Respiratory inhibition after crying in infants

Neonatal respiratory inhibition

OBJECTIVE

To present information on neonatal respiratory inhibition (NRI) to the medical staff caring for infants.

METHODS

The author reviewed investigations of the above conditions. NRI is defined as severe hypoxemia accompanied by clinical manifestations of central cyanosis and a decrease in SpO₂ to less than 70%. Neonatal respiratory inhibition consists of respiratory inhibition after crying (RIAC), feeding hypoxemia, and respiratory inhibition after gastroesophageal reflux (RIGER). The infants were monitored continuously via pulse oximetry from birth until discharge. To identify the details of NRI, we analyzed detailed notes taken by both parents and medical staff during monitoring using specific software designed to interpret pulse oximetry measurements.

RESULTS

Among infants who weighed at least 2000 g and who were born at a gestational age of at least 36 weeks, NRI was observed in ∼50% of infants, including RIAC in ∼25%, feeding hypoxemia in 40%, and RIGER in 2 ∼ 4%, respectively. Among the infants with NRI, ∼40% experienced one or more episodes of prolonged cyanosis for at least 60 s. RIAC, feeding hypoxemia, and RIGER is significantly associated with each other. Among perinatal factors, NRI was related to maternal diabetes mellitus, twin pregnancy, asymmetric intrauterine growth restriction, threatened premature labor, cesarean section, shorter gestational periods, and abnormal ultrasound findings, including increased echogenicity in the ganglionic eminence (GE), a cyst in the GE, a subependymal cyst, and slight lateral ventricular enlargement. Almost all infants with RIAC and RIGER, even those with severe cases, recovered until discharge around day 5. Despite the provision of nursing guidance in feeding control, ∼60% of infants experienced feeding hypoxemia continuously. The more frequently the infants experienced feeding hypoxemia, the more severe the degree of feeding hypoxemia became. Breastfeeding reduced the frequency and degree of feeding hypoxemia compared to bottle feeding. Approximately 40% of infants with feeding hypoxemia required additional feeding control after being discharged.

CONCLUSIONS

NRI is very common and occurs in many infants worldwide. The infants with NRI experienced repeated severe hypoxemia due to RIAC, feeding hypoxemia, and RIGER after birth. Breastfeeding and careful feeding control should be recommended to mothers of infants with repeated feeding hypoxemia. Spreading knowledge about NRI worldwide is very important.

Neonatal respiratory inhibition causes repeated severe hypoxemia

Objective: The goal of this study was to verify the details of neonatal respiratory inhibition (NRI) in healthy infants.Methods: We screened for NRI in 521 infants who weighed at least 2000 g and who were born at a gestational age of at least 36 weeks. Respiratory inhibition was defined as severe hypoxemia, accompanied by clinical manifestations of central cyanosis and a decrease in SpO₂ to less than 70%. NRI consists of feeding hypoxemia, respiratory inhibition after crying (RIAC), and respiratory inhibition after gastroesophageal reflux (RIGER). The subjects were monitored continuously via pulse oximetry from birth until discharge. To identify the details of NRI, we analyzed detailed notes taken by both parents and medical staff during monitoring using specific software designed to interpret pulse oximetry measurements. The mothers of infants with feeding hypoxemia received nursing guidance.Results: NRI was observed in 268 (51.4%) infants (feeding hypoxemia in 227 (43.6%); RIAC in 121 (23.2%); and RIGER in 12 (2.3%)). Among perinatal factors, NRI was related to diabetes mellitus (p = .008; odds ratio = 3.290; 95% CI: 1.371-7.895), twin pregnancy (p = .032; odds ratio = 2.061; 95% CI: 1.062-3.998), and cesarean section (p = .036; odds ratio = 1.537; 95% CI: 1.027-2.299) using multiple logistic regression analysis. Almost all infants with RIAC and RIGER, even those with severe cases, recovered until discharge. However, 93 (41.0%) infants with feeding hypoxemia needed additional feeding control after being discharged. Despite the provision of nursing guidance in feeding control, 143 (63.0%) infants experienced feeding hypoxemia continuously. The more frequently the infants experienced feeding hypoxemia, the more severe the degree of feeding hypoxemia became. Breastfeeding reduced the frequency and degree of feeding hypoxemia compared to bottle-feeding.Conclusions: NRI was often observed in healthy infants. Breastfeeding and careful feeding control should be recommended to mothers of infants with repeated feeding hypoxemia.

