A new apparatus for measuring lung function using forced inspired oxygen gas sinewaves

肺功能测试通常在专门的肺功能实验室或世界各地医院的心脏科对患者进行。通常在医院门诊患者中进行各种心肺功能测试，这些测试需要患者的合作以及临床医生与患者之间的融洽关系。这些患者可能患有从哮喘到慢性阻塞性肺疾病的各种肺部疾病。相比之下，医院重症监护室（ICU）的患者依赖于复杂的生命支持和监测设备，因此无法轻松将他们转移到肺功能实验室。进入ICU的最常见原因是需要机械辅助支持，通常被称为“生命支持”。这些患者不能参与任何形式的涉及自主操作的肺功能测试，也不能轻易转移这些患者或将其与呼吸支持分离。重症疾病，包括严重脓毒症和机械通气本身，可导致严重的肺异常，有效肺容量减少，肺与血液之间的气体交换效率降低。因此，具有讽刺意味的是，那些最能从肺功能和心肺功能测试中受益的患者，是最难以通过常规手段进行评估的。此外，它们将很可能依赖于吸入气体中的高氧气浓度，并且将不耐受如在某些肺功能测试中所要求的短时间呼吸较低的吸入氧气浓度。此外，通气患者将具有多种呼吸模式，这对进行心肺功能和肺功能测试的能力具有重要影响。由于上述原因，除了在某些卓越中心或出于详细的研究目的外，很少可能对ICU中的通气患者进行肺功能测试。在手术室里的麻醉病人的情况下，也出现了类似的论点。由于无意识的患者不能参与自主呼吸动作，因此不容易测量肺功能。因此，非常需要能够用相对简单的设备和常规可用的气体非侵入性地进行这些测量，这就是本赠款项目工作的目的。我们的研究计划是（在24个月的时间内）开发一种使用氧气作为测量气体的新仪器，以不需要患者合作并且不干扰他/她的呼吸模式/无论患者是自主呼吸还是机械通气的方式测量肺容量（最终也测量通过肺的血流量）。一台笔记本电脑将控制该装置，来自气体分析和气体流量传感器的信号将被输入到一个人肺的计算机模型中，以在床边确定患者的呼气末和死腔肺容量。作为项目工作的一部分，该装置将首先在一个机械台肺模型上进行测试，然后在我们实验室的自主呼吸志愿者身上进行测试。然后将设备和技术转移到医院ICU进行日常使用。

Lung function tests are commonly performed on patients in specialised Pulmonary Function Laboratories or in Cardiopulmonary Units in hospitals worldwide. Various cardiopulmonary function tests are performed, usually in hospital outpatients, and these require the co-operation of the patient and a rapport between the clinician and patient. These patients can be suffering from a wide variety of lung disorders ranging from asthma to chronic obstructive pulmonary disease.In contrast, patients in hospital Intensive Care Units (ICUs) are dependent upon complex life support and monitoring equipment, such that they cannot be moved easily to the Pulmonary Function Laboratory. The commonest reason for admission to the ICU is the need for mechanical ventilatory support, usually what is popularly known as 'life-support'. Such patients are not able to participate in any form of lung function testing involving volitional manoeuvres, nor can these patients be easily transferred or disconnected from their ventilatory support. Critical illness, including severe sepsis and mechanical ventilation itself, can lead to severe lung abnormalities decreased effective lung volume and decreased efficiency of gas exchange between the lung and the blood.It is therefore ironic that those patients who would benefit most from lung function and cardiopulmonary tests, are the most difficult to be assessed by conventional means.Furthermore, they will most likely be dependent upon high oxygen concentrations in the inspired gases and will not tolerate brief periods of breathing lower inspired oxygen concentrations, as is required in some lung function tests. Moreover, ventilated patients will have a variety of ventilatory modes and this has an important influence on the ability to perform cardiorespiratory and lung function tests. For the above reasons, it is seldom possible to perform lung function tests on the ventilated patient in the ICU, except in certain centres of excellence or for detailed research purposes. A similar argument arises in the case of the anaesthetised patient in the operating theatre. It is not easily possible to measure lung function since the unconscious patient is unable to participate in volitional respiratory manoeuvres.A great need therefore exists for these measurements to be able to be made non-invasively, with relatively simple equipment and gases that are routinely available, and that is the purpose of this grant project work. Our research proposal is to develop (over a period of 24 months) a new apparatus using oxygen as the measurement gas, to measure lung volume (and ultimately also blood flow through the lung) in a way that does not require patient co-operation and does not interfere with his/her breathing pattern / whether the patient is breathing spontaneously or is being mechanically ventilated. A lap-top computer will control this apparatus, and the signals from gas analysis and gas flow sensors will be fed into a computer model of the human lung to determine at the bed side the patient's end-expired and dead-space lung volumes.This apparatus will be tested as part of the project work first on a mechanical bench lung model and then on spontaneously breathing volunteers in our laboratory. The apparatus and technique will then be transferred to the hospital ICU for routine daily use.