Dynamic hyperinflation--the anaesthetist applying a tourniquet to the right heart.

Dynamic hyperinflation—the anaesthetist applying a tourniquet to the right heart " The leperous distilment; whose effect holds such an enmity with blood of man that, swift as quicksilver, it courses through the natural gates and alleys of the body,.... " Hamlet, Act 1 Scene 5 Even though the play antedates the publication of De Motu Cordis by nearly 30 years, the quotation was used as evidence that Shakespeare was familiar with William Harvey's concept of circulation of blood. 1 There has been a tendency for clinicians to underrate the importance of the right heart 2 to flow " through the natural gates and alleys ". Transoesophageal echocar-diography is opening a window under operative conditions and through it can be seen, in a way previously not possible, the changes of preload and afterload on atrial, ventricular, tricuspid valve and outflow tract function. 2 Functionally, lying in a Russian doll's nest of anatomic and pressure layers, the right heart is weakened by being juxtaposed between the muscle-bound left ventricle and the lungs, and is sensitive and vulnerable to disease of both these organs and the pericardium. Anaesthetic insults primarily act on the myocardium and pulmonary vasculature but, by taking control of the airway with a tracheal tube, an anaesthetist breaches the integrity of, and imposes forces, that markedly influence the climate of the intrapleural layer. Additional, supranormal pressures of positive pressure ventilation (IPPV) may be enough to override the protective cushioning of the peri-cardium so that the right heart is compromised; sometimes, particularly in those with a predisposing pathophysiology, this effect is critical. Ultimately, it is intra-alveolar pressure within the intrapleural layer that dictates forward flow of blood through the lungs. It is pathologically raised in several well known states encountered by anaesthetists. If expiratory airflow obstruction occurs then intra-alveolar pressure may remain positive throughout much of the respiration cycle. This auto or intrinsic PEEP (PEEPi) effect, 3 is typically part of acute and chronic obstructive airways disease, notably asthma and emphysema, arid of adult respiratory distress syndrome. 4 Recently introduced treatment options for respiratory failure like lung transplanta-tion, 5 minimal access thoracic surgery 5 and lung volume reduction 7 have swelled the ranks of the pre-disposed and susceptible. Large airways, too, can be dysfunctional such that PEEPi is generated: classically , for example, in the presence of inhaled foreign bodies, and central airways compression. 8 To the list of primed can …