Emission of 22 kHz vocalizations in rats as an evolutionary equivalent of human crying: Relationship to depression

There is no clear relationship between crying and depression based on human neuropsychiatric observations. This situation originates from lack of suitable animal models of human crying. In the present article, an attempt will be made to answer the question whether emission of rat aversive vocalizations (22 kHz calls) may be regarded as an evolutionary equivalent of adult human crying. Using this comparison, the symptom of crying in depressed human patients will be reanalyzed. Numerous features and characteristics of rat 22 kHz aversive vocalizations and human crying vocalizations are equivalent. Comparing evolutionary, biological, physiological, neurophysiological, social, pharmacological, and pathological aspects have shown vast majority of common features. It is concluded that emission of rat 22 kHz vocalizations may be treated as an evolutionary vocal homolog of human crying, although emission of 22 kHz calls is not exactly the same phenomenon because of significant differences in cognitive processes between these species. It is further concluded that rat 22 kHz vocalizations and human crying vocalizations are both expressing anxiety and not depression. Analysis of the relationship between anxiety and depression reported in clinical studies supports this conclusion regardless of the nature and extent of comorbidity between these pathological states.

The prognosis of infants with neonatal respiratory inhibition syndrome

Objective: The goal of this study was to investigate the prognosis of infants with neonatal respiratory inhibition syndrome (NRIS).Methods: Infants with a gestational age of at least 36 weeks and a birth weight of at least 2000 g who were born at Nara Prefecture General Medical Center, in Nara, Japan, between March 2013 and June 2016 were screened for NRIS using our established method. NRIS was defined as severe hypoxemia caused by respiratory inhibition immediately after crying (RIAC) or gastroesophageal reflux (RIGER) or as a respiratory pause during feeding (feeding hypoxemia), accompanied clinically by central cyanosis and a decrease in SpO₂ to less than 70%. All infants were monitored using pulse oximetry immediately after birth. Diagnosis of RIAC, feeding hypoxemia, and RIGER are based on observation by both parents and medical staff as well as on on-screen computer analysis using specific software. All infants were examined at a one-month check-up. Parents of the infants who experienced one or more episodes of NRIS accompanied by a decrease in SpO₂ to less than 70% for more than approximately 60 s received a questionnaire by mail about their child's development. We conducted a logistic regression analysis with developmental problems as the dependent variable.Results: NRIS was observed in 362 (28.5%) infants; 216 (17.0%) infants showed RIAC, 254 (20.0%) infants showed feeding hypoxemia, and 54 (4.2%) infants showed RIGER. Although all infants were monitored in the maternity ward nursery, 184 (85.2%) infants with RIAC and 111 (43.7%) infants with feeding hypoxemia were overlooked. All infants with NRIS were found to have successfully recovered at one month after birth. Sixty-two cases were examined in the follow-up study by the mailed questionnaire. The median age of the subjects at time of study was 22 months. Fourteen cases (22.6%) exhibited developmental problems including delayed speech development, stereotyped interests and behaviors, sensory disturbance, hyperactivity, delayed motor development, and short stature. Developmental problems tended to relate to shorter gestational age (odds ratio, 0.622; p = .068; 95% CI, 0.373-1.036), smaller birth weight (odds ratio, 0.998; p = .069; 95% CI, 0.997-1.000), and maximum duration of SpO₂ to less than 70% by RIAC (odds ratio, 1.009; p = .086; 95% CI, 0.999-1.020). All cases had experienced severe hypoxemia accompanied by a decrease in SpO₂ to less than 60%. Seven cases had experienced prolonged hypoxemia accompanied by a decrease in SpO₂ to less than 70% for at least 2 min. Among the subjects, 19 infants were examined closely, and their natural course of NRIS was observed in the neonatal intensive care unit. No cases demonstrated abnormal findings with blood examinations, chest-abdominal X-ray, echocardiogram, laryngoendoscopy, hearing loss screening, or mass screening. Only one case had a small intracranial hemorrhage as evidenced in a magnetic resonance imaging of the head.Conclusions: The infants with severe NRIS tended to have developmental problems. Spreading knowledge about NRIS worldwide is thought to be very important.

Respiratory inhibition after crying or gastroesophageal reflux and feeding hypoxemia in infants

OBJECTIVE

The objective of this study is to present information on respiratory inhibition after crying (RIAC), feeding hypoxemia, and respiratory inhibition after gastroesophageal reflux (RIGER) to medical staff caring for infants.

METHODS

The author reviewed investigations of these conditions.

RESULTS

These conditions have been observed in full-term healthy infants, and they are accompanied clinically by central cyanosis and a decrease in SpO2 to less than 70%. These conditions are easily diagnosed using pulse oximetry. Among Japanese infants with a gestational age of 36 weeks or older, the incidence of RIAC and feeding hypoxemia is 24% and 32%, respectively. The incidence of RIGER is approximately 4%. Feeding hypoxemia occurs significantly more often during bottle-feeding than during breastfeeding. RIAC, feeding hypoxemia, and RIGER are significantly associated with each other. The risk factors are maternal smoking during pregnancy, threatened premature labor, twin gestation, asymmetric intrauterine growth restriction, and abnormal cranial ultrasound findings. Almost all infants recover from RIAC by day 7 after birth. Some infants with feeding hypoxemia require additional assistance and monitoring by nursing staff until the day of discharge.

