Psychogenic Dyspnoea
G John Gibson in Clinical Tests of Respiratory Function, 2008
A useful finding on simple respiratory function testing is that many subjects with hyperventilation syndrome experience considerable difficulty in performing simple tests in a reproducible manner. An experienced clinical physiologist may suspect the aetiology simply from the forced expiratory spirogram, which may show the consequences of incomplete and inconsistent efforts during the forced manoeuvre or during the preceding full inspiration (Fig. 26.1). Individuals with ‘sighing breathing’ have been reported to have a smaller VC and consequently larger RV than those with a more normal breathing pattern,6 but overall the results of spirometry, lung volumes and carbon monoxide diffusing capacity (DLCO) are within normal limits,4 provided that the subject is able to perform the tests adequately. Arterial PO2 is characteristically higher than normal due to the alveolar hyperventilation.
Neck
Keith Hopcroft, Vincent Forte in Symptom Sorter, 2020
This chapter presents a discussion on the causes, diagnosis, and investigation of symptoms related to neck. It provides a general practitioner overview, differential diagnosis, possible investigations, and top tips for dealing with symptoms related to neck in patients. The symptoms discussed are difficulty in swallowing, hoarseness, neck lumps, sore throat, stiff neck, and stridor in children. The differential diagnosis include common, occasional, and rare causes of the symptoms. Acute stridor is a very frightening experience for both child and parents. The respiratory effort can lead to hyperventilation, making things worse. ‘Difficult’ or ‘noisy’ breathing in a child quite commonly leads to a request for an out-of-hours visit in winter.
Acute hypoxia and hyperventilation
Nicholas Green, Steven Gaydos, Hutchison Ewan, Edward Nicol in Handbook of Aviation and Space Medicine, 2019
Hypoxia is an insufficient supply of oxygen reaching the tissues. Acute hypoxia refers to effects experienced over a few seconds to a few hours; chronic effects of hypoxia predominate over days to weeks. There are four main forms of hypoxia: hypoxic, anaemic, ischaemic and histotoxic. In the aviation environment, main cause of acute hypoxia is insufficient alveolar oxygen as a result of reduced atmospheric pressure – Hypoxic hypoxia. Multiple types of hypoxia can coexist. Alveolar gas equation is used to calculate alveolar oxygen content. Alveolar water vapour pressure remains constant with ascent to altitude, and so becomes increasingly important component of alveolar content. Hypoxic ventilatory response is a reflex which increases ventilatory drive in an attempt to maintain oxygen levels. Hyperventilation is defined as breathing in excess of metabolic needs, eliminating more carbon dioxide than is produced, to produce hypocapnia.
Effects of heavy hyperventilation on transcutaneous and arterial oxygen tensions in healthy adults
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 1989
H. H. Steenfos, N. Tromholt, J. Dúelund Jacobsen, P. D. Wimberley
Transcutaneous pO2 on thorax and the volar part of the forearm was measured in six healthy volunteers during heavy hyperventilation, and the values compared with simultaneously measured arterial blood pO2. We found a significant rise in arterial pO2 during hyperventilation with a lesser increase in thoracic transcutaneous pO2. When measured on arm the transcutaneous pO2 did not even rise significantly. After hyperventilation pO2 fell to values below the resting level. The transcutaneous/arterial pO2 index, fell significantly during hyperventilation with the greatest reduction in the arm index. After hyperventilation the arm index returned to the control values, whereas the thoracic index remained low. We suggest, that the significant fall in transcutaneous/arterial blood pO2 index during hyperventilation is caused primarily by skin vasoconstriction, whereas the fall in pO2 after hyperventilation is caused by hypoxia. When measured on areas with increased muscular activity transcutaneouspO2 might depend on the local blood flow and skin oxygen consumption also, causing problems in interpretation with certain patient groups.
Voluntary hypocapnic hyperventilation lasting 5 min and 20 min similarly reduce aerobic metabolism without affecting power outputs during Wingate anaerobic test
Published in European Journal of Sport Science, 2021
Kohei Dobashi, Naoto Fujii, Masashi Ichinose, Tomomi Fujimoto, Takeshi Nishiyasu
Twenty minutes of voluntary hypocapnic hyperventilation prior to exercise reduces the aerobic metabolic rate with a compensatory increase in the anaerobic metabolic rate without affecting exercise performance during the Wingate anaerobic test (WAnT). Thus, pre-exercise hypocapnic hyperventilation may be a useful means of stressing the anaerobic energy system during training, ultimately improving anaerobic exercise performance. However, it remains unclear whether a shorter (e.g., 5 min) pre-exercise hypocapnic hyperventilation is sufficient to reduce the aerobic metabolic rate during high-intensity exercise. We therefore compared the effects of 5-min and 20-min pre-exercise hypocapnic hyperventilation on aerobic metabolism during the 30-s WAnT. Ten healthy young males and one female performed the WAnT following 20 min of spontaneous breathing (control trial) or 5 or 20 min of voluntary hypocapnic hyperventilation. Both the 5-min and 20-min hyperventilation reduced end-tidal CO2 partial pressure (an index of arterial CO2 partial pressure) to ∼23 mmHg, whereas it remained unchanged during the spontaneous breathing. The peak, mean and minimum power outputs during the WAnT did not differ among the three trials. Oxygen uptake during the WAnT was lower in both the 5-min (1493 ± 257 mL min−1) and 20-min (1397 ± 447 mL min−1) hyperventilation trials than during the control trial (1847 ± 286 mL min−1), and was similar in the two hyperventilation trials. These results suggest that 5 min of pre-exercise hypocapnic hyperventilation reduces aerobic metabolism during the 30-s WAnT to a level similar to that seen with the 20-min hyperventilation. Moreover, exercise performance was unaffected, which implies anaerobic metabolism was enhanced.
Arabization of Nijmegen questionnaire and study of the prevalence of hyperventilation in dizzy patients
Published in Hearing, Balance and Communication, 2019
Hossam Saneyelbahaa Talaat, Asmaa Salah Moaty, Mai Ahmed Elsayed
Objectives: To develop and adapt the Arabic version of Nijmegen questionnaire (NQ) for assessment of hyperventilation and to determine the prevalence of hyperventilation in dizzy patients. Methods: The adapted NQ was translated following cross-cultural adaptation guidelines which includes forward and backward translation, Expert committee review, pretesting and final version of NQ. The adapted Arabic NQ was completed by 100 normal controls (control group) and 50 patients with hyperventilation symptoms (hyperventilation group) then the Arabic NQ was administered to 100 dizzy patients (dizzy group). Patients with disturbed consciousness and severe mental health disorders were excluded. Validity and reliability of the questionnaire were examined. Reliability included internal consistency and test–retest reliability. The validation of the questionnaire including content and construct validity was performed. Receiver operating characteristic (ROC) curve was used to determine the possible cutoff points. The prevalence of hyperventilation in dizzy patients was determined. Results: The Arabic NQ showed good internal consistency (Cronbach’s alpha = 0.819 for controls and Cronbach’s alpha = 0.920 for hyperventilation group). Test-retest correlation for repeatability was high (r = 0.987 among controls, and r = 0.927 among cases). Construct validity showed high negative correlations between the total score of the questionnaire and the partial pressure of carbon dioxide (PCO2) outcome (r = –0.916, p < .001). Twenty-eight percent of patients in the dizzy group give positive NQ score. Conclusion: This study showed that the adapted Arabic version of NQ is a valid and reliable questionnaire for the assessment of hyperventilation in Egyptian adults and the most sensitive cutoff point for diagnosing hyperventilation was (26.5). The prevalence of hyperventilation in dizzy patients was 28%.