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Lung Disease: Pathophysiology, Medical and Exercise Programming Overview of Pathophysiology Ventilatory Impairments Increased airway resistance Reduced compliance Increased work of breathing Ventilatory muscle weakness Ventilatory inefficiency Ventilatory muscle fatigue Ventilatory failure Pulmonary Diseases Subtypes Obstructive Restrictive Mixed Pulmonary Vascular Hypertension 1 Overview of Pathophysiology Abnormalities of Gas Exchange Destruction of the alveolaralveolar-capillary membrane VentilationVentilation-perfusion inequality Cardiovascular Impairments Cardiovascular deconditioning Reduced pulmonary vascular conductance Overview of Pathophysiology Muscular Impairments Peripheral muscle deconditioning Symptomatic Limitations Breathlessness (dyspnea) Psychological Disturbances Chronic Anxiety Depression Obstructive Diseases Result of narrowing of the airways leading to uneven distribution of ventilation Low FEV1/FVC ratio and FEF 2525-75 Chronic Bronchitis, Emphysema, Asthma “Blue Bloater” Bloater” 2 Restrictive Diseases Restriction of lung volume by disease involving the thorax or the lung parenchyma Diseases of the rib cage and spine – scoliosis, spinal cord injury, pleuritis, pleuritis, obesity Involves inflammation of the interstitium and alveolar tissue w/ accompanying fibrosis “Pink Puffer” Puffer” “Blue Bloater” Obstructive Diseases “Pink Puffer” Restrictive Diseases 3 Pulmonary Rehabilitation 4 Pulmonary Vascular Disease Most common is thromboembolism Causes include – bed rest, pregnancy, chronic cardiac or pulmonary disease, peripheral venous insufficiency Dead space ventilation increases as alveoli distal to clot are not ventilated properly Reduced lung diffusion capacity due to reduced available vascular bed and fluid leakage into the interstitium May develop pulmonary hypertension Hypoventilation Syndromes Obstructive Sleep Apnea Central Apnea Mixed apnea ObesityObesity-hypoventilation syndrome – “Pickwickian syndrome” syndrome” 5 Exercise Response Blunting of ventilatory response Mechanical limitation of air flow and respiratory muscle function Impairment of gas exchange by VA/Q mismatch, Shunting Diffusion limitation Ventilatory Limitations Effecting Exercise Response Ventilatory response limitations Mechanical Ventilatory Limitation – VE/MVV; 60 to 70 % is normal. Usually, one will find elevated ratio in those with disease (also called ventilatory reserve) Breathing patterns 6 Pulmonary Gas Exchange Limitations Effecting the Exercise Response Related to hypoventilation, diffusion limitation, or shunting Saturation (SaO2) – helps to determine hypoxemia < 90% EndEnd-Tidal CO2 – helps to determine hypercapnia, normal resting PETCO2 is 36 – 42 mmHg and increases slightly during submaximal exercise and decreases during maximal exercise (implies changes in PaCO2) Arterial blood gasses – if there is a significant decrease with steady state exercise of PaO2 (>20 mmHg), may be associated with disease Dead space limitation – VD/VT, normally 40% at rest and declines to about 20% during exercise. In disease patient, VD/VT is increased at rest and may not decrease during exercise Pulse oximeter – SaO2 monitoring A source of light originates from the probe at two wavelengths (650nm and 805nm). The light is partly absorbed by hemoglobin, by amounts which differ depending on whether it is saturated or desaturated with oxygen. By calculating the absorption at the two wavelengths the processor can compute the proportion of haemoglobin which is oxygenated. Pulmonary Gas Exchange Limitations Effecting the Exercise... 7 Cardiovascular Responses Most pulmonary patients show a “deconditioned” deconditioned” response to exercise May not reach true maximum heart rate Normal HR/VO2 response Normal Q/ VO2 response but stop at a lower level Medical Management: Goals Optimizing respiratory mechanics Correction of hypoxemia Breathing retraining Desensitization to symptoms Improving mechanical efficiency Exercise essential in preventing further decrements in functioning 8 Medical Management: Medications Sympathomimetic agonists (albuterol, metaproterenol, and salmeterol) – selective beta2beta2adrenoreceptor agonists Be aware of effect on peripheral vascular resistance Methylxanthines (theophylline and aminophyilline) – bronchodilator effect, but side effects of tachycardia, dysrhythmias, and central nervous system stimulation Medical Management: Medications Thiazide diuretics (HCTZ) and loop diuretics (furosemide) – control fluid retention cor pulmonale. Be aware of hypokalemia, arrhythmias, and muscle weakness Glucocorticoids (prednisone) - prescribed to reduce inflammation in those with longlong-standing COPD. Be aware of side effects on skeletal muscle. Antidepressants (tricyclics) Optimization of medical therapy Controlled breathing techniques Nutritional therapy Chest physical therapy Psychosocial support Assessment and Education Exercise training Continuing care programs http://www.lung.ca/asthma/exercise/ 9 Exercise Management: Prescription Goals of exercise therapy Increase functional capacity Increase vital capacity Decrease respiratory rate Decrease dyspnea Exercise Management: Prescription Peak Met Capacity = 3 - 4 METs Mode Walking, cycling, rowing Intensity 50% of VO2pk Above lactate threshold 100% of peak as tolerated by symptoms 3 to 6 on Borg dyspnea chart Frequency/Duration Short, intermittent bouts of activity Exercise Management: Special Issues Pursed lips breathing Supplemental Oxygen – blood oxygenation should be monitored during each exercise session (oximetry) Supplemental oxygen required if PaO2 < 55 mmHg or SaO2 < 88% while breathing room air 10 Exercise Management: Special Issues Upper body resistance – high repetition, low intensity efforts of the arm and shoulders muscles Ventilatory Muscle Training – use to increase respiratory muscle strength Train inspiratory side 4 to 5 days/wk 30% of PImax measured at functional residual capacity 2, 15 min sessions per day 11
