Basic Respiratory Function PDF

Basic Respiratory Function Clin Asst Prof Sewa Duu Wen Duke-NUS School of Medicine Director, Medical Intensive Care Unit Singapore General Hospital 1 Content Respiratory anatomy Respiratory physiology Respiratory Failure Functions of the Respirator...

Basic Respiratory Function Clin Asst Prof Sewa Duu Wen Duke-NUS School of Medicine Director, Medical Intensive Care Unit Singapore General Hospital 1 Content Respiratory anatomy Respiratory physiology Respiratory Failure Functions of the Respiratory System Gas exchange between air and bloodstream Moves air in and out of the body Filters, warm and humidify the incoming air Vocalization: Speech Anatomy  Upper airway tract Hair and mucous membrane trap particles like dust and smoke Inhaled air is moistened, warmed During exhalation the nasal cavity collects and retains the moisture from the air that is leaving the body Larynx and epiglottis Larynx allows the passage of air through the trachea With the help of the epiglottis, the larynx prevents food or liquid from entering the lower respiratory tract while swallowing Lower respiratory tract Conducting Zone Trachea to bronchus No gas exchange occurs Supported by cartilages Respiratory zone Bronchioles with alveoli Gas exchange occurs here  Alveoli The alveoli are moist, thin walled pockets which are site of gas exchange A slightly oily surfactant prevents the alveoli walls from collapsing and sticking together Lungs and the thoracic wall  Ventilation – Inspiration and Expiration 10  Control of ventilation 11  Gas exchange 12 Oxygen delivery  Circulation and gas exchange 14  Respiratory failure When the lung fails to oxygenate the arterial blood adequately +/- fails to prevent carbon dioxide retention – Hypoxemia Partial pressure of oxygen (PO2) < 60mmHg Type I Respiratory Failure Can lead to tissue hypoxia – Hypercapnia Type II Respiratory Failure Partial pressure of carbon dioxide (PCO2) > 50mmHg Hypoxemia: Reduced PO2 in arterial blood (PaO2) – Spectrum of symptoms depending on severity Mild: Impairment of mental performance, diminished visual acuity, tachypnea Profound: – CNS: Headache, seizures, somnolence, loss of consciousness – CVS: Palpitations, chest pain – Respiratory: Shortness of breath Causes Of Hypoxemia: Tissue Hypoxia: Inadequate oxygenation at cellular level – CNS – Hypoxic ischemic encephalopathy – Myocardium – Acute myocardial infarction – Renal – Acute kidney injury – Vascular – Vasoconstriction (e.g. pulmonary vasculature) Hypercapnia: Increased PCO2 in arterial blood (PaCO2) – Spectrum of symptoms depending on severity Restlessness, tremor, slurred speech, asterixis Headache Altered mental status, loss of consciousness, comatose state – Symptoms and signs of condition resulting in respiratory failure  Conditions causing hypercapnia 20 Principles of Management of Respiratory failure Vital signs GCS Identify Respiratory findings – Clinical symptoms and signs Airway Breathing Resuscitate / stabilize Circulation Investigate Blood - ABG Radiological – CXR, CT Treat the cause  Identify patient with respiratory failure: Symptoms – Respiratory: Shortness of breath, wheeze, chest tightness, cough – CNS: Light headedness, giddiness, lethargy, headache, anxious, confusion, delirium, seizures – Constitutional, manifestations a/w underlying disorder History – Significant medical history Pulmonary, central, neuromuscular, thoracic cage disorders – Drug history Sedatives – Smoking  š Signs š Vital parameters šBlood pressure: hypo/hypertension šHeart rate: brady/tachyarrhythmias šOxygen saturation: hypoxemia šRespiratory rate: hypopnea/tachypnea š Habitus š Thoracic cage deformitites š Pulmonary examination šWheeze, decreased breath sounds š Neuro-axis examination šGCS: Somnolence šAsterixis šLimbs: Reflexes, power 23  Investigations: ABG Arterial blood gas – Measures amounts of oxygen and carbon dioxide dissolved in arterial blood – Invasive Radial, brachial, femoral artery Investigations: Radiology Thoracic – Chest radiograph – CT thorax – contrast, pulmonary angiogram Neuro-axis – CT, MRI – brain, cervical/thoracic spine – **Nerve conduction study (NCS), electromyography (EMG) 26