EXAMINATION OF THE RESPIRATORY SYSTEM
In thoracic medicine the history, physical examination
,chest X-ray and pulmonary function tests all contribute todiagnosis and assessment in a complementary manner.The chest X-ray gives accurate information on thoracicanatomy, whereas the clinical examination is much moreuseful in assessing pathophysiology.
Before the clinical examination, many relevant observations will have been made while talking to the patientconcerning breathlessness, pain, cough and general appearance.In addition, the history will have served to focus attention on particular diagnostic probabilities and possibilitiesthat subsequent examination will confirm or refute.If already available, the information from the chest X-raywill similarly direct the physician's examination of the patient.
Examination of the hands Examination of the hands may give valuable information:
Finger and toe clubbing is an important physicalsign. The four criteria for documenting finger clubbingare: increased sponginess of the nailbed; loss of theusual acute angle between the nail and the nailbed;increased nail curvature; and increased bulk of the softtissues over the terminal phalanges. The majority ofpatients with clubbing have pulmonary disease. Clubbing is occasionally familial in otherwisenormal subjects. It can develop very rapidly, within a few weeks (e.g. with an empyema), but its onset is usually gradual. The mechanism of clubbing is not understood.The bones of the fingers and toes are normal. If theunderlying cause is successfully treated clubbing usually resolves.
Hypertrophic pulmonary osteoarthropathy (HPOA).Virtually all patients with this unusual condition have clubbing, but only a few patients with clubbing have HPOA. There is arthralgia and joint swelling affecting particularly the wrists and ankles. X-rays show subperiostealnew bone formation in the long bones of the lower limbs and forearm, the bone scan demonstrates increased activity, and often the serum alkaline phosphatase is raised. Ninety per cent of cases are associatedwith bronchogenic carcinoma, particularly peripheral squamous cell tumours.
Examination of the nails. This may show that some or allof them are thickened and yellow or greenish in appearance.This occurs in the yellow nail syndrome, in which clubbing is associated with lymphoedema, exudative pleural effusions, bronchiectasis and sinusitis.
Carbon dioxide retention. When there is carbondioxide retention, peripheral vascular dilatation greatlyenhances blood flow and the hands are strikingly warm.With severe and acute carbon dioxide retention theremay also be an irregular flapping tremor of the outstretchedhands. The fingers may be blue (peripheralcyanosis), and if the limb is warm this is likely to reflect central cyanosis rather than poor peripheral perfusion.
Cyanosis
In patients with a normal haemoglobin concentration,oxygen saturation must fall to 85%, corresponding to anarterial oxygen tension of 7-8 kPa (approximately 55-60mmHg), before cyanosis can be clinically detected. As aconsequence of the sigmoid shape of the oxygen dissociation curve,further small falls in oxygen tensionthen produce large, dangerous falls in saturation. Inanaemia, severe hypoxia is required to produce the quantityof reduced haemoglobin (about 1.5g/dL) necessaryto cause cyanosis, whereas patients with polycythaemiabecome cyanosed at higher arterial oxygen tensions.
The bluish colour of central cyanosis is best appreciatedby examination of the tongue in adequate daylight.
Pulsus paradoxus
The curious term 'pulsus paradoxus' is used to describe agreater than normal fall in blood pressure during inspiration.In normal subjects the systolic blood pressure falls bya few mmHg during inspiration. This fall is greater (notparadoxical) when venous return to the right heart isimpaired, e.g. in patients with hypovolaemia, cardiac tamponadeor massive pulmonary embolism. In respiratorydisorders pulsus paradoxus is seen when there are largepressure swings within the thorax during the respiratorycycle. This is particularly likely to occur in severe acuteasthma, when the extent of paradox is related to the severityof airways obstruction, and systolic blood pressure mayfall by 40 mmHg on inspiration. The degree of paradox isbest documented using a sphygmomanometer: as the pressureof the cuff is reduced, the systolic sound is initiallyonly audible on expiration, but with a further reductionin cuff pressure it becomes audible throughout inspiration too.
Jugular venous pressure
The jugular venous pressure is raised in right heart failure,which is itself frequently due to pulmonary disorders suchas chronic bronchitis. The venous pressure is also elevatedif the resting pressure in the thorax is raised, as with atension pneumothorax. When there is severe airwaysobstruction the pressure swings within the thorax are large;intrathoracic pressure is positive during expiration, owingto active recruitment of the expiratory muscles and thepositive recoil pressure of the respiratory system whenexpiration is halted by airway collapse at a lung volumewell above normal FRC. This positive intrathoracicpressure elevates the jugular venous pressure, which thenfalls during inspiration. Thus, interpretation of the jugularvenous pressure in the tachypnoeic patient, particularlywith severe airways obstruction, is difficult.
Peripheral oedema
Peripheral oedema associated with severe pulmonarydisease (cor pulmonale) is relatively common, and is mostoften seen with chronic bronchitis, in which there is hypercapniaas well as hypoxia. Patients with hypoxic normocapnicrespiratory failure seldom have oedema. In somepatients with oedema the jugular venous pressure is notelevated, the cardiac output is normal and fluid accumulationis related to factors other than right heart failure,perhaps mediated through the action of hypoxia andhypercapnia on renal blood flow and function.
EXAMINATION OF THE RESPIRATORY SYSTEM
By: Dr Izharul Hasan
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