From Mark Schreiner MD (retired)
The recent PAAD (10/01/2024: https://ronlitman.substack.com/p/tonsillectomy-and-postoperative-respiratory) on using the Respiratory volume monitor RVM to detect respiratory events after T&A in the immediate recovery period fails to identify a number of crucial flaws with the paper.
The study enrolled only high-risk children in what is described as a cohort study. A cohort study, enrolls both those with and without the risk factor of interest (e.g. smoking/non-smoking) and then follows through to the determine the number in each group that develop the outcome of interest (e.g. lung cancer).
What this study really is, is a single arm, very preliminary investigation of a diagnostic test. However, given the study design, it is not possible to calculate the sensitivity, specificity, PPV, NPV, Likelihood ratio of a positive test (LR+) or negative test (LR-). The study does not appear to help determine who may be safely cared for at home and who should be in the ICU.
It appears that the sensitivity for detecting respiratory events in the PACU is greater than for standard monitoring. However, events in the PACU are a surrogate of unknown significance for later serious respiratory events. SPin and SNout are useful concepts in this regard. A negative test result (sensivity) rules out cases as being at risk (SNout). With the RVM almost everyone is ruled in. However, what is really missing is the specificity of those events for later serious events leading to morbidity, mortality or extra resource utilization on the ward. Specificity rules in cases as being at risk (SPin).
Since 65% of the children had a respiratory event, the investigators have established that children identified by their medical history as being at high risk of having respiratory events have a lot of respiratory events. The significance of those events for actual mortality or morbidity is not known.
Future studies should follow the STARD guidelines and establish the characteristics of this diagnostic test.
1) Altman DG, Bland JM. Diagnostic tests. 1: Sensitivity and specificity. BMJ. 1994 Jun 11;308(6943):1552.
2) Altman DG, Bland JM. Diagnostic tests 2: Predictive values. BMJ. 1994 Jul 9;309(6947):102.
3) Deeks JJ, Altman DG. Diagnostic tests 4: likelihood ratios. BMJ. 2004 Jul 17;329(7458):168-9.
4) Bossuyt PM, Reitsma JB, Bruns DE, et. al. STARD 2015: an updated list of essential items for reporting diagnostic accuracy studies. BMJ. 2015 Oct 28;351:h5527.
5) Cohen JF, Korevaar DA, Altman DG, et al. STARD 2015 guidelines for reporting diagnostic accuracy studies: explanation and elaboration. BMJ Open. 2016 Nov 14;6(11):e012799.
From Nancy Finnel medical writer who sends Myron frequent updates on medical issues for the PAAD
An emerging social media trend has a new generation using an old drug -- nitrous oxide -- with a new name: Galaxy Gas.
The trend of inhaling nitrous oxide canisters, also known as "whippets," has found a new following with the Galaxy Gas brand that markets these products in colorful canisters with enticing flavors, like blueberry mango or vanilla cupcake.
While the canisters are bright and reminiscent of pleasant foods, misuse of nitrous oxide comes with very real risks, including deathopens in a new tab or window. Despite their dangers, these canisters can be bought from most major retailers, including Amazon and Walmart -- though Galaxy Gas has reportedly stopped sales opens in a new tab or window "out of an abundance of caution."