Prolonged Insufflation Research Articles

Interactions patient–ventilateur

During assisted ventilation like inspiratory pressure support or assist-control ventilation, patient–ventilator asynchrony may occur when the patient's inspiration fails to coincide exactly with the ventilator's insufflation. The new generation of ventilators with large screens facilitate the detection of gross asynchronies by careful examination of flow and airway-pressure tracings. The main asynchrony is ineffective triggering, defined as failure of a patient's inspiratory effort to trigger a ventilator breath. Ineffective triggering is caused by dynamic hyperinflation at the time of a triggering attempt. Other major asynchronies include double triggering, in which two consecutive ventilator cycles are triggered by a single patient effort; and autotriggering, in which the ventilator is triggered by signals that do not come from the patient. More discreet asynchronies such as prolonged insufflation during pressure-support ventilation or inadequate flow rate during assist-control ventilation can also be suspected from the flow and airway-pressure traces. Simple delays in triggering or cycling are extremely common but difficult to detect. At least one study suggests that nearly one-fourth of intubated patients exhibit frequent asynchronies (> 10%) during assisted ventilation. A frequent occurrence of asynchrony is associated with a longer duration of mechanical ventilation. This may reflect not only greater disease severity, but also inappropriate ventilator settings. Optimizing the ventilator settings, most notably by reducing ventilatory support or insufflation time, can minimize ineffective triggering. Whether optimizing ventilation shortens the duration of mechanical ventilation by reducing the occurrence of asynchrony is still an open question.

Pain after laparoscopy.

In the context of the much-heralded advantages of laparoscopic surgery, it can be easy to overlook postlaparoscopy pain as a serious problem, yet as many as 80% of patients will require opioid analgesia. It generally is accepted that pain after laparoscopy is multifactorial, and the surgeon is in a unique position to influence many of the putative causes by relatively minor changes in technique. This article reviews the relevant literature concerning the topic of pain after laparoscopy. The following factors, in varying degrees, have been implicated in postlaparoscopy pain: distension-induced neuropraxia of the phrenic nerves, acid intraperitoneal milieu during the operation, residual intra-abdominal gas after laparoscopy, humidity of the insufflated gas, volume of the insufflated gas, wound size, presence of drains, anesthetic drugs and their postoperation effects, and sociocultural and individual factors. On the basis of the factors implicated in postlaparoscopy pain, the following recommendations can be made in an attempt to reduce such pain: emphathically consider each patients' unique sociocultural and individual pain experience; inject port sites with local anesthesia at the start of the operation; keep intra-abdominal pressure during pneumoperitoneum below 15 mmHg, avoiding pressure peaks and prolonged insufflation; use humidified gas at body temperature if available; use nonsteroidal anti-inflammatory drugs at the time of induction; attempt to evacuate all intraperitoneal gas at the end of the operation; and use drains only when required, rather than as a routine.

Effects of recruitment of collapsed lung units on the elastic pressure-volume relationship in anaesthetised healthy adults.

The elastic pressure-volume (Pel-V) curve of the respiratory system can be used as a guide for improved ventilator management. The understanding of curves recorded for sick patients can be improved with better knowledge of the Pel-V relationship observed in healthy humans. Dynamic Pel-V curves were determined over an extended volume range in 15 anaesthetised and muscle-relaxed healthy humans. The influence of a recruitment manoeuvre was studied. Dynamic Pel-V curves were determined during a single prolonged insufflation before and after the recruitment manoeuvre. A mathematical three-segment model of the curve including a linear intermediate segment, delineated by the lower (LIP) and upper (UIP) inflection points, was used for characterisation of the recorded curves. The model gave an adequate description of the recorded Pel-V curves. Before the recruitment manoeuvre, compliance increased until the LIP was reached at 20 cm H2O (1.9 L). Then followed a long linear segment. After the recruitment manoeuvre, compliance increased during insufflation until a LIP was reached at 13 cm H2O (1.2 L). Above the LIP followed a shorter linear segment (compliance = 140 mL/cm H2O) and then an upper segment with decreasing compliance. Pel-V curves recorded before and after the recruitment manoeuvre show that large lung compartments close during anaesthesia and that high pressures are needed to achieve recruitment even in the normal lung. Accordingly, the LIP does not define the end of recruitment during insufflation.

Hyperkalaemia associated with prolonged insufflation of carbon dioxide into the peritoneal cavity

We measured plasma potassium concentrations in five anaesthetized pigs over a 3.5 h period during which a carbon dioxide pneumoperitoneum was maintained. During this period the abdominal pressure was kept at 1.96 kPa and normocapnia was maintained by intermittent positive pressure ventilation. The potassium concentration was found to increase with time to a mean of 5.63 (SD 0.44) mmol litre-1. Consideration should be given to monitoring plasma potassium concentration in patients undergoing prolonged laparoscopic surgery.