Post on 24-May-2015
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RESPIRATORY SYSTEM
Dr. A. R. JOSHIProfessor of Physiology
RESPIRATORY SYSTEM
• Respiration means exchange of gases
• Types :
– External respiration at lungs
– Internal respiration at tissues
BASIC FUNCTIONS OF LUNGS
• Ventilation of air
– Inspiration
– Expiration
• Diffusion of gases
• Perfusion of lungs by blood through pulmonary circulation
NORMAL BREATHING PATTERN
• Respiratory rate : 14 to 18 /minute
• Tidal volume: 350 to 500ml
• RMV : 6 to 8 litres/minute
• Inspiration (active) : 2.5 to 3 sec
• Expiration (passive): 2 to 2.5 sec
MUSCLES OF RESPIRATION
• Inspiratory Muscles
• Expiratory Muscles
• Accessary Muscles
INSPIRATORY MUSCLES
• Diaphragm:– Chief muscle– Big surface area– Changes vertical diameter of chest– Innervation by phrenic nerves– No fatigue– Works like involuntary muscle
INSPIRATORY MUSCLES
• External Intercostal Muscles:
• Bucket handle movement of ribs
(Lower part of chest)• Pump handle movement of sternum
(Upper part of chest)
OTHER MUSCLES
• Muscles of expiration• Work only while coughing or sneezing
• Accessary muscles of respiration• Work during exercise or disease
PREVENTION OF LUNG COLLAPSE
•Role of negative intra-pleural pressure
•Role of surfactant
REGULATION OF RESPIRATION
• Nervous regulation – Role of ponto-medullary respiratory centers:• Inspiratory Center (DRGN)• Expiratory Center (VRGN)• Apneustic Center• Pneumotaxic Center
• Chemical- Role of Carbon dioxide
Hydrogen ions
Lack of Oxygen
REGULATION OF RESPIRATION
• Nervous regulation– Role of reflexes:• Coughing reflex• Sneezing reflex• Hiccough • Deglutition reflex
Chemical Regulation
Role of carbon dioxide: powerful action
1.Central action (chemo sensitive area)
2.Peripheral action (carotid and aortic bodies)
Role of hydrogen ions
Role of lack of oxygen
DIFFUSION ACROSS RESPIRATORY MEMBRANE
• Structure• Factors affecting diffusion : ● thickness of membrane ● surface area of membrane ● pressure gradient of gas• Diseases : Pulmonary fibrosis & oedema
TRANSPORT OF GASES: OXYGEN
• Arterial O2 19 ml / 100ml of blood
• Venous O2 14 ml / 100 ml of blood
• Oxygen carried by Hb – 98%
dissolved form – 2%
• O2- Hb dissociation curve and its significance
OXYGEN CONCENTRATION IN VARIOUS TISSUES
• Alveolar PO2 : 104 mm of Hg
• Arterial PO2 : 95 mm of Hg
• Venous PO2 : 40 mm of Hg
O2dissociation curve…
O2 Dissociation Curve
TRANSPORT OF GASES : CARBON DIOXIDE
• Arterial CO2 level : 48 ml/100ml blood • Venous CO2 level : 52 ml/100ml blood• Transported as: ● bicarbonates : 70% ● carbamino compounds : 23% ● dissolved state : 7%
CARBON DIOXIDE CONCENTRATION IN VARIOUS TISSUES
• Alveolar PCO2 : 40 mm of Hg
• Arterial PCO2 : 40 mm of Hg
• Venous PCO2 : 45 mm of Hg
HYPOXIA (Lack of Oxygen at tissue level)
1. Hypoxic Hypoxia
• High Altitude
• Ventilatory defects like Asthma
• Diffusion defects like Pulmonary edema
• AV shunts like Fallots Tetrology
(PO2 of arterial blood is low)
HYPOXIA ( CONT..)
2. Anaemic Hypoxia e.g. Anaemia Carbon Monoxide poisoning3. Stagnant Hypoxia e.g. Congestive heart failure4. Histotoxic Hypoxia e.g. Cyanide poisoning (Note : Oxygen therapy is useful only in
cases of hypoxic hypoxia, when PO2 of Arterial Blood is low )
OXYGEN THERAPY
• Useful in hypoxic hypoxia (high altitude, hypoventilation, impaired diffusion )
• Limited value in other types of hypoxia
• Oxygen with small quantity of Carbon dioxide to maintain respiratory drive
HYPERBARIC OXYGEN THERAPY
• Increases dissolved Oxygen – at 2 atm.pressure - 4ml additional/dl
at 3 atm.pressure - 6ml additional/dl.• Useful in CO poisoning, dysbarism,
acute mountain sickness, locally in delayed wound healing & gas gangrene.
HAZARDS – OXYGEN THERAPY
• Irritation of airways
• Bronchopneumonia
• Retinopathy ( in premature babies )
• Derangement of cerebral activity
• Convulsions
ASPHYXIA(Lack of oxygen and excess of carbon dioxide)
• Causes:Foreign body obstruction in tracheaStrangulation Paralysis of respiratory muscles
Drowning Stages: Stage of Hyperpnea Stage of Central excitation Stage of Central failureTreatment: Tracheostomy & oxygen therapy
For assistance in Clinical Physiology
• Dr. A.R. Joshi
Professor of Physiology
(mobile : 9423523322)
email: aniruddharj@hotmail.com