ventral lung tissue to be optimally/maximally ventilated, even in healthy, young animal Most alveoli V/Q 1.0, some 0.8

27. �Normal� V/Q ratio 0.8 � 1.0 Slightly less ventilation than perfusion If air and blood flow are not synchronized => �ventilation-perfusion mismatch� or V/Q mismatch Minor deviations normal

28. V/Q mismatch Pneumonia (adequate perfusion, compromised ventilation) V/Q ratio <<< 1.0 In extreme cases V/Q = 0 Zero ventilation � �x� units perfusion = 0

29. V/Q mismatch Heart disease (adequate ventilation, reduced blood flow) V/Q ratio >>> 1.0 In extreme cases, V/Q = 0�x� units ventilation � zero perfusion = 0

30. Right-to-leftshunts Defect inseptal wallallows bloodto flowdirectlyfrom RVto LV,bypassingpulmonic loop

31. Right-to-leftshunts Moreventilationthan perfusion V/Q > 1.0

32. Respiratory disease or pathology Infectious disease Bacterial, viral, fungal Lung tissue consolidation Trauma to airway or assoc�d tissues Ethmoid hematoma Damage to muscles, nerves innervating airways

34. Neuromuscular disease Direct or indirect effect on nerves and muscles innervating airway structures Guttural pouch disease Recurrent hemiplegia Partial or complete paralysis of arytenoid fold � decreased air flow

35. Respiratory disease => more perfusion than ventilation V/Q <<< 1.0