Failure of Conventional Respiratory Monitoring to Detect Hypoxia

Abstract

Ris ens. arid W.G. Z l s t r a . From t h e x o m S t a t e -Un v e r s l t y ,-I-+-Gron ngen ~letlierlands(Spon. by M. Klaus) Recent reports Indicate t h a t both heat production and heat l o s s i n low birthweight Infants i n incubators exceed the "basal"values. This i s thought t o be a r e s u l t of non-optimal environriental conditions i n the Incubator. To study t h f s we measured both heat production and evaporative and non-evaporative heat l o s s simultaneously in r e s t i n g newborn Infants i n a metabolic chamber a t neutral a i r and wall temperature, moderate humidity and low a i r velocity. A t o t a l of 100 measurements were obtained i n 30 newborn Infants (birthweight 0.88-2.88 Kg) during the f i r s t two weeks of l i f e .Results f o r t h e f i r s t week of l i f e a r e shown in t h e t a b l e . I n t h e very low birthweisht i n f a n t s e v a~o r a t i v e heat l o s s Proved t o be s u r p r i s i n g l y h i g h . -~e s t i n g heat production i n a l l weight groups was c o n s i s t e n t l y 20-30% higher than the "basal" values reported previously. The increase i n c a l o r i c intake t h a t has occurred from 1968 t o 1976 might explain the incrfased heat production. W e suggest t h a t standards f o r "basal heat productt l o n and heat l o s s should be re-evaluated. Overhead radlant wannlno devices facilitate the c a r e of s i c k newborn infants. Howaver -no data a r e a v a i l a b l e on the energy ex pend1ture)oxygen consumpt/on)of infants under radlant energy warme r s compared t o convantlonal incubators. This stud was conducted t o compare oxygen consumptlon of normal, two da ord f u l l term in f a n t s subjected t o non-ionizing radiant w a r m r s !~~~-~~-6 6 0 ) and t o convent lonal incubators (Servo-Care Armstrong Incubators, Ohio Medical Products). Oxygen consumption was determined using the "closed system technique1' employing nasal pron s a CO analyzer the Beckman OM-11 0 analyzer and the Hewlett !a;kard ~H P ) .Pneumotach with a t t a c h d n t s t o the respiratory integrator of the HP 7700 multichannel recording system. All infants were fed 20 minutes p r i o r t o each recording period. Each Infant was a l t e r n a t e l y placed gn the radiant warmer and the incubator(servo-control s e t t o 36.5 C)and a f t e r an i n l t i a l s t a b l l l z l n g period of 20-30 mlnutr t h e 0 consumptlon was determined f o r 3-5-minutes while in q u i e t sleep?characteristlc EEG,ECG, muscle a c t i v i t y and r e s p l r a t i o n l . The aundiced neonate is a t r i s k t o b i l i r u b i n t o x i c i t i f i t s serum albumin has a diminished capacity t o f u r t h e r bind ~i l i r u b i n 98.f~dif;jgf b y h i f h s a t u r a t i o n index SI) of 2 8% is s udy r e o r t s 8 jaundiced i n f a n t s 1318 ! 1.8 mi%) with high S ! (8.4 * O.qX1 and ease o r drug intake. The i n f a n t s were -days t h e r feeding poorly on formula o r i n s u f f i i e n t l y on t h e breast w t e r su plement. Glucose in(lusion was given a t a with glucos, I" r a t e o...

Apnoea, bradycardia, and oxygen saturation in preterm infants.

“…'2 As episodes of apnoea that result in bradycardia start with a relatively low SaO2, one would also expect a greater reduction in SaO2 during an episode of bradycardia compared with an episode of apnoea not accompanied by bradycardia. We have shown this, but using a six seconds averaging time on our oximeter we were unable to study the temporal relationship between a fall in SaO2 and the onset of bradycardia as described by Henderson-Smart et al 3 They postulated that bradycardia was a peripheral chemoreflex response to falling SaO2. We feel, however, that one should be wary of ascribing cause and effect to this relationship, as bradycardia is more common when there is an obstructive element to the apnoea,'4 and episodes of apnoea with such an element may also be associated with a more pronounced reduction in SaO2.…”

Anemia, Apnea of Prematurity, and Blood Transfusions

“…Many of these studies defined apnea events from nursing charts, which have been demonstrated by us 13 and others 14,15 to underreport and inaccurately identify apnea events. The current study, as well as a report by Belal et al, 16 quantifies apnea events from a computer analysis of waveforms continuously collected from bedside monitors.…”

Review article

“…19 shows that baseline heart rate was not significantly different in infants with normoxemia and hypoxemia. PEABODY has reported that of 178 apnoeic episodes resulting in tcPo 2 less than 40 mm Hg, heart rate feil to below 100 beats/min in less than 60% and thoracic impedance alarms detected less than 40% [53]. Fig.…”

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