We studied the correspondence betwen fluctuations of esophageal squeezing measured before and after placement of a nasogastric (NG) tube in six normal tenders Flow.

We studied the correspondence betwen fluctuations of esophageal squeezing measured before and after placement of a nasogastric (NG) tube in six normal tenders Flow, airway pressure, and esophageal crushing data from at least 20 breaths were recorded in seven ventilatory conditions in sum of two units body postures: 0[degrees] (supine) and 60[degrees] (upright). the conditions studied included normal quiet breathing, added resistance, reduc compliance, increased oftenness increased tidal volume, continuous positive airway constraining force and volume-cycled ventilation with positive influence During recording with the NG tube in place, the make subordinate targeted the same tidal mass (VT), respiratory rate, and inspiratory time fraction (TI/TTOT) recorded before NG tube placement. A computer program gooded for analysis only those recorded breaths with and without an NG tube that were "matched" within 5 percent for the couple VT and TI. We calculated average VT TI, and esophageal press fluctuation ([delta]Pes) for the matched breaths from each enslave during every condition. The [delta]Pes values with and without NG tube were not statistically different in any criterioned condition (p>0.05). Our data indicate that the carriage of an NG tube does not invalidate the accuracy of [delta]Pes measurements made using a well-positioned balloon catheter in the criterioned conditions.

(Chest 1994; 106:137-41)

C=compliance;

CPAP=continuous positive airway pressure;

f=respiratory frequency;

NG=nasogastric;

Pes=esophageal pressure;

[delta]Pes=fluctuations of esophageal pressure;

RI=inspiratory resistance;

TI=inspiratory time;

TI/TTOT=inspiratory time fraction;

VT=tidal volume

elucidation words: esophageal pressure; intensive care; monitoring; nasogastric tube; respiratory mechanics

Fluctuations of esophageal crushing ([delta]Pes) reflect changes in average pleural urgency that occur during tidal breathing, passive inflation, or respiratory maneuvers. In the clinical setting, [delta]Pes has been measured to ascertain breathing effort, to assess and partition the impedance to inflation (compliance and resistance), and to quantify auto-PEEP during spontaneous breathing.(1) Moreover, knowledge of esophageal compressing (Pes) can help to interpret similar hemodynamic variables as the pulmonary artery occlusion compressing (wedge) or to determine the hurry applied across the alveolus when high airway crushings are needed to ventilate patients with abnormal lung and chest wall mechanics.(1)

The accuracy and stability of the [delta]Pes measurement hang on balloon volume and upon such variables as the pattern of breathing, dead body posture, and position of the balloon within the esophagus.(2)(3)(4)(5)(6)(7)(8)(9) As exemplified by dint of swallowing artifact, measurement accuracy may also hang on factors that influence the balloon's local (intraesophageal) environment. Although measurements made with specially designed combination esophageal/nasogastric tubes appear to think [delta]Pes with accuracy sufficient for clinical purposes(10)(11) the ne for placing similar a specialized balloon/tube catheter is frequently difficult to anticipate. Moreover, other adumbrations of nasoenteric tubes designed for feeding are povertyed for intermediate and long-term nutritional support. Consequently a nasogastric (NG) or feeding tube may be placed before or after inserting an esophageal balloon catheter. We questioned whether the neighborhood of a nasoenteric tube used for decompression or feeding distorts the flaccid esophagus sufficiently to interfere with the Pe estimation of pleural pressure

METHODS

enslaves and Apparatus

We studied six cooperative normal offers (five male, one female; ages 23 to 37 years) who understood the design of the study and protocol. Each had normal material substance habitus (within 10 percent of ideal dead body weight), no history of cardiopulmonary disease, and normal values during forced spirometry (mean [[+ or -] SD] forced vital capacity [FVC] of 492[+ or -]080 L [106[+ or -]9 percent of predicted] and a mean [[+ or -] SD] forced expiratory book in 1 s [[FEV.sub.1]] of 397 [+ or -] 056 L [102 [+ or -] 9 percent] of predicted). In the first three enslaves ("first set"), the specialized esophageal balloon catheter of a commercially available hypothesis for measuring lung mechanics (Smart Cath, Bicore Monitoring rules Irvine, Calif) was inserted transnasally, positioned by the agency of mouth occlusion technique,(8) and attached to an integrated signal conditioning and display unit (Bicore CP-100 Irvine, Calif). In three other make submissives ("second set"), a conventional esophageal balloon catheter was positioned in similar fashion and link togethered to a pressure transducer (Validyne MP-45 Northridge, Calif) and display classification The distal end of each catheter was shielded with a flaccid balloon (10 cm long) and filled with 08 to 10 ml of air during use. the two types of esophageal catheter were 7F in diameter and were perforated on multiple holes in the balloon-covered segment

Participants were beg fored to breathe through a mouthpiece combineed to a rotameter-calibrated pneumotachograph. Inspiratory and expiratory proceeds were recorded either from a Fleischstyle pneumotachograph (Hans Rudolph archetype No. 4719, Kansas City, Mo) or from a variable orifice spring transducer (VarFlex, Bicore Monitoring arrangements Irvine, Calif). Lateral airway hurry was tapped at the mouthpiece. A nose clip sealed the airway. Tidal whirl excursions were recorded independently, using a DC-coupl inductive plethysmograph (Noninvasive Monitoring hypothesiss Respigraph, Miami Beach).

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