CONCLUSIONS

Medical staff caring for infants should note the presence of RIAC, feeding hypoxemia, and RIGER.

Timing of injury in utero causing respiratory inhibition after crying

BACKGROUND

The aim of this study was to clarify the timing of injuries in utero that cause respiratory inhibition after crying (RIAC). We evaluated infants with cranial ultrasound abnormalities diagnosed during hospitalization.

METHODS

We retrospectively examined the medical records of preterm infants who were treated in the neonatal intensive care unit at Nara Prefectural Hospital in Nara, Japan from January 2006 through December 2010. Inclusion criterion was gestational age less than 34 weeks. We evaluated the perinatal factors and cranial ultrasound abnormalities associated with RIAC, feeding hypoxemia, and prolonged apnea. We also evaluated the timing of appearance of cranial ultrasound abnormalities.

RESULTS

A total of 125 infants were examined. Mean gestational age was 30.6 ± 2.4 weeks and mean birthweight was 1465 ± 454 g. The numbers of infants who showed RIAC, feeding hypoxemia, and prolonged apnea were 44, 48, and 63, respectively. Among 91 infants who showed cranial ultrasound abnormalities, 67 had increased echogenicity in the ganglionic eminence (GE). There was a significant correlation between increased echogenicity and RIAC (P < 0.001). Of the infants who showed increased echogenicity in the GE, 19 had this finding during the course of hospitalization. In these 19 infants, however, gestational age of those with RIAC was less than 31 weeks.

CONCLUSION

We speculate that the timing of intrauterine injury resulting in RIAC in infants is less than 31 gestational weeks.

Might asphyxia cause respiratory inhibition after crying in mature infants?

BACKGROUND

To clarify the timing of injury in utero causing respiratory inhibition after crying (RIAC), the relationship between asphyxia and RIAC was investigated in infants whose gestational age was ≥ 36 weeks.

METHODS

RIAC and cranial ultrasound abnormalities were examined for retrospectively in infants treated in the neonatal intensive care unit from April 2004 through March 2009. All included infants were gestational age ≥ 36 weeks and had an Apgar score <4 points at 1 min. The relationship between RIAC and perinatal factors was also examined.

RESULTS

Twenty-six infants were included. Three infants had RIAC, seven infants had poor prognosis, and nine infants had ultrasound abnormalities in the ganglionic eminence (GE). There was a significant relationship between RIAC and ultrasound abnormalities in the GE (P= 0.032). Poor prognosis was significantly associated with low Apgar score at 5 min (P ≤ 0.001), disseminated intravascular coagulation (P= 0.047), hypoxic ischemic encephalopathy (P= 0.028), and brain hypothermia therapy (P= 0.028). There was no significant relationship between RIAC and poor prognosis. All infants had ultrasound abnormalities in the GE on the day of birth.

CONCLUSION

Damage occurring in utero prior to 36 weeks gestation might cause increased echogenicity or cyst formation in the GE, potentially disturbing maturation of the respiratory center with the development of RIAC.

Effective method for screening for respiratory inhibition after crying in infants

BACKGROUND

 In order to establish an effective screening method for respiratory inhibition after crying (RIAC), we prospectively studied the correlations between infant RIAC and perinatal factors.

METHODS

We monitored infants (n=141) born from May through July 2009 with polygraphy and evaluated the presence of RIAC and respiratory pause that occurred when feeding was initiated immediately after crying with a decrease in oxygen saturation (SpO(2) ) to <60%. The infants were screened for increased echogenicity, a cyst in the ganglionic eminence (GE), or a subependymal cyst by cranial ultrasound. Furthermore, we evaluated the correlations between RIAC and perinatal factors.

RESULTS

  Eleven infants displayed RIAC and 31 experienced respiratory pause during feeding with a decrease in SpO(2) to <60%. There were no significant correlations between RIAC and perinatal factors. Forty infants had ultrasound abnormalities (increased echogenicity in the GE, 26; cyst in the GE, nine; and subependymal cyst, seven). Sensitivity, specificity, and efficiency of abnormal cranial ultrasound findings for RIAC were 1.00, 0.777, and 0.794, respectively. The odds ratio, sensitivity, specificity, and efficiency of the combination of abnormal cranial ultrasound findings and respiratory pause during feeding with a decrease in SpO(2) to <60% and RIAC were 35.9 (P<0.001), 0.727, 0.931, and 0.915, respectively.

CONCLUSION

  The combination of abnormal cranial ultrasound findings and respiratory pause during feeding with a decrease in SpO(2) appears to be an effective method of screening for RIAC.