A timed reexpansion inspiratory manoeuvre (TRIM) for treating oxyhaemoglobin desaturation in children following a period of apnoea—studies in an animal model

Abstract

Our clinical experience has shown that the use of a constant distending airway pressure of 30 cm water for 10 s, termed a timed reexpansion inspiratory manoeuvre (TRIM), is often successful in correcting oxyhaemoglobin desaturation in anaesthetized children. The aim of this study was to assess the efficacy of TRIM in lambs. Following a standard relaxant anaesthetic, ventilation was stopped and oxyhaemoglobin saturation allowed to fall to 70% and the time taken to return to baseline was compared between three groups. The median time was 42.5 s when ventilation was restarted with 33% oxygen in nitrous oxide (33% group), 30 s when ventilation was restarted with 100% oxygen (100% group) and 22.5 s with a TRIM before restarting ventilation with 33% oxygen in nitrous oxide (TRIM group). The correction of desaturation was more rapid in the TRIM group compared with the 33% group (P < 0.004) and the 100% group (P < 0.003). Oxyhaemoglobin desaturation due to apnoea in anaesthetized lambs is more effectively treated with a TRIM than by increasing the inspired oxygen fraction.

Pulmonary volume recruitment manoeuvre restores pulmonary compliance and resistance after apnoea in anaesthetized lambs

“…Lung function of the control group did not return to baseline even at the end of 3 min of normal ventilation, suggesting the development of atelectasis postapnoea. A TRIM with 30% oxygen in nitrous oxide (T1) restores the oxygen saturation quicker to baseline than the control group with normal ventilation alone, confirming results from earlier studies (6). The practice of preoxygenation is also reinforced by our results as the lambs maintained maximal oxygen saturation if they were ventilated with 100% oxygen prior to the 2 min of apnoea, although there is new evidence suggesting that preoxygenation may aggravate atelectasis (5,10).…”

“…Since it is not possible to subject children to this type of study, a lamb model was therefore used; however, they suffered no obvious insult and made apparent normal recoveries. We have previously used this model successfully and found that lambs responded in a similar way to anaesthetized patients (6,7). We therefore believe this to be an acceptable model but acknowledge that caution must used in extrapolating our results to human practice.…”

“…Our clinical experience in anaesthetized children has shown that the application of a constant distending pressure of 30 cmH 2 O for 10 s is effective in correcting oxyhaemoglobin desaturation. We have termed this corrective technique a timed reexpansion inspiratory manoeuvre (TRIM) and have validated its effectiveness in an anaesthetized apnoeic lamb model (6). The theory underlying this manoeuvre is that collapsed alveoli are subject to Laplace's law, requiring a high inspiratory pressure to expand atelectatic lung units which must be maintained long enough to recruit the `slow alveoli' with prolonged time constants.…”

Oxygen – elixir of life or Trojan horse? Part 2: oxygen and neonatal anesthesia

“…Marcus et al (20) demonstrated that the use of 100% oxygen may worsen pulmonary compliance in children <2 years. MacDonald et al (22) showed that oxygen tension was restored faster in apneic lambs after a volume recruitment maneuver ventilated with 33% oxygen in nitrous oxide compared with 100% oxygen. The benefit of an alveolar volume recruitment manoeuver has been demonstrated in children (20,23).…”

Abstracts

“…One of the ten men and one of the eight premenopausal women had mildly elevated (and probably insignificant) prolactin levels. The incidence of PONV is 60-70% with major gynaecological procedures 1 .…”